netdev - [PATCH] Set DF bit for IPv4 GRE tunnels with fixed TTL

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 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:	Sat, 5 Dec 2015 22:55:13 +0200
From:	Konstantin Shemyak <konstantin@...myak.com>
To:	David Miller <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	pshelar@...ira.com
Subject: [PATCH] Set DF bit for IPv4 GRE tunnels with fixed TTL

The DF bit on IPv4 GRE tunnels with fixed TTL is enforced in order
to prevent networking loops. This was the original behavior of GRE
tunnels, lost in the refactoring.

Signed-off-by: Konstantin Shemyak <konstantin@...myak.com>
---
  net/ipv4/ip_gre.c | 4 ++++
  1 file changed, 4 insertions(+)

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index 6145214..485bf27 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -679,6 +679,10 @@ static int ipgre_tunnel_ioctl(struct net_device *dev,
  		    ((p.i_flags|p.o_flags)&(GRE_VERSION|GRE_ROUTING)))
  			return -EINVAL;
  	}
+
+        if (p.iph.ttl)
+                p.iph.frag_off |= htons(IP_DF);
+
  	p.i_flags = gre_flags_to_tnl_flags(p.i_flags);
  	p.o_flags = gre_flags_to_tnl_flags(p.o_flags);

-- 
1.9.1

--
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