[PATCH net-next] ipv6: Allow the l3mdev to be a loopback

[Mike Manning]

There is no way currently for an IPv6 client connect using a loopback
address in a VRF, whereas for IPv4 the loopback address can be added:

    $ sudo ip addr add dev vrfred 127.0.0.1/8
    $ sudo ip -6 addr add ::1/128 dev vrfred
    RTNETLINK answers: Cannot assign requested address

So allow ::1 to be configured on an L3 master device. In order for
this to be usable ip_route_output_flags needs to not consider ::1 to
be a link scope address (since oif == l3mdev and so it would be
dropped), and ipv6_rcv needs to consider the l3mdev to be a loopback
device so that it doesn't drop the packets.

Signed-off-by: Robert Shearman <rshea...@vyatta.att-mail.com>
---
 net/ipv6/addrconf.c  | 1 +
 net/ipv6/ip6_input.c | 3 ++-
 net/ipv6/route.c     | 3 ++-
 3 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index d4733160e6b7..bfe3ec7ecb14 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -997,6 +997,7 @@ ipv6_add_addr(struct inet6_dev *idev, struct ifa6_config 
*cfg,
        if (addr_type == IPV6_ADDR_ANY ||
            addr_type & IPV6_ADDR_MULTICAST ||
            (!(idev->dev->flags & IFF_LOOPBACK) &&
+            !netif_is_l3_master(idev->dev) &&
             addr_type & IPV6_ADDR_LOOPBACK))
                return ERR_PTR(-EADDRNOTAVAIL);
 
diff --git a/net/ipv6/ip6_input.c b/net/ipv6/ip6_input.c
index 6242682be876..96577e742afd 100644
--- a/net/ipv6/ip6_input.c
+++ b/net/ipv6/ip6_input.c
@@ -178,7 +178,8 @@ static struct sk_buff *ip6_rcv_core(struct sk_buff *skb, 
struct net_device *dev,
         */
        if ((ipv6_addr_loopback(&hdr->saddr) ||
             ipv6_addr_loopback(&hdr->daddr)) &&
-            !(dev->flags & IFF_LOOPBACK))
+           !(dev->flags & IFF_LOOPBACK) &&
+           !netif_is_l3_master(dev))
                goto err;
 
        /* RFC4291 Errata ID: 3480
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 0fa62acc923c..f36ee8a3314f 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2098,7 +2098,8 @@ struct dst_entry *ip6_route_output_flags(struct net *net, 
const struct sock *sk,
 {
        bool any_src;
 
-       if (rt6_need_strict(&fl6->daddr)) {
+       if (ipv6_addr_type(&fl6->daddr) &
+           (IPV6_ADDR_MULTICAST | IPV6_ADDR_LINKLOCAL)) {
                struct dst_entry *dst;
 
                dst = l3mdev_link_scope_lookup(net, fl6);
-- 
2.11.0