[PATCH net-next 1/2] net: vrf: Add support for sends to local broadcast address

[David Ahern <dsahern@gmail.com>]

Sukumar reported that sends to the local broadcast address
(255.255.255.255) are broken. Check for the address in vrf driver
and do not redirect to the VRF device - similar to multicast
packets.

With this change sockets can use SO_BINDTODEVICE to specify an
egress interface and receive responses. Note: the egress interface
can not be a VRF device but needs to be the enslaved device.

https://bugzilla.kernel.org/show_bug.cgi?id=198521

Reported-by: Sukumar Gopalakrishnan <sukumarg1973@gmail.com>
Signed-off-by: David Ahern <dsahern@gmail.com>

---
Dave: Really this is a day 1 bug that goes back to the beginning of VRF.
IMO, backport to the 4.14 LTS kernel is sufficient; the multicast
handling for IPv4 was only complete as of the 4.12 kernel. I directed
this at net-next because it is not urgent for the 4.15 merge window.

 drivers/net/vrf.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/vrf.c b/drivers/net/vrf.c
index feb1b2e15c2e..139c61c8244a 100644
--- a/drivers/net/vrf.c
+++ b/drivers/net/vrf.c
@@ -673,8 +673,9 @@ static struct sk_buff *vrf_ip_out(struct net_device *vrf_dev,
 				  struct sock *sk,
 				  struct sk_buff *skb)
 {
-	/* don't divert multicast */
-	if (ipv4_is_multicast(ip_hdr(skb)->daddr))
+	/* don't divert multicast or local broadcast */
+	if (ipv4_is_multicast(ip_hdr(skb)->daddr) ||
+	    ipv4_is_lbcast(ip_hdr(skb)->daddr))
 		return skb;
 
 	if (qdisc_tx_is_default(vrf_dev))
-- 
2.11.0