Merge tag 'net-next-6.4' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next

Pull networking updates from Paolo Abeni:
 "Core:

   - Introduce a config option to tweak MAX_SKB_FRAGS. Increasing the
     default value allows for better BIG TCP performances

   - Reduce compound page head access for zero-copy data transfers

   - RPS/RFS improvements, avoiding unneeded NET_RX_SOFTIRQ when
     possible

   - Threaded NAPI improvements, adding defer skb free support and
     unneeded softirq avoidance

   - Address dst_entry reference count scalability issues, via false
     sharing avoidance and optimize refcount tracking

   - Add lockless accesses annotation to sk_err[_soft]

   - Optimize again the skb struct layout

   - Extends the skb drop reasons to make it usable by multiple
     subsystems

   - Better const qualifier awareness for socket casts

  BPF:

   - Add skb and XDP typed dynptrs which allow BPF programs for more
     ergonomic and less brittle iteration through data and
     variable-sized accesses

   - Add a new BPF netfilter program type and minimal support to hook
     BPF programs to netfilter hooks such as prerouting or forward

   - Add more precise memory usage reporting for all BPF map types

   - Adds support for using {FOU,GUE} encap with an ipip device
     operating in collect_md mode and add a set of BPF kfuncs for
     controlling encap params

   - Allow BPF programs to detect at load time whether a particular
     kfunc exists or not, and also add support for this in light
     skeleton

   - Bigger batch of BPF verifier improvements to prepare for upcoming
     BPF open-coded iterators allowing for less restrictive looping
     capabilities

   - Rework RCU enforcement in the verifier, add kptr_rcu and enforce
     BPF programs to NULL-check before passing such pointers into kfunc

   - Add support for kptrs in percpu hashmaps, percpu LRU hashmaps and
     in local storage maps

   - Enable RCU semantics for task BPF kptrs and allow referenced kptr
     tasks to be stored in BPF maps

   - Add support for refcounted local kptrs to the verifier for allowing
     shared ownership, useful for adding a node to both the BPF list and
     rbtree

   - Add BPF verifier support for ST instructions in
     convert_ctx_access() which will help new -mcpu=v4 clang flag to
     start emitting them

   - Add ARM32 USDT support to libbpf

   - Improve bpftool's visual program dump which produces the control
     flow graph in a DOT format by adding C source inline annotations

  Protocols:

   - IPv4: Allow adding to IPv4 address a 'protocol' tag. Such value
     indicates the provenance of the IP address

   - IPv6: optimize route lookup, dropping unneeded R/W lock acquisition

   - Add the handshake upcall mechanism, allowing the user-space to
     implement generic TLS handshake on kernel's behalf

   - Bridge: support per-{Port, VLAN} neighbor suppression, increasing
     resilience to nodes failures

   - SCTP: add support for Fair Capacity and Weighted Fair Queueing
     schedulers

   - MPTCP: delay first subflow allocation up to its first usage. This
     will allow for later better LSM interaction

   - xfrm: Remove inner/outer modes from input/output path. These are
     not needed anymore

   - WiFi:
      - reduced neighbor report (RNR) handling for AP mode
      - HW timestamping support
      - support for randomized auth/deauth TA for PASN privacy
      - per-link debugfs for multi-link
      - TC offload support for mac80211 drivers
      - mac80211 mesh fast-xmit and fast-rx support
      - enable Wi-Fi 7 (EHT) mesh support

  Netfilter:

   - Add nf_tables 'brouting' support, to force a packet to be routed
     instead of being bridged

   - Update bridge netfilter and ovs conntrack helpers to handle IPv6
     Jumbo packets properly, i.e. fetch the packet length from
     hop-by-hop extension header. This is needed for BIT TCP support

   - The iptables 32bit compat interface isn't compiled in by default
     anymore

   - Move ip(6)tables builtin icmp matches to the udptcp one. This has
     the advantage that icmp/icmpv6 match doesn't load the
     iptables/ip6tables modules anymore when iptables-nft is used

   - Extended netlink error report for netdevice in flowtables and
     netdev/chains. Allow for incrementally add/delete devices to netdev
     basechain. Allow to create netdev chain without device

  Driver API:

   - Remove redundant Device Control Error Reporting Enable, as PCI core
     has already error reporting enabled at enumeration time

   - Move Multicast DB netlink handlers to core, allowing devices other
     then bridge to use them

   - Allow the page_pool to directly recycle the pages from safely
     localized NAPI

   - Implement lockless TX queue stop/wake combo macros, allowing for
     further code de-duplication and sanitization

   - Add YNL support for user headers and struct attrs

   - Add partial YNL specification for devlink

   - Add partial YNL specification for ethtool

   - Add tc-mqprio and tc-taprio support for preemptible traffic classes

   - Add tx push buf len param to ethtool, specifies the maximum number
     of bytes of a transmitted packet a driver can push directly to the
     underlying device

   - Add basic LED support for switch/phy

   - Add NAPI documentation, stop relaying on external links

   - Convert dsa_master_ioctl() to netdev notifier. This is a
     preparatory work to make the hardware timestamping layer selectable
     by user space

   - Add transceiver support and improve the error messages for CAN-FD
     controllers

  New hardware / drivers:

   - Ethernet:
      - AMD/Pensando core device support
      - MediaTek MT7981 SoC
      - MediaTek MT7988 SoC
      - Broadcom BCM53134 embedded switch
      - Texas Instruments CPSW9G ethernet switch
      - Qualcomm EMAC3 DWMAC ethernet
      - StarFive JH7110 SoC
      - NXP CBTX ethernet PHY

   - WiFi:
      - Apple M1 Pro/Max devices
      - RealTek rtl8710bu/rtl8188gu
      - RealTek rtl8822bs, rtl8822cs and rtl8821cs SDIO chipset

   - Bluetooth:
      - Realtek RTL8821CS, RTL8851B, RTL8852BS
      - Mediatek MT7663, MT7922
      - NXP w8997
      - Actions Semi ATS2851
      - QTI WCN6855
      - Marvell 88W8997

   - Can:
      - STMicroelectronics bxcan stm32f429

  Drivers:

   - Ethernet NICs:
      - Intel (1G, icg):
         - add tracking and reporting of QBV config errors
         - add support for configuring max SDU for each Tx queue
      - Intel (100G, ice):
         - refactor mailbox overflow detection to support Scalable IOV
         - GNSS interface optimization
      - Intel (i40e):
         - support XDP multi-buffer
      - nVidia/Mellanox:
         - add the support for linux bridge multicast offload
         - enable TC offload for egress and engress MACVLAN over bond
         - add support for VxLAN GBP encap/decap flows offload
         - extend packet offload to fully support libreswan
         - support tunnel mode in mlx5 IPsec packet offload
         - extend XDP multi-buffer support
         - support MACsec VLAN offload
         - add support for dynamic msix vectors allocation
         - drop RX page_cache and fully use page_pool
         - implement thermal zone to report NIC temperature
      - Netronome/Corigine:
         - add support for multi-zone conntrack offload
      - Solarflare/Xilinx:
         - support offloading TC VLAN push/pop actions to the MAE
         - support TC decap rules
         - support unicast PTP

   - Other NICs:
      - Broadcom (bnxt): enforce software based freq adjustments only on
        shared PHC NIC
      - RealTek (r8169): refactor to addess ASPM issues during NAPI poll
      - Micrel (lan8841): add support for PTP_PF_PEROUT
      - Cadence (macb): enable PTP unicast
      - Engleder (tsnep): add XDP socket zero-copy support
      - virtio-net: implement exact header length guest feature
      - veth: add page_pool support for page recycling
      - vxlan: add MDB data path support
      - gve: add XDP support for GQI-QPL format
      - geneve: accept every ethertype
      - macvlan: allow some packets to bypass broadcast queue
      - mana: add support for jumbo frame

   - Ethernet high-speed switches:
      - Microchip (sparx5): Add support for TC flower templates

   - Ethernet embedded switches:
      - Broadcom (b54):
         - configure 6318 and 63268 RGMII ports
      - Marvell (mv88e6xxx):
         - faster C45 bus scan
      - Microchip:
         - lan966x:
            - add support for IS1 VCAP
            - better TX/RX from/to CPU performances
         - ksz9477: add ETS Qdisc support
         - ksz8: enhance static MAC table operations and error handling
         - sama7g5: add PTP capability
      - NXP (ocelot):
         - add support for external ports
         - add support for preemptible traffic classes
      - Texas Instruments:
         - add CPSWxG SGMII support for J7200 and J721E

   - Intel WiFi (iwlwifi):
      - preparation for Wi-Fi 7 EHT and multi-link support
      - EHT (Wi-Fi 7) sniffer support
      - hardware timestamping support for some devices/firwmares
      - TX beacon protection on newer hardware

   - Qualcomm 802.11ax WiFi (ath11k):
      - MU-MIMO parameters support
      - ack signal support for management packets

   - RealTek WiFi (rtw88):
      - SDIO bus support
      - better support for some SDIO devices (e.g. MAC address from
        efuse)

   - RealTek WiFi (rtw89):
      - HW scan support for 8852b
      - better support for 6 GHz scanning
      - support for various newer firmware APIs
      - framework firmware backwards compatibility

   - MediaTek WiFi (mt76):
      - P2P support
      - mesh A-MSDU support
      - EHT (Wi-Fi 7) support
      - coredump support"

* tag 'net-next-6.4' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (2078 commits)
  net: phy: hide the PHYLIB_LEDS knob
  net: phy: marvell-88x2222: remove unnecessary (void*) conversions
  tcp/udp: Fix memleaks of sk and zerocopy skbs with TX timestamp.
  net: amd: Fix link leak when verifying config failed
  net: phy: marvell: Fix inconsistent indenting in led_blink_set
  lan966x: Don't use xdp_frame when action is XDP_TX
  tsnep: Add XDP socket zero-copy TX support
  tsnep: Add XDP socket zero-copy RX support
  tsnep: Move skb receive action to separate function
  tsnep: Add functions for queue enable/disable
  tsnep: Rework TX/RX queue initialization
  tsnep: Replace modulo operation with mask
  net: phy: dp83867: Add led_brightness_set support
  net: phy: Fix reading LED reg property
  drivers: nfc: nfcsim: remove return value check of `dev_dir`
  net: phy: dp83867: Remove unnecessary (void*) conversions
  net: ethtool: coalesce: try to make user settings stick twice
  net: mana: Check if netdev/napi_alloc_frag returns single page
  net: mana: Rename mana_refill_rxoob and remove some empty lines
  net: veth: add page_pool stats
  ...

1 files changed, 243 insertions, 33 deletions

diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index ece9870cab68..d3f0a4825fa6 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -11,11 +11,13 @@
 #include <linux/refcount.h>
 #include <linux/mutex.h>
 #include <linux/btf_ids.h>
+#include <linux/rcupdate_wait.h>
 
 enum bpf_struct_ops_state {
 	BPF_STRUCT_OPS_STATE_INIT,
 	BPF_STRUCT_OPS_STATE_INUSE,
 	BPF_STRUCT_OPS_STATE_TOBEFREE,
+	BPF_STRUCT_OPS_STATE_READY,
 };
 
 #define BPF_STRUCT_OPS_COMMON_VALUE			\
@@ -58,6 +60,13 @@ struct bpf_struct_ops_map {
 	struct bpf_struct_ops_value kvalue;
 };
 
+struct bpf_struct_ops_link {
+	struct bpf_link link;
+	struct bpf_map __rcu *map;
+};
+
+static DEFINE_MUTEX(update_mutex);
+
 #define VALUE_PREFIX "bpf_struct_ops_"
 #define VALUE_PREFIX_LEN (sizeof(VALUE_PREFIX) - 1)
 
@@ -249,6 +258,7 @@ int bpf_struct_ops_map_sys_lookup_elem(struct bpf_map *map, void *key,
 	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;
+	s64 refcnt;
 
 	if (unlikely(*(u32 *)key != 0))
 		return -ENOENT;
@@ -267,7 +277,14 @@ int bpf_struct_ops_map_sys_lookup_elem(struct bpf_map *map, void *key,
 	uvalue = value;
 	memcpy(uvalue, st_map->uvalue, map->value_size);
 	uvalue->state = state;
-	refcount_set(&uvalue->refcnt, refcount_read(&kvalue->refcnt));
+
+	/* This value offers the user space a general estimate of how
+	 * many sockets are still utilizing this struct_ops for TCP
+	 * congestion control. The number might not be exact, but it
+	 * should sufficiently meet our present goals.
+	 */
+	refcnt = atomic64_read(&map->refcnt) - atomic64_read(&map->usercnt);
+	refcount_set(&uvalue->refcnt, max_t(s64, refcnt, 0));
 
 	return 0;
 }
@@ -349,8 +366,8 @@ int bpf_struct_ops_prepare_trampoline(struct bpf_tramp_links *tlinks,
 					   model, flags, tlinks, NULL);
 }
 
-static int bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
-					  void *value, u64 flags)
+static long 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;
@@ -491,12 +508,29 @@ static int bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
 		*(unsigned long *)(udata + moff) = prog->aux->id;
 	}
 
-	refcount_set(&kvalue->refcnt, 1);
-	bpf_map_inc(map);
+	if (st_map->map.map_flags & BPF_F_LINK) {
+		err = st_ops->validate(kdata);
+		if (err)
+			goto reset_unlock;
+		set_memory_rox((long)st_map->image, 1);
+		/* Let bpf_link handle registration & unregistration.
+		 *
+		 * Pair with smp_load_acquire() during lookup_elem().
+		 */
+		smp_store_release(&kvalue->state, BPF_STRUCT_OPS_STATE_READY);
+		goto unlock;
+	}
 
 	set_memory_rox((long)st_map->image, 1);
 	err = st_ops->reg(kdata);
 	if (likely(!err)) {
+		/* This refcnt increment on the map here after
+		 * 'st_ops->reg()' is secure since the state of the
+		 * map must be set to INIT at this moment, and thus
+		 * bpf_struct_ops_map_delete_elem() can't unregister
+		 * or transition it to TOBEFREE concurrently.
+		 */
+		bpf_map_inc(map);
 		/* 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.
@@ -512,7 +546,6 @@ static int bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
 	 */
 	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);
@@ -524,20 +557,22 @@ unlock:
 	return err;
 }
 
-static int bpf_struct_ops_map_delete_elem(struct bpf_map *map, void *key)
+static long 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;
+	if (st_map->map.map_flags & BPF_F_LINK)
+		return -EOPNOTSUPP;
+
 	prev_state = cmpxchg(&st_map->kvalue.state,
 			     BPF_STRUCT_OPS_STATE_INUSE,
 			     BPF_STRUCT_OPS_STATE_TOBEFREE);
 	switch (prev_state) {
 	case 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);
+		bpf_map_put(map);
 		return 0;
 	case BPF_STRUCT_OPS_STATE_TOBEFREE:
 		return -EINPROGRESS;
@@ -570,7 +605,7 @@ static void bpf_struct_ops_map_seq_show_elem(struct bpf_map *map, void *key,
 	kfree(value);
 }
 
-static void bpf_struct_ops_map_free(struct bpf_map *map)
+static void __bpf_struct_ops_map_free(struct bpf_map *map)
 {
 	struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
 
@@ -582,10 +617,32 @@ static void bpf_struct_ops_map_free(struct bpf_map *map)
 	bpf_map_area_free(st_map);
 }
 
+static void bpf_struct_ops_map_free(struct bpf_map *map)
+{
+	/* The struct_ops's function may switch to another struct_ops.
+	 *
+	 * For example, bpf_tcp_cc_x->init() may switch to
+	 * another tcp_cc_y by calling
+	 * setsockopt(TCP_CONGESTION, "tcp_cc_y").
+	 * During the switch,  bpf_struct_ops_put(tcp_cc_x) is called
+	 * and its refcount may reach 0 which then free its
+	 * trampoline image while tcp_cc_x is still running.
+	 *
+	 * A vanilla rcu gp is to wait for all bpf-tcp-cc prog
+	 * to finish. bpf-tcp-cc prog is non sleepable.
+	 * A rcu_tasks gp is to wait for the last few insn
+	 * in the tramopline image to finish before releasing
+	 * the trampoline image.
+	 */
+	synchronize_rcu_mult(call_rcu, call_rcu_tasks);
+
+	__bpf_struct_ops_map_free(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)
+	    (attr->map_flags & ~BPF_F_LINK) || !attr->btf_vmlinux_value_type_id)
 		return -EINVAL;
 	return 0;
 }
@@ -609,6 +666,9 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
 	if (attr->value_size != vt->size)
 		return ERR_PTR(-EINVAL);
 
+	if (attr->map_flags & BPF_F_LINK && (!st_ops->validate || !st_ops->update))
+		return ERR_PTR(-EOPNOTSUPP);
+
 	t = st_ops->type;
 
 	st_map_size = sizeof(*st_map) +
@@ -630,7 +690,7 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
 				   NUMA_NO_NODE);
 	st_map->image = bpf_jit_alloc_exec(PAGE_SIZE);
 	if (!st_map->uvalue || !st_map->links || !st_map->image) {
-		bpf_struct_ops_map_free(map);
+		__bpf_struct_ops_map_free(map);
 		return ERR_PTR(-ENOMEM);
 	}
 
@@ -641,6 +701,21 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
 	return map;
 }
 
+static u64 bpf_struct_ops_map_mem_usage(const struct bpf_map *map)
+{
+	struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
+	const struct bpf_struct_ops *st_ops = st_map->st_ops;
+	const struct btf_type *vt = st_ops->value_type;
+	u64 usage;
+
+	usage = sizeof(*st_map) +
+			vt->size - sizeof(struct bpf_struct_ops_value);
+	usage += vt->size;
+	usage += btf_type_vlen(vt) * sizeof(struct bpf_links *);
+	usage += PAGE_SIZE;
+	return usage;
+}
+
 BTF_ID_LIST_SINGLE(bpf_struct_ops_map_btf_ids, struct, bpf_struct_ops_map)
 const struct bpf_map_ops bpf_struct_ops_map_ops = {
 	.map_alloc_check = bpf_struct_ops_map_alloc_check,
@@ -651,6 +726,7 @@ const struct bpf_map_ops bpf_struct_ops_map_ops = {
 	.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,
+	.map_mem_usage = bpf_struct_ops_map_mem_usage,
 	.map_btf_id = &bpf_struct_ops_map_btf_ids[0],
 };
 
@@ -660,41 +736,175 @@ const struct bpf_map_ops bpf_struct_ops_map_ops = {
 bool bpf_struct_ops_get(const void *kdata)
 {
 	struct bpf_struct_ops_value *kvalue;
+	struct bpf_struct_ops_map *st_map;
+	struct bpf_map *map;
 
 	kvalue = container_of(kdata, struct bpf_struct_ops_value, data);
+	st_map = container_of(kvalue, struct bpf_struct_ops_map, kvalue);
 
-	return refcount_inc_not_zero(&kvalue->refcnt);
+	map = __bpf_map_inc_not_zero(&st_map->map, false);
+	return !IS_ERR(map);
 }
 
-static void bpf_struct_ops_put_rcu(struct rcu_head *head)
+void bpf_struct_ops_put(const void *kdata)
 {
+	struct bpf_struct_ops_value *kvalue;
 	struct bpf_struct_ops_map *st_map;
 
-	st_map = container_of(head, struct bpf_struct_ops_map, rcu);
+	kvalue = container_of(kdata, struct bpf_struct_ops_value, data);
+	st_map = container_of(kvalue, struct bpf_struct_ops_map, kvalue);
+
 	bpf_map_put(&st_map->map);
 }
 
-void bpf_struct_ops_put(const void *kdata)
+static bool bpf_struct_ops_valid_to_reg(struct bpf_map *map)
 {
-	struct bpf_struct_ops_value *kvalue;
+	struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
 
-	kvalue = container_of(kdata, struct bpf_struct_ops_value, data);
-	if (refcount_dec_and_test(&kvalue->refcnt)) {
-		struct bpf_struct_ops_map *st_map;
+	return map->map_type == BPF_MAP_TYPE_STRUCT_OPS &&
+		map->map_flags & BPF_F_LINK &&
+		/* Pair with smp_store_release() during map_update */
+		smp_load_acquire(&st_map->kvalue.state) == BPF_STRUCT_OPS_STATE_READY;
+}
 
-		st_map = container_of(kvalue, struct bpf_struct_ops_map,
-				      kvalue);
-		/* The struct_ops's function may switch to another struct_ops.
-		 *
-		 * For example, bpf_tcp_cc_x->init() may switch to
-		 * another tcp_cc_y by calling
-		 * setsockopt(TCP_CONGESTION, "tcp_cc_y").
-		 * During the switch,  bpf_struct_ops_put(tcp_cc_x) is called
-		 * and its map->refcnt may reach 0 which then free its
-		 * trampoline image while tcp_cc_x is still running.
-		 *
-		 * Thus, a rcu grace period is needed here.
+static void bpf_struct_ops_map_link_dealloc(struct bpf_link *link)
+{
+	struct bpf_struct_ops_link *st_link;
+	struct bpf_struct_ops_map *st_map;
+
+	st_link = container_of(link, struct bpf_struct_ops_link, link);
+	st_map = (struct bpf_struct_ops_map *)
+		rcu_dereference_protected(st_link->map, true);
+	if (st_map) {
+		/* st_link->map can be NULL if
+		 * bpf_struct_ops_link_create() fails to register.
 		 */
-		call_rcu(&st_map->rcu, bpf_struct_ops_put_rcu);
+		st_map->st_ops->unreg(&st_map->kvalue.data);
+		bpf_map_put(&st_map->map);
 	}
+	kfree(st_link);
+}
+
+static void bpf_struct_ops_map_link_show_fdinfo(const struct bpf_link *link,
+					    struct seq_file *seq)
+{
+	struct bpf_struct_ops_link *st_link;
+	struct bpf_map *map;
+
+	st_link = container_of(link, struct bpf_struct_ops_link, link);
+	rcu_read_lock();
+	map = rcu_dereference(st_link->map);
+	seq_printf(seq, "map_id:\t%d\n", map->id);
+	rcu_read_unlock();
 }
+
+static int bpf_struct_ops_map_link_fill_link_info(const struct bpf_link *link,
+					       struct bpf_link_info *info)
+{
+	struct bpf_struct_ops_link *st_link;
+	struct bpf_map *map;
+
+	st_link = container_of(link, struct bpf_struct_ops_link, link);
+	rcu_read_lock();
+	map = rcu_dereference(st_link->map);
+	info->struct_ops.map_id = map->id;
+	rcu_read_unlock();
+	return 0;
+}
+
+static int bpf_struct_ops_map_link_update(struct bpf_link *link, struct bpf_map *new_map,
+					  struct bpf_map *expected_old_map)
+{
+	struct bpf_struct_ops_map *st_map, *old_st_map;
+	struct bpf_map *old_map;
+	struct bpf_struct_ops_link *st_link;
+	int err = 0;
+
+	st_link = container_of(link, struct bpf_struct_ops_link, link);
+	st_map = container_of(new_map, struct bpf_struct_ops_map, map);
+
+	if (!bpf_struct_ops_valid_to_reg(new_map))
+		return -EINVAL;
+
+	mutex_lock(&update_mutex);
+
+	old_map = rcu_dereference_protected(st_link->map, lockdep_is_held(&update_mutex));
+	if (expected_old_map && old_map != expected_old_map) {
+		err = -EPERM;
+		goto err_out;
+	}
+
+	old_st_map = container_of(old_map, struct bpf_struct_ops_map, map);
+	/* The new and old struct_ops must be the same type. */
+	if (st_map->st_ops != old_st_map->st_ops) {
+		err = -EINVAL;
+		goto err_out;
+	}
+
+	err = st_map->st_ops->update(st_map->kvalue.data, old_st_map->kvalue.data);
+	if (err)
+		goto err_out;
+
+	bpf_map_inc(new_map);
+	rcu_assign_pointer(st_link->map, new_map);
+	bpf_map_put(old_map);
+
+err_out:
+	mutex_unlock(&update_mutex);
+
+	return err;
+}
+
+static const struct bpf_link_ops bpf_struct_ops_map_lops = {
+	.dealloc = bpf_struct_ops_map_link_dealloc,
+	.show_fdinfo = bpf_struct_ops_map_link_show_fdinfo,
+	.fill_link_info = bpf_struct_ops_map_link_fill_link_info,
+	.update_map = bpf_struct_ops_map_link_update,
+};
+
+int bpf_struct_ops_link_create(union bpf_attr *attr)
+{
+	struct bpf_struct_ops_link *link = NULL;
+	struct bpf_link_primer link_primer;
+	struct bpf_struct_ops_map *st_map;
+	struct bpf_map *map;
+	int err;
+
+	map = bpf_map_get(attr->link_create.map_fd);
+	if (IS_ERR(map))
+		return PTR_ERR(map);
+
+	st_map = (struct bpf_struct_ops_map *)map;
+
+	if (!bpf_struct_ops_valid_to_reg(map)) {
+		err = -EINVAL;
+		goto err_out;
+	}
+
+	link = kzalloc(sizeof(*link), GFP_USER);
+	if (!link) {
+		err = -ENOMEM;
+		goto err_out;
+	}
+	bpf_link_init(&link->link, BPF_LINK_TYPE_STRUCT_OPS, &bpf_struct_ops_map_lops, NULL);
+
+	err = bpf_link_prime(&link->link, &link_primer);
+	if (err)
+		goto err_out;
+
+	err = st_map->st_ops->reg(st_map->kvalue.data);
+	if (err) {
+		bpf_link_cleanup(&link_primer);
+		link = NULL;
+		goto err_out;
+	}
+	RCU_INIT_POINTER(link->map, map);
+
+	return bpf_link_settle(&link_primer);
+
+err_out:
+	bpf_map_put(map);
+	kfree(link);
+	return err;
+}
+