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tcp: don't include Fast Open option in SYN-ACK on pure SYN-data
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>
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parent
223ab8ffeb
commit
531c94a968
1 changed files with 8 additions and 5 deletions
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@ -255,6 +255,9 @@ bool tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
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struct tcp_fastopen_cookie valid_foc = { .len = -1 };
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bool syn_data = TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq + 1;
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if (foc->len == 0) /* Client requests a cookie */
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NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENCOOKIEREQD);
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if (!((sysctl_tcp_fastopen & TFO_SERVER_ENABLE) &&
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(syn_data || foc->len >= 0) &&
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tcp_fastopen_queue_check(sk))) {
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@ -265,7 +268,8 @@ bool tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
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if (syn_data && (sysctl_tcp_fastopen & TFO_SERVER_COOKIE_NOT_REQD))
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goto fastopen;
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if (tcp_fastopen_cookie_gen(req, skb, &valid_foc) &&
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if (foc->len >= 0 && /* Client presents or requests a cookie */
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tcp_fastopen_cookie_gen(req, skb, &valid_foc) &&
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foc->len == TCP_FASTOPEN_COOKIE_SIZE &&
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foc->len == valid_foc.len &&
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!memcmp(foc->val, valid_foc.val, foc->len)) {
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@ -284,11 +288,10 @@ bool tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
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LINUX_MIB_TCPFASTOPENPASSIVE);
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return true;
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}
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}
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NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
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} else if (foc->len > 0) /* Client presents an invalid cookie */
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NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
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NET_INC_STATS_BH(sock_net(sk), foc->len ?
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LINUX_MIB_TCPFASTOPENPASSIVEFAIL :
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LINUX_MIB_TCPFASTOPENCOOKIEREQD);
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*foc = valid_foc;
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return false;
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}
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