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authorEric Dumazet <edumazet@google.com>2012-07-17 12:29:30 +0000
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-01-11 09:03:48 -0800
commit282190eab6442da4789ae3c3037c7b19d65eaf52 (patch)
tree9ce2ae90e7978a7fd74f65bec892b8e85dd27129 /net/ipv4/tcp_input.c
parentab5c718d0fd643ba6f2112235e12ea5222f4edf3 (diff)
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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/ipv4/tcp_input.c')
-rw-r--r--net/ipv4/tcp_input.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index bf79a5a..2598822 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5214,8 +5214,11 @@ 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;
}
@@ -5245,6 +5248,7 @@ 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);