tcp: add tcp_syncookies mode to allow unconditionally generation of syncookies

[~andy/linux] / net / ipv4 / tcp_ipv4.c

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 2a5d5c469d17f720ca6076fe738b541711fe876d..280efe5f19c1c86385bf8e15c146d8ac31135198 100644 (file)
--- 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;