Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [ 63/80] tcp: refine SYN handling in tcp_validate_incoming | Date | Wed, 9 Jan 2013 12:35:55 -0800 |
| |
3.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric Dumazet <edumazet@google.com>
[ 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- net/ipv4/tcp_input.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
--- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -5314,8 +5314,11 @@ static bool tcp_validate_incoming(struct * 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; } @@ -5345,6 +5348,7 @@ static bool tcp_validate_incoming(struct * 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);
| |