From 67da22d23fa6f3324e03bcd0580b914b2e4afbf3 Mon Sep 17 00:00:00 2001 From: Yuchung Cheng Date: Thu, 19 Jul 2012 06:43:11 +0000 Subject: [PATCH] net-tcp: Fast Open client - cookie-less mode 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 Acked-by: Eric Dumazet Signed-off-by: David S. Miller --- Documentation/networking/ip-sysctl.txt | 2 ++ include/linux/tcp.h | 1 + include/net/tcp.h | 1 + net/ipv4/tcp_input.c | 8 ++++++-- net/ipv4/tcp_output.c | 6 +++++- 5 files changed, 15 insertions(+), 3 deletions(-) diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt index 03964e08818..5f3ef7f7fce 100644 --- a/Documentation/networking/ip-sysctl.txt +++ b/Documentation/networking/ip-sysctl.txt @@ -476,6 +476,8 @@ tcp_fastopen - INTEGER The values (bitmap) are: 1: Enables sending data in the opening SYN on the client + 5: Enables sending data in the opening SYN on the client regardless + of cookie availability. Default: 0 diff --git a/include/linux/tcp.h b/include/linux/tcp.h index 1edf96afab4..9febfb685c3 100644 --- a/include/linux/tcp.h +++ b/include/linux/tcp.h @@ -387,6 +387,7 @@ struct tcp_sock { u8 repair_queue; u8 do_early_retrans:1,/* Enable RFC5827 early-retransmit */ early_retrans_delayed:1, /* Delayed ER timer installed */ + syn_data:1, /* SYN includes data */ syn_fastopen:1; /* SYN includes Fast Open option */ /* RTT measurement */ diff --git a/include/net/tcp.h b/include/net/tcp.h index e07878d246a..bc7c134ec05 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -214,6 +214,7 @@ extern void tcp_time_wait(struct sock *sk, int state, int timeo); /* Bit Flags for sysctl_tcp_fastopen */ #define TFO_CLIENT_ENABLE 1 +#define TFO_CLIENT_NO_COOKIE 4 /* Data in SYN w/o cookie option */ extern struct inet_timewait_death_row tcp_death_row; diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index c49a4fc175b..e67d685a6c0 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -5650,7 +5650,7 @@ static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack, struct tcp_fastopen_cookie *cookie) { struct tcp_sock *tp = tcp_sk(sk); - struct sk_buff *data = tcp_write_queue_head(sk); + struct sk_buff *data = tp->syn_data ? tcp_write_queue_head(sk) : NULL; u16 mss = tp->rx_opt.mss_clamp; bool syn_drop; @@ -5665,6 +5665,9 @@ static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack, mss = opt.mss_clamp; } + if (!tp->syn_fastopen) /* Ignore an unsolicited cookie */ + cookie->len = -1; + /* The SYN-ACK neither has cookie nor acknowledges the data. Presumably * the remote receives only the retransmitted (regular) SYNs: either * the original SYN-data or the corresponding SYN-ACK is lost. @@ -5816,7 +5819,8 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, tcp_finish_connect(sk, skb); - if (tp->syn_fastopen && tcp_rcv_fastopen_synack(sk, skb, &foc)) + if ((tp->syn_fastopen || tp->syn_data) && + tcp_rcv_fastopen_synack(sk, skb, &foc)) return -1; if (sk->sk_write_pending || diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index c5cfd5ec318..27a32acfdb6 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -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; } -- 2.41.0