tcp: Change possible SYN flooding messages
"Possible SYN flooding on port xxxx " messages can fill logs on servers.
Change logic to log the message only once per listener, and add two new
SNMP counters to track :
TCPReqQFullDoCookies : number of times a SYNCOOKIE was replied to client
TCPReqQFullDrop : number of times a SYN request was dropped because
syncookies were not enabled.
Based on a prior patch from Tom Herbert, and suggestions from David.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index d1fb63f..3c9fa61 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -531,20 +531,6 @@
return tcp_v6_send_synack(sk, req, rvp);
}
-static inline void syn_flood_warning(struct sk_buff *skb)
-{
-#ifdef CONFIG_SYN_COOKIES
- if (sysctl_tcp_syncookies)
- printk(KERN_INFO
- "TCPv6: Possible SYN flooding on port %d. "
- "Sending cookies.\n", ntohs(tcp_hdr(skb)->dest));
- else
-#endif
- printk(KERN_INFO
- "TCPv6: Possible SYN flooding on port %d. "
- "Dropping request.\n", ntohs(tcp_hdr(skb)->dest));
-}
-
static void tcp_v6_reqsk_destructor(struct request_sock *req)
{
kfree_skb(inet6_rsk(req)->pktopts);
@@ -1179,11 +1165,7 @@
struct tcp_sock *tp = tcp_sk(sk);
__u32 isn = TCP_SKB_CB(skb)->when;
struct dst_entry *dst = NULL;
-#ifdef CONFIG_SYN_COOKIES
int want_cookie = 0;
-#else
-#define want_cookie 0
-#endif
if (skb->protocol == htons(ETH_P_IP))
return tcp_v4_conn_request(sk, skb);
@@ -1192,14 +1174,9 @@
goto drop;
if (inet_csk_reqsk_queue_is_full(sk) && !isn) {
- if (net_ratelimit())
- syn_flood_warning(skb);
-#ifdef CONFIG_SYN_COOKIES
- if (sysctl_tcp_syncookies)
- want_cookie = 1;
- else
-#endif
- goto drop;
+ want_cookie = tcp_syn_flood_action(sk, skb, "TCPv6");
+ if (!want_cookie)
+ goto drop;
}
if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1)
@@ -1249,9 +1226,7 @@
while (l-- > 0)
*c++ ^= *hash_location++;
-#ifdef CONFIG_SYN_COOKIES
want_cookie = 0; /* not our kind of cookie */
-#endif
tmp_ext.cookie_out_never = 0; /* false */
tmp_ext.cookie_plus = tmp_opt.cookie_plus;
} else if (!tp->rx_opt.cookie_in_always) {