tcp: rate limit synflood warnings further

Convert pr_info to net_info_ratelimited to limit the total number of
synflood warnings.

Commit 946cedccbd73 ("tcp: Change possible SYN flooding messages")
rate limits synflood warnings to one per listener.

Workloads that open many listener sockets can still see a high rate of
log messages. Syzkaller is one frequent example.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 4c2dd9f..4cf2f7b 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6367,8 +6367,8 @@ static bool tcp_syn_flood_action(const struct sock *sk,
        if (!queue->synflood_warned &&
            net->ipv4.sysctl_tcp_syncookies != 2 &&
            xchg(&queue->synflood_warned, 1) == 0)
-               pr_info("%s: Possible SYN flooding on port %d. %s.  Check SNMP counters.\n",
-                       proto, ntohs(tcp_hdr(skb)->dest), msg);
+               net_info_ratelimited("%s: Possible SYN flooding on port %d. %s.  Check SNMP counters.\n",
+                                    proto, ntohs(tcp_hdr(skb)->dest), msg);
 
        return want_cookie;
 }