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net-tcp: Fast Open client - cookie-less mode

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In trusted networks, e.g., intranet, data-center, the client does not
need to use Fast Open cookie to mitigate DoS attacks. In cookie-less
mode, sendmsg() with MSG_FASTOPEN flag will send SYN-data regardless
of cookie availability.

Signed-off-by: Yuchung Cheng <ycheng@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
2012-07-19 06:43:11 +00:00
committed by David S. Miller
parent aab4874355
commit 67da22d23f
5 changed files with 15 additions and 3 deletions
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6
net/ipv4/tcp_output.c
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@@ -2864,6 +2864,7 @@ static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
struct sk_buff *syn_data = NULL, *data;
unsigned long last_syn_loss = 0;
tp->rx_opt.mss_clamp = tp->advmss; /* If MSS is not cached */
tcp_fastopen_cache_get(sk, &tp->rx_opt.mss_clamp, &fo->cookie,
&syn_loss, &last_syn_loss);
/* Recurring FO SYN losses: revert to regular handshake temporarily */
@@ -2873,7 +2874,9 @@ static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
goto fallback;
}
if (fo->cookie.len <= 0)
if (sysctl_tcp_fastopen & TFO_CLIENT_NO_COOKIE)
fo->cookie.len = -1;
else if (fo->cookie.len <= 0)
goto fallback;
/* MSS for SYN-data is based on cached MSS and bounded by PMTU and
@@ -2916,6 +2919,7 @@ static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
fo->copied = data->len;
if (tcp_transmit_skb(sk, syn_data, 0, sk->sk_allocation) == 0) {
tp->syn_data = (fo->copied > 0);
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENACTIVE);
goto done;
}