From 97e3ecd112ba45eb217cddab59f48659bc15d9d0 Mon Sep 17 00:00:00 2001 From: stephen hemminger Date: Thu, 18 Mar 2010 11:27:32 +0000 Subject: [PATCH] TCP: check min TTL on received ICMP packets This adds RFC5082 checks for TTL on received ICMP packets. It adds some security against spoofed ICMP packets disrupting GTSM protected sessions. Signed-off-by: Stephen Hemminger Signed-off-by: David S. Miller --- net/ipv4/tcp_ipv4.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 70df40980a87..f4df5f931f36 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -370,6 +370,11 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info) if (sk->sk_state == TCP_CLOSE) goto out; + if (unlikely(iph->ttl < inet_sk(sk)->min_ttl)) { + NET_INC_STATS_BH(net, LINUX_MIB_TCPMINTTLDROP); + goto out; + } + icsk = inet_csk(sk); tp = tcp_sk(sk); seq = ntohl(th->seq); -- 2.20.1