bpf, sockmap: convert to generic sk_msg interface

Add a generic sk_msg layer, and convert current sockmap and later
kTLS over to make use of it. While sk_buff handles network packet
representation from netdevice up to socket, sk_msg handles data
representation from application to socket layer.

This means that sk_msg framework spans across ULP users in the
kernel, and enables features such as introspection or filtering
of data with the help of BPF programs that operate on this data
structure.

Latter becomes in particular useful for kTLS where data encryption
is deferred into the kernel, and as such enabling the kernel to
perform L7 introspection and policy based on BPF for TLS connections
where the record is being encrypted after BPF has run and came to
a verdict. In order to get there, first step is to transform open
coding of scatter-gather list handling into a common core framework
that subsystems can use.

The code itself has been split and refactored into three bigger
pieces: i) the generic sk_msg API which deals with managing the
scatter gather ring, providing helpers for walking and mangling,
transferring application data from user space into it, and preparing
it for BPF pre/post-processing, ii) the plain sock map itself
where sockets can be attached to or detached from; these bits
are independent of i) which can now be used also without sock
map, and iii) the integration with plain TCP as one protocol
to be used for processing L7 application data (later this could
e.g. also be extended to other protocols like UDP). The semantics
are the same with the old sock map code and therefore no change
of user facing behavior or APIs. While pursuing this work it
also helped finding a number of bugs in the old sockmap code
that we've fixed already in earlier commits. The test_sockmap
kselftest suite passes through fine as well.

Joint work with John.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

2 files changed, 656 insertions, 0 deletions

diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile
index 7446b98661d8..58629314eae9 100644
--- a/net/ipv4/Makefile
+++ b/net/ipv4/Makefile
@@ -63,6 +63,7 @@ obj-$(CONFIG_TCP_CONG_SCALABLE) += tcp_scalable.o
 obj-$(CONFIG_TCP_CONG_LP) += tcp_lp.o
 obj-$(CONFIG_TCP_CONG_YEAH) += tcp_yeah.o
 obj-$(CONFIG_TCP_CONG_ILLINOIS) += tcp_illinois.o
+obj-$(CONFIG_NET_SOCK_MSG) += tcp_bpf.o
 obj-$(CONFIG_NETLABEL) += cipso_ipv4.o
 
 obj-$(CONFIG_XFRM) += xfrm4_policy.o xfrm4_state.o xfrm4_input.o \
diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c
new file mode 100644
index 000000000000..80debb0daf37
--- /dev/null
+++ b/net/ipv4/tcp_bpf.c
@@ -0,0 +1,655 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2017 - 2018 Covalent IO, Inc. http://covalent.io */
+
+#include <linux/skmsg.h>
+#include <linux/filter.h>
+#include <linux/bpf.h>
+#include <linux/init.h>
+#include <linux/wait.h>
+
+#include <net/inet_common.h>
+
+static bool tcp_bpf_stream_read(const struct sock *sk)
+{
+	struct sk_psock *psock;
+	bool empty = true;
+
+	rcu_read_lock();
+	psock = sk_psock(sk);
+	if (likely(psock))
+		empty = list_empty(&psock->ingress_msg);
+	rcu_read_unlock();
+	return !empty;
+}
+
+static int tcp_bpf_wait_data(struct sock *sk, struct sk_psock *psock,
+			     int flags, long timeo, int *err)
+{
+	DEFINE_WAIT_FUNC(wait, woken_wake_function);
+	int ret;
+
+	add_wait_queue(sk_sleep(sk), &wait);
+	sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk);
+	ret = sk_wait_event(sk, &timeo,
+			    !list_empty(&psock->ingress_msg) ||
+			    !skb_queue_empty(&sk->sk_receive_queue), &wait);
+	sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk);
+	remove_wait_queue(sk_sleep(sk), &wait);
+	return ret;
+}
+
+int __tcp_bpf_recvmsg(struct sock *sk, struct sk_psock *psock,
+		      struct msghdr *msg, int len)
+{
+	struct iov_iter *iter = &msg->msg_iter;
+	int i, ret, copied = 0;
+
+	while (copied != len) {
+		struct scatterlist *sge;
+		struct sk_msg *msg_rx;
+
+		msg_rx = list_first_entry_or_null(&psock->ingress_msg,
+						  struct sk_msg, list);
+		if (unlikely(!msg_rx))
+			break;
+
+		i = msg_rx->sg.start;
+		do {
+			struct page *page;
+			int copy;
+
+			sge = sk_msg_elem(msg_rx, i);
+			copy = sge->length;
+			page = sg_page(sge);
+			if (copied + copy > len)
+				copy = len - copied;
+			ret = copy_page_to_iter(page, sge->offset, copy, iter);
+			if (ret != copy) {
+				msg_rx->sg.start = i;
+				return -EFAULT;
+			}
+
+			copied += copy;
+			sge->offset += copy;
+			sge->length -= copy;
+			sk_mem_uncharge(sk, copy);
+			if (!sge->length) {
+				i++;
+				if (i == MAX_SKB_FRAGS)
+					i = 0;
+				if (!msg_rx->skb)
+					put_page(page);
+			}
+
+			if (copied == len)
+				break;
+		} while (i != msg_rx->sg.end);
+
+		msg_rx->sg.start = i;
+		if (!sge->length && msg_rx->sg.start == msg_rx->sg.end) {
+			list_del(&msg_rx->list);
+			if (msg_rx->skb)
+				consume_skb(msg_rx->skb);
+			kfree(msg_rx);
+		}
+	}
+
+	return copied;
+}
+EXPORT_SYMBOL_GPL(__tcp_bpf_recvmsg);
+
+int tcp_bpf_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
+		    int nonblock, int flags, int *addr_len)
+{
+	struct sk_psock *psock;
+	int copied, ret;
+
+	if (unlikely(flags & MSG_ERRQUEUE))
+		return inet_recv_error(sk, msg, len, addr_len);
+	if (!skb_queue_empty(&sk->sk_receive_queue))
+		return tcp_recvmsg(sk, msg, len, nonblock, flags, addr_len);
+
+	psock = sk_psock_get(sk);
+	if (unlikely(!psock))
+		return tcp_recvmsg(sk, msg, len, nonblock, flags, addr_len);
+	lock_sock(sk);
+msg_bytes_ready:
+	copied = __tcp_bpf_recvmsg(sk, psock, msg, len);
+	if (!copied) {
+		int data, err = 0;
+		long timeo;
+
+		timeo = sock_rcvtimeo(sk, nonblock);
+		data = tcp_bpf_wait_data(sk, psock, flags, timeo, &err);
+		if (data) {
+			if (skb_queue_empty(&sk->sk_receive_queue))
+				goto msg_bytes_ready;
+			release_sock(sk);
+			sk_psock_put(sk, psock);
+			return tcp_recvmsg(sk, msg, len, nonblock, flags, addr_len);
+		}
+		if (err) {
+			ret = err;
+			goto out;
+		}
+	}
+	ret = copied;
+out:
+	release_sock(sk);
+	sk_psock_put(sk, psock);
+	return ret;
+}
+
+static int bpf_tcp_ingress(struct sock *sk, struct sk_psock *psock,
+			   struct sk_msg *msg, u32 apply_bytes, int flags)
+{
+	bool apply = apply_bytes;
+	struct scatterlist *sge;
+	u32 size, copied = 0;
+	struct sk_msg *tmp;
+	int i, ret = 0;
+
+	tmp = kzalloc(sizeof(*tmp), __GFP_NOWARN | GFP_KERNEL);
+	if (unlikely(!tmp))
+		return -ENOMEM;
+
+	lock_sock(sk);
+	tmp->sg.start = msg->sg.start;
+	i = msg->sg.start;
+	do {
+		sge = sk_msg_elem(msg, i);
+		size = (apply && apply_bytes < sge->length) ?
+			apply_bytes : sge->length;
+		if (!sk_wmem_schedule(sk, size)) {
+			if (!copied)
+				ret = -ENOMEM;
+			break;
+		}
+
+		sk_mem_charge(sk, size);
+		sk_msg_xfer(tmp, msg, i, size);
+		copied += size;
+		if (sge->length)
+			get_page(sk_msg_page(tmp, i));
+		sk_msg_iter_var_next(i);
+		tmp->sg.end = i;
+		if (apply) {
+			apply_bytes -= size;
+			if (!apply_bytes)
+				break;
+		}
+	} while (i != msg->sg.end);
+
+	if (!ret) {
+		msg->sg.start = i;
+		msg->sg.size -= apply_bytes;
+		sk_psock_queue_msg(psock, tmp);
+		sk->sk_data_ready(sk);
+	} else {
+		sk_msg_free(sk, tmp);
+		kfree(tmp);
+	}
+
+	release_sock(sk);
+	return ret;
+}
+
+static int tcp_bpf_push(struct sock *sk, struct sk_msg *msg, u32 apply_bytes,
+			int flags, bool uncharge)
+{
+	bool apply = apply_bytes;
+	struct scatterlist *sge;
+	struct page *page;
+	int size, ret = 0;
+	u32 off;
+
+	while (1) {
+		sge = sk_msg_elem(msg, msg->sg.start);
+		size = (apply && apply_bytes < sge->length) ?
+			apply_bytes : sge->length;
+		off  = sge->offset;
+		page = sg_page(sge);
+
+		tcp_rate_check_app_limited(sk);
+retry:
+		ret = do_tcp_sendpages(sk, page, off, size, flags);
+		if (ret <= 0)
+			return ret;
+		if (apply)
+			apply_bytes -= ret;
+		msg->sg.size -= ret;
+		sge->offset += ret;
+		sge->length -= ret;
+		if (uncharge)
+			sk_mem_uncharge(sk, ret);
+		if (ret != size) {
+			size -= ret;
+			off  += ret;
+			goto retry;
+		}
+		if (!sge->length) {
+			put_page(page);
+			sk_msg_iter_next(msg, start);
+			sg_init_table(sge, 1);
+			if (msg->sg.start == msg->sg.end)
+				break;
+		}
+		if (apply && !apply_bytes)
+			break;
+	}
+
+	return 0;
+}
+
+static int tcp_bpf_push_locked(struct sock *sk, struct sk_msg *msg,
+			       u32 apply_bytes, int flags, bool uncharge)
+{
+	int ret;
+
+	lock_sock(sk);
+	ret = tcp_bpf_push(sk, msg, apply_bytes, flags, uncharge);
+	release_sock(sk);
+	return ret;
+}
+
+int tcp_bpf_sendmsg_redir(struct sock *sk, struct sk_msg *msg,
+			  u32 bytes, int flags)
+{
+	bool ingress = sk_msg_to_ingress(msg);
+	struct sk_psock *psock = sk_psock_get(sk);
+	int ret;
+
+	if (unlikely(!psock)) {
+		sk_msg_free(sk, msg);
+		return 0;
+	}
+	ret = ingress ? bpf_tcp_ingress(sk, psock, msg, bytes, flags) :
+			tcp_bpf_push_locked(sk, msg, bytes, flags, false);
+	sk_psock_put(sk, psock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(tcp_bpf_sendmsg_redir);
+
+static int tcp_bpf_send_verdict(struct sock *sk, struct sk_psock *psock,
+				struct sk_msg *msg, int *copied, int flags)
+{
+	bool cork = false, enospc = msg->sg.start == msg->sg.end;
+	struct sock *sk_redir;
+	u32 tosend;
+	int ret;
+
+more_data:
+	if (psock->eval == __SK_NONE)
+		psock->eval = sk_psock_msg_verdict(sk, psock, msg);
+
+	if (msg->cork_bytes &&
+	    msg->cork_bytes > msg->sg.size && !enospc) {
+		psock->cork_bytes = msg->cork_bytes - msg->sg.size;
+		if (!psock->cork) {
+			psock->cork = kzalloc(sizeof(*psock->cork),
+					      GFP_ATOMIC | __GFP_NOWARN);
+			if (!psock->cork)
+				return -ENOMEM;
+		}
+		memcpy(psock->cork, msg, sizeof(*msg));
+		return 0;
+	}
+
+	tosend = msg->sg.size;
+	if (psock->apply_bytes && psock->apply_bytes < tosend)
+		tosend = psock->apply_bytes;
+
+	switch (psock->eval) {
+	case __SK_PASS:
+		ret = tcp_bpf_push(sk, msg, tosend, flags, true);
+		if (unlikely(ret)) {
+			*copied -= sk_msg_free(sk, msg);
+			break;
+		}
+		sk_msg_apply_bytes(psock, tosend);
+		break;
+	case __SK_REDIRECT:
+		sk_redir = psock->sk_redir;
+		sk_msg_apply_bytes(psock, tosend);
+		if (psock->cork) {
+			cork = true;
+			psock->cork = NULL;
+		}
+		sk_msg_return(sk, msg, tosend);
+		release_sock(sk);
+		ret = tcp_bpf_sendmsg_redir(sk_redir, msg, tosend, flags);
+		lock_sock(sk);
+		if (unlikely(ret < 0)) {
+			int free = sk_msg_free_nocharge(sk, msg);
+
+			if (!cork)
+				*copied -= free;
+		}
+		if (cork) {
+			sk_msg_free(sk, msg);
+			kfree(msg);
+			msg = NULL;
+			ret = 0;
+		}
+		break;
+	case __SK_DROP:
+	default:
+		sk_msg_free_partial(sk, msg, tosend);
+		sk_msg_apply_bytes(psock, tosend);
+		*copied -= tosend;
+		return -EACCES;
+	}
+
+	if (likely(!ret)) {
+		if (!psock->apply_bytes) {
+			psock->eval =  __SK_NONE;
+			if (psock->sk_redir) {
+				sock_put(psock->sk_redir);
+				psock->sk_redir = NULL;
+			}
+		}
+		if (msg &&
+		    msg->sg.data[msg->sg.start].page_link &&
+		    msg->sg.data[msg->sg.start].length)
+			goto more_data;
+	}
+	return ret;
+}
+
+static int tcp_bpf_sendmsg(struct sock *sk, struct msghdr *msg, size_t size)
+{
+	struct sk_msg tmp, *msg_tx = NULL;
+	int flags = msg->msg_flags | MSG_NO_SHARED_FRAGS;
+	int copied = 0, err = 0;
+	struct sk_psock *psock;
+	long timeo;
+
+	psock = sk_psock_get(sk);
+	if (unlikely(!psock))
+		return tcp_sendmsg(sk, msg, size);
+
+	lock_sock(sk);
+	timeo = sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT);
+	while (msg_data_left(msg)) {
+		bool enospc = false;
+		u32 copy, osize;
+
+		if (sk->sk_err) {
+			err = -sk->sk_err;
+			goto out_err;
+		}
+
+		copy = msg_data_left(msg);
+		if (!sk_stream_memory_free(sk))
+			goto wait_for_sndbuf;
+		if (psock->cork) {
+			msg_tx = psock->cork;
+		} else {
+			msg_tx = &tmp;
+			sk_msg_init(msg_tx);
+		}
+
+		osize = msg_tx->sg.size;
+		err = sk_msg_alloc(sk, msg_tx, msg_tx->sg.size + copy, msg_tx->sg.end - 1);
+		if (err) {
+			if (err != -ENOSPC)
+				goto wait_for_memory;
+			enospc = true;
+			copy = msg_tx->sg.size - osize;
+		}
+
+		err = sk_msg_memcopy_from_iter(sk, &msg->msg_iter, msg_tx,
+					       copy);
+		if (err < 0) {
+			sk_msg_trim(sk, msg_tx, osize);
+			goto out_err;
+		}
+
+		copied += copy;
+		if (psock->cork_bytes) {
+			if (size > psock->cork_bytes)
+				psock->cork_bytes = 0;
+			else
+				psock->cork_bytes -= size;
+			if (psock->cork_bytes && !enospc)
+				goto out_err;
+			/* All cork bytes are accounted, rerun the prog. */
+			psock->eval = __SK_NONE;
+			psock->cork_bytes = 0;
+		}
+
+		err = tcp_bpf_send_verdict(sk, psock, msg_tx, &copied, flags);
+		if (unlikely(err < 0))
+			goto out_err;
+		continue;
+wait_for_sndbuf:
+		set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
+wait_for_memory:
+		err = sk_stream_wait_memory(sk, &timeo);
+		if (err) {
+			if (msg_tx && msg_tx != psock->cork)
+				sk_msg_free(sk, msg_tx);
+			goto out_err;
+		}
+	}
+out_err:
+	if (err < 0)
+		err = sk_stream_error(sk, msg->msg_flags, err);
+	release_sock(sk);
+	sk_psock_put(sk, psock);
+	return copied ? copied : err;
+}
+
+static int tcp_bpf_sendpage(struct sock *sk, struct page *page, int offset,
+			    size_t size, int flags)
+{
+	struct sk_msg tmp, *msg = NULL;
+	int err = 0, copied = 0;
+	struct sk_psock *psock;
+	bool enospc = false;
+
+	psock = sk_psock_get(sk);
+	if (unlikely(!psock))
+		return tcp_sendpage(sk, page, offset, size, flags);
+
+	lock_sock(sk);
+	if (psock->cork) {
+		msg = psock->cork;
+	} else {
+		msg = &tmp;
+		sk_msg_init(msg);
+	}
+
+	/* Catch case where ring is full and sendpage is stalled. */
+	if (unlikely(sk_msg_full(msg)))
+		goto out_err;
+
+	sk_msg_page_add(msg, page, size, offset);
+	sk_mem_charge(sk, size);
+	copied = size;
+	if (sk_msg_full(msg))
+		enospc = true;
+	if (psock->cork_bytes) {
+		if (size > psock->cork_bytes)
+			psock->cork_bytes = 0;
+		else
+			psock->cork_bytes -= size;
+		if (psock->cork_bytes && !enospc)
+			goto out_err;
+		/* All cork bytes are accounted, rerun the prog. */
+		psock->eval = __SK_NONE;
+		psock->cork_bytes = 0;
+	}
+
+	err = tcp_bpf_send_verdict(sk, psock, msg, &copied, flags);
+out_err:
+	release_sock(sk);
+	sk_psock_put(sk, psock);
+	return copied ? copied : err;
+}
+
+static void tcp_bpf_remove(struct sock *sk, struct sk_psock *psock)
+{
+	struct sk_psock_link *link;
+
+	sk_psock_cork_free(psock);
+	__sk_psock_purge_ingress_msg(psock);
+	while ((link = sk_psock_link_pop(psock))) {
+		sk_psock_unlink(sk, link);
+		sk_psock_free_link(link);
+	}
+}
+
+static void tcp_bpf_unhash(struct sock *sk)
+{
+	void (*saved_unhash)(struct sock *sk);
+	struct sk_psock *psock;
+
+	rcu_read_lock();
+	psock = sk_psock(sk);
+	if (unlikely(!psock)) {
+		rcu_read_unlock();
+		if (sk->sk_prot->unhash)
+			sk->sk_prot->unhash(sk);
+		return;
+	}
+
+	saved_unhash = psock->saved_unhash;
+	tcp_bpf_remove(sk, psock);
+	rcu_read_unlock();
+	saved_unhash(sk);
+}
+
+static void tcp_bpf_close(struct sock *sk, long timeout)
+{
+	void (*saved_close)(struct sock *sk, long timeout);
+	struct sk_psock *psock;
+
+	lock_sock(sk);
+	rcu_read_lock();
+	psock = sk_psock(sk);
+	if (unlikely(!psock)) {
+		rcu_read_unlock();
+		release_sock(sk);
+		return sk->sk_prot->close(sk, timeout);
+	}
+
+	saved_close = psock->saved_close;
+	tcp_bpf_remove(sk, psock);
+	rcu_read_unlock();
+	release_sock(sk);
+	saved_close(sk, timeout);
+}
+
+enum {
+	TCP_BPF_IPV4,
+	TCP_BPF_IPV6,
+	TCP_BPF_NUM_PROTS,
+};
+
+enum {
+	TCP_BPF_BASE,
+	TCP_BPF_TX,
+	TCP_BPF_NUM_CFGS,
+};
+
+static struct proto *tcpv6_prot_saved __read_mostly;
+static DEFINE_SPINLOCK(tcpv6_prot_lock);
+static struct proto tcp_bpf_prots[TCP_BPF_NUM_PROTS][TCP_BPF_NUM_CFGS];
+
+static void tcp_bpf_rebuild_protos(struct proto prot[TCP_BPF_NUM_CFGS],
+				   struct proto *base)
+{
+	prot[TCP_BPF_BASE]			= *base;
+	prot[TCP_BPF_BASE].unhash		= tcp_bpf_unhash;
+	prot[TCP_BPF_BASE].close		= tcp_bpf_close;
+	prot[TCP_BPF_BASE].recvmsg		= tcp_bpf_recvmsg;
+	prot[TCP_BPF_BASE].stream_memory_read	= tcp_bpf_stream_read;
+
+	prot[TCP_BPF_TX]			= prot[TCP_BPF_BASE];
+	prot[TCP_BPF_TX].sendmsg		= tcp_bpf_sendmsg;
+	prot[TCP_BPF_TX].sendpage		= tcp_bpf_sendpage;
+}
+
+static void tcp_bpf_check_v6_needs_rebuild(struct sock *sk, struct proto *ops)
+{
+	if (sk->sk_family == AF_INET6 &&
+	    unlikely(ops != smp_load_acquire(&tcpv6_prot_saved))) {
+		spin_lock_bh(&tcpv6_prot_lock);
+		if (likely(ops != tcpv6_prot_saved)) {
+			tcp_bpf_rebuild_protos(tcp_bpf_prots[TCP_BPF_IPV6], ops);
+			smp_store_release(&tcpv6_prot_saved, ops);
+		}
+		spin_unlock_bh(&tcpv6_prot_lock);
+	}
+}
+
+static int __init tcp_bpf_v4_build_proto(void)
+{
+	tcp_bpf_rebuild_protos(tcp_bpf_prots[TCP_BPF_IPV4], &tcp_prot);
+	return 0;
+}
+core_initcall(tcp_bpf_v4_build_proto);
+
+static void tcp_bpf_update_sk_prot(struct sock *sk, struct sk_psock *psock)
+{
+	int family = sk->sk_family == AF_INET6 ? TCP_BPF_IPV6 : TCP_BPF_IPV4;
+	int config = psock->progs.msg_parser   ? TCP_BPF_TX   : TCP_BPF_BASE;
+
+	sk_psock_update_proto(sk, psock, &tcp_bpf_prots[family][config]);
+}
+
+static void tcp_bpf_reinit_sk_prot(struct sock *sk, struct sk_psock *psock)
+{
+	int family = sk->sk_family == AF_INET6 ? TCP_BPF_IPV6 : TCP_BPF_IPV4;
+	int config = psock->progs.msg_parser   ? TCP_BPF_TX   : TCP_BPF_BASE;
+
+	/* Reinit occurs when program types change e.g. TCP_BPF_TX is removed
+	 * or added requiring sk_prot hook updates. We keep original saved
+	 * hooks in this case.
+	 */
+	sk->sk_prot = &tcp_bpf_prots[family][config];
+}
+
+static int tcp_bpf_assert_proto_ops(struct proto *ops)
+{
+	/* In order to avoid retpoline, we make assumptions when we call
+	 * into ops if e.g. a psock is not present. Make sure they are
+	 * indeed valid assumptions.
+	 */
+	return ops->recvmsg  == tcp_recvmsg &&
+	       ops->sendmsg  == tcp_sendmsg &&
+	       ops->sendpage == tcp_sendpage ? 0 : -ENOTSUPP;
+}
+
+void tcp_bpf_reinit(struct sock *sk)
+{
+	struct sk_psock *psock;
+
+	sock_owned_by_me(sk);
+
+	rcu_read_lock();
+	psock = sk_psock(sk);
+	tcp_bpf_reinit_sk_prot(sk, psock);
+	rcu_read_unlock();
+}
+
+int tcp_bpf_init(struct sock *sk)
+{
+	struct proto *ops = READ_ONCE(sk->sk_prot);
+	struct sk_psock *psock;
+
+	sock_owned_by_me(sk);
+
+	rcu_read_lock();
+	psock = sk_psock(sk);
+	if (unlikely(!psock || psock->sk_proto ||
+		     tcp_bpf_assert_proto_ops(ops))) {
+		rcu_read_unlock();
+		return -EINVAL;
+	}
+	tcp_bpf_check_v6_needs_rebuild(sk, ops);
+	tcp_bpf_update_sk_prot(sk, psock);
+	rcu_read_unlock();
+	return 0;
+}