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[IPv6] Fix wrong routing mechanism for Link Local IPv6 packets

Message ID MWHPR1201MB01730F7F4A6BE57ADFB92EAFCAE60@MWHPR1201MB0173.namprd12.prod.outlook.com
State Rejected, archived
Delegated to: David Miller
Headers show

Commit Message

Michael Ulmer May 16, 2017, 3:37 p.m. UTC 
Blast from the past. 10 years back Wei Dong submitted the patch found (amongst several places) here:
http://lists.openwall.net/netdev/2007/01/30/20

Problem:
I have a firewall rule that DNATs ipv6 traffic from a destination address to ::1. The route lookup gives me the Main table & forwards that DNAT'd traffic instead of sending it to local process.

Example:
Looking at this from a netfilter point of view, a client (IP of fd00::5) requests a web page at [2000::25:0:0:1]:8080. The firewall rule DNATs it to ::1 (note that I threw a -j TRACE in raw's REROUTING).
TRACE: nat:PREROUTING:rule:2 SRC=fd00::5 DST=2000::25:0:0:1
TRACE: mangle:FORWARD:rule:1 SRC=fd00::5 DST=::1

The patch is verbatim (as is the subject line for this email). Traffic DNAT'd to ::1 now goes to mangle's INPUT chain after routing decision. I'm not sure why it was removed--I'm assuming it was an accident--as I can't find a record in the mailing list archive.

Comments

David Miller May 17, 2017, 3:39 p.m. UTC | #1 
From: Michael Ulmer <mulmer@cradlepoint.com>
Date: Tue, 16 May 2017 15:37:39 +0000

> Blast from the past. 10 years back Wei Dong submitted the patch found (amongst several places) here:
> http://lists.openwall.net/netdev/2007/01/30/20
> 
> Problem:
> I have a firewall rule that DNATs ipv6 traffic from a destination address to ::1. The route lookup gives me the Main table & forwards that DNAT'd traffic instead of sending it to local process.
> 
> Example:
> Looking at this from a netfilter point of view, a client (IP of fd00::5) requests a web page at [2000::25:0:0:1]:8080. The firewall rule DNATs it to ::1 (note that I threw a -j TRACE in raw's REROUTING).
> TRACE: nat:PREROUTING:rule:2 SRC=fd00::5 DST=2000::25:0:0:1
> TRACE: mangle:FORWARD:rule:1 SRC=fd00::5 DST=::1
> 
> The patch is verbatim (as is the subject line for this
> email). Traffic DNAT'd to ::1 now goes to mangle's INPUT chain after
> routing decision. I'm not sure why it was removed--I'm assuming it
> was an accident--as I can't find a record in the mailing list
> archive.

It's not by accident, he received feedback from Yoshifuji and suggested
alternative ways to fix his problem:

http://marc.info/?l=linux-netdev&m=117020569620697&w=2

In fact, Yoshifuji stated that some of the behaviors are indeed
intentional.
diff mbox

Patch

diff --git a/gpl/kernel/linux/net/ipv6/route.c b/gpl/kernel/linux/net/ipv6/route.c
index 3809ca2..2a2563f 100644
--- a/gpl/kernel/linux/net/ipv6/route.c
+++ b/gpl/kernel/linux/net/ipv6/route.c
@@ -611,7 +611,7 @@  static int rt6_score_route(struct rt6_info *rt, int oif,
        int m;
 
        m = rt6_check_dev(rt, oif);
-       if (!m && (strict & RT6_LOOKUP_F_IFACE))
+       if (!m && (rt->rt6i_flags & RTF_CACHE) && (strict & RT6_LOOKUP_F_IFACE))
                return RT6_NUD_FAIL_HARD;
 #ifdef CONFIG_IPV6_ROUTER_PREF
        m |= IPV6_DECODE_PREF(IPV6_EXTRACT_PREF(rt->rt6i_flags)) << 2;