net: vrf: Add support for sends to local broadcast address

[ Upstream commit 1e19c4d ]

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>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/net/vrf.c

@@ -674,8 +674,9 @@ 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))