Re: [Devil-linux-develop] Enable "nameif" to associate MAC address with correct interface name

[Heiko Z. <he...@zu...>]

Any opinions on this?

 

Heiko

 

From: Steve Ralph [mailto:Ste...@sa...] 
Sent: Tuesday, May 04, 2010 1:04 PM
To: dev...@li...
Subject: Re: [Devil-linux-develop] Enable "nameif" to associate MAC
address with correct interface name

 

Hi,

 

I have just submitted a mantis-patch for "/etc/init.d/network" that
calls nameif to name network interfaces based on MAC addresses. The call
is only made if the required "/etc/mactab" file exists and is readable.
Nameif is called on a per-interface basis after the module has been
modprob'ed into place.

 

Please note that the version of "/etc/init.d/network" that was used as a
starting point was "# $Revision: 1.44 $" which is has been patched for
interface aliases and has a higher revision number than version 1.43
that ships with DL-1.4-RC3.

 

There are two distinct but linked patches contained in the one file.
They could be separated quite easily, if required. 

 

The first patch that calls nameif/mactab is:

@@ -162,8 +163,18 @@

                     if [ "$MODULE" != "UNKNOWN" ] && [ "$MODULE" !=
"autoselect" ] ; then

                                 modprobe $MODULE $MODULE_OPTS >
/dev/null

                     fi

                 fi

+               # Using /etc/mactab (may have been created from
/etc/mactable.conf

+               #       Process IF for active Media Access Control
(Ethernet MAC) Address.

+               # Only process interfaces which DON'T have a :-_.
(Colon/dash/underscore/dot) in them.

+               #

+               if [ -r /etc/mactab ]; then

+                       if [ `expr index "$IF" ":-_."` == 0 ];   then

+                               UseIFMac=`/bin/grep --ignore-case "^$IF"
/etc/mactab`

+                               /sbin/nameif -s $UseIFMac

+                       fi

+               fi

 

 

                 if [ "$WIRELESS" = "yes" ]; then

                         setup_wireless $DEVICE

 

The format for the optional configuration file "/etc/mactab" may be
taken from my proposed "/etc/mactab.sample":

 

        #--- /etc/mactab.sample

        #

        #       Example format for /etc/mactab. 

        #       Used by nameif to name network interfaces based on MAC
addresses

        #

        eth0    00:40:f4:b8:db:2f

        eth1    00:40:f4:b8:db:2e

        eth2    00:40:f4:b8:db:2d

        #

        #--- End

 

I believe this implements standard functionality to control network
interfaces names based on MAC addresses. 

 

If implemented, this would prevent udev shuffling interface names across
a system reboot.

 

The second part of the patch introduces new functionality with the
specific aim to allow a single DL-etc-mods.tar.bz2 config to be moved
onto a cold-standby unit, and automatically receive the correct
(preconfigured) interface assignments.

 

The patch is a follows:

 

@@ -376,8 +387,16 @@

                 # if vlan tools are installed set vlan naming shema

                 #

                 test -x $VLAN && $VLAN set_name_type
VLAN_PLUS_VID_NO_PAD &> /dev/null

 

+               # if /etc/mactable.conf is readable then

+               #       extract lines for each available MAC Address we
have

+               #       and create/overwrite /etc/mactab

+               if [ -r /etc/mactable.conf ]; then

+                       MacList=`/sbin/ip addr show | /bin/grep
"link/ether" | /bin/sed "s#.*link\/ether \| brd #\|#ig" | /usr/bin/cut
-f2 -d'|'`

+                       /bin/grep -F "$MacList" /etc/mactable.conf |
/usr/bin/cut -f-2 -d'|' | /bin/sed "s#|# #" >/etc/mactab

+               fi

+

                 #

                 # physical interfaces are brought up first

                 #

                 for interface in $(cd ${CONFIG_DIR}; ls -1
${CONFIG_FILE}* 2>/dev/null | sed \

 

The key here is the use of a new "/etc/mactable.conf " config file which
is preconfigured with interface and MAC details for both the production
and the standby hardware.

 

Again, the format for the optional configuration file
"/etc/mactable.conf" may be taken from my proposed
"/etc/mactable.conf.sample":

 

        #--- /etc/mactable.conf.sample

        #

        # Interface name | MAC Address | Comment

        #

        eth0|00:40:f4:b8:db:2f| Gannet01 (Production fw) lan1

        eth1|00:40:f4:b8:db:2e| Gannet01 (Production fw) lan2

        eth2|00:40:f4:b8:db:2d| Gannet01 (Production fw) lan3

        #

        eth0|00:30:18:49:5f:08| Gannet02 (Cold Standby fw) lan1

        eth1|00:30:18:49:5f:07| Gannet02 (Cold Standby fw) lan2

        eth2|00:30:18:49:5f:06| Gannet02 (Cold Standby fw) lan3

        #

        eth0|00:11:85:10:be:f9| Hippopotamus (Development/testbed) eth0

        eth1|00:10:5a:28:51:36| Hippopotamus (Development/testbed) eth1

        eth2|00:50:04:3a:aa:5b| Hippopotamus (Development/testbed) eth2

        #

        #--- End

 

Here three systems have their interface and mac details catalogued. When
the patched "/etc/init.d/network" file is run, it extracts mac-addresses
from "/etc/mactable.conf " that match the physically identified
interfaces, and repopulates "/etc/mactab" ready for nameif to use, but
containing only details appropriate for (in the sample) "Gannet01",
"Gannet02", or "Hippopotamus".

 

If the first "/etc/mactab" patch is rejected, then the second
"/etc/mactable.conf" automatically falls, as it depends on nameif being
run against the newly created " /etc/mactab" file.

 

This will, I believe, give Stefan [ma...@en...] the ability to
have a replacement firewall on cold-standby.

 

Much of the above code must be credited to my colleague Roy Barnard.

 

Regards - Steve.

 

Stephen H F Ralph

Principal Computer Officer | Integration Team | ICT Services | Transform
Sandwell 

Sandwell MBC | Freeth Street | Oldbury | West Midlands | B69 3DE

Tel: 0121 569 3132 | Fax: 0121 569 3493

Email: ste...@sa...