Larry Finger wrote:
On 03/28/2010 12:14 PM, Nicolas de Pesloüan wrote:
Larry Finger wrote:
On 03/24/2010 02:21 PM, Michael Buesch wrote:
On Wednesday 24 March 2010 15:16:03 Larry Finger wrote:
I have modified ssb to supply a MAC address of 80:80:80:80:80:80,
rather than
What about also setting the local-assignment bit for this temporary
address?
The one remaining problem is that the interface has already been
renamed before
60-persistent-b43-mac.rules is processed. In my case, the interface
is wlan13,
not wlan0. After I manually modified 60-..., then the new address is
applied.
I'm still working on this problem.
Well, udev scripts are processed in alphabetical order. Can't you
simply run
the persistent mac rules before the persistent ifname rules?
I finally figured out the problem I was having. The address attribute
was not
being changed by the "ifconfig" call that changed the hardware
address. The fix
is to create a new environment when the hardware address and lock out
the rule
generation process when that value is detected. The new code for
/lib/udev/rules.d/65-persistent-b43-mac-generator.rules is as follows
(Note:
These files are line-wrapped here.):
#=======================================
#
# Rules file to assign a unique, permanent address to BCM43XX devices
without
# an SPROM.
#
# Copyright (c) 2010 by Calvin Walton <calvin.walton@xxxxxxxxx>
# Copyright (c) 2010 by Larry Finger <Larry.Finger@xxxxxxxxxxxx>
# skip this code if action is not add, i.e. change or remove
ACTION!="add", GOTO="persistent_b43_mac_generator_end"
# Use the value of the MAC_CHANGED environment variable to see if the
address
# has already been changed.
ENV{MAC_CHANGED}=="yes", GOTO="persistent_b43_mac_generator_end"
# Call script to get a random address - if this device previously
encountered,
# the address will already have been changed.
SUBSYSTEM=="net", ATTR{address}=="82:82:82:82:82:82",
IMPORT{program}="write_persistent_b43_mac"
# Apply the new hardware address returned by the script
SUBSYSTEM=="net", ATTR{address}=="82:82:82:82:82:82",
RUN+="/sbin/ifconfig
$env{INTERFACE} hw ether $env{MACADDRESS_NEW}"
Why do you use ifconfig hw ether instead of ip link set address ?
LABEL="persistent_b43_mac_generator_end"
#=======================================
The code for /lib/udev/write_persistent_b43_mac is as follows:
#=======================================
#!/bin/bash
# Script to Generate a random MAC address for a BCM43XX device without
# an SPROM.
#
# Copyright (c) 2010 by Calvin Walton <calvin.walton@xxxxxxxxx>
# Copyright (c) 2010 by Larry Finger <Larry.Finger@xxxxxxxxxxxx>
# Use /dev/urandom to generate the last 5 bytes of the address.
# Make the first byte 2 to avoid generating a multicast address and to
set
# the locally administered address bit.
MACADDRESS=$(/bin/dd if=/dev/urandom bs=1 count=5 2>/dev/null |
/usr/bin/od -tx1
| /usr/bin/head -1 | \
/usr/bin/cut -d' ' -f2- | /usr/bin/awk '{ print
"02:"$1":"$2":"$3":"$4":"$5 }')
A suggest the following :
- 6 bytes of randomness and force lower half of first byte to 2 if the
value does not have bit #2 set.
- sed, instead of head|cut|awk
MACADDRESS=$(/bin/dd if=/dev/random bs=1 count=6 2>/dev/null |
/usr/bin/od -tx1 |
sed -ne '1{;s/0000000 //;s/^\(.\)[014589cd]/\12/;y/ /:/;p}'
It also needs to be even as an odd value would be a broadcast address. Using
only sed instead of head|cut|awk does have merit and the randomness is increased
by 6 bits. It will take me a while to understand the sed here. Regular
expressions are not my thing.
Yes, you are right, so I need to change a few things, in order to keep the highest possible level of
randomness while ensuring the lower half of first byte is 2, 6, a or e.
dd if=/dev/random bs=1 count=6 2>/dev/null |
od -tx1 |
sed -ne '1{;s/0000000 //;
s/^\(.\)[013]/\12/;s/^\(.\)[457]/\16/;
s/^\(.\)[89b]/\1a/;s/^\(.\)[cdf]/\1e/;
y/ /:/;p}'
Translation to humain form :
# for the first line only,
# If second char is 0, 1 or 3, replace it with 2.
# If second char is 4, 5 or 7, replace it with 6.
# If second char is 8, 9 or b, replace it with a.
# If second char is c, d or f, replace it with e.
# Replace all spaces with ':'.
# print
# Print nothing for other lines, thanks to -n option.
# Define the output rules file
RULES_FILE='/etc/udev/rules.d/60-persistent-b43-mac.rules'
. /lib/udev/rule_generator.functions
# Prevent concurrent processes from modifying the file at the same time.
lock_rules_file
# Check if the rules file is writeable.
choose_rules_file
# The rule should apply for all wlan devices -s some other wireless
driver might
# be loaded first - change wlanNN to wlan*
GEN_PATH=$(echo $DEVPATH | /usr/bin/sed s/wlan[0-9]*/wlan*/)
sed should be quoted here : /usr/bin/sed -e 's/wlan[0-9]*/wlan*/'
Else, it might be fun if you happen to have a file called s/wlan7/wlan15
in current directory.
OK - I see your point. As the current directory is /lib/udev, the presence of
such a file is unlikely, but better to protect against the problem.
# Output new rule
echo "SUBSYSTEM==\"net\", DEVPATH==\"$GEN_PATH\",
ATTR{address}==\"82:82:82:82:82:82\", ENV{MAC_CHANGED}=\"yes\",
RUN+=\"/sbin/ifconfig \$env{INTERFACE} hw ether $MACADDRESS\"" >>
$RULES_FILE
If DEVPATH is "generic" (wlan*), how would you distinguish between two
broadcom NIC present in the system, both without an SPROM ?
That is covered by the /devices/pci0000:00/0000:00:0d.0/0000:04:00.0/... part of
DEVPATH. A second device on the same bridge would have ...04:01.0... and a
device on a different bridge would change some other part of the string. The
change to wlan* handles the case where the BCM43XX device is discovered first
with some configuration, and second when another device is plugged in at
discovery time.
Ok, sounds good for me. Did you had the opportunity to test with two such devices ?
Larry
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