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

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Date:   Wed, 24 Jan 2018 19:37:37 -0800
From:   David Ahern <dsahern@...il.com>
To:     netdev@...r.kernel.org
Cc:     David Ahern <dsahern@...il.com>
Subject: [PATCH net-next 1/2] net: vrf: Add support for sends to local broadcast address

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@...il.com>
Signed-off-by: David Ahern <dsahern@...il.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