Merge branch 'bpf-sockmap-ulp'

John Fastabend says:

====================
This series adds a BPF hook for sendmsg and senfile by using
the ULP infrastructure and sockmap. A simple pseudocode example
would be,

  // load the programs
  bpf_prog_load(SOCKMAP_TCP_MSG_PROG, BPF_PROG_TYPE_SK_MSG,
                &obj, &msg_prog);

  // lookup the sockmap
  bpf_map_msg = bpf_object__find_map_by_name(obj, "my_sock_map");

  // get fd for sockmap
  map_fd_msg = bpf_map__fd(bpf_map_msg);

  // attach program to sockmap
  bpf_prog_attach(msg_prog, map_fd_msg, BPF_SK_MSG_VERDICT, 0);

  // Add a socket 'fd' to sockmap at location 'i'
  bpf_map_update_elem(map_fd_msg, &i, fd, BPF_ANY);

After the above snippet any socket attached to the map would run
msg_prog on sendmsg and sendfile system calls.

Three additional helpers are added bpf_msg_apply_bytes(),
bpf_msg_cork_bytes(), and bpf_msg_pull_data(). With
bpf_msg_apply_bytes BPF programs can tell the infrastructure how
many bytes the given verdict should apply to. This has two cases.
First, a BPF program applies verdict to fewer bytes than in the
current sendmsg/sendfile msg this will apply the verdict to the
first N bytes of the message then run the BPF program again with
data pointers recalculated to the N+1 byte. The second case is the
BPF program applies a verdict to more bytes than the current sendmsg
or sendfile system call. In this case the infrastructure will cache
the verdict and apply it to future sendmsg/sendfile calls until the
byte limit is reached. This avoids the overhead of running BPF
programs on large payloads.

The helper bpf_msg_cork_bytes() handles a different case where
a BPF program can not reach a verdict on a msg until it receives
more bytes AND the program doesn't want to forward the packet
until it is known to be "good". The example case being a user
(albeit a dumb one probably) sends a N byte header in 1B system
calls. The BPF program can call bpf_msg_cork_bytes with the
required byte limit to reach a verdict and then the program will
only be called again once N bytes are received.

The last helper added in this series is bpf_msg_pull_data(). It
is used to pull data in for modification or reading. Similar to
how sk_pull_data() works msg_pull_data can be used to access data
not in the initial (data_start, data_end) range. For sendpage()
calls this is needed if any data is accessed because the BPF
sendpage hook initializes the data_start and data_end pointers to
zero. We do this because sendpage data is shared with the user
and can be modified during or after the BPF verdict possibly
invalidating any verdict the BPF program decides. For sendmsg
the data is already copied by the sendmsg bpf infrastructure so
we only copy the data if the user request a data range that is
not already linearized. This happens if the user requests larger
blocks of data that are not in a single scatterlist element. The
common case seems to be accessing headers which normally are
in the first scatterlist element and already linearized.

For more examples please review the sample program. There are
examples for all the actions and helpers there.

Patches 1-8 implement the above sockmap/BPF infrastructure. The
remaining patches flush out some minimal selftests and the sample
sockmap program. The sockmap sample program is the main vehicle
for testing this infrastructure and will be moved into selftests
shortly. The final patch in this series is a simple shell script
to run a set of tests. These are the tests I run after any changes
to sockmap. The next task on the list after this series is to
push those into selftests so we can avoid manually testing.

Couple notes on future items in the pipeline,

  0. move sample sockmap programs into selftests (noted above)
  1. add additional support for tcp flags, most are ignored now.
  2. add a Documentation/bpf/sockmap file with these details
  3. support stacked ULP types to allow this and ktls to cooperate
  4. Ingress flag support, redirect only supports egress here. The
     other redirect helpers support ingress and egress flags.
  5. add optimizations, I cut a few optimizations here in the
     first iteration of the code for later study/implementation

-v3 updates
  : u32 data pointers in msg_md changed to void *
  : page_address NULL check and flag verification in msg_pull_data
  : remove old note in commit msg that is no longer relevant
  : remove enum sk_msg_action its not used anywhere
  : fixup test_verifier W -> DW insn to account for data pointers
  : unintentionally dropped a smap_stop_tx() call in sockmap.c

I propagated the ACKs forward because above changes were small
one/two line changes.

-v2 updates (discussion):

Dave noticed that sendpage call was previously (in v1) running
on the data directly. This allowed users to potentially modify
the data after or during the BPF program. However doing a copy
automatically even if the data is not accessed has measurable
performance impact. So we added another helper modeled after
the existing skb_pull_data() helper to allow users to selectively
pull data from the msg. This is also useful in the sendmsg case
when users need to access data outside the first scatterlist
element or across scatterlist boundaries.

While doing this I also unified the sendmsg and sendfile handlers
a bit. Originally the sendfile call was optimized for never
touching the data. I've decided for a first submission to drop
this optimization and we can add it back later. It introduced
unnecessary complexity, at least for a first posting, for a
use case I have not entirely flushed out yet. When the use
case is deployed we can add it back if needed. Then we can
review concrete performance deltas as well on real-world
use-cases/applications.

Lastly, I reorganized the patches a bit. Now all sockmap
changes are in a single patch and each helper gets its own
patch. This, at least IMO, makes it easier to review because
sockmap changes are not spread across the patch series. On
the other hand now apply_bytes, cork_bytes logic is only
activated later in the series. But that should be OK.
====================

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

4 files changed, 343 insertions, 64 deletions

diff --git a/net/core/filter.c b/net/core/filter.c
index 33edfa8372fd..c86f03fd9ea5 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -1890,6 +1890,202 @@ static const struct bpf_func_proto bpf_sk_redirect_map_proto = {
 	.arg4_type      = ARG_ANYTHING,
 };
 
+BPF_CALL_4(bpf_msg_redirect_map, struct sk_msg_buff *, msg,
+	   struct bpf_map *, map, u32, key, u64, flags)
+{
+	/* If user passes invalid input drop the packet. */
+	if (unlikely(flags))
+		return SK_DROP;
+
+	msg->key = key;
+	msg->flags = flags;
+	msg->map = map;
+
+	return SK_PASS;
+}
+
+struct sock *do_msg_redirect_map(struct sk_msg_buff *msg)
+{
+	struct sock *sk = NULL;
+
+	if (msg->map) {
+		sk = __sock_map_lookup_elem(msg->map, msg->key);
+
+		msg->key = 0;
+		msg->map = NULL;
+	}
+
+	return sk;
+}
+
+static const struct bpf_func_proto bpf_msg_redirect_map_proto = {
+	.func           = bpf_msg_redirect_map,
+	.gpl_only       = false,
+	.ret_type       = RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+	.arg2_type      = ARG_CONST_MAP_PTR,
+	.arg3_type      = ARG_ANYTHING,
+	.arg4_type      = ARG_ANYTHING,
+};
+
+BPF_CALL_2(bpf_msg_apply_bytes, struct sk_msg_buff *, msg, u32, bytes)
+{
+	msg->apply_bytes = bytes;
+	return 0;
+}
+
+static const struct bpf_func_proto bpf_msg_apply_bytes_proto = {
+	.func           = bpf_msg_apply_bytes,
+	.gpl_only       = false,
+	.ret_type       = RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+	.arg2_type      = ARG_ANYTHING,
+};
+
+BPF_CALL_2(bpf_msg_cork_bytes, struct sk_msg_buff *, msg, u32, bytes)
+{
+	msg->cork_bytes = bytes;
+	return 0;
+}
+
+static const struct bpf_func_proto bpf_msg_cork_bytes_proto = {
+	.func           = bpf_msg_cork_bytes,
+	.gpl_only       = false,
+	.ret_type       = RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+	.arg2_type      = ARG_ANYTHING,
+};
+
+BPF_CALL_4(bpf_msg_pull_data,
+	   struct sk_msg_buff *, msg, u32, start, u32, end, u64, flags)
+{
+	unsigned int len = 0, offset = 0, copy = 0;
+	struct scatterlist *sg = msg->sg_data;
+	int first_sg, last_sg, i, shift;
+	unsigned char *p, *to, *from;
+	int bytes = end - start;
+	struct page *page;
+
+	if (unlikely(flags || end <= start))
+		return -EINVAL;
+
+	/* First find the starting scatterlist element */
+	i = msg->sg_start;
+	do {
+		len = sg[i].length;
+		offset += len;
+		if (start < offset + len)
+			break;
+		i++;
+		if (i == MAX_SKB_FRAGS)
+			i = 0;
+	} while (i != msg->sg_end);
+
+	if (unlikely(start >= offset + len))
+		return -EINVAL;
+
+	if (!msg->sg_copy[i] && bytes <= len)
+		goto out;
+
+	first_sg = i;
+
+	/* At this point we need to linearize multiple scatterlist
+	 * elements or a single shared page. Either way we need to
+	 * copy into a linear buffer exclusively owned by BPF. Then
+	 * place the buffer in the scatterlist and fixup the original
+	 * entries by removing the entries now in the linear buffer
+	 * and shifting the remaining entries. For now we do not try
+	 * to copy partial entries to avoid complexity of running out
+	 * of sg_entry slots. The downside is reading a single byte
+	 * will copy the entire sg entry.
+	 */
+	do {
+		copy += sg[i].length;
+		i++;
+		if (i == MAX_SKB_FRAGS)
+			i = 0;
+		if (bytes < copy)
+			break;
+	} while (i != msg->sg_end);
+	last_sg = i;
+
+	if (unlikely(copy < end - start))
+		return -EINVAL;
+
+	page = alloc_pages(__GFP_NOWARN | GFP_ATOMIC, get_order(copy));
+	if (unlikely(!page))
+		return -ENOMEM;
+	p = page_address(page);
+	offset = 0;
+
+	i = first_sg;
+	do {
+		from = sg_virt(&sg[i]);
+		len = sg[i].length;
+		to = p + offset;
+
+		memcpy(to, from, len);
+		offset += len;
+		sg[i].length = 0;
+		put_page(sg_page(&sg[i]));
+
+		i++;
+		if (i == MAX_SKB_FRAGS)
+			i = 0;
+	} while (i != last_sg);
+
+	sg[first_sg].length = copy;
+	sg_set_page(&sg[first_sg], page, copy, 0);
+
+	/* To repair sg ring we need to shift entries. If we only
+	 * had a single entry though we can just replace it and
+	 * be done. Otherwise walk the ring and shift the entries.
+	 */
+	shift = last_sg - first_sg - 1;
+	if (!shift)
+		goto out;
+
+	i = first_sg + 1;
+	do {
+		int move_from;
+
+		if (i + shift >= MAX_SKB_FRAGS)
+			move_from = i + shift - MAX_SKB_FRAGS;
+		else
+			move_from = i + shift;
+
+		if (move_from == msg->sg_end)
+			break;
+
+		sg[i] = sg[move_from];
+		sg[move_from].length = 0;
+		sg[move_from].page_link = 0;
+		sg[move_from].offset = 0;
+
+		i++;
+		if (i == MAX_SKB_FRAGS)
+			i = 0;
+	} while (1);
+	msg->sg_end -= shift;
+	if (msg->sg_end < 0)
+		msg->sg_end += MAX_SKB_FRAGS;
+out:
+	msg->data = sg_virt(&sg[i]) + start - offset;
+	msg->data_end = msg->data + bytes;
+
+	return 0;
+}
+
+static const struct bpf_func_proto bpf_msg_pull_data_proto = {
+	.func		= bpf_msg_pull_data,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+	.arg2_type	= ARG_ANYTHING,
+	.arg3_type	= ARG_ANYTHING,
+	.arg4_type	= ARG_ANYTHING,
+};
+
 BPF_CALL_1(bpf_get_cgroup_classid, const struct sk_buff *, skb)
 {
 	return task_get_classid(skb);
@@ -2831,7 +3027,8 @@ bool bpf_helper_changes_pkt_data(void *func)
 	    func == bpf_l3_csum_replace ||
 	    func == bpf_l4_csum_replace ||
 	    func == bpf_xdp_adjust_head ||
-	    func == bpf_xdp_adjust_meta)
+	    func == bpf_xdp_adjust_meta ||
+	    func == bpf_msg_pull_data)
 		return true;
 
 	return false;
@@ -3591,6 +3788,22 @@ static const struct bpf_func_proto *
 	}
 }
 
+static const struct bpf_func_proto *sk_msg_func_proto(enum bpf_func_id func_id)
+{
+	switch (func_id) {
+	case BPF_FUNC_msg_redirect_map:
+		return &bpf_msg_redirect_map_proto;
+	case BPF_FUNC_msg_apply_bytes:
+		return &bpf_msg_apply_bytes_proto;
+	case BPF_FUNC_msg_cork_bytes:
+		return &bpf_msg_cork_bytes_proto;
+	case BPF_FUNC_msg_pull_data:
+		return &bpf_msg_pull_data_proto;
+	default:
+		return bpf_base_func_proto(func_id);
+	}
+}
+
 static const struct bpf_func_proto *sk_skb_func_proto(enum bpf_func_id func_id)
 {
 	switch (func_id) {
@@ -3980,6 +4193,32 @@ static bool sk_skb_is_valid_access(int off, int size,
 	return bpf_skb_is_valid_access(off, size, type, info);
 }
 
+static bool sk_msg_is_valid_access(int off, int size,
+				   enum bpf_access_type type,
+				   struct bpf_insn_access_aux *info)
+{
+	if (type == BPF_WRITE)
+		return false;
+
+	switch (off) {
+	case offsetof(struct sk_msg_md, data):
+		info->reg_type = PTR_TO_PACKET;
+		break;
+	case offsetof(struct sk_msg_md, data_end):
+		info->reg_type = PTR_TO_PACKET_END;
+		break;
+	}
+
+	if (off < 0 || off >= sizeof(struct sk_msg_md))
+		return false;
+	if (off % size != 0)
+		return false;
+	if (size != sizeof(__u64))
+		return false;
+
+	return true;
+}
+
 static u32 bpf_convert_ctx_access(enum bpf_access_type type,
 				  const struct bpf_insn *si,
 				  struct bpf_insn *insn_buf,
@@ -4778,6 +5017,29 @@ static u32 sk_skb_convert_ctx_access(enum bpf_access_type type,
 	return insn - insn_buf;
 }
 
+static u32 sk_msg_convert_ctx_access(enum bpf_access_type type,
+				     const struct bpf_insn *si,
+				     struct bpf_insn *insn_buf,
+				     struct bpf_prog *prog, u32 *target_size)
+{
+	struct bpf_insn *insn = insn_buf;
+
+	switch (si->off) {
+	case offsetof(struct sk_msg_md, data):
+		*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_msg_buff, data),
+				      si->dst_reg, si->src_reg,
+				      offsetof(struct sk_msg_buff, data));
+		break;
+	case offsetof(struct sk_msg_md, data_end):
+		*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_msg_buff, data_end),
+				      si->dst_reg, si->src_reg,
+				      offsetof(struct sk_msg_buff, data_end));
+		break;
+	}
+
+	return insn - insn_buf;
+}
+
 const struct bpf_verifier_ops sk_filter_verifier_ops = {
 	.get_func_proto		= sk_filter_func_proto,
 	.is_valid_access	= sk_filter_is_valid_access,
@@ -4868,6 +5130,15 @@ const struct bpf_verifier_ops sk_skb_verifier_ops = {
 const struct bpf_prog_ops sk_skb_prog_ops = {
 };
 
+const struct bpf_verifier_ops sk_msg_verifier_ops = {
+	.get_func_proto		= sk_msg_func_proto,
+	.is_valid_access	= sk_msg_is_valid_access,
+	.convert_ctx_access	= sk_msg_convert_ctx_access,
+};
+
+const struct bpf_prog_ops sk_msg_prog_ops = {
+};
+
 int sk_detach_filter(struct sock *sk)
 {
 	int ret = -ENOENT;
diff --git a/net/core/sock.c b/net/core/sock.c
index 27f218bba43f..4f92c2910200 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2239,6 +2239,67 @@ bool sk_page_frag_refill(struct sock *sk, struct page_frag *pfrag)
 }
 EXPORT_SYMBOL(sk_page_frag_refill);
 
+int sk_alloc_sg(struct sock *sk, int len, struct scatterlist *sg,
+		int sg_start, int *sg_curr_index, unsigned int *sg_curr_size,
+		int first_coalesce)
+{
+	int sg_curr = *sg_curr_index, use = 0, rc = 0;
+	unsigned int size = *sg_curr_size;
+	struct page_frag *pfrag;
+	struct scatterlist *sge;
+
+	len -= size;
+	pfrag = sk_page_frag(sk);
+
+	while (len > 0) {
+		unsigned int orig_offset;
+
+		if (!sk_page_frag_refill(sk, pfrag)) {
+			rc = -ENOMEM;
+			goto out;
+		}
+
+		use = min_t(int, len, pfrag->size - pfrag->offset);
+
+		if (!sk_wmem_schedule(sk, use)) {
+			rc = -ENOMEM;
+			goto out;
+		}
+
+		sk_mem_charge(sk, use);
+		size += use;
+		orig_offset = pfrag->offset;
+		pfrag->offset += use;
+
+		sge = sg + sg_curr - 1;
+		if (sg_curr > first_coalesce && sg_page(sg) == pfrag->page &&
+		    sg->offset + sg->length == orig_offset) {
+			sg->length += use;
+		} else {
+			sge = sg + sg_curr;
+			sg_unmark_end(sge);
+			sg_set_page(sge, pfrag->page, use, orig_offset);
+			get_page(pfrag->page);
+			sg_curr++;
+
+			if (sg_curr == MAX_SKB_FRAGS)
+				sg_curr = 0;
+
+			if (sg_curr == sg_start) {
+				rc = -ENOSPC;
+				break;
+			}
+		}
+
+		len -= use;
+	}
+out:
+	*sg_curr_size = size;
+	*sg_curr_index = sg_curr;
+	return rc;
+}
+EXPORT_SYMBOL(sk_alloc_sg);
+
 static void __lock_sock(struct sock *sk)
 	__releases(&sk->sk_lock.slock)
 	__acquires(&sk->sk_lock.slock)
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index fb350f740f69..f90ec24c2cc8 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -994,7 +994,9 @@ new_segment:
 			get_page(page);
 			skb_fill_page_desc(skb, i, page, offset, copy);
 		}
-		skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;
+
+		if (!(flags & MSG_NO_SHARED_FRAGS))
+			skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;
 
 		skb->len += copy;
 		skb->data_len += copy;
diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index f26376e954ae..057a558ed6d7 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -87,71 +87,16 @@ static void trim_both_sgl(struct sock *sk, int target_size)
 		target_size);
 }
 
-static int alloc_sg(struct sock *sk, int len, struct scatterlist *sg,
-		    int *sg_num_elem, unsigned int *sg_size,
-		    int first_coalesce)
-{
-	struct page_frag *pfrag;
-	unsigned int size = *sg_size;
-	int num_elem = *sg_num_elem, use = 0, rc = 0;
-	struct scatterlist *sge;
-	unsigned int orig_offset;
-
-	len -= size;
-	pfrag = sk_page_frag(sk);
-
-	while (len > 0) {
-		if (!sk_page_frag_refill(sk, pfrag)) {
-			rc = -ENOMEM;
-			goto out;
-		}
-
-		use = min_t(int, len, pfrag->size - pfrag->offset);
-
-		if (!sk_wmem_schedule(sk, use)) {
-			rc = -ENOMEM;
-			goto out;
-		}
-
-		sk_mem_charge(sk, use);
-		size += use;
-		orig_offset = pfrag->offset;
-		pfrag->offset += use;
-
-		sge = sg + num_elem - 1;
-		if (num_elem > first_coalesce && sg_page(sg) == pfrag->page &&
-		    sg->offset + sg->length == orig_offset) {
-			sg->length += use;
-		} else {
-			sge++;
-			sg_unmark_end(sge);
-			sg_set_page(sge, pfrag->page, use, orig_offset);
-			get_page(pfrag->page);
-			++num_elem;
-			if (num_elem == MAX_SKB_FRAGS) {
-				rc = -ENOSPC;
-				break;
-			}
-		}
-
-		len -= use;
-	}
-	goto out;
-
-out:
-	*sg_size = size;
-	*sg_num_elem = num_elem;
-	return rc;
-}
-
 static int alloc_encrypted_sg(struct sock *sk, int len)
 {
 	struct tls_context *tls_ctx = tls_get_ctx(sk);
 	struct tls_sw_context *ctx = tls_sw_ctx(tls_ctx);
 	int rc = 0;
 
-	rc = alloc_sg(sk, len, ctx->sg_encrypted_data,
-		      &ctx->sg_encrypted_num_elem, &ctx->sg_encrypted_size, 0);
+	rc = sk_alloc_sg(sk, len,
+			 ctx->sg_encrypted_data, 0,
+			 &ctx->sg_encrypted_num_elem,
+			 &ctx->sg_encrypted_size, 0);
 
 	return rc;
 }
@@ -162,9 +107,9 @@ static int alloc_plaintext_sg(struct sock *sk, int len)
 	struct tls_sw_context *ctx = tls_sw_ctx(tls_ctx);
 	int rc = 0;
 
-	rc = alloc_sg(sk, len, ctx->sg_plaintext_data,
-		      &ctx->sg_plaintext_num_elem, &ctx->sg_plaintext_size,
-		      tls_ctx->pending_open_record_frags);
+	rc = sk_alloc_sg(sk, len, ctx->sg_plaintext_data, 0,
+			 &ctx->sg_plaintext_num_elem, &ctx->sg_plaintext_size,
+			 tls_ctx->pending_open_record_frags);
 
 	return rc;
 }