net/bridge: Add 'hairpin' port forwarding mode

This patch adds a 'hairpin' (also called 'reflective relay') mode
port configuration to the Linux Ethernet bridge kernel module.
A bridge supporting hairpin forwarding mode can send frames back
out through the port the frame was received on.

Hairpin mode is required to support basic VEPA (Virtual
Ethernet Port Aggregator) capabilities.

You can find additional information on VEPA here:
http://tech.groups.yahoo.com/group/evb/
http://www.ieee802.org/1/files/public/docs2009/new-hudson-vepa_seminar-20090514d.pdf
http://www.internet2.edu/presentations/jt2009jul/20090719-congdon.pdf

An additional patch 'bridge-utils: Add 'hairpin' port forwarding mode'
is provided to allow configuring hairpin mode from userspace tools.

Signed-off-by: Paul Congdon <paul.congdon@hp.com>
Signed-off-by: Anna Fischer <anna.fischer@hp.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 1 deletions

diff --git a/net/bridge/br_forward.c b/net/bridge/br_forward.c
index d2c27c808d3b..bc1704ac6cd9 100644
--- a/net/bridge/br_forward.c
+++ b/net/bridge/br_forward.c
@@ -22,7 +22,8 @@
 static inline int should_deliver(const struct net_bridge_port *p,
                                  const struct sk_buff *skb)
 {
-        return (skb->dev != p->dev && p->state == BR_STATE_FORWARDING);
+        return (((p->flags & BR_HAIRPIN_MODE) || skb->dev != p->dev) &&
+                p->state == BR_STATE_FORWARDING);
 }
 
 static inline unsigned packet_length(const struct sk_buff *skb)