netdev - [PATCH net] ipv6: Allow IPv4-mapped address as next-hop

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Message-ID: <76e59d76-7905-bb14-43d6-d4aaba51f0f9@arista.com>
Date:   Mon, 28 Nov 2016 15:27:05 -0800
From:   Erik Nordmark <nordmark@...sta.com>
To:     "David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        James Morris <jmorris@...ei.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Patrick McHardy <kaber@...sh.net>
Cc:     netdev@...r.kernel.org, Bob Gilligan <gilligan@...sta.com>
Subject: [PATCH net] ipv6: Allow IPv4-mapped address as next-hop

Made kernel accept IPv6 routes with IPv4-mapped address as next-hop.

It is possible to configure IP interfaces with IPv4-mapped addresses, and
one can add IPv6 routes for IPv4-mapped destinations/prefixes, yet prior
to this fix the kernel returned an EINVAL when attempting to add an IPv6
route with an IPv4-mapped address as a nexthop/gateway.

RFC 4798 (a proposed standard RFC) uses IPv4-mapped addresses as nexthops,
thus in order to support that type of address configuration the kernel
needs to allow IPv4-mapped addresses as nexthops.

Signed-off-by: Erik Nordmark <nordmark@...sta.com>
Signed-off-by: Bob Gilligan <gilligan@...sta.com>"

Index: net/net/ipv6/route.c
===================================================================
--- net.orig/net/ipv6/route.c
+++ net/net/ipv6/route.c
@@ -1995,8 +1995,11 @@ static struct rt6_info *ip6_route_info_c
  			   It is very good, but in some (rare!) circumstances
  			   (SIT, PtP, NBMA NOARP links) it is handy to allow
  			   some exceptions. --ANK
+			   We allow IPv4-mapped nexthops to support RFC4798-type
+			   addressing
  			 */
-			if (!(gwa_type & IPV6_ADDR_UNICAST))
+			if (!(gwa_type & (IPV6_ADDR_UNICAST |
+					  IPV6_ADDR_MAPPED)))
  				goto out;

  			if (cfg->fc_table) {