From d9282e48c6088105a98b98153a707fdbcdbf75b1 Mon Sep 17 00:00:00 2001 From: Jamie Bainbridge Date: Mon, 14 Nov 2022 12:00:08 +1100 Subject: [PATCH] tcp: Add listening address to SYN flood message The SYN flood message prints the listening port number, but with many processes bound to the same port on different IPs, it's impossible to tell which socket is the problem. Add the listen IP address to the SYN flood message. For IPv6 use "[IP]:port" as per RFC-5952 and to provide ease of copy-paste to "ss" filters. For IPv4 use "IP:port" to match. Each protcol's "any" address and a host address now look like: Possible SYN flooding on port 0.0.0.0:9001. Possible SYN flooding on port 127.0.0.1:9001. Possible SYN flooding on port [::]:9001. Possible SYN flooding on port [fc00::1]:9001. Signed-off-by: Jamie Bainbridge Reviewed-by: Eric Dumazet Reviewed-by: Stephen Hemminger Link: https://lore.kernel.org/r/4fedab7ce54a389aeadbdc639f6b4f4988e9d2d7.1668386107.git.jamie.bainbridge@gmail.com Signed-off-by: Jakub Kicinski --- net/ipv4/tcp_input.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index d764b5854dfc..94024fdc2da1 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -6842,9 +6842,17 @@ static bool tcp_syn_flood_action(const struct sock *sk, const char *proto) __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPREQQFULLDROP); if (!queue->synflood_warned && syncookies != 2 && - xchg(&queue->synflood_warned, 1) == 0) - net_info_ratelimited("%s: Possible SYN flooding on port %d. %s. Check SNMP counters.\n", - proto, sk->sk_num, msg); + xchg(&queue->synflood_warned, 1) == 0) { + if (IS_ENABLED(CONFIG_IPV6) && sk->sk_family == AF_INET6) { + net_info_ratelimited("%s: Possible SYN flooding on port [%pI6c]:%u. %s.\n", + proto, &sk->sk_v6_rcv_saddr, + sk->sk_num, msg); + } else { + net_info_ratelimited("%s: Possible SYN flooding on port %pI4:%u. %s.\n", + proto, &sk->sk_rcv_saddr, + sk->sk_num, msg); + } + } return want_cookie; }