Commit 8b5ac68f authored by Kuniyuki Iwashima's avatar Kuniyuki Iwashima Committed by Alexei Starovoitov
Browse files

bpf: tcp: Handle BPF SYN Cookie in skb_steal_sock(). 



We will support arbitrary SYN Cookie with BPF.

If BPF prog validates ACK and kfunc allocates a reqsk, it will
be carried to TCP stack as skb->sk with req->syncookie 1.  Also,
the reqsk has its listener as req->rsk_listener with no refcnt
taken.

When the TCP stack looks up a socket from the skb, we steal
inet_reqsk(skb->sk)->rsk_listener in skb_steal_sock() so that
the skb will be processed in cookie_v[46]_check() with the
listener.

Note that we do not clear skb->sk and skb->destructor so that we
can carry the reqsk to cookie_v[46]_check().

Signed-off-by: default avatarKuniyuki Iwashima <kuniyu@amazon.com>
Link: https://lore.kernel.org/r/20240115205514.68364-4-kuniyu@amazon.com


Signed-off-by: default avatarMartin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 95e752b5

include/net/request_sock.h

+13 −2
Original line number Diff line number Diff line
@@ -101,10 +101,21 @@ static inline struct sock *skb_steal_sock(struct sk_buff *skb, 
	}



	*prefetched = skb_sk_is_prefetched(skb);

	if (*prefetched)

	if (*prefetched) {

#if IS_ENABLED(CONFIG_SYN_COOKIES)

		if (sk->sk_state == TCP_NEW_SYN_RECV && inet_reqsk(sk)->syncookie) {

			struct request_sock *req = inet_reqsk(sk);



			*refcounted = false;

			sk = req->rsk_listener;

			req->rsk_listener = NULL;

			return sk;

		}

#endif

		*refcounted = sk_is_refcounted(sk);

	else

	} else {

		*refcounted = true;

	}



	skb->destructor = NULL;

	skb->sk = NULL;