diff options
| author | Eric Dumazet <edumazet@google.com> | 2012-07-17 12:29:30 +0000 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2013-01-16 01:13:26 +0000 |
| commit | d37f92d306c41ebd908bcdef373dea512b17cafb (patch) | |
| tree | 82d27d22c8a6bbe89a02bcd9468614721a3cbea6 /net | |
| parent | 481079c4df95e11d3893b92fa4000f58e1cd713b (diff) | |
tcp: refine SYN handling in tcp_validate_incoming
[ Upstream commit e371589917011efe6ff8c7dfb4e9e81934ac5855 ]
Followup of commit 0c24604b68fc (tcp: implement RFC 5961 4.2)
As reported by Vijay Subramanian, we should send a challenge ACK
instead of a dup ack if a SYN flag is set on a packet received out of
window.
This permits the ratelimiting to work as intended, and to increase
correct SNMP counters.
Suggested-by: Vijay Subramanian <subramanian.vijay@gmail.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Vijay Subramanian <subramanian.vijay@gmail.com>
Cc: Kiran Kumar Kella <kkiran@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'net')
| -rw-r--r-- | net/ipv4/tcp_input.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 0b9d8d4d92d..de434bc4355 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -5289,8 +5289,11 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb, * an acknowledgment should be sent in reply (unless the RST * bit is set, if so drop the segment and return)". */ - if (!th->rst) + if (!th->rst) { + if (th->syn) + goto syn_challenge; tcp_send_dupack(sk, skb); + } goto discard; } @@ -5320,6 +5323,7 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb, * RFC 5691 4.2 : Send a challenge ack */ if (th->syn) { +syn_challenge: if (syn_inerr) TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS); NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSYNCHALLENGE); |