Just sirious why do we need printk each 1 second (60*HZ) about possible syn-flood? It really floods dmesg. Is there something dengerous? I have suggestion to turn off printk about sending tcp cookie each 1 second.
Something like this:
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index fe193e5..5574adc 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1230,8 +1230,10 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
__u32 isn = TCP_SKB_CB(skb)->when;
#ifdef CONFIG_SYN_COOKIES
int want_cookie = 0;
+ int want_cookie_no_warn = 0;
#else
#define want_cookie 0 /* Argh, why doesn't gcc optimize this :( */
+#define want_cookie_no_warn 0
#endif
/* Never answer to SYNs send to broadcast or multicast */
@@ -1246,7 +1248,10 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
#ifdef CONFIG_SYN_COOKIES
if (sysctl_tcp_syncookies) {
want_cookie = 1;
- } else
+ if (sysctl_tcp_syncookies == 2)
+ want_cookie_no_warn = 1;
+ }
+ else
#endif
goto drop;
}
@@ -1296,6 +1301,7 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
#ifdef CONFIG_SYN_COOKIES
want_cookie = 0; /* not our kind of cookie */
+ want_cookie_no_warn = 0; /* no printk on syn flood */
#endif
tmp_ext.cookie_out_never = 0; /* false */
tmp_ext.cookie_plus = tmp_opt.cookie_plus;
@@ -1328,7 +1334,8 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
if (want_cookie) {
#ifdef CONFIG_SYN_COOKIES
- syn_flood_warning(skb);
+ if (!want_cookie_no_warn)
+ syn_flood_warning(skb);
req->cookie_ts = tmp_opt.tstamp_ok;
#endif
isn = cookie_v4_init_sequence(sk, skb, &req->mss);
--
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