Merge branch 'tcp-bpf-cc'

Martin Lau says:

====================
This series introduces BPF STRUCT_OPS.  It is an infra to allow
implementing some specific kernel's function pointers in BPF.
The first use case included in this series is to implement
TCP congestion control algorithm in BPF  (i.e. implement
struct tcp_congestion_ops in BPF).

There has been attempt to move the TCP CC to the user space
(e.g. CCP in TCP).   The common arguments are faster turn around,
get away from long-tail kernel versions in production...etc,
which are legit points.

BPF has been the continuous effort to join both kernel and
userspace upsides together (e.g. XDP to gain the performance
advantage without bypassing the kernel).  The recent BPF
advancements (in particular BTF-aware verifier, BPF trampoline,
BPF CO-RE...) made implementing kernel struct ops (e.g. tcp cc)
possible in BPF.

The idea is to allow implementing tcp_congestion_ops in bpf.
It allows a faster turnaround for testing algorithm in the
production while leveraging the existing (and continue growing) BPF
feature/framework instead of building one specifically for
userspace TCP CC.

Please see individual patch for details.

The bpftool support will be posted in follow-up patches.

v4:
- Expose tcp_ca_find() to tcp.h in patch 7.
  It is used to check the same bpf-tcp-cc
  does not exist to guarantee the register()
  will succeed.
- set_memory_ro() and then set_memory_x() only after all
  trampolines are written to the image in patch 6. (Daniel)
  spinlock is replaced by mutex because set_memory_*
  requires sleepable context.

v3:
- Fix kbuild error by considering CONFIG_BPF_SYSCALL (kbuild)
- Support anonymous bitfield in patch 4 (Andrii, Yonghong)
- Push boundary safety check to a specific arch's trampoline function
  (in patch 6) (Yonghong).
  Reuse the WANR_ON_ONCE check in arch_prepare_bpf_trampoline() in x86.
- Check module field is 0 in udata in patch 6 (Yonghong)
- Check zero holes in patch 6 (Andrii)
- s/_btf_vmlinux/btf/ in patch 5 and 7 (Andrii)
- s/check_xxx/is_xxx/ in patch 7 (Andrii)
- Use "struct_ops/" convention in patch 11 (Andrii)
- Use the skel instead of bpf_object in patch 11 (Andrii)
- libbpf: Decide BPF_PROG_TYPE_STRUCT_OPS at open phase by using
          find_sec_def()
- libbpf: Avoid a debug message at open phase (Andrii)
- libbpf: Add bpf_program__(is|set)_struct_ops() for consistency (Andrii)
- libbpf: Add "struct_ops" to section_defs (Andrii)
- libbpf: Some code shuffling in init_kern_struct_ops() (Andrii)
- libbpf: A few safety checks (Andrii)

v2:
- Dropped cubic for now.  They will be reposted
  once there are more clarity in "jiffies" on both
  bpf side (about the helper) and
  tcp_cubic side (some of jiffies usages are being replaced
  by tp->tcp_mstamp)
- Remove unnecssary check on bitfield support from btf_struct_access()
  (Yonghong)
- BTF_TYPE_EMIT macro (Yonghong, Andrii)
- value_name's length check to avoid an unlikely
  type match during truncation case (Yonghong)
- BUILD_BUG_ON to ensure no trampoline-image overrun
  in the future (Yonghong)
- Simplify get_next_key() (Yonghong)
- Added comment to explain how to check mandatory
  func ptr in net/ipv4/bpf_tcp_ca.c (Yonghong)
- Rename "__bpf_" to "bpf_struct_ops_" for value prefix (Andrii)
- Add comment to highlight the bpf_dctcp.c is not necessarily
  the same as tcp_dctcp.c. (Alexei, Eric)
- libbpf: Renmae "struct_ops" to ".struct_ops" for elf sec (Andrii)
- libbpf: Expose struct_ops as a bpf_map (Andrii)
- libbpf: Support multiple struct_ops in SEC(".struct_ops") (Andrii)
- libbpf: Add bpf_map__attach_struct_ops()  (Andrii)
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

32 files changed, 2654 insertions, 148 deletions

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 4c8a2d1f8470..9ba08e9abc09 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -1328,7 +1328,7 @@ emit_jmp:
 	return proglen;
 }
 
-static void save_regs(struct btf_func_model *m, u8 **prog, int nr_args,
+static void save_regs(const struct btf_func_model *m, u8 **prog, int nr_args,
 		      int stack_size)
 {
 	int i;
@@ -1344,7 +1344,7 @@ static void save_regs(struct btf_func_model *m, u8 **prog, int nr_args,
 			 -(stack_size - i * 8));
 }
 
-static void restore_regs(struct btf_func_model *m, u8 **prog, int nr_args,
+static void restore_regs(const struct btf_func_model *m, u8 **prog, int nr_args,
 			 int stack_size)
 {
 	int i;
@@ -1361,7 +1361,7 @@ static void restore_regs(struct btf_func_model *m, u8 **prog, int nr_args,
 			 -(stack_size - i * 8));
 }
 
-static int invoke_bpf(struct btf_func_model *m, u8 **pprog,
+static int invoke_bpf(const struct btf_func_model *m, u8 **pprog,
 		      struct bpf_prog **progs, int prog_cnt, int stack_size)
 {
 	u8 *prog = *pprog;
@@ -1456,7 +1456,8 @@ static int invoke_bpf(struct btf_func_model *m, u8 **pprog,
  * add rsp, 8                      // skip eth_type_trans's frame
  * ret                             // return to its caller
  */
-int arch_prepare_bpf_trampoline(void *image, struct btf_func_model *m, u32 flags,
+int arch_prepare_bpf_trampoline(void *image, void *image_end,
+				const struct btf_func_model *m, u32 flags,
 				struct bpf_prog **fentry_progs, int fentry_cnt,
 				struct bpf_prog **fexit_progs, int fexit_cnt,
 				void *orig_call)
@@ -1523,13 +1524,10 @@ int arch_prepare_bpf_trampoline(void *image, struct btf_func_model *m, u32 flags
 		/* skip our return address and return to parent */
 		EMIT4(0x48, 0x83, 0xC4, 8); /* add rsp, 8 */
 	EMIT1(0xC3); /* ret */
-	/* One half of the page has active running trampoline.
-	 * Another half is an area for next trampoline.
-	 * Make sure the trampoline generation logic doesn't overflow.
-	 */
-	if (WARN_ON_ONCE(prog - (u8 *)image > PAGE_SIZE / 2 - BPF_INSN_SAFETY))
+	/* Make sure the trampoline generation logic doesn't overflow */
+	if (WARN_ON_ONCE(prog > (u8 *)image_end - BPF_INSN_SAFETY))
 		return -EFAULT;
-	return 0;
+	return prog - (u8 *)image;
 }
 
 static int emit_cond_near_jump(u8 **pprog, void *func, void *ip, u8 jmp_cond)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index b14e51d56a82..a7bfe8a388c6 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -17,6 +17,7 @@
 #include <linux/u64_stats_sync.h>
 #include <linux/refcount.h>
 #include <linux/mutex.h>
+#include <linux/module.h>
 
 struct bpf_verifier_env;
 struct bpf_verifier_log;
@@ -106,6 +107,7 @@ struct bpf_map {
 	struct btf *btf;
 	struct bpf_map_memory memory;
 	char name[BPF_OBJ_NAME_LEN];
+	u32 btf_vmlinux_value_type_id;
 	bool unpriv_array;
 	bool frozen; /* write-once; write-protected by freeze_mutex */
 	/* 22 bytes hole */
@@ -183,7 +185,8 @@ static inline bool bpf_map_offload_neutral(const struct bpf_map *map)
 
 static inline bool bpf_map_support_seq_show(const struct bpf_map *map)
 {
-	return map->btf && map->ops->map_seq_show_elem;
+	return (map->btf_value_type_id || map->btf_vmlinux_value_type_id) &&
+		map->ops->map_seq_show_elem;
 }
 
 int map_check_no_btf(const struct bpf_map *map,
@@ -349,6 +352,10 @@ struct bpf_verifier_ops {
 				  const struct bpf_insn *src,
 				  struct bpf_insn *dst,
 				  struct bpf_prog *prog, u32 *target_size);
+	int (*btf_struct_access)(struct bpf_verifier_log *log,
+				 const struct btf_type *t, int off, int size,
+				 enum bpf_access_type atype,
+				 u32 *next_btf_id);
 };
 
 struct bpf_prog_offload_ops {
@@ -437,7 +444,8 @@ struct btf_func_model {
  *      fentry = a set of program to run before calling original function
  *      fexit = a set of program to run after original function
  */
-int arch_prepare_bpf_trampoline(void *image, struct btf_func_model *m, u32 flags,
+int arch_prepare_bpf_trampoline(void *image, void *image_end,
+				const struct btf_func_model *m, u32 flags,
 				struct bpf_prog **fentry_progs, int fentry_cnt,
 				struct bpf_prog **fexit_progs, int fexit_cnt,
 				void *orig_call);
@@ -668,6 +676,73 @@ struct bpf_array_aux {
 	struct work_struct work;
 };
 
+struct bpf_struct_ops_value;
+struct btf_type;
+struct btf_member;
+
+#define BPF_STRUCT_OPS_MAX_NR_MEMBERS 64
+struct bpf_struct_ops {
+	const struct bpf_verifier_ops *verifier_ops;
+	int (*init)(struct btf *btf);
+	int (*check_member)(const struct btf_type *t,
+			    const struct btf_member *member);
+	int (*init_member)(const struct btf_type *t,
+			   const struct btf_member *member,
+			   void *kdata, const void *udata);
+	int (*reg)(void *kdata);
+	void (*unreg)(void *kdata);
+	const struct btf_type *type;
+	const struct btf_type *value_type;
+	const char *name;
+	struct btf_func_model func_models[BPF_STRUCT_OPS_MAX_NR_MEMBERS];
+	u32 type_id;
+	u32 value_id;
+};
+
+#if defined(CONFIG_BPF_JIT) && defined(CONFIG_BPF_SYSCALL)
+#define BPF_MODULE_OWNER ((void *)((0xeB9FUL << 2) + POISON_POINTER_DELTA))
+const struct bpf_struct_ops *bpf_struct_ops_find(u32 type_id);
+void bpf_struct_ops_init(struct btf *btf);
+bool bpf_struct_ops_get(const void *kdata);
+void bpf_struct_ops_put(const void *kdata);
+int bpf_struct_ops_map_sys_lookup_elem(struct bpf_map *map, void *key,
+				       void *value);
+static inline bool bpf_try_module_get(const void *data, struct module *owner)
+{
+	if (owner == BPF_MODULE_OWNER)
+		return bpf_struct_ops_get(data);
+	else
+		return try_module_get(owner);
+}
+static inline void bpf_module_put(const void *data, struct module *owner)
+{
+	if (owner == BPF_MODULE_OWNER)
+		bpf_struct_ops_put(data);
+	else
+		module_put(owner);
+}
+#else
+static inline const struct bpf_struct_ops *bpf_struct_ops_find(u32 type_id)
+{
+	return NULL;
+}
+static inline void bpf_struct_ops_init(struct btf *btf) { }
+static inline bool bpf_try_module_get(const void *data, struct module *owner)
+{
+	return try_module_get(owner);
+}
+static inline void bpf_module_put(const void *data, struct module *owner)
+{
+	module_put(owner);
+}
+static inline int bpf_struct_ops_map_sys_lookup_elem(struct bpf_map *map,
+						     void *key,
+						     void *value)
+{
+	return -EINVAL;
+}
+#endif
+
 struct bpf_array {
 	struct bpf_map map;
 	u32 elem_size;
diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h
index 93740b3614d7..9f326e6ef885 100644
--- a/include/linux/bpf_types.h
+++ b/include/linux/bpf_types.h
@@ -65,6 +65,10 @@ BPF_PROG_TYPE(BPF_PROG_TYPE_LIRC_MODE2, lirc_mode2,
 BPF_PROG_TYPE(BPF_PROG_TYPE_SK_REUSEPORT, sk_reuseport,
 	      struct sk_reuseport_md, struct sk_reuseport_kern)
 #endif
+#if defined(CONFIG_BPF_JIT)
+BPF_PROG_TYPE(BPF_PROG_TYPE_STRUCT_OPS, bpf_struct_ops,
+	      void *, void *)
+#endif
 
 BPF_MAP_TYPE(BPF_MAP_TYPE_ARRAY, array_map_ops)
 BPF_MAP_TYPE(BPF_MAP_TYPE_PERCPU_ARRAY, percpu_array_map_ops)
@@ -105,3 +109,6 @@ BPF_MAP_TYPE(BPF_MAP_TYPE_REUSEPORT_SOCKARRAY, reuseport_array_ops)
 #endif
 BPF_MAP_TYPE(BPF_MAP_TYPE_QUEUE, queue_map_ops)
 BPF_MAP_TYPE(BPF_MAP_TYPE_STACK, stack_map_ops)
+#if defined(CONFIG_BPF_JIT)
+BPF_MAP_TYPE(BPF_MAP_TYPE_STRUCT_OPS, bpf_struct_ops_map_ops)
+#endif
diff --git a/include/linux/btf.h b/include/linux/btf.h
index 79d4abc2556a..881e9b76ef49 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -7,6 +7,8 @@
 #include <linux/types.h>
 #include <uapi/linux/btf.h>
 
+#define BTF_TYPE_EMIT(type) ((void)(type *)0)
+
 struct btf;
 struct btf_member;
 struct btf_type;
@@ -53,6 +55,22 @@ bool btf_member_is_reg_int(const struct btf *btf, const struct btf_type *s,
 			   u32 expected_offset, u32 expected_size);
 int btf_find_spin_lock(const struct btf *btf, const struct btf_type *t);
 bool btf_type_is_void(const struct btf_type *t);
+s32 btf_find_by_name_kind(const struct btf *btf, const char *name, u8 kind);
+const struct btf_type *btf_type_skip_modifiers(const struct btf *btf,
+					       u32 id, u32 *res_id);
+const struct btf_type *btf_type_resolve_ptr(const struct btf *btf,
+					    u32 id, u32 *res_id);
+const struct btf_type *btf_type_resolve_func_ptr(const struct btf *btf,
+						 u32 id, u32 *res_id);
+const struct btf_type *
+btf_resolve_size(const struct btf *btf, const struct btf_type *type,
+		 u32 *type_size, const struct btf_type **elem_type,
+		 u32 *total_nelems);
+
+#define for_each_member(i, struct_type, member)			\
+	for (i = 0, member = btf_type_member(struct_type);	\
+	     i < btf_type_vlen(struct_type);			\
+	     i++, member++)
 
 static inline bool btf_type_is_ptr(const struct btf_type *t)
 {
@@ -84,6 +102,35 @@ static inline bool btf_type_is_func_proto(const struct btf_type *t)
 	return BTF_INFO_KIND(t->info) == BTF_KIND_FUNC_PROTO;
 }
 
+static inline u16 btf_type_vlen(const struct btf_type *t)
+{
+	return BTF_INFO_VLEN(t->info);
+}
+
+static inline bool btf_type_kflag(const struct btf_type *t)
+{
+	return BTF_INFO_KFLAG(t->info);
+}
+
+static inline u32 btf_member_bit_offset(const struct btf_type *struct_type,
+					const struct btf_member *member)
+{
+	return btf_type_kflag(struct_type) ? BTF_MEMBER_BIT_OFFSET(member->offset)
+					   : member->offset;
+}
+
+static inline u32 btf_member_bitfield_size(const struct btf_type *struct_type,
+					   const struct btf_member *member)
+{
+	return btf_type_kflag(struct_type) ? BTF_MEMBER_BITFIELD_SIZE(member->offset)
+					   : 0;
+}
+
+static inline const struct btf_member *btf_type_member(const struct btf_type *t)
+{
+	return (const struct btf_member *)(t + 1);
+}
+
 #ifdef CONFIG_BPF_SYSCALL
 const struct btf_type *btf_type_by_id(const struct btf *btf, u32 type_id);
 const char *btf_name_by_offset(const struct btf *btf, u32 offset);
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 70e6dd960bca..a366a0b64a57 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -843,6 +843,8 @@ int bpf_prog_create(struct bpf_prog **pfp, struct sock_fprog_kern *fprog);
 int bpf_prog_create_from_user(struct bpf_prog **pfp, struct sock_fprog *fprog,
 			      bpf_aux_classic_check_t trans, bool save_orig);
 void bpf_prog_destroy(struct bpf_prog *fp);
+const struct bpf_func_proto *
+bpf_base_func_proto(enum bpf_func_id func_id);
 
 int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk);
 int sk_attach_bpf(u32 ufd, struct sock *sk);
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 7df37e2fddca..9dd975be7fdf 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1007,6 +1007,7 @@ enum tcp_ca_ack_event_flags {
 #define TCP_CONG_NON_RESTRICTED 0x1
 /* Requires ECN/ECT set on all packets */
 #define TCP_CONG_NEEDS_ECN	0x2
+#define TCP_CONG_MASK	(TCP_CONG_NON_RESTRICTED | TCP_CONG_NEEDS_ECN)
 
 union tcp_cc_info;
 
@@ -1101,6 +1102,7 @@ u32 tcp_reno_undo_cwnd(struct sock *sk);
 void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked);
 extern struct tcp_congestion_ops tcp_reno;
 
+struct tcp_congestion_ops *tcp_ca_find(const char *name);
 struct tcp_congestion_ops *tcp_ca_find_key(u32 key);
 u32 tcp_ca_get_key_by_name(struct net *net, const char *name, bool *ecn_ca);
 #ifdef CONFIG_INET
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 7df436da542d..2d6a2e572f56 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -136,6 +136,7 @@ enum bpf_map_type {
 	BPF_MAP_TYPE_STACK,
 	BPF_MAP_TYPE_SK_STORAGE,
 	BPF_MAP_TYPE_DEVMAP_HASH,
+	BPF_MAP_TYPE_STRUCT_OPS,
 };
 
 /* Note that tracing related programs such as
@@ -174,6 +175,7 @@ enum bpf_prog_type {
 	BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE,
 	BPF_PROG_TYPE_CGROUP_SOCKOPT,
 	BPF_PROG_TYPE_TRACING,
+	BPF_PROG_TYPE_STRUCT_OPS,
 };
 
 enum bpf_attach_type {
@@ -397,6 +399,10 @@ union bpf_attr {
 		__u32	btf_fd;		/* fd pointing to a BTF type data */
 		__u32	btf_key_type_id;	/* BTF type_id of the key */
 		__u32	btf_value_type_id;	/* BTF type_id of the value */
+		__u32	btf_vmlinux_value_type_id;/* BTF type_id of a kernel-
+						   * struct stored as the
+						   * map value
+						   */
 	};
 
 	struct { /* anonymous struct used by BPF_MAP_*_ELEM commands */
@@ -2831,6 +2837,14 @@ union bpf_attr {
  * 	Return
  * 		On success, the strictly positive length of the string,	including
  * 		the trailing NUL character. On error, a negative value.
+ *
+ * int bpf_tcp_send_ack(void *tp, u32 rcv_nxt)
+ *	Description
+ *		Send out a tcp-ack. *tp* is the in-kernel struct tcp_sock.
+ *		*rcv_nxt* is the ack_seq to be sent out.
+ *	Return
+ *		0 on success, or a negative error in case of failure.
+ *
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -2948,7 +2962,8 @@ union bpf_attr {
 	FN(probe_read_user),		\
 	FN(probe_read_kernel),		\
 	FN(probe_read_user_str),	\
-	FN(probe_read_kernel_str),
+	FN(probe_read_kernel_str),	\
+	FN(tcp_send_ack),
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
  * function eBPF program intends to call
@@ -3349,7 +3364,7 @@ struct bpf_map_info {
 	__u32 map_flags;
 	char  name[BPF_OBJ_NAME_LEN];
 	__u32 ifindex;
-	__u32 :32;
+	__u32 btf_vmlinux_value_type_id;
 	__u64 netns_dev;
 	__u64 netns_ino;
 	__u32 btf_id;
diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
index d4f330351f87..046ce5d98033 100644
--- a/kernel/bpf/Makefile
+++ b/kernel/bpf/Makefile
@@ -27,3 +27,6 @@ endif
 ifeq ($(CONFIG_SYSFS),y)
 obj-$(CONFIG_DEBUG_INFO_BTF) += sysfs_btf.o
 endif
+ifeq ($(CONFIG_BPF_JIT),y)
+obj-$(CONFIG_BPF_SYSCALL) += bpf_struct_ops.o
+endif
diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
new file mode 100644
index 000000000000..ddf48f49914b
--- /dev/null
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -0,0 +1,628 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright (c) 2019 Facebook */
+
+#include <linux/bpf.h>
+#include <linux/bpf_verifier.h>
+#include <linux/btf.h>
+#include <linux/filter.h>
+#include <linux/slab.h>
+#include <linux/numa.h>
+#include <linux/seq_file.h>
+#include <linux/refcount.h>
+#include <linux/mutex.h>
+
+enum bpf_struct_ops_state {
+	BPF_STRUCT_OPS_STATE_INIT,
+	BPF_STRUCT_OPS_STATE_INUSE,
+	BPF_STRUCT_OPS_STATE_TOBEFREE,
+};
+
+#define BPF_STRUCT_OPS_COMMON_VALUE			\
+	refcount_t refcnt;				\
+	enum bpf_struct_ops_state state
+
+struct bpf_struct_ops_value {
+	BPF_STRUCT_OPS_COMMON_VALUE;
+	char data[0] ____cacheline_aligned_in_smp;
+};
+
+struct bpf_struct_ops_map {
+	struct bpf_map map;
+	const struct bpf_struct_ops *st_ops;
+	/* protect map_update */
+	struct mutex lock;
+	/* progs has all the bpf_prog that is populated
+	 * to the func ptr of the kernel's struct
+	 * (in kvalue.data).
+	 */
+	struct bpf_prog **progs;
+	/* image is a page that has all the trampolines
+	 * that stores the func args before calling the bpf_prog.
+	 * A PAGE_SIZE "image" is enough to store all trampoline for
+	 * "progs[]".
+	 */
+	void *image;
+	/* uvalue->data stores the kernel struct
+	 * (e.g. tcp_congestion_ops) that is more useful
+	 * to userspace than the kvalue.  For example,
+	 * the bpf_prog's id is stored instead of the kernel
+	 * address of a func ptr.
+	 */
+	struct bpf_struct_ops_value *uvalue;
+	/* kvalue.data stores the actual kernel's struct
+	 * (e.g. tcp_congestion_ops) that will be
+	 * registered to the kernel subsystem.
+	 */
+	struct bpf_struct_ops_value kvalue;
+};
+
+#define VALUE_PREFIX "bpf_struct_ops_"
+#define VALUE_PREFIX_LEN (sizeof(VALUE_PREFIX) - 1)
+
+/* bpf_struct_ops_##_name (e.g. bpf_struct_ops_tcp_congestion_ops) is
+ * the map's value exposed to the userspace and its btf-type-id is
+ * stored at the map->btf_vmlinux_value_type_id.
+ *
+ */
+#define BPF_STRUCT_OPS_TYPE(_name)				\
+extern struct bpf_struct_ops bpf_##_name;			\
+								\
+struct bpf_struct_ops_##_name {						\
+	BPF_STRUCT_OPS_COMMON_VALUE;				\
+	struct _name data ____cacheline_aligned_in_smp;		\
+};
+#include "bpf_struct_ops_types.h"
+#undef BPF_STRUCT_OPS_TYPE
+
+enum {
+#define BPF_STRUCT_OPS_TYPE(_name) BPF_STRUCT_OPS_TYPE_##_name,
+#include "bpf_struct_ops_types.h"
+#undef BPF_STRUCT_OPS_TYPE
+	__NR_BPF_STRUCT_OPS_TYPE,
+};
+
+static struct bpf_struct_ops * const bpf_struct_ops[] = {
+#define BPF_STRUCT_OPS_TYPE(_name)				\
+	[BPF_STRUCT_OPS_TYPE_##_name] = &bpf_##_name,
+#include "bpf_struct_ops_types.h"
+#undef BPF_STRUCT_OPS_TYPE
+};
+
+const struct bpf_verifier_ops bpf_struct_ops_verifier_ops = {
+};
+
+const struct bpf_prog_ops bpf_struct_ops_prog_ops = {
+};
+
+static const struct btf_type *module_type;
+
+void bpf_struct_ops_init(struct btf *btf)
+{
+	s32 type_id, value_id, module_id;
+	const struct btf_member *member;
+	struct bpf_struct_ops *st_ops;
+	struct bpf_verifier_log log = {};
+	const struct btf_type *t;
+	char value_name[128];
+	const char *mname;
+	u32 i, j;
+
+	/* Ensure BTF type is emitted for "struct bpf_struct_ops_##_name" */
+#define BPF_STRUCT_OPS_TYPE(_name) BTF_TYPE_EMIT(struct bpf_struct_ops_##_name);
+#include "bpf_struct_ops_types.h"
+#undef BPF_STRUCT_OPS_TYPE
+
+	module_id = btf_find_by_name_kind(btf, "module", BTF_KIND_STRUCT);
+	if (module_id < 0) {
+		pr_warn("Cannot find struct module in btf_vmlinux\n");
+		return;
+	}
+	module_type = btf_type_by_id(btf, module_id);
+
+	for (i = 0; i < ARRAY_SIZE(bpf_struct_ops); i++) {
+		st_ops = bpf_struct_ops[i];
+
+		if (strlen(st_ops->name) + VALUE_PREFIX_LEN >=
+		    sizeof(value_name)) {
+			pr_warn("struct_ops name %s is too long\n",
+				st_ops->name);
+			continue;
+		}
+		sprintf(value_name, "%s%s", VALUE_PREFIX, st_ops->name);
+
+		value_id = btf_find_by_name_kind(btf, value_name,
+						 BTF_KIND_STRUCT);
+		if (value_id < 0) {
+			pr_warn("Cannot find struct %s in btf_vmlinux\n",
+				value_name);
+			continue;
+		}
+
+		type_id = btf_find_by_name_kind(btf, st_ops->name,
+						BTF_KIND_STRUCT);
+		if (type_id < 0) {
+			pr_warn("Cannot find struct %s in btf_vmlinux\n",
+				st_ops->name);
+			continue;
+		}
+		t = btf_type_by_id(btf, type_id);
+		if (btf_type_vlen(t) > BPF_STRUCT_OPS_MAX_NR_MEMBERS) {
+			pr_warn("Cannot support #%u members in struct %s\n",
+				btf_type_vlen(t), st_ops->name);
+			continue;
+		}
+
+		for_each_member(j, t, member) {
+			const struct btf_type *func_proto;
+
+			mname = btf_name_by_offset(btf, member->name_off);
+			if (!*mname) {
+				pr_warn("anon member in struct %s is not supported\n",
+					st_ops->name);
+				break;
+			}
+
+			if (btf_member_bitfield_size(t, member)) {
+				pr_warn("bit field member %s in struct %s is not supported\n",
+					mname, st_ops->name);
+				break;
+			}
+
+			func_proto = btf_type_resolve_func_ptr(btf,
+							       member->type,
+							       NULL);
+			if (func_proto &&
+			    btf_distill_func_proto(&log, btf,
+						   func_proto, mname,
+						   &st_ops->func_models[j])) {
+				pr_warn("Error in parsing func ptr %s in struct %s\n",
+					mname, st_ops->name);
+				break;
+			}
+		}
+
+		if (j == btf_type_vlen(t)) {
+			if (st_ops->init(btf)) {
+				pr_warn("Error in init bpf_struct_ops %s\n",
+					st_ops->name);
+			} else {
+				st_ops->type_id = type_id;
+				st_ops->type = t;
+				st_ops->value_id = value_id;
+				st_ops->value_type = btf_type_by_id(btf,
+								    value_id);
+			}
+		}
+	}
+}
+
+extern struct btf *btf_vmlinux;
+
+static const struct bpf_struct_ops *
+bpf_struct_ops_find_value(u32 value_id)
+{
+	unsigned int i;
+
+	if (!value_id || !btf_vmlinux)
+		return NULL;
+
+	for (i = 0; i < ARRAY_SIZE(bpf_struct_ops); i++) {
+		if (bpf_struct_ops[i]->value_id == value_id)
+			return bpf_struct_ops[i];
+	}
+
+	return NULL;
+}
+
+const struct bpf_struct_ops *bpf_struct_ops_find(u32 type_id)
+{
+	unsigned int i;
+
+	if (!type_id || !btf_vmlinux)
+		return NULL;
+
+	for (i = 0; i < ARRAY_SIZE(bpf_struct_ops); i++) {
+		if (bpf_struct_ops[i]->type_id == type_id)
+			return bpf_struct_ops[i];
+	}
+
+	return NULL;
+}
+
+static int bpf_struct_ops_map_get_next_key(struct bpf_map *map, void *key,
+					   void *next_key)
+{
+	if (key && *(u32 *)key == 0)
+		return -ENOENT;
+
+	*(u32 *)next_key = 0;
+	return 0;
+}
+
+int bpf_struct_ops_map_sys_lookup_elem(struct bpf_map *map, void *key,
+				       void *value)
+{
+	struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
+	struct bpf_struct_ops_value *uvalue, *kvalue;
+	enum bpf_struct_ops_state state;
+
+	if (unlikely(*(u32 *)key != 0))
+		return -ENOENT;
+
+	kvalue = &st_map->kvalue;
+	/* Pair with smp_store_release() during map_update */
+	state = smp_load_acquire(&kvalue->state);
+	if (state == BPF_STRUCT_OPS_STATE_INIT) {
+		memset(value, 0, map->value_size);
+		return 0;
+	}
+
+	/* No lock is needed.  state and refcnt do not need
+	 * to be updated together under atomic context.
+	 */
+	uvalue = (struct bpf_struct_ops_value *)value;
+	memcpy(uvalue, st_map->uvalue, map->value_size);
+	uvalue->state = state;
+	refcount_set(&uvalue->refcnt, refcount_read(&kvalue->refcnt));
+
+	return 0;
+}
+
+static void *bpf_struct_ops_map_lookup_elem(struct bpf_map *map, void *key)
+{
+	return ERR_PTR(-EINVAL);
+}
+
+static void bpf_struct_ops_map_put_progs(struct bpf_struct_ops_map *st_map)
+{
+	const struct btf_type *t = st_map->st_ops->type;
+	u32 i;
+
+	for (i = 0; i < btf_type_vlen(t); i++) {
+		if (st_map->progs[i]) {
+			bpf_prog_put(st_map->progs[i]);
+			st_map->progs[i] = NULL;
+		}
+	}
+}
+
+static int check_zero_holes(const struct btf_type *t, void *data)
+{
+	const struct btf_member *member;
+	u32 i, moff, msize, prev_mend = 0;
+	const struct btf_type *mtype;
+
+	for_each_member(i, t, member) {
+		moff = btf_member_bit_offset(t, member) / 8;
+		if (moff > prev_mend &&
+		    memchr_inv(data + prev_mend, 0, moff - prev_mend))
+			return -EINVAL;
+
+		mtype = btf_type_by_id(btf_vmlinux, member->type);
+		mtype = btf_resolve_size(btf_vmlinux, mtype, &msize,
+					 NULL, NULL);
+		if (IS_ERR(mtype))
+			return PTR_ERR(mtype);
+		prev_mend = moff + msize;
+	}
+
+	if (t->size > prev_mend &&
+	    memchr_inv(data + prev_mend, 0, t->size - prev_mend))
+		return -EINVAL;
+
+	return 0;
+}
+
+static int bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
+					  void *value, u64 flags)
+{
+	struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
+	const struct bpf_struct_ops *st_ops = st_map->st_ops;
+	struct bpf_struct_ops_value *uvalue, *kvalue;
+	const struct btf_member *member;
+	const struct btf_type *t = st_ops->type;
+	void *udata, *kdata;
+	int prog_fd, err = 0;
+	void *image;
+	u32 i;
+
+	if (flags)
+		return -EINVAL;
+
+	if (*(u32 *)key != 0)
+		return -E2BIG;
+
+	err = check_zero_holes(st_ops->value_type, value);
+	if (err)
+		return err;
+
+	uvalue = (struct bpf_struct_ops_value *)value;
+	err = check_zero_holes(t, uvalue->data);
+	if (err)
+		return err;
+
+	if (uvalue->state || refcount_read(&uvalue->refcnt))
+		return -EINVAL;
+
+	uvalue = (struct bpf_struct_ops_value *)st_map->uvalue;
+	kvalue = (struct bpf_struct_ops_value *)&st_map->kvalue;
+
+	mutex_lock(&st_map->lock);
+
+	if (kvalue->state != BPF_STRUCT_OPS_STATE_INIT) {
+		err = -EBUSY;
+		goto unlock;
+	}
+
+	memcpy(uvalue, value, map->value_size);
+
+	udata = &uvalue->data;
+	kdata = &kvalue->data;
+	image = st_map->image;
+
+	for_each_member(i, t, member) {
+		const struct btf_type *mtype, *ptype;
+		struct bpf_prog *prog;
+		u32 moff;
+
+		moff = btf_member_bit_offset(t, member) / 8;
+		ptype = btf_type_resolve_ptr(btf_vmlinux, member->type, NULL);
+		if (ptype == module_type) {
+			if (*(void **)(udata + moff))
+				goto reset_unlock;
+			*(void **)(kdata + moff) = BPF_MODULE_OWNER;
+			continue;
+		}
+
+		err = st_ops->init_member(t, member, kdata, udata);
+		if (err < 0)
+			goto reset_unlock;
+
+		/* The ->init_member() has handled this member */
+		if (err > 0)
+			continue;
+
+		/* If st_ops->init_member does not handle it,
+		 * we will only handle func ptrs and zero-ed members
+		 * here.  Reject everything else.
+		 */
+
+		/* All non func ptr member must be 0 */
+		if (!ptype || !btf_type_is_func_proto(ptype)) {
+			u32 msize;
+
+			mtype = btf_type_by_id(btf_vmlinux, member->type);
+			mtype = btf_resolve_size(btf_vmlinux, mtype, &msize,
+						 NULL, NULL);
+			if (IS_ERR(mtype)) {
+				err = PTR_ERR(mtype);
+				goto reset_unlock;
+			}
+
+			if (memchr_inv(udata + moff, 0, msize)) {
+				err = -EINVAL;
+				goto reset_unlock;
+			}
+
+			continue;
+		}
+
+		prog_fd = (int)(*(unsigned long *)(udata + moff));
+		/* Similar check as the attr->attach_prog_fd */
+		if (!prog_fd)
+			continue;
+
+		prog = bpf_prog_get(prog_fd);
+		if (IS_ERR(prog)) {
+			err = PTR_ERR(prog);
+			goto reset_unlock;
+		}
+		st_map->progs[i] = prog;
+
+		if (prog->type != BPF_PROG_TYPE_STRUCT_OPS ||
+		    prog->aux->attach_btf_id != st_ops->type_id ||
+		    prog->expected_attach_type != i) {
+			err = -EINVAL;
+			goto reset_unlock;
+		}
+
+		err = arch_prepare_bpf_trampoline(image,
+						  st_map->image + PAGE_SIZE,
+						  &st_ops->func_models[i], 0,
+						  &prog, 1, NULL, 0, NULL);
+		if (err < 0)
+			goto reset_unlock;
+
+		*(void **)(kdata + moff) = image;
+		image += err;
+
+		/* put prog_id to udata */
+		*(unsigned long *)(udata + moff) = prog->aux->id;
+	}
+
+	refcount_set(&kvalue->refcnt, 1);
+	bpf_map_inc(map);
+
+	set_memory_ro((long)st_map->image, 1);
+	set_memory_x((long)st_map->image, 1);
+	err = st_ops->reg(kdata);
+	if (likely(!err)) {
+		/* Pair with smp_load_acquire() during lookup_elem().
+		 * It ensures the above udata updates (e.g. prog->aux->id)
+		 * can be seen once BPF_STRUCT_OPS_STATE_INUSE is set.
+		 */
+		smp_store_release(&kvalue->state, BPF_STRUCT_OPS_STATE_INUSE);
+		goto unlock;
+	}
+
+	/* Error during st_ops->reg().  It is very unlikely since
+	 * the above init_member() should have caught it earlier
+	 * before reg().  The only possibility is if there was a race
+	 * in registering the struct_ops (under the same name) to
+	 * a sub-system through different struct_ops's maps.
+	 */
+	set_memory_nx((long)st_map->image, 1);
+	set_memory_rw((long)st_map->image, 1);
+	bpf_map_put(map);
+
+reset_unlock:
+	bpf_struct_ops_map_put_progs(st_map);
+	memset(uvalue, 0, map->value_size);
+	memset(kvalue, 0, map->value_size);
+unlock:
+	mutex_unlock(&st_map->lock);
+	return err;
+}
+
+static int bpf_struct_ops_map_delete_elem(struct bpf_map *map, void *key)
+{
+	enum bpf_struct_ops_state prev_state;
+	struct bpf_struct_ops_map *st_map;
+
+	st_map = (struct bpf_struct_ops_map *)map;
+	prev_state = cmpxchg(&st_map->kvalue.state,
+			     BPF_STRUCT_OPS_STATE_INUSE,
+			     BPF_STRUCT_OPS_STATE_TOBEFREE);
+	if (prev_state == BPF_STRUCT_OPS_STATE_INUSE) {
+		st_map->st_ops->unreg(&st_map->kvalue.data);
+		if (refcount_dec_and_test(&st_map->kvalue.refcnt))
+			bpf_map_put(map);
+	}
+
+	return 0;
+}
+
+static void bpf_struct_ops_map_seq_show_elem(struct bpf_map *map, void *key,
+					     struct seq_file *m)
+{
+	void *value;
+
+	value = bpf_struct_ops_map_lookup_elem(map, key);
+	if (!value)
+		return;
+
+	btf_type_seq_show(btf_vmlinux, map->btf_vmlinux_value_type_id,
+			  value, m);
+	seq_puts(m, "\n");
+}
+
+static void bpf_struct_ops_map_free(struct bpf_map *map)
+{
+	struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
+
+	if (st_map->progs)
+		bpf_struct_ops_map_put_progs(st_map);
+	bpf_map_area_free(st_map->progs);
+	bpf_jit_free_exec(st_map->image);
+	bpf_map_area_free(st_map->uvalue);
+	bpf_map_area_free(st_map);
+}
+
+static int bpf_struct_ops_map_alloc_check(union bpf_attr *attr)
+{
+	if (attr->key_size != sizeof(unsigned int) || attr->max_entries != 1 ||
+	    attr->map_flags || !attr->btf_vmlinux_value_type_id)
+		return -EINVAL;
+	return 0;
+}
+
+static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
+{
+	const struct bpf_struct_ops *st_ops;
+	size_t map_total_size, st_map_size;
+	struct bpf_struct_ops_map *st_map;
+	const struct btf_type *t, *vt;
+	struct bpf_map_memory mem;
+	struct bpf_map *map;
+	int err;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return ERR_PTR(-EPERM);
+
+	st_ops = bpf_struct_ops_find_value(attr->btf_vmlinux_value_type_id);
+	if (!st_ops)
+		return ERR_PTR(-ENOTSUPP);
+
+	vt = st_ops->value_type;
+	if (attr->value_size != vt->size)
+		return ERR_PTR(-EINVAL);
+
+	t = st_ops->type;
+
+	st_map_size = sizeof(*st_map) +
+		/* kvalue stores the
+		 * struct bpf_struct_ops_tcp_congestions_ops
+		 */
+		(vt->size - sizeof(struct bpf_struct_ops_value));
+	map_total_size = st_map_size +
+		/* uvalue */
+		sizeof(vt->size) +
+		/* struct bpf_progs **progs */
+		 btf_type_vlen(t) * sizeof(struct bpf_prog *);
+	err = bpf_map_charge_init(&mem, map_total_size);
+	if (err < 0)
+		return ERR_PTR(err);
+
+	st_map = bpf_map_area_alloc(st_map_size, NUMA_NO_NODE);
+	if (!st_map) {
+		bpf_map_charge_finish(&mem);
+		return ERR_PTR(-ENOMEM);
+	}
+	st_map->st_ops = st_ops;
+	map = &st_map->map;
+
+	st_map->uvalue = bpf_map_area_alloc(vt->size, NUMA_NO_NODE);
+	st_map->progs =
+		bpf_map_area_alloc(btf_type_vlen(t) * sizeof(struct bpf_prog *),
+				   NUMA_NO_NODE);
+	st_map->image = bpf_jit_alloc_exec(PAGE_SIZE);
+	if (!st_map->uvalue || !st_map->progs || !st_map->image) {
+		bpf_struct_ops_map_free(map);
+		bpf_map_charge_finish(&mem);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	mutex_init(&st_map->lock);
+	set_vm_flush_reset_perms(st_map->image);
+	bpf_map_init_from_attr(map, attr);
+	bpf_map_charge_move(&map->memory, &mem);
+
+	return map;
+}
+
+const struct bpf_map_ops bpf_struct_ops_map_ops = {
+	.map_alloc_check = bpf_struct_ops_map_alloc_check,
+	.map_alloc = bpf_struct_ops_map_alloc,
+	.map_free = bpf_struct_ops_map_free,
+	.map_get_next_key = bpf_struct_ops_map_get_next_key,
+	.map_lookup_elem = bpf_struct_ops_map_lookup_elem,
+	.map_delete_elem = bpf_struct_ops_map_delete_elem,
+	.map_update_elem = bpf_struct_ops_map_update_elem,
+	.map_seq_show_elem = bpf_struct_ops_map_seq_show_elem,
+};
+
+/* "const void *" because some subsystem is
+ * passing a const (e.g. const struct tcp_congestion_ops *)
+ */
+bool bpf_struct_ops_get(const void *kdata)
+{
+	struct bpf_struct_ops_value *kvalue;
+
+	kvalue = container_of(kdata, struct bpf_struct_ops_value, data);
+
+	return refcount_inc_not_zero(&kvalue->refcnt);
+}
+
+void bpf_struct_ops_put(const void *kdata)
+{
+	struct bpf_struct_ops_value *kvalue;
+
+	kvalue = container_of(kdata, struct bpf_struct_ops_value, data);
+	if (refcount_dec_and_test(&kvalue->refcnt)) {
+		struct bpf_struct_ops_map *st_map;
+
+		st_map = container_of(kvalue, struct bpf_struct_ops_map,
+				      kvalue);
+		bpf_map_put(&st_map->map);
+	}
+}
diff --git a/kernel/bpf/bpf_struct_ops_types.h b/kernel/bpf/bpf_struct_ops_types.h
new file mode 100644
index 000000000000..066d83ea1c99
--- /dev/null
+++ b/kernel/bpf/bpf_struct_ops_types.h
@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* internal file - do not include directly */
+
+#ifdef CONFIG_BPF_JIT
+#ifdef CONFIG_INET
+#include <net/tcp.h>
+BPF_STRUCT_OPS_TYPE(tcp_congestion_ops)
+#endif
+#endif
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index ed2075884724..81d9cf75cacd 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -180,11 +180,6 @@
  */
 #define BTF_MAX_SIZE (16 * 1024 * 1024)
 
-#define for_each_member(i, struct_type, member)			\
-	for (i = 0, member = btf_type_member(struct_type);	\
-	     i < btf_type_vlen(struct_type);			\
-	     i++, member++)
-
 #define for_each_member_from(i, from, struct_type, member)		\
 	for (i = from, member = btf_type_member(struct_type) + from;	\
 	     i < btf_type_vlen(struct_type);				\
@@ -382,6 +377,65 @@ static bool btf_type_is_datasec(const struct btf_type *t)
 	return BTF_INFO_KIND(t->info) == BTF_KIND_DATASEC;
 }
 
+s32 btf_find_by_name_kind(const struct btf *btf, const char *name, u8 kind)
+{
+	const struct btf_type *t;
+	const char *tname;
+	u32 i;
+
+	for (i = 1; i <= btf->nr_types; i++) {
+		t = btf->types[i];
+		if (BTF_INFO_KIND(t->info) != kind)
+			continue;
+
+		tname = btf_name_by_offset(btf, t->name_off);
+		if (!strcmp(tname, name))
+			return i;
+	}
+
+	return -ENOENT;
+}
+
+const struct btf_type *btf_type_skip_modifiers(const struct btf *btf,
+					       u32 id, u32 *res_id)
+{
+	const struct btf_type *t = btf_type_by_id(btf, id);
+
+	while (btf_type_is_modifier(t)) {
+		id = t->type;
+		t = btf_type_by_id(btf, t->type);
+	}
+
+	if (res_id)
+		*res_id = id;
+
+	return t;
+}
+
+const struct btf_type *btf_type_resolve_ptr(const struct btf *btf,
+					    u32 id, u32 *res_id)
+{
+	const struct btf_type *t;
+
+	t = btf_type_skip_modifiers(btf, id, NULL);
+	if (!btf_type_is_ptr(t))
+		return NULL;
+
+	return btf_type_skip_modifiers(btf, t->type, res_id);
+}
+
+const struct btf_type *btf_type_resolve_func_ptr(const struct btf *btf,
+						 u32 id, u32 *res_id)
+{
+	const struct btf_type *ptype;
+
+	ptype = btf_type_resolve_ptr(btf, id, res_id);
+	if (ptype && btf_type_is_func_proto(ptype))
+		return ptype;
+
+	return NULL;
+}
+
 /* Types that act only as a source, not sink or intermediate
  * type when resolving.
  */
@@ -446,30 +500,6 @@ static const char *btf_int_encoding_str(u8 encoding)
 		return "UNKN";
 }
 
-static u16 btf_type_vlen(const struct btf_type *t)
-{
-	return BTF_INFO_VLEN(t->info);
-}
-
-static bool btf_type_kflag(const struct btf_type *t)
-{
-	return BTF_INFO_KFLAG(t->info);
-}
-
-static u32 btf_member_bit_offset(const struct btf_type *struct_type,
-			     const struct btf_member *member)
-{
-	return btf_type_kflag(struct_type) ? BTF_MEMBER_BIT_OFFSET(member->offset)
-					   : member->offset;
-}
-
-static u32 btf_member_bitfield_size(const struct btf_type *struct_type,
-				    const struct btf_member *member)
-{
-	return btf_type_kflag(struct_type) ? BTF_MEMBER_BITFIELD_SIZE(member->offset)
-					   : 0;
-}
-
 static u32 btf_type_int(const struct btf_type *t)
 {
 	return *(u32 *)(t + 1);
@@ -480,11 +510,6 @@ static const struct btf_array *btf_type_array(const struct btf_type *t)
 	return (const struct btf_array *)(t + 1);
 }
 
-static const struct btf_member *btf_type_member(const struct btf_type *t)
-{
-	return (const struct btf_member *)(t + 1);
-}
-
 static const struct btf_enum *btf_type_enum(const struct btf_type *t)
 {
 	return (const struct btf_enum *)(t + 1);
@@ -1057,7 +1082,7 @@ static const struct resolve_vertex *env_stack_peak(struct btf_verifier_env *env)
  * *elem_type: same as return type ("struct X")
  * *total_nelems: 1
  */
-static const struct btf_type *
+const struct btf_type *
 btf_resolve_size(const struct btf *btf, const struct btf_type *type,
 		 u32 *type_size, const struct btf_type **elem_type,
 		 u32 *total_nelems)
@@ -1111,8 +1136,10 @@ resolved:
 		return ERR_PTR(-EINVAL);
 
 	*type_size = nelems * size;
-	*total_nelems = nelems;
-	*elem_type = type;
+	if (total_nelems)
+		*total_nelems = nelems;
+	if (elem_type)
+		*elem_type = type;
 
 	return array_type ? : type;
 }
@@ -1826,7 +1853,10 @@ static void btf_modifier_seq_show(const struct btf *btf,
 				  u32 type_id, void *data,
 				  u8 bits_offset, struct seq_file *m)
 {
-	t = btf_type_id_resolve(btf, &type_id);
+	if (btf->resolved_ids)
+		t = btf_type_id_resolve(btf, &type_id);
+	else
+		t = btf_type_skip_modifiers(btf, type_id, NULL);
 
 	btf_type_ops(t)->seq_show(btf, t, type_id, data, bits_offset, m);
 }
@@ -3605,6 +3635,8 @@ struct btf *btf_parse_vmlinux(void)
 		goto errout;
 	}
 
+	bpf_struct_ops_init(btf);
+
 	btf_verifier_env_free(env);
 	refcount_set(&btf->refcnt, 1);
 	return btf;
@@ -3677,7 +3709,7 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type,
 	/* skip modifiers */
 	while (btf_type_is_modifier(t))
 		t = btf_type_by_id(btf, t->type);
-	if (btf_type_is_int(t))
+	if (btf_type_is_int(t) || btf_type_is_enum(t))
 		/* accessing a scalar */
 		return true;
 	if (!btf_type_is_ptr(t)) {
@@ -3697,7 +3729,6 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type,
 
 	/* this is a pointer to another type */
 	info->reg_type = PTR_TO_BTF_ID;
-	info->btf_id = t->type;
 
 	if (tgt_prog) {
 		ret = btf_translate_to_vmlinux(log, btf, t, tgt_prog->type);
@@ -3708,10 +3739,14 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type,
 			return false;
 		}
 	}
+
+	info->btf_id = t->type;
 	t = btf_type_by_id(btf, t->type);
 	/* skip modifiers */
-	while (btf_type_is_modifier(t))
+	while (btf_type_is_modifier(t)) {
+		info->btf_id = t->type;
 		t = btf_type_by_id(btf, t->type);
+	}
 	if (!btf_type_is_struct(t)) {
 		bpf_log(log,
 			"func '%s' arg%d type %s is not a struct\n",
@@ -3737,23 +3772,57 @@ int btf_struct_access(struct bpf_verifier_log *log,
 again:
 	tname = __btf_name_by_offset(btf_vmlinux, t->name_off);
 	if (!btf_type_is_struct(t)) {
-		bpf_log(log, "Type '%s' is not a struct", tname);
+		bpf_log(log, "Type '%s' is not a struct\n", tname);
 		return -EINVAL;
 	}
 
-	for_each_member(i, t, member) {
-		if (btf_member_bitfield_size(t, member))
-			/* bitfields are not supported yet */
-			continue;
+	if (off + size > t->size) {
+		bpf_log(log, "access beyond struct %s at off %u size %u\n",
+			tname, off, size);
+		return -EACCES;
+	}
 
+	for_each_member(i, t, member) {
 		/* offset of the field in bytes */
 		moff = btf_member_bit_offset(t, member) / 8;
 		if (off + size <= moff)
 			/* won't find anything, field is already too far */
 			break;
+
+		if (btf_member_bitfield_size(t, member)) {
+			u32 end_bit = btf_member_bit_offset(t, member) +
+				btf_member_bitfield_size(t, member);
+
+			/* off <= moff instead of off == moff because clang
+			 * does not generate a BTF member for anonymous
+			 * bitfield like the ":16" here:
+			 * struct {
+			 *	int :16;
+			 *	int x:8;
+			 * };
+			 */
+			if (off <= moff &&
+			    BITS_ROUNDUP_BYTES(end_bit) <= off + size)
+				return SCALAR_VALUE;
+
+			/* off may be accessing a following member
+			 *
+			 * or
+			 *
+			 * Doing partial access at either end of this
+			 * bitfield.  Continue on this case also to
+			 * treat it as not accessing this bitfield
+			 * and eventually error out as field not
+			 * found to keep it simple.
+			 * It could be relaxed if there was a legit
+			 * partial access case later.
+			 */
+			continue;
+		}
+
 		/* In case of "off" is pointing to holes of a struct */
 		if (off < moff)
-			continue;
+			break;
 
 		/* type of the field */
 		mtype = btf_type_by_id(btf_vmlinux, member->type);
diff --git a/kernel/bpf/map_in_map.c b/kernel/bpf/map_in_map.c
index 5e9366b33f0f..b3c48d1533cb 100644
--- a/kernel/bpf/map_in_map.c
+++ b/kernel/bpf/map_in_map.c
@@ -22,7 +22,8 @@ struct bpf_map *bpf_map_meta_alloc(int inner_map_ufd)
 	 */
 	if (inner_map->map_type == BPF_MAP_TYPE_PROG_ARRAY ||
 	    inner_map->map_type == BPF_MAP_TYPE_CGROUP_STORAGE ||
-	    inner_map->map_type == BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE) {
+	    inner_map->map_type == BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE ||
+	    inner_map->map_type == BPF_MAP_TYPE_STRUCT_OPS) {
 		fdput(f);
 		return ERR_PTR(-ENOTSUPP);
 	}
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 81ee8595dfee..f9db72a96ec0 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -628,7 +628,7 @@ static int map_check_btf(struct bpf_map *map, const struct btf *btf,
 	return ret;
 }
 
-#define BPF_MAP_CREATE_LAST_FIELD btf_value_type_id
+#define BPF_MAP_CREATE_LAST_FIELD btf_vmlinux_value_type_id
 /* called via syscall */
 static int map_create(union bpf_attr *attr)
 {
@@ -642,6 +642,14 @@ static int map_create(union bpf_attr *attr)
 	if (err)
 		return -EINVAL;
 
+	if (attr->btf_vmlinux_value_type_id) {
+		if (attr->map_type != BPF_MAP_TYPE_STRUCT_OPS ||
+		    attr->btf_key_type_id || attr->btf_value_type_id)
+			return -EINVAL;
+	} else if (attr->btf_key_type_id && !attr->btf_value_type_id) {
+		return -EINVAL;
+	}
+
 	f_flags = bpf_get_file_flag(attr->map_flags);
 	if (f_flags < 0)
 		return f_flags;
@@ -664,32 +672,35 @@ static int map_create(union bpf_attr *attr)
 	atomic64_set(&map->usercnt, 1);
 	mutex_init(&map->freeze_mutex);
 
-	if (attr->btf_key_type_id || attr->btf_value_type_id) {
+	map->spin_lock_off = -EINVAL;
+	if (attr->btf_key_type_id || attr->btf_value_type_id ||
+	    /* Even the map's value is a kernel's struct,
+	     * the bpf_prog.o must have BTF to begin with
+	     * to figure out the corresponding kernel's
+	     * counter part.  Thus, attr->btf_fd has
+	     * to be valid also.
+	     */
+	    attr->btf_vmlinux_value_type_id) {
 		struct btf *btf;
 
-		if (!attr->btf_value_type_id) {
-			err = -EINVAL;
-			goto free_map;
-		}
-
 		btf = btf_get_by_fd(attr->btf_fd);
 		if (IS_ERR(btf)) {
 			err = PTR_ERR(btf);
 			goto free_map;
 		}
+		map->btf = btf;
 
-		err = map_check_btf(map, btf, attr->btf_key_type_id,
-				    attr->btf_value_type_id);
-		if (err) {
-			btf_put(btf);
-			goto free_map;
+		if (attr->btf_value_type_id) {
+			err = map_check_btf(map, btf, attr->btf_key_type_id,
+					    attr->btf_value_type_id);
+			if (err)
+				goto free_map;
 		}
 
-		map->btf = btf;
 		map->btf_key_type_id = attr->btf_key_type_id;
 		map->btf_value_type_id = attr->btf_value_type_id;
-	} else {
-		map->spin_lock_off = -EINVAL;
+		map->btf_vmlinux_value_type_id =
+			attr->btf_vmlinux_value_type_id;
 	}
 
 	err = security_bpf_map_alloc(map);
@@ -888,6 +899,9 @@ static int map_lookup_elem(union bpf_attr *attr)
 	} else if (map->map_type == BPF_MAP_TYPE_QUEUE ||
 		   map->map_type == BPF_MAP_TYPE_STACK) {
 		err = map->ops->map_peek_elem(map, value);
+	} else if (map->map_type == BPF_MAP_TYPE_STRUCT_OPS) {
+		/* struct_ops map requires directly updating "value" */
+		err = bpf_struct_ops_map_sys_lookup_elem(map, key, value);
 	} else {
 		rcu_read_lock();
 		if (map->ops->map_lookup_elem_sys_only)
@@ -1003,7 +1017,8 @@ static int map_update_elem(union bpf_attr *attr)
 		goto out;
 	} else if (map->map_type == BPF_MAP_TYPE_CPUMAP ||
 		   map->map_type == BPF_MAP_TYPE_SOCKHASH ||
-		   map->map_type == BPF_MAP_TYPE_SOCKMAP) {
+		   map->map_type == BPF_MAP_TYPE_SOCKMAP ||
+		   map->map_type == BPF_MAP_TYPE_STRUCT_OPS) {
 		err = map->ops->map_update_elem(map, key, value, attr->flags);
 		goto out;
 	} else if (IS_FD_PROG_ARRAY(map)) {
@@ -1092,7 +1107,9 @@ static int map_delete_elem(union bpf_attr *attr)
 	if (bpf_map_is_dev_bound(map)) {
 		err = bpf_map_offload_delete_elem(map, key);
 		goto out;
-	} else if (IS_FD_PROG_ARRAY(map)) {
+	} else if (IS_FD_PROG_ARRAY(map) ||
+		   map->map_type == BPF_MAP_TYPE_STRUCT_OPS) {
+		/* These maps require sleepable context */
 		err = map->ops->map_delete_elem(map, key);
 		goto out;
 	}
@@ -1672,17 +1689,22 @@ bpf_prog_load_check_attach(enum bpf_prog_type prog_type,
 			   enum bpf_attach_type expected_attach_type,
 			   u32 btf_id, u32 prog_fd)
 {
-	switch (prog_type) {
-	case BPF_PROG_TYPE_TRACING:
+	if (btf_id) {
 		if (btf_id > BTF_MAX_TYPE)
 			return -EINVAL;
-		break;
-	default:
-		if (btf_id || prog_fd)
+
+		switch (prog_type) {
+		case BPF_PROG_TYPE_TRACING:
+		case BPF_PROG_TYPE_STRUCT_OPS:
+			break;
+		default:
 			return -EINVAL;
-		break;
+		}
 	}
 
+	if (prog_fd && prog_type != BPF_PROG_TYPE_TRACING)
+		return -EINVAL;
+
 	switch (prog_type) {
 	case BPF_PROG_TYPE_CGROUP_SOCK:
 		switch (expected_attach_type) {
@@ -2817,6 +2839,7 @@ static int bpf_map_get_info_by_fd(struct bpf_map *map,
 		info.btf_key_type_id = map->btf_key_type_id;
 		info.btf_value_type_id = map->btf_value_type_id;
 	}
+	info.btf_vmlinux_value_type_id = map->btf_vmlinux_value_type_id;
 
 	if (bpf_map_is_dev_bound(map)) {
 		err = bpf_map_offload_info_fill(&info, map);
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index 505f4e4b31d2..79a04417050d 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -160,11 +160,12 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr)
 	if (fexit_cnt)
 		flags = BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_SKIP_FRAME;
 
-	err = arch_prepare_bpf_trampoline(new_image, &tr->func.model, flags,
+	err = arch_prepare_bpf_trampoline(new_image, new_image + PAGE_SIZE / 2,
+					  &tr->func.model, flags,
 					  fentry, fentry_cnt,
 					  fexit, fexit_cnt,
 					  tr->func.addr);
-	if (err)
+	if (err < 0)
 		goto out;
 
 	if (tr->selector)
@@ -296,7 +297,8 @@ void notrace __bpf_prog_exit(struct bpf_prog *prog, u64 start)
 }
 
 int __weak
-arch_prepare_bpf_trampoline(void *image, struct btf_func_model *m, u32 flags,
+arch_prepare_bpf_trampoline(void *image, void *image_end,
+			    const struct btf_func_model *m, u32 flags,
 			    struct bpf_prog **fentry_progs, int fentry_cnt,
 			    struct bpf_prog **fexit_progs, int fexit_cnt,
 			    void *orig_call)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index d433d70022fd..f5af759a8a5f 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2859,11 +2859,6 @@ static int check_ptr_to_btf_access(struct bpf_verifier_env *env,
 	u32 btf_id;
 	int ret;
 
-	if (atype != BPF_READ) {
-		verbose(env, "only read is supported\n");
-		return -EACCES;
-	}
-
 	if (off < 0) {
 		verbose(env,
 			"R%d is ptr_%s invalid negative access: off=%d\n",
@@ -2880,17 +2875,32 @@ static int check_ptr_to_btf_access(struct bpf_verifier_env *env,
 		return -EACCES;
 	}
 
-	ret = btf_struct_access(&env->log, t, off, size, atype, &btf_id);
+	if (env->ops->btf_struct_access) {
+		ret = env->ops->btf_struct_access(&env->log, t, off, size,
+						  atype, &btf_id);
+	} else {
+		if (atype != BPF_READ) {
+			verbose(env, "only read is supported\n");
+			return -EACCES;
+		}
+
+		ret = btf_struct_access(&env->log, t, off, size, atype,
+					&btf_id);
+	}
+
 	if (ret < 0)
 		return ret;
 
-	if (ret == SCALAR_VALUE) {
-		mark_reg_unknown(env, regs, value_regno);
-		return 0;
+	if (atype == BPF_READ) {
+		if (ret == SCALAR_VALUE) {
+			mark_reg_unknown(env, regs, value_regno);
+			return 0;
+		}
+		mark_reg_known_zero(env, regs, value_regno);
+		regs[value_regno].type = PTR_TO_BTF_ID;
+		regs[value_regno].btf_id = btf_id;
 	}
-	mark_reg_known_zero(env, regs, value_regno);
-	regs[value_regno].type = PTR_TO_BTF_ID;
-	regs[value_regno].btf_id = btf_id;
+
 	return 0;
 }
 
@@ -6349,8 +6359,30 @@ static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn)
 static int check_return_code(struct bpf_verifier_env *env)
 {
 	struct tnum enforce_attach_type_range = tnum_unknown;
+	const struct bpf_prog *prog = env->prog;
 	struct bpf_reg_state *reg;
 	struct tnum range = tnum_range(0, 1);
+	int err;
+
+	/* The struct_ops func-ptr's return type could be "void" */
+	if (env->prog->type == BPF_PROG_TYPE_STRUCT_OPS &&
+	    !prog->aux->attach_func_proto->type)
+		return 0;
+
+	/* eBPF calling convetion is such that R0 is used
+	 * to return the value from eBPF program.
+	 * Make sure that it's readable at this time
+	 * of bpf_exit, which means that program wrote
+	 * something into it earlier
+	 */
+	err = check_reg_arg(env, BPF_REG_0, SRC_OP);
+	if (err)
+		return err;
+
+	if (is_pointer_value(env, BPF_REG_0)) {
+		verbose(env, "R0 leaks addr as return value\n");
+		return -EACCES;
+	}
 
 	switch (env->prog->type) {
 	case BPF_PROG_TYPE_CGROUP_SOCK_ADDR:
@@ -8016,21 +8048,6 @@ static int do_check(struct bpf_verifier_env *env)
 				if (err)
 					return err;
 
-				/* eBPF calling convetion is such that R0 is used
-				 * to return the value from eBPF program.
-				 * Make sure that it's readable at this time
-				 * of bpf_exit, which means that program wrote
-				 * something into it earlier
-				 */
-				err = check_reg_arg(env, BPF_REG_0, SRC_OP);
-				if (err)
-					return err;
-
-				if (is_pointer_value(env, BPF_REG_0)) {
-					verbose(env, "R0 leaks addr as return value\n");
-					return -EACCES;
-				}
-
 				err = check_return_code(env);
 				if (err)
 					return err;
@@ -8138,6 +8155,11 @@ static int check_map_prog_compatibility(struct bpf_verifier_env *env,
 		return -EINVAL;
 	}
 
+	if (map->map_type == BPF_MAP_TYPE_STRUCT_OPS) {
+		verbose(env, "bpf_struct_ops map cannot be used in prog\n");
+		return -EINVAL;
+	}
+
 	return 0;
 }
 
@@ -8829,12 +8851,14 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
 			convert_ctx_access = bpf_xdp_sock_convert_ctx_access;
 			break;
 		case PTR_TO_BTF_ID:
-			if (type == BPF_WRITE) {
+			if (type == BPF_READ) {
+				insn->code = BPF_LDX | BPF_PROBE_MEM |
+					BPF_SIZE((insn)->code);
+				env->prog->aux->num_exentries++;
+			} else if (env->prog->type != BPF_PROG_TYPE_STRUCT_OPS) {
 				verbose(env, "Writes through BTF pointers are not allowed\n");
 				return -EINVAL;
 			}
-			insn->code = BPF_LDX | BPF_PROBE_MEM | BPF_SIZE((insn)->code);
-			env->prog->aux->num_exentries++;
 			continue;
 		default:
 			continue;
@@ -9502,6 +9526,58 @@ static void print_verification_stats(struct bpf_verifier_env *env)
 		env->peak_states, env->longest_mark_read_walk);
 }
 
+static int check_struct_ops_btf_id(struct bpf_verifier_env *env)
+{
+	const struct btf_type *t, *func_proto;
+	const struct bpf_struct_ops *st_ops;
+	const struct btf_member *member;
+	struct bpf_prog *prog = env->prog;
+	u32 btf_id, member_idx;
+	const char *mname;
+
+	btf_id = prog->aux->attach_btf_id;
+	st_ops = bpf_struct_ops_find(btf_id);
+	if (!st_ops) {
+		verbose(env, "attach_btf_id %u is not a supported struct\n",
+			btf_id);
+		return -ENOTSUPP;
+	}
+
+	t = st_ops->type;
+	member_idx = prog->expected_attach_type;
+	if (member_idx >= btf_type_vlen(t)) {
+		verbose(env, "attach to invalid member idx %u of struct %s\n",
+			member_idx, st_ops->name);
+		return -EINVAL;
+	}
+
+	member = &btf_type_member(t)[member_idx];
+	mname = btf_name_by_offset(btf_vmlinux, member->name_off);
+	func_proto = btf_type_resolve_func_ptr(btf_vmlinux, member->type,
+					       NULL);
+	if (!func_proto) {
+		verbose(env, "attach to invalid member %s(@idx %u) of struct %s\n",
+			mname, member_idx, st_ops->name);
+		return -EINVAL;
+	}
+
+	if (st_ops->check_member) {
+		int err = st_ops->check_member(t, member);
+
+		if (err) {
+			verbose(env, "attach to unsupported member %s of struct %s\n",
+				mname, st_ops->name);
+			return err;
+		}
+	}
+
+	prog->aux->attach_func_proto = func_proto;
+	prog->aux->attach_func_name = mname;
+	env->ops = st_ops->verifier_ops;
+
+	return 0;
+}
+
 static int check_attach_btf_id(struct bpf_verifier_env *env)
 {
 	struct bpf_prog *prog = env->prog;
@@ -9517,6 +9593,9 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
 	long addr;
 	u64 key;
 
+	if (prog->type == BPF_PROG_TYPE_STRUCT_OPS)
+		return check_struct_ops_btf_id(env);
+
 	if (prog->type != BPF_PROG_TYPE_TRACING)
 		return 0;
 
diff --git a/net/core/filter.c b/net/core/filter.c
index 42fd17c48c5f..a702761ef369 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5935,7 +5935,7 @@ bool bpf_helper_changes_pkt_data(void *func)
 	return false;
 }
 
-static const struct bpf_func_proto *
+const struct bpf_func_proto *
 bpf_base_func_proto(enum bpf_func_id func_id)
 {
 	switch (func_id) {
diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile
index d57ecfaf89d4..9d97bace13c8 100644
--- a/net/ipv4/Makefile
+++ b/net/ipv4/Makefile
@@ -65,3 +65,7 @@ obj-$(CONFIG_NETLABEL) += cipso_ipv4.o
 
 obj-$(CONFIG_XFRM) += xfrm4_policy.o xfrm4_state.o xfrm4_input.o \
 		      xfrm4_output.o xfrm4_protocol.o
+
+ifeq ($(CONFIG_BPF_JIT),y)
+obj-$(CONFIG_BPF_SYSCALL) += bpf_tcp_ca.o
+endif
diff --git a/net/ipv4/bpf_tcp_ca.c b/net/ipv4/bpf_tcp_ca.c
new file mode 100644
index 000000000000..574972bc7299
--- /dev/null
+++ b/net/ipv4/bpf_tcp_ca.c
@@ -0,0 +1,252 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2019 Facebook  */
+
+#include <linux/types.h>
+#include <linux/bpf_verifier.h>
+#include <linux/bpf.h>
+#include <linux/btf.h>
+#include <linux/filter.h>
+#include <net/tcp.h>
+
+static u32 optional_ops[] = {
+	offsetof(struct tcp_congestion_ops, init),
+	offsetof(struct tcp_congestion_ops, release),
+	offsetof(struct tcp_congestion_ops, set_state),
+	offsetof(struct tcp_congestion_ops, cwnd_event),
+	offsetof(struct tcp_congestion_ops, in_ack_event),
+	offsetof(struct tcp_congestion_ops, pkts_acked),
+	offsetof(struct tcp_congestion_ops, min_tso_segs),
+	offsetof(struct tcp_congestion_ops, sndbuf_expand),
+	offsetof(struct tcp_congestion_ops, cong_control),
+};
+
+static u32 unsupported_ops[] = {
+	offsetof(struct tcp_congestion_ops, get_info),
+};
+
+static const struct btf_type *tcp_sock_type;
+static u32 tcp_sock_id, sock_id;
+
+static int bpf_tcp_ca_init(struct btf *btf)
+{
+	s32 type_id;
+
+	type_id = btf_find_by_name_kind(btf, "sock", BTF_KIND_STRUCT);
+	if (type_id < 0)
+		return -EINVAL;
+	sock_id = type_id;
+
+	type_id = btf_find_by_name_kind(btf, "tcp_sock", BTF_KIND_STRUCT);
+	if (type_id < 0)
+		return -EINVAL;
+	tcp_sock_id = type_id;
+	tcp_sock_type = btf_type_by_id(btf, tcp_sock_id);
+
+	return 0;
+}
+
+static bool is_optional(u32 member_offset)
+{
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(optional_ops); i++) {
+		if (member_offset == optional_ops[i])
+			return true;
+	}
+
+	return false;
+}
+
+static bool is_unsupported(u32 member_offset)
+{
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(unsupported_ops); i++) {
+		if (member_offset == unsupported_ops[i])
+			return true;
+	}
+
+	return false;
+}
+
+extern struct btf *btf_vmlinux;
+
+static bool bpf_tcp_ca_is_valid_access(int off, int size,
+				       enum bpf_access_type type,
+				       const struct bpf_prog *prog,
+				       struct bpf_insn_access_aux *info)
+{
+	if (off < 0 || off >= sizeof(__u64) * MAX_BPF_FUNC_ARGS)
+		return false;
+	if (type != BPF_READ)
+		return false;
+	if (off % size != 0)
+		return false;
+
+	if (!btf_ctx_access(off, size, type, prog, info))
+		return false;
+
+	if (info->reg_type == PTR_TO_BTF_ID && info->btf_id == sock_id)
+		/* promote it to tcp_sock */
+		info->btf_id = tcp_sock_id;
+
+	return true;
+}
+
+static int bpf_tcp_ca_btf_struct_access(struct bpf_verifier_log *log,
+					const struct btf_type *t, int off,
+					int size, enum bpf_access_type atype,
+					u32 *next_btf_id)
+{
+	size_t end;
+
+	if (atype == BPF_READ)
+		return btf_struct_access(log, t, off, size, atype, next_btf_id);
+
+	if (t != tcp_sock_type) {
+		bpf_log(log, "only read is supported\n");
+		return -EACCES;
+	}
+
+	switch (off) {
+	case bpf_ctx_range(struct inet_connection_sock, icsk_ca_priv):
+		end = offsetofend(struct inet_connection_sock, icsk_ca_priv);
+		break;
+	case offsetof(struct inet_connection_sock, icsk_ack.pending):
+		end = offsetofend(struct inet_connection_sock,
+				  icsk_ack.pending);
+		break;
+	case offsetof(struct tcp_sock, snd_cwnd):
+		end = offsetofend(struct tcp_sock, snd_cwnd);
+		break;
+	case offsetof(struct tcp_sock, snd_cwnd_cnt):
+		end = offsetofend(struct tcp_sock, snd_cwnd_cnt);
+		break;
+	case offsetof(struct tcp_sock, snd_ssthresh):
+		end = offsetofend(struct tcp_sock, snd_ssthresh);
+		break;
+	case offsetof(struct tcp_sock, ecn_flags):
+		end = offsetofend(struct tcp_sock, ecn_flags);
+		break;
+	default:
+		bpf_log(log, "no write support to tcp_sock at off %d\n", off);
+		return -EACCES;
+	}
+
+	if (off + size > end) {
+		bpf_log(log,
+			"write access at off %d with size %d beyond the member of tcp_sock ended at %zu\n",
+			off, size, end);
+		return -EACCES;
+	}
+
+	return NOT_INIT;
+}
+
+BPF_CALL_2(bpf_tcp_send_ack, struct tcp_sock *, tp, u32, rcv_nxt)
+{
+	/* bpf_tcp_ca prog cannot have NULL tp */
+	__tcp_send_ack((struct sock *)tp, rcv_nxt);
+	return 0;
+}
+
+static const struct bpf_func_proto bpf_tcp_send_ack_proto = {
+	.func		= bpf_tcp_send_ack,
+	.gpl_only	= false,
+	/* In case we want to report error later */
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_BTF_ID,
+	.arg2_type	= ARG_ANYTHING,
+	.btf_id		= &tcp_sock_id,
+};
+
+static const struct bpf_func_proto *
+bpf_tcp_ca_get_func_proto(enum bpf_func_id func_id,
+			  const struct bpf_prog *prog)
+{
+	switch (func_id) {
+	case BPF_FUNC_tcp_send_ack:
+		return &bpf_tcp_send_ack_proto;
+	default:
+		return bpf_base_func_proto(func_id);
+	}
+}
+
+static const struct bpf_verifier_ops bpf_tcp_ca_verifier_ops = {
+	.get_func_proto		= bpf_tcp_ca_get_func_proto,
+	.is_valid_access	= bpf_tcp_ca_is_valid_access,
+	.btf_struct_access	= bpf_tcp_ca_btf_struct_access,
+};
+
+static int bpf_tcp_ca_init_member(const struct btf_type *t,
+				  const struct btf_member *member,
+				  void *kdata, const void *udata)
+{
+	const struct tcp_congestion_ops *utcp_ca;
+	struct tcp_congestion_ops *tcp_ca;
+	size_t tcp_ca_name_len;
+	int prog_fd;
+	u32 moff;
+
+	utcp_ca = (const struct tcp_congestion_ops *)udata;
+	tcp_ca = (struct tcp_congestion_ops *)kdata;
+
+	moff = btf_member_bit_offset(t, member) / 8;
+	switch (moff) {
+	case offsetof(struct tcp_congestion_ops, flags):
+		if (utcp_ca->flags & ~TCP_CONG_MASK)
+			return -EINVAL;
+		tcp_ca->flags = utcp_ca->flags;
+		return 1;
+	case offsetof(struct tcp_congestion_ops, name):
+		tcp_ca_name_len = strnlen(utcp_ca->name, sizeof(utcp_ca->name));
+		if (!tcp_ca_name_len ||
+		    tcp_ca_name_len == sizeof(utcp_ca->name))
+			return -EINVAL;
+		if (tcp_ca_find(utcp_ca->name))
+			return -EEXIST;
+		memcpy(tcp_ca->name, utcp_ca->name, sizeof(tcp_ca->name));
+		return 1;
+	}
+
+	if (!btf_type_resolve_func_ptr(btf_vmlinux, member->type, NULL))
+		return 0;
+
+	/* Ensure bpf_prog is provided for compulsory func ptr */
+	prog_fd = (int)(*(unsigned long *)(udata + moff));
+	if (!prog_fd && !is_optional(moff) && !is_unsupported(moff))
+		return -EINVAL;
+
+	return 0;
+}
+
+static int bpf_tcp_ca_check_member(const struct btf_type *t,
+				   const struct btf_member *member)
+{
+	if (is_unsupported(btf_member_bit_offset(t, member) / 8))
+		return -ENOTSUPP;
+	return 0;
+}
+
+static int bpf_tcp_ca_reg(void *kdata)
+{
+	return tcp_register_congestion_control(kdata);
+}
+
+static void bpf_tcp_ca_unreg(void *kdata)
+{
+	tcp_unregister_congestion_control(kdata);
+}
+
+/* Avoid sparse warning.  It is only used in bpf_struct_ops.c. */
+extern struct bpf_struct_ops bpf_tcp_congestion_ops;
+
+struct bpf_struct_ops bpf_tcp_congestion_ops = {
+	.verifier_ops = &bpf_tcp_ca_verifier_ops,
+	.reg = bpf_tcp_ca_reg,
+	.unreg = bpf_tcp_ca_unreg,
+	.check_member = bpf_tcp_ca_check_member,
+	.init_member = bpf_tcp_ca_init_member,
+	.init = bpf_tcp_ca_init,
+	.name = "tcp_congestion_ops",
+};
diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
index 3737ec096650..3172e31987be 100644
--- a/net/ipv4/tcp_cong.c
+++ b/net/ipv4/tcp_cong.c
@@ -21,7 +21,7 @@ static DEFINE_SPINLOCK(tcp_cong_list_lock);
 static LIST_HEAD(tcp_cong_list);
 
 /* Simple linear search, don't expect many entries! */
-static struct tcp_congestion_ops *tcp_ca_find(const char *name)
+struct tcp_congestion_ops *tcp_ca_find(const char *name)
 {
 	struct tcp_congestion_ops *e;
 
@@ -162,7 +162,7 @@ void tcp_assign_congestion_control(struct sock *sk)
 
 	rcu_read_lock();
 	ca = rcu_dereference(net->ipv4.tcp_congestion_control);
-	if (unlikely(!try_module_get(ca->owner)))
+	if (unlikely(!bpf_try_module_get(ca, ca->owner)))
 		ca = &tcp_reno;
 	icsk->icsk_ca_ops = ca;
 	rcu_read_unlock();
@@ -208,7 +208,7 @@ void tcp_cleanup_congestion_control(struct sock *sk)
 
 	if (icsk->icsk_ca_ops->release)
 		icsk->icsk_ca_ops->release(sk);
-	module_put(icsk->icsk_ca_ops->owner);
+	bpf_module_put(icsk->icsk_ca_ops, icsk->icsk_ca_ops->owner);
 }
 
 /* Used by sysctl to change default congestion control */
@@ -222,12 +222,12 @@ int tcp_set_default_congestion_control(struct net *net, const char *name)
 	ca = tcp_ca_find_autoload(net, name);
 	if (!ca) {
 		ret = -ENOENT;
-	} else if (!try_module_get(ca->owner)) {
+	} else if (!bpf_try_module_get(ca, ca->owner)) {
 		ret = -EBUSY;
 	} else {
 		prev = xchg(&net->ipv4.tcp_congestion_control, ca);
 		if (prev)
-			module_put(prev->owner);
+			bpf_module_put(prev, prev->owner);
 
 		ca->flags |= TCP_CONG_NON_RESTRICTED;
 		ret = 0;
@@ -366,19 +366,19 @@ int tcp_set_congestion_control(struct sock *sk, const char *name, bool load,
 	} else if (!load) {
 		const struct tcp_congestion_ops *old_ca = icsk->icsk_ca_ops;
 
-		if (try_module_get(ca->owner)) {
+		if (bpf_try_module_get(ca, ca->owner)) {
 			if (reinit) {
 				tcp_reinit_congestion_control(sk, ca);
 			} else {
 				icsk->icsk_ca_ops = ca;
-				module_put(old_ca->owner);
+				bpf_module_put(old_ca, old_ca->owner);
 			}
 		} else {
 			err = -EBUSY;
 		}
 	} else if (!((ca->flags & TCP_CONG_NON_RESTRICTED) || cap_net_admin)) {
 		err = -EPERM;
-	} else if (!try_module_get(ca->owner)) {
+	} else if (!bpf_try_module_get(ca, ca->owner)) {
 		err = -EBUSY;
 	} else {
 		tcp_reinit_congestion_control(sk, ca);
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 4adac9c75343..317ccca548a2 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2678,7 +2678,8 @@ static void __net_exit tcp_sk_exit(struct net *net)
 	int cpu;
 
 	if (net->ipv4.tcp_congestion_control)
-		module_put(net->ipv4.tcp_congestion_control->owner);
+		bpf_module_put(net->ipv4.tcp_congestion_control,
+			       net->ipv4.tcp_congestion_control->owner);
 
 	for_each_possible_cpu(cpu)
 		inet_ctl_sock_destroy(*per_cpu_ptr(net->ipv4.tcp_sk, cpu));
@@ -2785,7 +2786,8 @@ static int __net_init tcp_sk_init(struct net *net)
 
 	/* Reno is always built in */
 	if (!net_eq(net, &init_net) &&
-	    try_module_get(init_net.ipv4.tcp_congestion_control->owner))
+	    bpf_try_module_get(init_net.ipv4.tcp_congestion_control,
+			       init_net.ipv4.tcp_congestion_control->owner))
 		net->ipv4.tcp_congestion_control = init_net.ipv4.tcp_congestion_control;
 	else
 		net->ipv4.tcp_congestion_control = &tcp_reno;
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index c802bc80c400..ad3b56d9fa71 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -414,7 +414,7 @@ void tcp_ca_openreq_child(struct sock *sk, const struct dst_entry *dst)
 
 		rcu_read_lock();
 		ca = tcp_ca_find_key(ca_key);
-		if (likely(ca && try_module_get(ca->owner))) {
+		if (likely(ca && bpf_try_module_get(ca, ca->owner))) {
 			icsk->icsk_ca_dst_locked = tcp_ca_dst_locked(dst);
 			icsk->icsk_ca_ops = ca;
 			ca_got_dst = true;
@@ -425,7 +425,7 @@ void tcp_ca_openreq_child(struct sock *sk, const struct dst_entry *dst)
 	/* If no valid choice made yet, assign current system default ca. */
 	if (!ca_got_dst &&
 	    (!icsk->icsk_ca_setsockopt ||
-	     !try_module_get(icsk->icsk_ca_ops->owner)))
+	     !bpf_try_module_get(icsk->icsk_ca_ops, icsk->icsk_ca_ops->owner)))
 		tcp_assign_congestion_control(sk);
 
 	tcp_set_ca_state(sk, TCP_CA_Open);
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 58c92a7d671c..377cfab422df 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3368,8 +3368,8 @@ static void tcp_ca_dst_init(struct sock *sk, const struct dst_entry *dst)
 
 	rcu_read_lock();
 	ca = tcp_ca_find_key(ca_key);
-	if (likely(ca && try_module_get(ca->owner))) {
-		module_put(icsk->icsk_ca_ops->owner);
+	if (likely(ca && bpf_try_module_get(ca, ca->owner))) {
+		bpf_module_put(icsk->icsk_ca_ops, icsk->icsk_ca_ops->owner);
 		icsk->icsk_ca_dst_locked = tcp_ca_dst_locked(dst);
 		icsk->icsk_ca_ops = ca;
 	}
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 7df436da542d..2d6a2e572f56 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -136,6 +136,7 @@ enum bpf_map_type {
 	BPF_MAP_TYPE_STACK,
 	BPF_MAP_TYPE_SK_STORAGE,
 	BPF_MAP_TYPE_DEVMAP_HASH,
+	BPF_MAP_TYPE_STRUCT_OPS,
 };
 
 /* Note that tracing related programs such as
@@ -174,6 +175,7 @@ enum bpf_prog_type {
 	BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE,
 	BPF_PROG_TYPE_CGROUP_SOCKOPT,
 	BPF_PROG_TYPE_TRACING,
+	BPF_PROG_TYPE_STRUCT_OPS,
 };
 
 enum bpf_attach_type {
@@ -397,6 +399,10 @@ union bpf_attr {
 		__u32	btf_fd;		/* fd pointing to a BTF type data */
 		__u32	btf_key_type_id;	/* BTF type_id of the key */
 		__u32	btf_value_type_id;	/* BTF type_id of the value */
+		__u32	btf_vmlinux_value_type_id;/* BTF type_id of a kernel-
+						   * struct stored as the
+						   * map value
+						   */
 	};
 
 	struct { /* anonymous struct used by BPF_MAP_*_ELEM commands */
@@ -2831,6 +2837,14 @@ union bpf_attr {
  * 	Return
  * 		On success, the strictly positive length of the string,	including
  * 		the trailing NUL character. On error, a negative value.
+ *
+ * int bpf_tcp_send_ack(void *tp, u32 rcv_nxt)
+ *	Description
+ *		Send out a tcp-ack. *tp* is the in-kernel struct tcp_sock.
+ *		*rcv_nxt* is the ack_seq to be sent out.
+ *	Return
+ *		0 on success, or a negative error in case of failure.
+ *
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -2948,7 +2962,8 @@ union bpf_attr {
 	FN(probe_read_user),		\
 	FN(probe_read_kernel),		\
 	FN(probe_read_user_str),	\
-	FN(probe_read_kernel_str),
+	FN(probe_read_kernel_str),	\
+	FN(tcp_send_ack),
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
  * function eBPF program intends to call
@@ -3349,7 +3364,7 @@ struct bpf_map_info {
 	__u32 map_flags;
 	char  name[BPF_OBJ_NAME_LEN];
 	__u32 ifindex;
-	__u32 :32;
+	__u32 btf_vmlinux_value_type_id;
 	__u64 netns_dev;
 	__u64 netns_ino;
 	__u32 btf_id;
diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index a787d53699c8..b0ecbe9ef2d4 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -95,7 +95,11 @@ int bpf_create_map_xattr(const struct bpf_create_map_attr *create_attr)
 	attr.btf_key_type_id = create_attr->btf_key_type_id;
 	attr.btf_value_type_id = create_attr->btf_value_type_id;
 	attr.map_ifindex = create_attr->map_ifindex;
-	attr.inner_map_fd = create_attr->inner_map_fd;
+	if (attr.map_type == BPF_MAP_TYPE_STRUCT_OPS)
+		attr.btf_vmlinux_value_type_id =
+			create_attr->btf_vmlinux_value_type_id;
+	else
+		attr.inner_map_fd = create_attr->inner_map_fd;
 
 	return sys_bpf(BPF_MAP_CREATE, &attr, sizeof(attr));
 }
@@ -228,7 +232,9 @@ int bpf_load_program_xattr(const struct bpf_load_program_attr *load_attr,
 	memset(&attr, 0, sizeof(attr));
 	attr.prog_type = load_attr->prog_type;
 	attr.expected_attach_type = load_attr->expected_attach_type;
-	if (attr.prog_type == BPF_PROG_TYPE_TRACING) {
+	if (attr.prog_type == BPF_PROG_TYPE_STRUCT_OPS) {
+		attr.attach_btf_id = load_attr->attach_btf_id;
+	} else if (attr.prog_type == BPF_PROG_TYPE_TRACING) {
 		attr.attach_btf_id = load_attr->attach_btf_id;
 		attr.attach_prog_fd = load_attr->attach_prog_fd;
 	} else {
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index f0ab8519986e..56341d117e5b 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -46,7 +46,10 @@ struct bpf_create_map_attr {
 	__u32 btf_key_type_id;
 	__u32 btf_value_type_id;
 	__u32 map_ifindex;
-	__u32 inner_map_fd;
+	union {
+		__u32 inner_map_fd;
+		__u32 btf_vmlinux_value_type_id;
+	};
 };
 
 LIBBPF_API int
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 7513165b104f..35a4422ef655 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -70,6 +70,13 @@
 
 #define __printf(a, b)	__attribute__((format(printf, a, b)))
 
+static struct btf *bpf_find_kernel_btf(void);
+static struct bpf_map *bpf_object__add_map(struct bpf_object *obj);
+static struct bpf_program *bpf_object__find_prog_by_idx(struct bpf_object *obj,
+							int idx);
+static const struct btf_type *
+skip_mods_and_typedefs(const struct btf *btf, __u32 id, __u32 *res_id);
+
 static int __base_pr(enum libbpf_print_level level, const char *format,
 		     va_list args)
 {
@@ -229,10 +236,32 @@ struct bpf_program {
 	__u32 prog_flags;
 };
 
+struct bpf_struct_ops {
+	const char *tname;
+	const struct btf_type *type;
+	struct bpf_program **progs;
+	__u32 *kern_func_off;
+	/* e.g. struct tcp_congestion_ops in bpf_prog's btf format */
+	void *data;
+	/* e.g. struct bpf_struct_ops_tcp_congestion_ops in
+	 *      btf_vmlinux's format.
+	 * struct bpf_struct_ops_tcp_congestion_ops {
+	 *	[... some other kernel fields ...]
+	 *	struct tcp_congestion_ops data;
+	 * }
+	 * kern_vdata-size == sizeof(struct bpf_struct_ops_tcp_congestion_ops)
+	 * bpf_map__init_kern_struct_ops() will populate the "kern_vdata"
+	 * from "data".
+	 */
+	void *kern_vdata;
+	__u32 type_id;
+};
+
 #define DATA_SEC ".data"
 #define BSS_SEC ".bss"
 #define RODATA_SEC ".rodata"
 #define KCONFIG_SEC ".kconfig"
+#define STRUCT_OPS_SEC ".struct_ops"
 
 enum libbpf_map_type {
 	LIBBPF_MAP_UNSPEC,
@@ -259,10 +288,12 @@ struct bpf_map {
 	struct bpf_map_def def;
 	__u32 btf_key_type_id;
 	__u32 btf_value_type_id;
+	__u32 btf_vmlinux_value_type_id;
 	void *priv;
 	bpf_map_clear_priv_t clear_priv;
 	enum libbpf_map_type libbpf_type;
 	void *mmaped;
+	struct bpf_struct_ops *st_ops;
 	char *pin_path;
 	bool pinned;
 	bool reused;
@@ -326,6 +357,7 @@ struct bpf_object {
 		Elf_Data *data;
 		Elf_Data *rodata;
 		Elf_Data *bss;
+		Elf_Data *st_ops_data;
 		size_t strtabidx;
 		struct {
 			GElf_Shdr shdr;
@@ -339,6 +371,7 @@ struct bpf_object {
 		int data_shndx;
 		int rodata_shndx;
 		int bss_shndx;
+		int st_ops_shndx;
 	} efile;
 	/*
 	 * All loaded bpf_object is linked in a list, which is
@@ -566,6 +599,359 @@ static __u32 get_kernel_version(void)
 	return KERNEL_VERSION(major, minor, patch);
 }
 
+static const struct btf_member *
+find_member_by_offset(const struct btf_type *t, __u32 bit_offset)
+{
+	struct btf_member *m;
+	int i;
+
+	for (i = 0, m = btf_members(t); i < btf_vlen(t); i++, m++) {
+		if (btf_member_bit_offset(t, i) == bit_offset)
+			return m;
+	}
+
+	return NULL;
+}
+
+static const struct btf_member *
+find_member_by_name(const struct btf *btf, const struct btf_type *t,
+		    const char *name)
+{
+	struct btf_member *m;
+	int i;
+
+	for (i = 0, m = btf_members(t); i < btf_vlen(t); i++, m++) {
+		if (!strcmp(btf__name_by_offset(btf, m->name_off), name))
+			return m;
+	}
+
+	return NULL;
+}
+
+#define STRUCT_OPS_VALUE_PREFIX "bpf_struct_ops_"
+#define STRUCT_OPS_VALUE_PREFIX_LEN (sizeof(STRUCT_OPS_VALUE_PREFIX) - 1)
+
+static int
+find_struct_ops_kern_types(const struct btf *btf, const char *tname,
+			   const struct btf_type **type, __u32 *type_id,
+			   const struct btf_type **vtype, __u32 *vtype_id,
+			   const struct btf_member **data_member)
+{
+	const struct btf_type *kern_type, *kern_vtype;
+	const struct btf_member *kern_data_member;
+	__s32 kern_vtype_id, kern_type_id;
+	char vtname[128] = STRUCT_OPS_VALUE_PREFIX;
+	__u32 i;
+
+	kern_type_id = btf__find_by_name_kind(btf, tname, BTF_KIND_STRUCT);
+	if (kern_type_id < 0) {
+		pr_warn("struct_ops init_kern: struct %s is not found in kernel BTF\n",
+			tname);
+		return kern_type_id;
+	}
+	kern_type = btf__type_by_id(btf, kern_type_id);
+
+	/* Find the corresponding "map_value" type that will be used
+	 * in map_update(BPF_MAP_TYPE_STRUCT_OPS).  For example,
+	 * find "struct bpf_struct_ops_tcp_congestion_ops" from the
+	 * btf_vmlinux.
+	 */
+	strncat(vtname + STRUCT_OPS_VALUE_PREFIX_LEN, tname,
+		sizeof(vtname) - STRUCT_OPS_VALUE_PREFIX_LEN - 1);
+	kern_vtype_id = btf__find_by_name_kind(btf, vtname,
+					       BTF_KIND_STRUCT);
+	if (kern_vtype_id < 0) {
+		pr_warn("struct_ops init_kern: struct %s is not found in kernel BTF\n",
+			vtname);
+		return kern_vtype_id;
+	}
+	kern_vtype = btf__type_by_id(btf, kern_vtype_id);
+
+	/* Find "struct tcp_congestion_ops" from
+	 * struct bpf_struct_ops_tcp_congestion_ops {
+	 *	[ ... ]
+	 *	struct tcp_congestion_ops data;
+	 * }
+	 */
+	kern_data_member = btf_members(kern_vtype);
+	for (i = 0; i < btf_vlen(kern_vtype); i++, kern_data_member++) {
+		if (kern_data_member->type == kern_type_id)
+			break;
+	}
+	if (i == btf_vlen(kern_vtype)) {
+		pr_warn("struct_ops init_kern: struct %s data is not found in struct %s\n",
+			tname, vtname);
+		return -EINVAL;
+	}
+
+	*type = kern_type;
+	*type_id = kern_type_id;
+	*vtype = kern_vtype;
+	*vtype_id = kern_vtype_id;
+	*data_member = kern_data_member;
+
+	return 0;
+}
+
+static bool bpf_map__is_struct_ops(const struct bpf_map *map)
+{
+	return map->def.type == BPF_MAP_TYPE_STRUCT_OPS;
+}
+
+/* Init the map's fields that depend on kern_btf */
+static int bpf_map__init_kern_struct_ops(struct bpf_map *map,
+					 const struct btf *btf,
+					 const struct btf *kern_btf)
+{
+	const struct btf_member *member, *kern_member, *kern_data_member;
+	const struct btf_type *type, *kern_type, *kern_vtype;
+	__u32 i, kern_type_id, kern_vtype_id, kern_data_off;
+	struct bpf_struct_ops *st_ops;
+	void *data, *kern_data;
+	const char *tname;
+	int err;
+
+	st_ops = map->st_ops;
+	type = st_ops->type;
+	tname = st_ops->tname;
+	err = find_struct_ops_kern_types(kern_btf, tname,
+					 &kern_type, &kern_type_id,
+					 &kern_vtype, &kern_vtype_id,
+					 &kern_data_member);
+	if (err)
+		return err;
+
+	pr_debug("struct_ops init_kern %s: type_id:%u kern_type_id:%u kern_vtype_id:%u\n",
+		 map->name, st_ops->type_id, kern_type_id, kern_vtype_id);
+
+	map->def.value_size = kern_vtype->size;
+	map->btf_vmlinux_value_type_id = kern_vtype_id;
+
+	st_ops->kern_vdata = calloc(1, kern_vtype->size);
+	if (!st_ops->kern_vdata)
+		return -ENOMEM;
+
+	data = st_ops->data;
+	kern_data_off = kern_data_member->offset / 8;
+	kern_data = st_ops->kern_vdata + kern_data_off;
+
+	member = btf_members(type);
+	for (i = 0; i < btf_vlen(type); i++, member++) {
+		const struct btf_type *mtype, *kern_mtype;
+		__u32 mtype_id, kern_mtype_id;
+		void *mdata, *kern_mdata;
+		__s64 msize, kern_msize;
+		__u32 moff, kern_moff;
+		__u32 kern_member_idx;
+		const char *mname;
+
+		mname = btf__name_by_offset(btf, member->name_off);
+		kern_member = find_member_by_name(kern_btf, kern_type, mname);
+		if (!kern_member) {
+			pr_warn("struct_ops init_kern %s: Cannot find member %s in kernel BTF\n",
+				map->name, mname);
+			return -ENOTSUP;
+		}
+
+		kern_member_idx = kern_member - btf_members(kern_type);
+		if (btf_member_bitfield_size(type, i) ||
+		    btf_member_bitfield_size(kern_type, kern_member_idx)) {
+			pr_warn("struct_ops init_kern %s: bitfield %s is not supported\n",
+				map->name, mname);
+			return -ENOTSUP;
+		}
+
+		moff = member->offset / 8;
+		kern_moff = kern_member->offset / 8;
+
+		mdata = data + moff;
+		kern_mdata = kern_data + kern_moff;
+
+		mtype = skip_mods_and_typedefs(btf, member->type, &mtype_id);
+		kern_mtype = skip_mods_and_typedefs(kern_btf, kern_member->type,
+						    &kern_mtype_id);
+		if (BTF_INFO_KIND(mtype->info) !=
+		    BTF_INFO_KIND(kern_mtype->info)) {
+			pr_warn("struct_ops init_kern %s: Unmatched member type %s %u != %u(kernel)\n",
+				map->name, mname, BTF_INFO_KIND(mtype->info),
+				BTF_INFO_KIND(kern_mtype->info));
+			return -ENOTSUP;
+		}
+
+		if (btf_is_ptr(mtype)) {
+			struct bpf_program *prog;
+
+			mtype = skip_mods_and_typedefs(btf, mtype->type, &mtype_id);
+			kern_mtype = skip_mods_and_typedefs(kern_btf,
+							    kern_mtype->type,
+							    &kern_mtype_id);
+			if (!btf_is_func_proto(mtype) ||
+			    !btf_is_func_proto(kern_mtype)) {
+				pr_warn("struct_ops init_kern %s: non func ptr %s is not supported\n",
+					map->name, mname);
+				return -ENOTSUP;
+			}
+
+			prog = st_ops->progs[i];
+			if (!prog) {
+				pr_debug("struct_ops init_kern %s: func ptr %s is not set\n",
+					 map->name, mname);
+				continue;
+			}
+
+			prog->attach_btf_id = kern_type_id;
+			prog->expected_attach_type = kern_member_idx;
+
+			st_ops->kern_func_off[i] = kern_data_off + kern_moff;
+
+			pr_debug("struct_ops init_kern %s: func ptr %s is set to prog %s from data(+%u) to kern_data(+%u)\n",
+				 map->name, mname, prog->name, moff,
+				 kern_moff);
+
+			continue;
+		}
+
+		msize = btf__resolve_size(btf, mtype_id);
+		kern_msize = btf__resolve_size(kern_btf, kern_mtype_id);
+		if (msize < 0 || kern_msize < 0 || msize != kern_msize) {
+			pr_warn("struct_ops init_kern %s: Error in size of member %s: %zd != %zd(kernel)\n",
+				map->name, mname, (ssize_t)msize,
+				(ssize_t)kern_msize);
+			return -ENOTSUP;
+		}
+
+		pr_debug("struct_ops init_kern %s: copy %s %u bytes from data(+%u) to kern_data(+%u)\n",
+			 map->name, mname, (unsigned int)msize,
+			 moff, kern_moff);
+		memcpy(kern_mdata, mdata, msize);
+	}
+
+	return 0;
+}
+
+static int bpf_object__init_kern_struct_ops_maps(struct bpf_object *obj)
+{
+	struct btf *kern_btf = NULL;
+	struct bpf_map *map;
+	size_t i;
+	int err;
+
+	for (i = 0; i < obj->nr_maps; i++) {
+		map = &obj->maps[i];
+
+		if (!bpf_map__is_struct_ops(map))
+			continue;
+
+		if (!kern_btf) {
+			kern_btf = bpf_find_kernel_btf();
+			if (IS_ERR(kern_btf))
+				return PTR_ERR(kern_btf);
+		}
+
+		err = bpf_map__init_kern_struct_ops(map, obj->btf, kern_btf);
+		if (err) {
+			btf__free(kern_btf);
+			return err;
+		}
+	}
+
+	btf__free(kern_btf);
+	return 0;
+}
+
+static int bpf_object__init_struct_ops_maps(struct bpf_object *obj)
+{
+	const struct btf_type *type, *datasec;
+	const struct btf_var_secinfo *vsi;
+	struct bpf_struct_ops *st_ops;
+	const char *tname, *var_name;
+	__s32 type_id, datasec_id;
+	const struct btf *btf;
+	struct bpf_map *map;
+	__u32 i;
+
+	if (obj->efile.st_ops_shndx == -1)
+		return 0;
+
+	btf = obj->btf;
+	datasec_id = btf__find_by_name_kind(btf, STRUCT_OPS_SEC,
+					    BTF_KIND_DATASEC);
+	if (datasec_id < 0) {
+		pr_warn("struct_ops init: DATASEC %s not found\n",
+			STRUCT_OPS_SEC);
+		return -EINVAL;
+	}
+
+	datasec = btf__type_by_id(btf, datasec_id);
+	vsi = btf_var_secinfos(datasec);
+	for (i = 0; i < btf_vlen(datasec); i++, vsi++) {
+		type = btf__type_by_id(obj->btf, vsi->type);
+		var_name = btf__name_by_offset(obj->btf, type->name_off);
+
+		type_id = btf__resolve_type(obj->btf, vsi->type);
+		if (type_id < 0) {
+			pr_warn("struct_ops init: Cannot resolve var type_id %u in DATASEC %s\n",
+				vsi->type, STRUCT_OPS_SEC);
+			return -EINVAL;
+		}
+
+		type = btf__type_by_id(obj->btf, type_id);
+		tname = btf__name_by_offset(obj->btf, type->name_off);
+		if (!tname[0]) {
+			pr_warn("struct_ops init: anonymous type is not supported\n");
+			return -ENOTSUP;
+		}
+		if (!btf_is_struct(type)) {
+			pr_warn("struct_ops init: %s is not a struct\n", tname);
+			return -EINVAL;
+		}
+
+		map = bpf_object__add_map(obj);
+		if (IS_ERR(map))
+			return PTR_ERR(map);
+
+		map->sec_idx = obj->efile.st_ops_shndx;
+		map->sec_offset = vsi->offset;
+		map->name = strdup(var_name);
+		if (!map->name)
+			return -ENOMEM;
+
+		map->def.type = BPF_MAP_TYPE_STRUCT_OPS;
+		map->def.key_size = sizeof(int);
+		map->def.value_size = type->size;
+		map->def.max_entries = 1;
+
+		map->st_ops = calloc(1, sizeof(*map->st_ops));
+		if (!map->st_ops)
+			return -ENOMEM;
+		st_ops = map->st_ops;
+		st_ops->data = malloc(type->size);
+		st_ops->progs = calloc(btf_vlen(type), sizeof(*st_ops->progs));
+		st_ops->kern_func_off = malloc(btf_vlen(type) *
+					       sizeof(*st_ops->kern_func_off));
+		if (!st_ops->data || !st_ops->progs || !st_ops->kern_func_off)
+			return -ENOMEM;
+
+		if (vsi->offset + type->size > obj->efile.st_ops_data->d_size) {
+			pr_warn("struct_ops init: var %s is beyond the end of DATASEC %s\n",
+				var_name, STRUCT_OPS_SEC);
+			return -EINVAL;
+		}
+
+		memcpy(st_ops->data,
+		       obj->efile.st_ops_data->d_buf + vsi->offset,
+		       type->size);
+		st_ops->tname = tname;
+		st_ops->type = type;
+		st_ops->type_id = type_id;
+
+		pr_debug("struct_ops init: struct %s(type_id=%u) %s found at offset %u\n",
+			 tname, type_id, var_name, vsi->offset);
+	}
+
+	return 0;
+}
+
 static struct bpf_object *bpf_object__new(const char *path,
 					  const void *obj_buf,
 					  size_t obj_buf_sz,
@@ -607,6 +993,7 @@ static struct bpf_object *bpf_object__new(const char *path,
 	obj->efile.data_shndx = -1;
 	obj->efile.rodata_shndx = -1;
 	obj->efile.bss_shndx = -1;
+	obj->efile.st_ops_shndx = -1;
 	obj->kconfig_map_idx = -1;
 
 	obj->kern_version = get_kernel_version();
@@ -630,6 +1017,7 @@ static void bpf_object__elf_finish(struct bpf_object *obj)
 	obj->efile.data = NULL;
 	obj->efile.rodata = NULL;
 	obj->efile.bss = NULL;
+	obj->efile.st_ops_data = NULL;
 
 	zfree(&obj->efile.reloc_sects);
 	obj->efile.nr_reloc_sects = 0;
@@ -815,6 +1203,9 @@ int bpf_object__section_size(const struct bpf_object *obj, const char *name,
 	} else if (!strcmp(name, RODATA_SEC)) {
 		if (obj->efile.rodata)
 			*size = obj->efile.rodata->d_size;
+	} else if (!strcmp(name, STRUCT_OPS_SEC)) {
+		if (obj->efile.st_ops_data)
+			*size = obj->efile.st_ops_data->d_size;
 	} else {
 		ret = bpf_object_search_section_size(obj, name, &d_size);
 		if (!ret)
@@ -1440,6 +1831,20 @@ skip_mods_and_typedefs(const struct btf *btf, __u32 id, __u32 *res_id)
 	return t;
 }
 
+static const struct btf_type *
+resolve_func_ptr(const struct btf *btf, __u32 id, __u32 *res_id)
+{
+	const struct btf_type *t;
+
+	t = skip_mods_and_typedefs(btf, id, NULL);
+	if (!btf_is_ptr(t))
+		return NULL;
+
+	t = skip_mods_and_typedefs(btf, t->type, res_id);
+
+	return btf_is_func_proto(t) ? t : NULL;
+}
+
 /*
  * Fetch integer attribute of BTF map definition. Such attributes are
  * represented using a pointer to an array, in which dimensionality of array
@@ -1787,6 +2192,7 @@ static int bpf_object__init_maps(struct bpf_object *obj,
 	err = err ?: bpf_object__init_user_btf_maps(obj, strict, pin_root_path);
 	err = err ?: bpf_object__init_global_data_maps(obj);
 	err = err ?: bpf_object__init_kconfig_map(obj);
+	err = err ?: bpf_object__init_struct_ops_maps(obj);
 	if (err)
 		return err;
 
@@ -1889,7 +2295,8 @@ static void bpf_object__sanitize_btf_ext(struct bpf_object *obj)
 static bool bpf_object__is_btf_mandatory(const struct bpf_object *obj)
 {
 	return obj->efile.btf_maps_shndx >= 0 ||
-	       obj->nr_extern > 0;
+		obj->efile.st_ops_shndx >= 0 ||
+		obj->nr_extern > 0;
 }
 
 static int bpf_object__init_btf(struct bpf_object *obj,
@@ -2088,6 +2495,9 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
 			} else if (strcmp(name, RODATA_SEC) == 0) {
 				obj->efile.rodata = data;
 				obj->efile.rodata_shndx = idx;
+			} else if (strcmp(name, STRUCT_OPS_SEC) == 0) {
+				obj->efile.st_ops_data = data;
+				obj->efile.st_ops_shndx = idx;
 			} else {
 				pr_debug("skip section(%d) %s\n", idx, name);
 			}
@@ -2097,7 +2507,8 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
 			int sec = sh.sh_info; /* points to other section */
 
 			/* Only do relo for section with exec instructions */
-			if (!section_have_execinstr(obj, sec)) {
+			if (!section_have_execinstr(obj, sec) &&
+			    strcmp(name, ".rel" STRUCT_OPS_SEC)) {
 				pr_debug("skip relo %s(%d) for section(%d)\n",
 					 name, idx, sec);
 				continue;
@@ -2599,8 +3010,12 @@ static int bpf_map_find_btf_info(struct bpf_object *obj, struct bpf_map *map)
 	__u32 key_type_id = 0, value_type_id = 0;
 	int ret;
 
-	/* if it's BTF-defined map, we don't need to search for type IDs */
-	if (map->sec_idx == obj->efile.btf_maps_shndx)
+	/* if it's BTF-defined map, we don't need to search for type IDs.
+	 * For struct_ops map, it does not need btf_key_type_id and
+	 * btf_value_type_id.
+	 */
+	if (map->sec_idx == obj->efile.btf_maps_shndx ||
+	    bpf_map__is_struct_ops(map))
 		return 0;
 
 	if (!bpf_map__is_internal(map)) {
@@ -3025,6 +3440,9 @@ bpf_object__create_maps(struct bpf_object *obj)
 		if (bpf_map_type__is_map_in_map(def->type) &&
 		    map->inner_map_fd >= 0)
 			create_attr.inner_map_fd = map->inner_map_fd;
+		if (bpf_map__is_struct_ops(map))
+			create_attr.btf_vmlinux_value_type_id =
+				map->btf_vmlinux_value_type_id;
 
 		if (obj->btf && !bpf_map_find_btf_info(obj, map)) {
 			create_attr.btf_fd = btf__fd(obj->btf);
@@ -3899,7 +4317,7 @@ cleanup:
  * Probe few well-known locations for vmlinux kernel image and try to load BTF
  * data out of it to use for target BTF.
  */
-static struct btf *bpf_core_find_kernel_btf(void)
+static struct btf *bpf_find_kernel_btf(void)
 {
 	struct {
 		const char *path_fmt;
@@ -4180,7 +4598,7 @@ bpf_core_reloc_fields(struct bpf_object *obj, const char *targ_btf_path)
 	if (targ_btf_path)
 		targ_btf = btf__parse_elf(targ_btf_path, NULL);
 	else
-		targ_btf = bpf_core_find_kernel_btf();
+		targ_btf = bpf_find_kernel_btf();
 	if (IS_ERR(targ_btf)) {
 		pr_warn("failed to get target BTF: %ld\n", PTR_ERR(targ_btf));
 		return PTR_ERR(targ_btf);
@@ -4379,6 +4797,10 @@ bpf_object__relocate(struct bpf_object *obj, const char *targ_btf_path)
 	return 0;
 }
 
+static int bpf_object__collect_struct_ops_map_reloc(struct bpf_object *obj,
+						    GElf_Shdr *shdr,
+						    Elf_Data *data);
+
 static int bpf_object__collect_reloc(struct bpf_object *obj)
 {
 	int i, err;
@@ -4399,6 +4821,15 @@ static int bpf_object__collect_reloc(struct bpf_object *obj)
 			return -LIBBPF_ERRNO__INTERNAL;
 		}
 
+		if (idx == obj->efile.st_ops_shndx) {
+			err = bpf_object__collect_struct_ops_map_reloc(obj,
+								       shdr,
+								       data);
+			if (err)
+				return err;
+			continue;
+		}
+
 		prog = bpf_object__find_prog_by_idx(obj, idx);
 		if (!prog) {
 			pr_warn("relocation failed: no section(%d)\n", idx);
@@ -4433,7 +4864,9 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt,
 	load_attr.insns = insns;
 	load_attr.insns_cnt = insns_cnt;
 	load_attr.license = license;
-	if (prog->type == BPF_PROG_TYPE_TRACING) {
+	if (prog->type == BPF_PROG_TYPE_STRUCT_OPS) {
+		load_attr.attach_btf_id = prog->attach_btf_id;
+	} else if (prog->type == BPF_PROG_TYPE_TRACING) {
 		load_attr.attach_prog_fd = prog->attach_prog_fd;
 		load_attr.attach_btf_id = prog->attach_btf_id;
 	} else {
@@ -4679,6 +5112,9 @@ __bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz,
 		enum bpf_prog_type prog_type;
 		enum bpf_attach_type attach_type;
 
+		if (prog->type != BPF_PROG_TYPE_UNSPEC)
+			continue;
+
 		err = libbpf_prog_type_by_name(prog->section_name, &prog_type,
 					       &attach_type);
 		if (err == -ESRCH)
@@ -4774,8 +5210,11 @@ int bpf_object__unload(struct bpf_object *obj)
 	if (!obj)
 		return -EINVAL;
 
-	for (i = 0; i < obj->nr_maps; i++)
+	for (i = 0; i < obj->nr_maps; i++) {
 		zclose(obj->maps[i].fd);
+		if (obj->maps[i].st_ops)
+			zfree(&obj->maps[i].st_ops->kern_vdata);
+	}
 
 	for (i = 0; i < obj->nr_programs; i++)
 		bpf_program__unload(&obj->programs[i]);
@@ -4891,6 +5330,7 @@ int bpf_object__load_xattr(struct bpf_object_load_attr *attr)
 	err = err ? : bpf_object__resolve_externs(obj, obj->kconfig);
 	err = err ? : bpf_object__sanitize_and_load_btf(obj);
 	err = err ? : bpf_object__sanitize_maps(obj);
+	err = err ? : bpf_object__init_kern_struct_ops_maps(obj);
 	err = err ? : bpf_object__create_maps(obj);
 	err = err ? : bpf_object__relocate(obj, attr->target_btf_path);
 	err = err ? : bpf_object__load_progs(obj, attr->log_level);
@@ -5478,6 +5918,13 @@ void bpf_object__close(struct bpf_object *obj)
 			map->mmaped = NULL;
 		}
 
+		if (map->st_ops) {
+			zfree(&map->st_ops->data);
+			zfree(&map->st_ops->progs);
+			zfree(&map->st_ops->kern_func_off);
+			zfree(&map->st_ops);
+		}
+
 		zfree(&map->name);
 		zfree(&map->pin_path);
 	}
@@ -5746,6 +6193,7 @@ BPF_PROG_TYPE_FNS(raw_tracepoint, BPF_PROG_TYPE_RAW_TRACEPOINT);
 BPF_PROG_TYPE_FNS(xdp, BPF_PROG_TYPE_XDP);
 BPF_PROG_TYPE_FNS(perf_event, BPF_PROG_TYPE_PERF_EVENT);
 BPF_PROG_TYPE_FNS(tracing, BPF_PROG_TYPE_TRACING);
+BPF_PROG_TYPE_FNS(struct_ops, BPF_PROG_TYPE_STRUCT_OPS);
 
 enum bpf_attach_type
 bpf_program__get_expected_attach_type(struct bpf_program *prog)
@@ -5899,6 +6347,7 @@ static const struct bpf_sec_def section_defs[] = {
 						BPF_CGROUP_GETSOCKOPT),
 	BPF_EAPROG_SEC("cgroup/setsockopt",	BPF_PROG_TYPE_CGROUP_SOCKOPT,
 						BPF_CGROUP_SETSOCKOPT),
+	BPF_PROG_SEC("struct_ops",		BPF_PROG_TYPE_STRUCT_OPS),
 };
 
 #undef BPF_PROG_SEC_IMPL
@@ -5975,11 +6424,141 @@ int libbpf_prog_type_by_name(const char *name, enum bpf_prog_type *prog_type,
 	return -ESRCH;
 }
 
+static struct bpf_map *find_struct_ops_map_by_offset(struct bpf_object *obj,
+						     size_t offset)
+{
+	struct bpf_map *map;
+	size_t i;
+
+	for (i = 0; i < obj->nr_maps; i++) {
+		map = &obj->maps[i];
+		if (!bpf_map__is_struct_ops(map))
+			continue;
+		if (map->sec_offset <= offset &&
+		    offset - map->sec_offset < map->def.value_size)
+			return map;
+	}
+
+	return NULL;
+}
+
+/* Collect the reloc from ELF and populate the st_ops->progs[] */
+static int bpf_object__collect_struct_ops_map_reloc(struct bpf_object *obj,
+						    GElf_Shdr *shdr,
+						    Elf_Data *data)
+{
+	const struct btf_member *member;
+	struct bpf_struct_ops *st_ops;
+	struct bpf_program *prog;
+	unsigned int shdr_idx;
+	const struct btf *btf;
+	struct bpf_map *map;
+	Elf_Data *symbols;
+	unsigned int moff;
+	const char *name;
+	u32 member_idx;
+	GElf_Sym sym;
+	GElf_Rel rel;
+	int i, nrels;
+
+	symbols = obj->efile.symbols;
+	btf = obj->btf;
+	nrels = shdr->sh_size / shdr->sh_entsize;
+	for (i = 0; i < nrels; i++) {
+		if (!gelf_getrel(data, i, &rel)) {
+			pr_warn("struct_ops reloc: failed to get %d reloc\n", i);
+			return -LIBBPF_ERRNO__FORMAT;
+		}
+
+		if (!gelf_getsym(symbols, GELF_R_SYM(rel.r_info), &sym)) {
+			pr_warn("struct_ops reloc: symbol %zx not found\n",
+				(size_t)GELF_R_SYM(rel.r_info));
+			return -LIBBPF_ERRNO__FORMAT;
+		}
+
+		name = elf_strptr(obj->efile.elf, obj->efile.strtabidx,
+				  sym.st_name) ? : "<?>";
+		map = find_struct_ops_map_by_offset(obj, rel.r_offset);
+		if (!map) {
+			pr_warn("struct_ops reloc: cannot find map at rel.r_offset %zu\n",
+				(size_t)rel.r_offset);
+			return -EINVAL;
+		}
+
+		moff = rel.r_offset - map->sec_offset;
+		shdr_idx = sym.st_shndx;
+		st_ops = map->st_ops;
+		pr_debug("struct_ops reloc %s: for %lld value %lld shdr_idx %u rel.r_offset %zu map->sec_offset %zu name %d (\'%s\')\n",
+			 map->name,
+			 (long long)(rel.r_info >> 32),
+			 (long long)sym.st_value,
+			 shdr_idx, (size_t)rel.r_offset,
+			 map->sec_offset, sym.st_name, name);
+
+		if (shdr_idx >= SHN_LORESERVE) {
+			pr_warn("struct_ops reloc %s: rel.r_offset %zu shdr_idx %u unsupported non-static function\n",
+				map->name, (size_t)rel.r_offset, shdr_idx);
+			return -LIBBPF_ERRNO__RELOC;
+		}
+
+		member = find_member_by_offset(st_ops->type, moff * 8);
+		if (!member) {
+			pr_warn("struct_ops reloc %s: cannot find member at moff %u\n",
+				map->name, moff);
+			return -EINVAL;
+		}
+		member_idx = member - btf_members(st_ops->type);
+		name = btf__name_by_offset(btf, member->name_off);
+
+		if (!resolve_func_ptr(btf, member->type, NULL)) {
+			pr_warn("struct_ops reloc %s: cannot relocate non func ptr %s\n",
+				map->name, name);
+			return -EINVAL;
+		}
+
+		prog = bpf_object__find_prog_by_idx(obj, shdr_idx);
+		if (!prog) {
+			pr_warn("struct_ops reloc %s: cannot find prog at shdr_idx %u to relocate func ptr %s\n",
+				map->name, shdr_idx, name);
+			return -EINVAL;
+		}
+
+		if (prog->type == BPF_PROG_TYPE_UNSPEC) {
+			const struct bpf_sec_def *sec_def;
+
+			sec_def = find_sec_def(prog->section_name);
+			if (sec_def &&
+			    sec_def->prog_type != BPF_PROG_TYPE_STRUCT_OPS) {
+				/* for pr_warn */
+				prog->type = sec_def->prog_type;
+				goto invalid_prog;
+			}
+
+			prog->type = BPF_PROG_TYPE_STRUCT_OPS;
+			prog->attach_btf_id = st_ops->type_id;
+			prog->expected_attach_type = member_idx;
+		} else if (prog->type != BPF_PROG_TYPE_STRUCT_OPS ||
+			   prog->attach_btf_id != st_ops->type_id ||
+			   prog->expected_attach_type != member_idx) {
+			goto invalid_prog;
+		}
+		st_ops->progs[member_idx] = prog;
+	}
+
+	return 0;
+
+invalid_prog:
+	pr_warn("struct_ops reloc %s: cannot use prog %s in sec %s with type %u attach_btf_id %u expected_attach_type %u for func ptr %s\n",
+		map->name, prog->name, prog->section_name, prog->type,
+		prog->attach_btf_id, prog->expected_attach_type, name);
+	return -EINVAL;
+}
+
 #define BTF_PREFIX "btf_trace_"
 int libbpf_find_vmlinux_btf_id(const char *name,
 			       enum bpf_attach_type attach_type)
 {
-	struct btf *btf = bpf_core_find_kernel_btf();
+	struct btf *btf = bpf_find_kernel_btf();
 	char raw_tp_btf[128] = BTF_PREFIX;
 	char *dst = raw_tp_btf + sizeof(BTF_PREFIX) - 1;
 	const char *btf_name;
@@ -6805,6 +7384,58 @@ struct bpf_link *bpf_program__attach(struct bpf_program *prog)
 	return sec_def->attach_fn(sec_def, prog);
 }
 
+static int bpf_link__detach_struct_ops(struct bpf_link *link)
+{
+	struct bpf_link_fd *l = (void *)link;
+	__u32 zero = 0;
+
+	if (bpf_map_delete_elem(l->fd, &zero))
+		return -errno;
+
+	return 0;
+}
+
+struct bpf_link *bpf_map__attach_struct_ops(struct bpf_map *map)
+{
+	struct bpf_struct_ops *st_ops;
+	struct bpf_link_fd *link;
+	__u32 i, zero = 0;
+	int err;
+
+	if (!bpf_map__is_struct_ops(map) || map->fd == -1)
+		return ERR_PTR(-EINVAL);
+
+	link = calloc(1, sizeof(*link));
+	if (!link)
+		return ERR_PTR(-EINVAL);
+
+	st_ops = map->st_ops;
+	for (i = 0; i < btf_vlen(st_ops->type); i++) {
+		struct bpf_program *prog = st_ops->progs[i];
+		void *kern_data;
+		int prog_fd;
+
+		if (!prog)
+			continue;
+
+		prog_fd = bpf_program__fd(prog);
+		kern_data = st_ops->kern_vdata + st_ops->kern_func_off[i];
+		*(unsigned long *)kern_data = prog_fd;
+	}
+
+	err = bpf_map_update_elem(map->fd, &zero, st_ops->kern_vdata, 0);
+	if (err) {
+		err = -errno;
+		free(link);
+		return ERR_PTR(err);
+	}
+
+	link->link.detach = bpf_link__detach_struct_ops;
+	link->fd = map->fd;
+
+	return (struct bpf_link *)link;
+}
+
 enum bpf_perf_event_ret
 bpf_perf_event_read_simple(void *mmap_mem, size_t mmap_size, size_t page_size,
 			   void **copy_mem, size_t *copy_size,
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 26bf539f1b3c..01639f9a1062 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -239,6 +239,8 @@ bpf_program__attach_raw_tracepoint(struct bpf_program *prog,
 
 LIBBPF_API struct bpf_link *
 bpf_program__attach_trace(struct bpf_program *prog);
+struct bpf_map;
+LIBBPF_API struct bpf_link *bpf_map__attach_struct_ops(struct bpf_map *map);
 struct bpf_insn;
 
 /*
@@ -315,6 +317,7 @@ LIBBPF_API int bpf_program__set_sched_act(struct bpf_program *prog);
 LIBBPF_API int bpf_program__set_xdp(struct bpf_program *prog);
 LIBBPF_API int bpf_program__set_perf_event(struct bpf_program *prog);
 LIBBPF_API int bpf_program__set_tracing(struct bpf_program *prog);
+LIBBPF_API int bpf_program__set_struct_ops(struct bpf_program *prog);
 
 LIBBPF_API enum bpf_prog_type bpf_program__get_type(struct bpf_program *prog);
 LIBBPF_API void bpf_program__set_type(struct bpf_program *prog,
@@ -335,6 +338,7 @@ LIBBPF_API bool bpf_program__is_sched_act(const struct bpf_program *prog);
 LIBBPF_API bool bpf_program__is_xdp(const struct bpf_program *prog);
 LIBBPF_API bool bpf_program__is_perf_event(const struct bpf_program *prog);
 LIBBPF_API bool bpf_program__is_tracing(const struct bpf_program *prog);
+LIBBPF_API bool bpf_program__is_struct_ops(const struct bpf_program *prog);
 
 /*
  * No need for __attribute__((packed)), all members of 'bpf_map_def'
@@ -354,7 +358,6 @@ struct bpf_map_def {
  * The 'struct bpf_map' in include/linux/bpf.h is internal to the kernel,
  * so no need to worry about a name clash.
  */
-struct bpf_map;
 LIBBPF_API struct bpf_map *
 bpf_object__find_map_by_name(const struct bpf_object *obj, const char *name);
 
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index b300d74c921a..a19f04e6e3d9 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -213,6 +213,7 @@ LIBBPF_0.0.7 {
 	global:
 		btf_dump__emit_type_decl;
 		bpf_link__disconnect;
+		bpf_map__attach_struct_ops;
 		bpf_object__find_program_by_name;
 		bpf_object__attach_skeleton;
 		bpf_object__destroy_skeleton;
@@ -223,5 +224,7 @@ LIBBPF_0.0.7 {
 		bpf_prog_attach_xattr;
 		bpf_program__attach;
 		bpf_program__name;
+		bpf_program__is_struct_ops;
+		bpf_program__set_struct_ops;
 		btf__align_of;
 } LIBBPF_0.0.6;
diff --git a/tools/lib/bpf/libbpf_probes.c b/tools/lib/bpf/libbpf_probes.c
index 221e6ad97012..320697f8e4c7 100644
--- a/tools/lib/bpf/libbpf_probes.c
+++ b/tools/lib/bpf/libbpf_probes.c
@@ -103,6 +103,7 @@ probe_load(enum bpf_prog_type prog_type, const struct bpf_insn *insns,
 	case BPF_PROG_TYPE_CGROUP_SYSCTL:
 	case BPF_PROG_TYPE_CGROUP_SOCKOPT:
 	case BPF_PROG_TYPE_TRACING:
+	case BPF_PROG_TYPE_STRUCT_OPS:
 	default:
 		break;
 	}
@@ -251,6 +252,7 @@ bool bpf_probe_map_type(enum bpf_map_type map_type, __u32 ifindex)
 	case BPF_MAP_TYPE_XSKMAP:
 	case BPF_MAP_TYPE_SOCKHASH:
 	case BPF_MAP_TYPE_REUSEPORT_SOCKARRAY:
+	case BPF_MAP_TYPE_STRUCT_OPS:
 	default:
 		break;
 	}
diff --git a/tools/testing/selftests/bpf/bpf_tcp_helpers.h b/tools/testing/selftests/bpf/bpf_tcp_helpers.h
new file mode 100644
index 000000000000..7da3e8db3adf
--- /dev/null
+++ b/tools/testing/selftests/bpf/bpf_tcp_helpers.h
@@ -0,0 +1,228 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __BPF_TCP_HELPERS_H
+#define __BPF_TCP_HELPERS_H
+
+#include <stdbool.h>
+#include <linux/types.h>
+#include <bpf_helpers.h>
+#include <bpf_core_read.h>
+#include "bpf_trace_helpers.h"
+
+/* "struct_ops/" is only a convention.  not a requirement. */
+#define BPF_TCP_OPS_0(fname, ret_type, ...) BPF_TRACE_x(0, "struct_ops/"#fname, fname, ret_type, __VA_ARGS__)
+#define BPF_TCP_OPS_1(fname, ret_type, ...) BPF_TRACE_x(1, "struct_ops/"#fname, fname, ret_type, __VA_ARGS__)
+#define BPF_TCP_OPS_2(fname, ret_type, ...) BPF_TRACE_x(2, "struct_ops/"#fname, fname, ret_type, __VA_ARGS__)
+#define BPF_TCP_OPS_3(fname, ret_type, ...) BPF_TRACE_x(3, "struct_ops/"#fname, fname, ret_type, __VA_ARGS__)
+#define BPF_TCP_OPS_4(fname, ret_type, ...) BPF_TRACE_x(4, "struct_ops/"#fname, fname, ret_type, __VA_ARGS__)
+#define BPF_TCP_OPS_5(fname, ret_type, ...) BPF_TRACE_x(5, "struct_ops/"#fname, fname, ret_type, __VA_ARGS__)
+
+struct sock_common {
+	unsigned char	skc_state;
+} __attribute__((preserve_access_index));
+
+struct sock {
+	struct sock_common	__sk_common;
+} __attribute__((preserve_access_index));
+
+struct inet_sock {
+	struct sock		sk;
+} __attribute__((preserve_access_index));
+
+struct inet_connection_sock {
+	struct inet_sock	  icsk_inet;
+	__u8			  icsk_ca_state:6,
+				  icsk_ca_setsockopt:1,
+				  icsk_ca_dst_locked:1;
+	struct {
+		__u8		  pending;
+	} icsk_ack;
+	__u64			  icsk_ca_priv[104 / sizeof(__u64)];
+} __attribute__((preserve_access_index));
+
+struct tcp_sock {
+	struct inet_connection_sock	inet_conn;
+
+	__u32	rcv_nxt;
+	__u32	snd_nxt;
+	__u32	snd_una;
+	__u8	ecn_flags;
+	__u32	delivered;
+	__u32	delivered_ce;
+	__u32	snd_cwnd;
+	__u32	snd_cwnd_cnt;
+	__u32	snd_cwnd_clamp;
+	__u32	snd_ssthresh;
+	__u8	syn_data:1,	/* SYN includes data */
+		syn_fastopen:1,	/* SYN includes Fast Open option */
+		syn_fastopen_exp:1,/* SYN includes Fast Open exp. option */
+		syn_fastopen_ch:1, /* Active TFO re-enabling probe */
+		syn_data_acked:1,/* data in SYN is acked by SYN-ACK */
+		save_syn:1,	/* Save headers of SYN packet */
+		is_cwnd_limited:1,/* forward progress limited by snd_cwnd? */
+		syn_smc:1;	/* SYN includes SMC */
+	__u32	max_packets_out;
+	__u32	lsndtime;
+	__u32	prior_cwnd;
+} __attribute__((preserve_access_index));
+
+static __always_inline struct inet_connection_sock *inet_csk(const struct sock *sk)
+{
+	return (struct inet_connection_sock *)sk;
+}
+
+static __always_inline void *inet_csk_ca(const struct sock *sk)
+{
+	return (void *)inet_csk(sk)->icsk_ca_priv;
+}
+
+static __always_inline struct tcp_sock *tcp_sk(const struct sock *sk)
+{
+	return (struct tcp_sock *)sk;
+}
+
+static __always_inline bool before(__u32 seq1, __u32 seq2)
+{
+	return (__s32)(seq1-seq2) < 0;
+}
+#define after(seq2, seq1) 	before(seq1, seq2)
+
+#define	TCP_ECN_OK		1
+#define	TCP_ECN_QUEUE_CWR	2
+#define	TCP_ECN_DEMAND_CWR	4
+#define	TCP_ECN_SEEN		8
+
+enum inet_csk_ack_state_t {
+	ICSK_ACK_SCHED	= 1,
+	ICSK_ACK_TIMER  = 2,
+	ICSK_ACK_PUSHED = 4,
+	ICSK_ACK_PUSHED2 = 8,
+	ICSK_ACK_NOW = 16	/* Send the next ACK immediately (once) */
+};
+
+enum tcp_ca_event {
+	CA_EVENT_TX_START = 0,
+	CA_EVENT_CWND_RESTART = 1,
+	CA_EVENT_COMPLETE_CWR = 2,
+	CA_EVENT_LOSS = 3,
+	CA_EVENT_ECN_NO_CE = 4,
+	CA_EVENT_ECN_IS_CE = 5,
+};
+
+enum tcp_ca_state {
+	TCP_CA_Open = 0,
+	TCP_CA_Disorder = 1,
+	TCP_CA_CWR = 2,
+	TCP_CA_Recovery = 3,
+	TCP_CA_Loss = 4
+};
+
+struct ack_sample {
+	__u32 pkts_acked;
+	__s32 rtt_us;
+	__u32 in_flight;
+} __attribute__((preserve_access_index));
+
+struct rate_sample {
+	__u64  prior_mstamp; /* starting timestamp for interval */
+	__u32  prior_delivered;	/* tp->delivered at "prior_mstamp" */
+	__s32  delivered;		/* number of packets delivered over interval */
+	long interval_us;	/* time for tp->delivered to incr "delivered" */
+	__u32 snd_interval_us;	/* snd interval for delivered packets */
+	__u32 rcv_interval_us;	/* rcv interval for delivered packets */
+	long rtt_us;		/* RTT of last (S)ACKed packet (or -1) */
+	int  losses;		/* number of packets marked lost upon ACK */
+	__u32  acked_sacked;	/* number of packets newly (S)ACKed upon ACK */
+	__u32  prior_in_flight;	/* in flight before this ACK */
+	bool is_app_limited;	/* is sample from packet with bubble in pipe? */
+	bool is_retrans;	/* is sample from retransmission? */
+	bool is_ack_delayed;	/* is this (likely) a delayed ACK? */
+} __attribute__((preserve_access_index));
+
+#define TCP_CA_NAME_MAX		16
+#define TCP_CONG_NEEDS_ECN	0x2
+
+struct tcp_congestion_ops {
+	char name[TCP_CA_NAME_MAX];
+	__u32 flags;
+
+	/* initialize private data (optional) */
+	void (*init)(struct sock *sk);
+	/* cleanup private data  (optional) */
+	void (*release)(struct sock *sk);
+
+	/* return slow start threshold (required) */
+	__u32 (*ssthresh)(struct sock *sk);
+	/* do new cwnd calculation (required) */
+	void (*cong_avoid)(struct sock *sk, __u32 ack, __u32 acked);
+	/* call before changing ca_state (optional) */
+	void (*set_state)(struct sock *sk, __u8 new_state);
+	/* call when cwnd event occurs (optional) */
+	void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev);
+	/* call when ack arrives (optional) */
+	void (*in_ack_event)(struct sock *sk, __u32 flags);
+	/* new value of cwnd after loss (required) */
+	__u32  (*undo_cwnd)(struct sock *sk);
+	/* hook for packet ack accounting (optional) */
+	void (*pkts_acked)(struct sock *sk, const struct ack_sample *sample);
+	/* override sysctl_tcp_min_tso_segs */
+	__u32 (*min_tso_segs)(struct sock *sk);
+	/* returns the multiplier used in tcp_sndbuf_expand (optional) */
+	__u32 (*sndbuf_expand)(struct sock *sk);
+	/* call when packets are delivered to update cwnd and pacing rate,
+	 * after all the ca_state processing. (optional)
+	 */
+	void (*cong_control)(struct sock *sk, const struct rate_sample *rs);
+};
+
+#define min(a, b) ((a) < (b) ? (a) : (b))
+#define max(a, b) ((a) > (b) ? (a) : (b))
+#define min_not_zero(x, y) ({			\
+	typeof(x) __x = (x);			\
+	typeof(y) __y = (y);			\
+	__x == 0 ? __y : ((__y == 0) ? __x : min(__x, __y)); })
+
+static __always_inline __u32 tcp_slow_start(struct tcp_sock *tp, __u32 acked)
+{
+	__u32 cwnd = min(tp->snd_cwnd + acked, tp->snd_ssthresh);
+
+	acked -= cwnd - tp->snd_cwnd;
+	tp->snd_cwnd = min(cwnd, tp->snd_cwnd_clamp);
+
+	return acked;
+}
+
+static __always_inline bool tcp_in_slow_start(const struct tcp_sock *tp)
+{
+	return tp->snd_cwnd < tp->snd_ssthresh;
+}
+
+static __always_inline bool tcp_is_cwnd_limited(const struct sock *sk)
+{
+	const struct tcp_sock *tp = tcp_sk(sk);
+
+	/* If in slow start, ensure cwnd grows to twice what was ACKed. */
+	if (tcp_in_slow_start(tp))
+		return tp->snd_cwnd < 2 * tp->max_packets_out;
+
+	return !!BPF_CORE_READ_BITFIELD(tp, is_cwnd_limited);
+}
+
+static __always_inline void tcp_cong_avoid_ai(struct tcp_sock *tp, __u32 w, __u32 acked)
+{
+	/* If credits accumulated at a higher w, apply them gently now. */
+	if (tp->snd_cwnd_cnt >= w) {
+		tp->snd_cwnd_cnt = 0;
+		tp->snd_cwnd++;
+	}
+
+	tp->snd_cwnd_cnt += acked;
+	if (tp->snd_cwnd_cnt >= w) {
+		__u32 delta = tp->snd_cwnd_cnt / w;
+
+		tp->snd_cwnd_cnt -= delta * w;
+		tp->snd_cwnd += delta;
+	}
+	tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_cwnd_clamp);
+}
+
+#endif
diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c b/tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c
new file mode 100644
index 000000000000..517318f05b1d
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c
@@ -0,0 +1,187 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2019 Facebook */
+
+#include <linux/err.h>
+#include <test_progs.h>
+#include "bpf_dctcp.skel.h"
+
+#define min(a, b) ((a) < (b) ? (a) : (b))
+
+static const unsigned int total_bytes = 10 * 1024 * 1024;
+static const struct timeval timeo_sec = { .tv_sec = 10 };
+static const size_t timeo_optlen = sizeof(timeo_sec);
+static int stop, duration;
+
+static int settimeo(int fd)
+{
+	int err;
+
+	err = setsockopt(fd, SOL_SOCKET, SO_RCVTIMEO, &timeo_sec,
+			 timeo_optlen);
+	if (CHECK(err == -1, "setsockopt(fd, SO_RCVTIMEO)", "errno:%d\n",
+		  errno))
+		return -1;
+
+	err = setsockopt(fd, SOL_SOCKET, SO_SNDTIMEO, &timeo_sec,
+			 timeo_optlen);
+	if (CHECK(err == -1, "setsockopt(fd, SO_SNDTIMEO)", "errno:%d\n",
+		  errno))
+		return -1;
+
+	return 0;
+}
+
+static int settcpca(int fd, const char *tcp_ca)
+{
+	int err;
+
+	err = setsockopt(fd, IPPROTO_TCP, TCP_CONGESTION, tcp_ca, strlen(tcp_ca));
+	if (CHECK(err == -1, "setsockopt(fd, TCP_CONGESTION)", "errno:%d\n",
+		  errno))
+		return -1;
+
+	return 0;
+}
+
+static void *server(void *arg)
+{
+	int lfd = (int)(long)arg, err = 0, fd;
+	ssize_t nr_sent = 0, bytes = 0;
+	char batch[1500];
+
+	fd = accept(lfd, NULL, NULL);
+	while (fd == -1) {
+		if (errno == EINTR)
+			continue;
+		err = -errno;
+		goto done;
+	}
+
+	if (settimeo(fd)) {
+		err = -errno;
+		goto done;
+	}
+
+	while (bytes < total_bytes && !READ_ONCE(stop)) {
+		nr_sent = send(fd, &batch,
+			       min(total_bytes - bytes, sizeof(batch)), 0);
+		if (nr_sent == -1 && errno == EINTR)
+			continue;
+		if (nr_sent == -1) {
+			err = -errno;
+			break;
+		}
+		bytes += nr_sent;
+	}
+
+	CHECK(bytes != total_bytes, "send", "%zd != %u nr_sent:%zd errno:%d\n",
+	      bytes, total_bytes, nr_sent, errno);
+
+done:
+	if (fd != -1)
+		close(fd);
+	if (err) {
+		WRITE_ONCE(stop, 1);
+		return ERR_PTR(err);
+	}
+	return NULL;
+}
+
+static void do_test(const char *tcp_ca)
+{
+	struct sockaddr_in6 sa6 = {};
+	ssize_t nr_recv = 0, bytes = 0;
+	int lfd = -1, fd = -1;
+	pthread_t srv_thread;
+	socklen_t addrlen = sizeof(sa6);
+	void *thread_ret;
+	char batch[1500];
+	int err;
+
+	WRITE_ONCE(stop, 0);
+
+	lfd = socket(AF_INET6, SOCK_STREAM, 0);
+	if (CHECK(lfd == -1, "socket", "errno:%d\n", errno))
+		return;
+	fd = socket(AF_INET6, SOCK_STREAM, 0);
+	if (CHECK(fd == -1, "socket", "errno:%d\n", errno)) {
+		close(lfd);
+		return;
+	}
+
+	if (settcpca(lfd, tcp_ca) || settcpca(fd, tcp_ca) ||
+	    settimeo(lfd) || settimeo(fd))
+		goto done;
+
+	/* bind, listen and start server thread to accept */
+	sa6.sin6_family = AF_INET6;
+	sa6.sin6_addr = in6addr_loopback;
+	err = bind(lfd, (struct sockaddr *)&sa6, addrlen);
+	if (CHECK(err == -1, "bind", "errno:%d\n", errno))
+		goto done;
+	err = getsockname(lfd, (struct sockaddr *)&sa6, &addrlen);
+	if (CHECK(err == -1, "getsockname", "errno:%d\n", errno))
+		goto done;
+	err = listen(lfd, 1);
+	if (CHECK(err == -1, "listen", "errno:%d\n", errno))
+		goto done;
+	err = pthread_create(&srv_thread, NULL, server, (void *)(long)lfd);
+	if (CHECK(err != 0, "pthread_create", "err:%d\n", err))
+		goto done;
+
+	/* connect to server */
+	err = connect(fd, (struct sockaddr *)&sa6, addrlen);
+	if (CHECK(err == -1, "connect", "errno:%d\n", errno))
+		goto wait_thread;
+
+	/* recv total_bytes */
+	while (bytes < total_bytes && !READ_ONCE(stop)) {
+		nr_recv = recv(fd, &batch,
+			       min(total_bytes - bytes, sizeof(batch)), 0);
+		if (nr_recv == -1 && errno == EINTR)
+			continue;
+		if (nr_recv == -1)
+			break;
+		bytes += nr_recv;
+	}
+
+	CHECK(bytes != total_bytes, "recv", "%zd != %u nr_recv:%zd errno:%d\n",
+	      bytes, total_bytes, nr_recv, errno);
+
+wait_thread:
+	WRITE_ONCE(stop, 1);
+	pthread_join(srv_thread, &thread_ret);
+	CHECK(IS_ERR(thread_ret), "pthread_join", "thread_ret:%ld",
+	      PTR_ERR(thread_ret));
+done:
+	close(lfd);
+	close(fd);
+}
+
+static void test_dctcp(void)
+{
+	struct bpf_dctcp *dctcp_skel;
+	struct bpf_link *link;
+
+	dctcp_skel = bpf_dctcp__open_and_load();
+	if (CHECK(!dctcp_skel, "bpf_dctcp__open_and_load", "failed\n"))
+		return;
+
+	link = bpf_map__attach_struct_ops(dctcp_skel->maps.dctcp);
+	if (CHECK(IS_ERR(link), "bpf_map__attach_struct_ops", "err:%ld\n",
+		  PTR_ERR(link))) {
+		bpf_dctcp__destroy(dctcp_skel);
+		return;
+	}
+
+	do_test("bpf_dctcp");
+
+	bpf_link__destroy(link);
+	bpf_dctcp__destroy(dctcp_skel);
+}
+
+void test_bpf_tcp_ca(void)
+{
+	if (test__start_subtest("dctcp"))
+		test_dctcp();
+}
diff --git a/tools/testing/selftests/bpf/progs/bpf_dctcp.c b/tools/testing/selftests/bpf/progs/bpf_dctcp.c
new file mode 100644
index 000000000000..5f9b613663e5
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bpf_dctcp.c
@@ -0,0 +1,210 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2019 Facebook */
+
+/* WARNING: This implemenation is not necessarily the same
+ * as the tcp_dctcp.c.  The purpose is mainly for testing
+ * the kernel BPF logic.
+ */
+
+#include <linux/bpf.h>
+#include <linux/types.h>
+#include "bpf_tcp_helpers.h"
+
+char _license[] SEC("license") = "GPL";
+
+#define DCTCP_MAX_ALPHA	1024U
+
+struct dctcp {
+	__u32 old_delivered;
+	__u32 old_delivered_ce;
+	__u32 prior_rcv_nxt;
+	__u32 dctcp_alpha;
+	__u32 next_seq;
+	__u32 ce_state;
+	__u32 loss_cwnd;
+};
+
+static unsigned int dctcp_shift_g = 4; /* g = 1/2^4 */
+static unsigned int dctcp_alpha_on_init = DCTCP_MAX_ALPHA;
+
+static __always_inline void dctcp_reset(const struct tcp_sock *tp,
+					struct dctcp *ca)
+{
+	ca->next_seq = tp->snd_nxt;
+
+	ca->old_delivered = tp->delivered;
+	ca->old_delivered_ce = tp->delivered_ce;
+}
+
+BPF_TCP_OPS_1(dctcp_init, void, struct sock *, sk)
+{
+	const struct tcp_sock *tp = tcp_sk(sk);
+	struct dctcp *ca = inet_csk_ca(sk);
+
+	ca->prior_rcv_nxt = tp->rcv_nxt;
+	ca->dctcp_alpha = min(dctcp_alpha_on_init, DCTCP_MAX_ALPHA);
+	ca->loss_cwnd = 0;
+	ca->ce_state = 0;
+
+	dctcp_reset(tp, ca);
+}
+
+BPF_TCP_OPS_1(dctcp_ssthresh, __u32, struct sock *, sk)
+{
+	struct dctcp *ca = inet_csk_ca(sk);
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	ca->loss_cwnd = tp->snd_cwnd;
+	return max(tp->snd_cwnd - ((tp->snd_cwnd * ca->dctcp_alpha) >> 11U), 2U);
+}
+
+BPF_TCP_OPS_2(dctcp_update_alpha, void,
+	      struct sock *, sk, __u32, flags)
+{
+	const struct tcp_sock *tp = tcp_sk(sk);
+	struct dctcp *ca = inet_csk_ca(sk);
+
+	/* Expired RTT */
+	if (!before(tp->snd_una, ca->next_seq)) {
+		__u32 delivered_ce = tp->delivered_ce - ca->old_delivered_ce;
+		__u32 alpha = ca->dctcp_alpha;
+
+		/* alpha = (1 - g) * alpha + g * F */
+
+		alpha -= min_not_zero(alpha, alpha >> dctcp_shift_g);
+		if (delivered_ce) {
+			__u32 delivered = tp->delivered - ca->old_delivered;
+
+			/* If dctcp_shift_g == 1, a 32bit value would overflow
+			 * after 8 M packets.
+			 */
+			delivered_ce <<= (10 - dctcp_shift_g);
+			delivered_ce /= max(1U, delivered);
+
+			alpha = min(alpha + delivered_ce, DCTCP_MAX_ALPHA);
+		}
+		ca->dctcp_alpha = alpha;
+		dctcp_reset(tp, ca);
+	}
+}
+
+static __always_inline void dctcp_react_to_loss(struct sock *sk)
+{
+	struct dctcp *ca = inet_csk_ca(sk);
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	ca->loss_cwnd = tp->snd_cwnd;
+	tp->snd_ssthresh = max(tp->snd_cwnd >> 1U, 2U);
+}
+
+BPF_TCP_OPS_2(dctcp_state, void, struct sock *, sk, __u8, new_state)
+{
+	if (new_state == TCP_CA_Recovery &&
+	    new_state != BPF_CORE_READ_BITFIELD(inet_csk(sk), icsk_ca_state))
+		dctcp_react_to_loss(sk);
+	/* We handle RTO in dctcp_cwnd_event to ensure that we perform only
+	 * one loss-adjustment per RTT.
+	 */
+}
+
+static __always_inline void dctcp_ece_ack_cwr(struct sock *sk, __u32 ce_state)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	if (ce_state == 1)
+		tp->ecn_flags |= TCP_ECN_DEMAND_CWR;
+	else
+		tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR;
+}
+
+/* Minimal DCTP CE state machine:
+ *
+ * S:	0 <- last pkt was non-CE
+ *	1 <- last pkt was CE
+ */
+static __always_inline
+void dctcp_ece_ack_update(struct sock *sk, enum tcp_ca_event evt,
+			  __u32 *prior_rcv_nxt, __u32 *ce_state)
+{
+	__u32 new_ce_state = (evt == CA_EVENT_ECN_IS_CE) ? 1 : 0;
+
+	if (*ce_state != new_ce_state) {
+		/* CE state has changed, force an immediate ACK to
+		 * reflect the new CE state. If an ACK was delayed,
+		 * send that first to reflect the prior CE state.
+		 */
+		if (inet_csk(sk)->icsk_ack.pending & ICSK_ACK_TIMER) {
+			dctcp_ece_ack_cwr(sk, *ce_state);
+			bpf_tcp_send_ack(sk, *prior_rcv_nxt);
+		}
+		inet_csk(sk)->icsk_ack.pending |= ICSK_ACK_NOW;
+	}
+	*prior_rcv_nxt = tcp_sk(sk)->rcv_nxt;
+	*ce_state = new_ce_state;
+	dctcp_ece_ack_cwr(sk, new_ce_state);
+}
+
+BPF_TCP_OPS_2(dctcp_cwnd_event, void,
+	      struct sock *, sk, enum tcp_ca_event, ev)
+{
+	struct dctcp *ca = inet_csk_ca(sk);
+
+	switch (ev) {
+	case CA_EVENT_ECN_IS_CE:
+	case CA_EVENT_ECN_NO_CE:
+		dctcp_ece_ack_update(sk, ev, &ca->prior_rcv_nxt, &ca->ce_state);
+		break;
+	case CA_EVENT_LOSS:
+		dctcp_react_to_loss(sk);
+		break;
+	default:
+		/* Don't care for the rest. */
+		break;
+	}
+}
+
+BPF_TCP_OPS_1(dctcp_cwnd_undo, __u32, struct sock *, sk)
+{
+	const struct dctcp *ca = inet_csk_ca(sk);
+
+	return max(tcp_sk(sk)->snd_cwnd, ca->loss_cwnd);
+}
+
+BPF_TCP_OPS_3(tcp_reno_cong_avoid, void,
+	      struct sock *, sk, __u32, ack, __u32, acked)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	if (!tcp_is_cwnd_limited(sk))
+		return;
+
+	/* In "safe" area, increase. */
+	if (tcp_in_slow_start(tp)) {
+		acked = tcp_slow_start(tp, acked);
+		if (!acked)
+			return;
+	}
+	/* In dangerous area, increase slowly. */
+	tcp_cong_avoid_ai(tp, tp->snd_cwnd, acked);
+}
+
+SEC(".struct_ops")
+struct tcp_congestion_ops dctcp_nouse = {
+	.init		= (void *)dctcp_init,
+	.set_state	= (void *)dctcp_state,
+	.flags		= TCP_CONG_NEEDS_ECN,
+	.name		= "bpf_dctcp_nouse",
+};
+
+SEC(".struct_ops")
+struct tcp_congestion_ops dctcp = {
+	.init		= (void *)dctcp_init,
+	.in_ack_event   = (void *)dctcp_update_alpha,
+	.cwnd_event	= (void *)dctcp_cwnd_event,
+	.ssthresh	= (void *)dctcp_ssthresh,
+	.cong_avoid	= (void *)tcp_reno_cong_avoid,
+	.undo_cwnd	= (void *)dctcp_cwnd_undo,
+	.set_state	= (void *)dctcp_state,
+	.flags		= TCP_CONG_NEEDS_ECN,
+	.name		= "bpf_dctcp",
+};