From: Antoine Tenart atenart@kernel.org
[ Upstream commit dc6456e938e938d64ffb6383a286b2ac9790a37f ]
The skb hash comes from sk->sk_txhash when using TCP, except for some IPv6 RST packets. This is because in tcp_v6_send_reset when not in TIME_WAIT the hash is taken from sk->sk_hash, while it should come from sk->sk_txhash as those two hashes are not computed the same way.
Packetdrill script to test the above,
0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3 +0 fcntl(3, F_SETFL, O_RDWR|O_NONBLOCK) = 0 +0 connect(3, ..., ...) = -1 EINPROGRESS (Operation now in progress)
+0 > (flowlabel 0x1) S 0:0(0) <...>
// Wrong ack seq, trigger a rst. +0 < S. 0:0(0) ack 0 win 4000
// Check the flowlabel matches prior one from SYN. +0 > (flowlabel 0x1) R 0:0(0) <...>
Fixes: 9258b8b1be2e ("ipv6: tcp: send consistent autoflowlabel in RST packets") Signed-off-by: Antoine Tenart atenart@kernel.org Reviewed-by: Eric Dumazet edumazet@google.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/ipv6/tcp_ipv6.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index e4da7267ed4bd..e0706c33e5472 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -1064,7 +1064,7 @@ static void tcp_v6_send_reset(const struct sock *sk, struct sk_buff *skb) if (np->repflow) label = ip6_flowlabel(ipv6h); priority = sk->sk_priority; - txhash = sk->sk_hash; + txhash = sk->sk_txhash; } if (sk->sk_state == TCP_TIME_WAIT) { label = cpu_to_be32(inet_twsk(sk)->tw_flowlabel);