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 <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 70df409..f4df5f9 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -370,6 +370,11 @@
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);