netdev - [PATCH net-next] tcp: rate limit synflood warnings further

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Date:   Sun,  9 Sep 2018 19:12:12 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     netdev@...r.kernel.org
Cc:     davem@...emloft.net, eric.dumazet@...il.com,
        Willem de Bruijn <willemb@...gle.com>
Subject: [PATCH net-next] tcp: rate limit synflood warnings further

From: Willem de Bruijn <willemb@...gle.com>

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@...gle.com>
---
 net/ipv4/tcp_input.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 62508a2f9b21..d9034073138c 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6380,8 +6380,8 @@ 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;
 }
-- 
2.19.0.rc2.392.g5ba43deb5a-goog