tcp: constify tcp_syn_flood_action() socket argument

tcp_syn_flood_action() will soon be called with unlocked socket.
In order to avoid SYN flood warning being emitted multiple times,
use xchg().
Extend max_qlen_log and synflood_warned fields in struct listen_sock
to u32

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

1 files changed, 5 insertions, 4 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 67b27aee8d28..e58cbcd2f07e 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6064,7 +6064,7 @@ EXPORT_SYMBOL(inet_reqsk_alloc);
 /*
  * Return true if a syncookie should be sent
  */
-static bool tcp_syn_flood_action(struct sock *sk,
+static bool tcp_syn_flood_action(const struct sock *sk,
                                  const struct sk_buff *skb,
                                  const char *proto)
 {
@@ -6082,11 +6082,12 @@ static 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 && sysctl_tcp_syncookies != 2) {
-                lopt->synflood_warned = 1;
+        if (!lopt->synflood_warned &&
+            sysctl_tcp_syncookies != 2 &&
+            xchg(&lopt->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);
-        }
+
         return want_cookie;
 }