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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 <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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
Documentation/networking/ip-sysctl.txt
View File

@ -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

1
include/linux/tcp.h
View File

@ -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 */

1
include/net/tcp.h
View File

@ -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;

8
net/ipv4/tcp_input.c
View File

@ -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 ||

6
net/ipv4/tcp_output.c
View File

@ -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;
}