[PATCH] net:ipv4: Packet is not forwarded when ingress interface is not configured with bc_forwarding

[Henry Shen]

When an IPv4 packet with a destination address of broadcast is received
on an ingress interface, it will not be forwarded out of the egress
interface if the ingress interface is not configured with bc_forwarding 
but the egress interface is. If both the ingress and egress interfaces
are configured with bc_forwarding, the packet can be forwarded successfully.

This patch is to be inline with Cisco's implementation that packet can be 
forwarded if ingress interface is NOT configured with bc_forwarding, 
but egress interface is.
---
 net/ipv4/route.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 02d81d79deeb..d082b199b8c6 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2101,6 +2101,8 @@ static int ip_route_input_slow(struct sk_buff *skb, 
__be32 daddr, __be32 saddr,
        struct rtable   *rth;
        struct flowi4   fl4;
        bool do_cache = true;
+       struct in_device *out_dev;
+       int             rcv_local = 0;
 
        /* IP on this device is disabled. */
 
@@ -2176,12 +2178,20 @@ static int ip_route_input_slow(struct sk_buff *skb, 
__be32 daddr, __be32 saddr,
        }
 
        if (res->type == RTN_BROADCAST) {
+               out_dev = in_dev_get(FIB_RES_DEV(*res));
+               if (!out_dev)
+                       goto out;
+
+               if (in_dev == out_dev)
+                       rcv_local = 1;
+               in_dev_put(out_dev);
                if (IN_DEV_BFORWARD(in_dev))
                        goto make_route;
                /* not do cache if bc_forwarding is enabled */
                if (IPV4_DEVCONF_ALL(net, BC_FORWARDING))
                        do_cache = false;
-               goto brd_input;
+               if (rcv_local)
+                       goto brd_input;
        }
 
        if (res->type == RTN_LOCAL) {
@@ -2197,7 +2207,8 @@ static int ip_route_input_slow(struct sk_buff *skb, 
__be32 daddr, __be32 saddr,
                goto no_route;
        }
        if (res->type != RTN_UNICAST)
-               goto martian_destination;
+               if (res->type != RTN_BROADCAST)
+                       goto martian_destination;
 
 make_route:
        err = ip_mkroute_input(skb, res, in_dev, daddr, saddr, tos, flkeys);
-- 
2.30.1