RFC Bridging plan

[Warren Togami <wtogami-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

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Attached is the parser of this bridging plan.  Bridge details if parsed 
from cmdline are written to /tmp/bridge.info for later use by network 
scripts with the following behavior.  Any comments?

SYNTAX
======
bridge=<bridgename>:<ethname>
If bridge without parameters, assume bridge=br0:eth0

BASIC IDEA
==========
* When <ethname> would be configured by network scripts, instead create 
a bridge named <bridgename> then add <ethname> to that bridge.
* <bridgename> automatically inherits the MAC address of <ethname>. 
BOOTIF thus should be optionally workable.
* Then $netif becomes <bridgename> instead of <ethname> and all existing 
scripts process netroot mount via this new $netif instead of <ethname>.
* Try only the one specified <ethname> interface, do not try others.  (I 
suppose trying others in the "bridge root=dhcp" case would be possible, 
but let's get the basics working first.)
* write-ifcfg.sh writes out both ifcfg-<bridgename> and ifcfg-<ethname> 
files for later use by NetworkManager.

BOOT EXAMPLE
============
ifconfig eth0 up
brctl addbr br0
brctl setfd br0 0
brctl addif br0 eth0
dhclient br0
ifconfig br0 <parameters>
mount -t nfs server:/path /sysroot
switch_root /sysroot

ifcfg-br0 example
=================
# Generated by dracut initrd
DEVICE=br0
TYPE=Bridge
ONBOOT=yes
BOOTPROTO=dhcp
STP=off
USERCTL=no

ifcfg-eth0 example
==================
# Generated by dracut initrd
TYPE=Ethernet
DEVICE=eth0
HWADDR=52:54:00:12:34:56
ONBOOT=yes
BRIDGE=br0
USERCTL=no

Warren Togami
wtogami-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org

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From 329b0b77e7d63ebe2092111de31f471fd22a5b06 Mon Sep 17 00:00:00 2001
From: Warren Togami <wtogami-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Date: Thu, 16 Jul 2009 00:09:07 -0400
Subject: [PATCH] Bridge parsing example

---
 modules.d/40network/check           |    2 +-
 modules.d/40network/install         |    3 +-
 modules.d/40network/parse-bridge.sh |   55 +++++++++++++++++++++++++++++++++++
 3 files changed, 58 insertions(+), 2 deletions(-)
 create mode 100755 modules.d/40network/parse-bridge.sh

diff --git a/modules.d/40network/check b/modules.d/40network/check
index 79a6d97..3d45030 100755
--- a/modules.d/40network/check
+++ b/modules.d/40network/check
@@ -1,4 +1,4 @@
 #!/bin/sh
-which ip dhclient hostname >/dev/null 2>&1 || exit 1
+which ip dhclient hostname brctl >/dev/null 2>&1 || exit 1
 exit 255
 
diff --git a/modules.d/40network/install b/modules.d/40network/install
index 0b76cbd..216d203 100755
--- a/modules.d/40network/install
+++ b/modules.d/40network/install
@@ -1,5 +1,5 @@
 #!/bin/bash
-dracut_install ip dhclient hostname
+dracut_install ip dhclient hostname brctl
 # Include wired net drivers, excluding wireless
 for modname in $(find "/lib/modules/$kernel/kernel/drivers" -name '*.ko'); do
   if nm -uPA $modname | grep -q eth_type_trans; then
@@ -18,6 +18,7 @@ instmods ecb arc4
 inst_hook pre-udev 60 "$moddir/net-genrules.sh"
 inst_hook cmdline 91 "$moddir/dhcp-root.sh"
 inst_hook cmdline 99 "$moddir/parse-ip-opts.sh"
+inst_hook cmdline 98 "$moddir/parse-bridge.sh"
 inst_hook pre-pivot 10 "$moddir/kill-dhclient.sh"
 
 # TODO ifcfg config style is redhat specific, this should probably
diff --git a/modules.d/40network/parse-bridge.sh b/modules.d/40network/parse-bridge.sh
new file mode 100755
index 0000000..adc28bb
--- /dev/null
+++ b/modules.d/40network/parse-bridge.sh
@@ -0,0 +1,55 @@
+#!/bin/sh
+#
+# Format:
+#	bridge=<bridgename>:<ethname>
+#
+#	bridge without parameters assumes bridge=br0:eth0
+#
+
+# return if bridge already parsed
+[ -n "$bridgename" ] && return
+
+# Check if bridge parameter is valid 
+if getarg ip= >/dev/null ; then
+    if [ -z "$netroot" ] ; then
+	die "No netboot configured, bridge is invalid"
+    fi
+fi
+
+parsebridge() {
+    local v=${1}:
+    set --
+    while [ -n "$v" ]; do
+        set -- "$@" "${v%%:*}"
+        v=${v#*:}
+    done
+
+    unset bridgename ethname
+    case $# in
+    0)  bridgename=br0; ethname=eth0 ;;
+    1)  die "bridge= requires two parameters" ;;
+    2)  bridgename=$1; ethname=$2 ;;
+    *)  die "bridge= requires two parameters" ;;
+    esac
+}
+
+unset bridgename ethname
+
+# Simple bridge
+if getarg bridge; then
+    bridgename=br0
+    ethname=eth0
+    echo "bridgename=$bridgename" > /tmp/bridge.info
+    echo "ethname=$ethname" >> /tmp/bridge.info
+    return
+fi
+
+# Defined bridge
+bridge="$(getarg bridge=)"
+if [ -n "$bridge" ]; then
+    parsebridge "$bridge"
+    unset bridge
+    echo "bridgename=$bridgename" > /tmp/bridge.info
+    echo "ethname=$ethname" >> /tmp/bridge.info
+    return
+fi
-- 
1.6.2.5