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>
dc6456e938