From 5ad37d5deee1ff7150a2d0602370101de158ad86 Mon Sep 17 00:00:00 2001 From: Hannes Frederic Sowa Date: Fri, 26 Jul 2013 17:43:23 +0200 Subject: tcp: add tcp_syncookies mode to allow unconditionally generation of syncookies | If you want to test which effects syncookies have to your | network connections you can set this knob to 2 to enable | unconditionally generation of syncookies. Original idea and first implementation by Eric Dumazet. Cc: Florian Westphal Cc: David Miller Signed-off-by: Eric Dumazet Signed-off-by: Hannes Frederic Sowa Signed-off-by: David S. Miller --- net/ipv4/tcp_ipv4.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'net/ipv4/tcp_ipv4.c') diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 2a5d5c469d17..280efe5f19c1 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -890,7 +890,7 @@ bool tcp_syn_flood_action(struct sock *sk, NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPREQQFULLDROP); lopt = inet_csk(sk)->icsk_accept_queue.listen_opt; - if (!lopt->synflood_warned) { + if (!lopt->synflood_warned && sysctl_tcp_syncookies != 2) { lopt->synflood_warned = 1; pr_info("%s: Possible SYN flooding on port %d. %s. Check SNMP counters.\n", proto, ntohs(tcp_hdr(skb)->dest), msg); @@ -1462,7 +1462,8 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb) * limitations, they conserve resources and peer is * evidently real one. */ - if (inet_csk_reqsk_queue_is_full(sk) && !isn) { + if ((sysctl_tcp_syncookies == 2 || + inet_csk_reqsk_queue_is_full(sk)) && !isn) { want_cookie = tcp_syn_flood_action(sk, skb, "TCP"); if (!want_cookie) goto drop; -- cgit v1.2.3-55-g7522