From 6e91413a4050f93d2d668e62ddf10e538f906883 Mon Sep 17 00:00:00 2001
From: Keir Fraser <keir@xensource.com>
Date: Fri, 5 Oct 2007 10:31:25 +0100
Subject: [PATCH] [NW scripts] Choose alternative interface if NFSroot is used.

Allow the network bridging setup script to choose an alternative
network interface if it is determined that the root is mounted using
NFS, which is assumed to be done over the NIC serving the default
gw. In this case the prefix of the device is used to find other
devices, i.e., if eth0 is the default device an alternative device may
be an other ones starting with 'eth'.

Signed-off-by: Stefan Berger <stefanb@us.ibm.com>
---
 tools/examples/network-bridge | 36 +++++++++++++++++++++++------------
 1 file changed, 24 insertions(+), 12 deletions(-)

diff --git a/tools/examples/network-bridge b/tools/examples/network-bridge
index 5440f51c1e..c287760328 100755
--- a/tools/examples/network-bridge
+++ b/tools/examples/network-bridge
@@ -56,8 +56,32 @@ dir=$(dirname "$0")
 findCommand "$@"
 evalVariables "$@"
 
+is_network_root () {
+    local rootfs=$(awk '{ if ($1 !~ /^[ \t]*#/ && $2 == "/") { print $3; }}' /etc/mtab)
+    local rootopts=$(awk '{ if ($1 !~ /^[ \t]*#/ && $2 == "/") { print $4; }}' /etc/mtab)
+
+    [[ "$rootfs" =~ "^nfs" ]] || [[ "$rootopts" =~ "_netdev" ]] && return 0 || return 1
+}
+
+find_alt_device () {
+    local interf=$1
+    local prefix=${interf%[[:digit:]]}
+    local ifs=$(ip link show | grep " $prefix" |\
+                gawk '{ printf ("%s",substr($2,1,length($2)-1)) }' |\
+                sed s/$interf//)
+    echo "$ifs"
+}
+
 netdev=${netdev:-$(ip route list | awk '/^default / { print $NF }' |
 		   sed 's/.* dev //')}
+if is_network_root ; then
+    altdevs=$(find_alt_device $netdev)
+    for netdev in $altdevs; do break; done
+    if [ -z "$netdev" ]; then
+        [ -x /usr/bin/logger ] && /usr/bin/logger "network-bridge: bridging not supported on network root; not starting"
+        exit
+    fi
+fi
 netdev=${netdev:-eth0}
 bridge=${bridge:-${netdev}}
 antispoof=${antispoof:-no}
@@ -173,23 +197,11 @@ show_status () {
     echo '============================================================'
 }
 
-is_network_root () {
-    local rootfs=$(awk '{ if ($1 !~ /^[ \t]*#/ && $2 == "/") { print $3; }}' /etc/mtab)
-    local rootopts=$(awk '{ if ($1 !~ /^[ \t]*#/ && $2 == "/") { print $4; }}' /etc/mtab)
-
-    [[ "$rootfs" =~ "^nfs" ]] || [[ "$rootopts" =~ "_netdev" ]] && return 0 || return 1
-}
-
 op_start () {
     if [ "${bridge}" = "null" ] ; then
 	return
     fi
 
-    if is_network_root ; then
-        [ -x /usr/bin/logger ] && /usr/bin/logger "network-bridge: bridging not supported on network root; not starting"
-        return
-    fi
-
     if link_exists "$pdev"; then
         # The device is already up.
         return
-- 
2.30.2