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| author | Eric Dumazet <edumazet@google.com> | 2012-07-17 16:29:30 +0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-01-11 21:07:15 +0400 |
| commit | f451931e294c83d811783799f8a6c29929fc8e85 (patch) | |
| tree | 2ea952d980f047320f2ad1358117dbb65877cc1d /net | |
| parent | d21383fcbb535f90b429279852988d675ed22d67 (diff) | |
| download | linux-f451931e294c83d811783799f8a6c29929fc8e85.tar.xz | |
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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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 2dc2e1531324..0070b9fafff4 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -5314,8 +5314,11 @@ 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; } @@ -5345,6 +5348,7 @@ 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); |