lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [day] [month] [year] [list]
Date:	Fri, 4 May 2012 14:04:53 -0700
From:	Stephen Hemminger <shemminger@...tta.com>
To:	Herbert Xu <herbert@...dor.apana.org.au>,
	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org
Subject: [RFC] MTU discovery not working over GRE

When using gretap, I am seeing that Path MTU discovery is not
working for packets going out over the tunnel interface. What happens
is that the driver correctly identifies the DF bit, and see IPv4
but since skb_dst(skb) is NULL, the icmp_send() ends up doing nothing.

The following fixes the problem but does not seem like the correct general
solution. IPv6 almost certainly has the same problem.
Perhaps we should just set the skb_dst() earlier (before the
MTU checks).

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index 1017460..da57bb0 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -838,8 +838,9 @@ static netdev_tx_t ipgre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev
 
 		if ((old_iph->frag_off&htons(IP_DF)) &&
 		    mtu < ntohs(old_iph->tot_len)) {
+			skb_dst_drop(skb);
+			skb_dst_set(skb, &rt->dst);
 			icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(mtu));
-			ip_rt_put(rt);
 			goto tx_error;
 		}
 	}
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Powered by blists - more mailing lists