tcp: accept RST without ACK flag

commit c3ae62a (tcp: should drop incoming frames without ACK flag set) added a regression on the handling of RST messages. RST should be allowed to come even without ACK bit set. We validate the RST by checking the exact sequence, as requested by RFC 793 and 5961 3.2, in tcp_validate_incoming() Reported-by: Eric Wong <[email protected]> Signed-off-by: Eric Dumazet <[email protected]> Acked-by: Neal Cardwell <[email protected]> Tested-by: Eric Wong <[email protected]> Signed-off-by: David S. Miller <[email protected]>
josf · Jan 11, 2013 · 7b514a8 · 7b514a8
1 parent cb59c87
commit 7b514a8
Showing 1 changed file with 2 additions and 2 deletions.
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
@@ -5543,7 +5543,7 @@ int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
 	if (len < (th->doff << 2) || tcp_checksum_complete_user(sk, skb))
 		goto csum_error;
 
-	if (!th->ack)
+	if (!th->ack && !th->rst)
 		goto discard;
 
 	/*
@@ -5988,7 +5988,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 			goto discard;
 	}
 
-	if (!th->ack)
+	if (!th->ack && !th->rst)
 		goto discard;
 
 	if (!tcp_validate_incoming(sk, skb, th, 0))