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, 17 insertions, 0 deletions

diff --git a/net/bridge/br_sysfs_if.c b/net/bridge/br_sysfs_if.c
index 4a3cdf8f3813..820643a3ba9c 100644
--- a/net/bridge/br_sysfs_if.c
+++ b/net/bridge/br_sysfs_if.c
@@ -143,6 +143,22 @@ static ssize_t store_flush(struct net_bridge_port *p, unsigned long v)
 }
 static BRPORT_ATTR(flush, S_IWUSR, NULL, store_flush);
 
+static ssize_t show_hairpin_mode(struct net_bridge_port *p, char *buf)
+{
+        int hairpin_mode = (p->flags & BR_HAIRPIN_MODE) ? 1 : 0;
+        return sprintf(buf, "%d\n", hairpin_mode);
+}
+static ssize_t store_hairpin_mode(struct net_bridge_port *p, unsigned long v)
+{
+        if (v)
+                p->flags |= BR_HAIRPIN_MODE;
+        else
+                p->flags &= ~BR_HAIRPIN_MODE;
+        return 0;
+}
+static BRPORT_ATTR(hairpin_mode, S_IRUGO | S_IWUSR,
+                   show_hairpin_mode, store_hairpin_mode);
+
 static struct brport_attribute *brport_attrs[] = {
         &brport_attr_path_cost,
         &brport_attr_priority,
@@ -159,6 +175,7 @@ static struct brport_attribute *brport_attrs[] = {
         &brport_attr_forward_delay_timer,
         &brport_attr_hold_timer,
         &brport_attr_flush,
+        &brport_attr_hairpin_mode,
         NULL
 };