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tcp: don't include Fast Open option in SYN-ACK on pure SYN-data

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If a server has enabled Fast Open and it receives a pure SYN-data
packet (without a Fast Open option), it won't accept the data but it
incorrectly returns a SYN-ACK with a Fast Open cookie and also
increments the SNMP stat LINUX_MIB_TCPFASTOPENPASSIVEFAIL.

This patch makes the server include a Fast Open cookie in SYN-ACK
only if the SYN has some Fast Open option (i.e., when client
requests or presents a cookie).

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Yuchung Cheng 2015-02-09 12:35:23 -08:00 committed by David S. Miller
parent 223ab8ffeb
commit 531c94a968
1 changed files with 8 additions and 5 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

13
net/ipv4/tcp_fastopen.c
View file

@ -255,6 +255,9 @@ bool tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
struct tcp_fastopen_cookie valid_foc = { .len = -1 };
bool syn_data = TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq + 1;
if (foc->len == 0) /* Client requests a cookie */
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENCOOKIEREQD);
if (!((sysctl_tcp_fastopen & TFO_SERVER_ENABLE) &&
(syn_data || foc->len >= 0) &&
tcp_fastopen_queue_check(sk))) {
@ -265,7 +268,8 @@ bool tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
if (syn_data && (sysctl_tcp_fastopen & TFO_SERVER_COOKIE_NOT_REQD))
goto fastopen;
if (tcp_fastopen_cookie_gen(req, skb, &valid_foc) &&
if (foc->len >= 0 && /* Client presents or requests a cookie */
tcp_fastopen_cookie_gen(req, skb, &valid_foc) &&
foc->len == TCP_FASTOPEN_COOKIE_SIZE &&
foc->len == valid_foc.len &&
!memcmp(foc->val, valid_foc.val, foc->len)) {
@ -284,11 +288,10 @@ bool tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
LINUX_MIB_TCPFASTOPENPASSIVE);
return true;
}
}
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
} else if (foc->len > 0) /* Client presents an invalid cookie */
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
NET_INC_STATS_BH(sock_net(sk), foc->len ?
LINUX_MIB_TCPFASTOPENPASSIVEFAIL :
LINUX_MIB_TCPFASTOPENCOOKIEREQD);
*foc = valid_foc;
return false;
}