udev duplicates entries in 70-persistent-net.rules

[James Thomas Moon]

[SRU justification]
Without this fix, duplicate entries may render the system unbootable

[Impact]
Under certain race condition, the file /etc/udev/rules.d/70-persistent-net.rules may contain duplicate entries.

[Fix]
Verify the content of the file prior to re-writing the rule.

[Test Case]
$ rm /etc/udev/rules.d/70-persistent-net.rules
$ typeset -i I=0 && while (( I <= 20));do echo add > /sys/class/net/eth0/uevent ;((I+=1));done

Without the patch, there will be 20 identical entries in the file.

[Regression]
None expected, the modification is already in Vivid, Wily and Debian

[Original description of the problem]
After a fresh installation of 14.04, I had various troubles with the ethernet NIC. Long story short, there were duplicate entries in /etc/udev/rules.d/70-persistent-net.rules .
The 70-persistent-net.rules file has 5 entries for a 4 port NIC (Broadcom Corporation NetXtreme BCM5720 Gigabit Ethernet PCIe).

-----

    # PCI device 0x14e4:0x165f (tg3)
    SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="54:9f:35:09:8f:69", ATTR{dev_id}=="0x0", ATTR{type}=="1", KERNEL=="eth*", NAME="eth1"

    # PCI device 0x14e4:0x165f (tg3)
    SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="54:9f:35:09:8f:6b", ATTR{dev_id}=="0x0", ATTR{type}=="1", KERNEL=="eth*", NAME="eth3"

    # PCI device 0x14e4:0x165f (tg3)
    SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="54:9f:35:09:8f:68", ATTR{dev_id}=="0x0", ATTR{type}=="1", KERNEL=="eth*", NAME="eth0"

    # PCI device 0x14e4:0x165f (tg3)
    SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="54:9f:35:09:8f:6a", ATTR{dev_id}=="0x0", ATTR{type}=="1", KERNEL=="eth*", NAME="eth2"

    # this last declaration was generated by udev but overrides prior command with same ATTR{address} value.
    # PCI device 0x14e4:0x165f (tg3)
    SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="54:9f:35:09:8f:68", ATTR{dev_id}=="0x0", ATTR{type}=="1", KERNEL=="eth*", NAME="eth4"

-----

lspci shows only 4 PCI devices.

-----
$ lspci -vn | grep -A 16 -F '14e4:165f'

    01:00.0 0200: 14e4:165f
     Subsystem: 1028:1f5b
     Flags: bus master, fast devsel, latency 0, IRQ 41
     Memory at 91b30000 (64-bit, prefetchable) [size=64K]
     Memory at 91b40000 (64-bit, prefetchable) [size=64K]
     Memory at 91b50000 (64-bit, prefetchable) [size=64K]
     Expansion ROM at 91b80000 [disabled] [size=256K]
     Capabilities: [48] Power Management version 3
     Capabilities: [50] Vital Product Data
     Capabilities: [58] MSI: Enable- Count=1/8 Maskable- 64bit+
     Capabilities: [a0] MSI-X: Enable+ Count=17 Masked-
     Capabilities: [ac] Express Endpoint, MSI 00
     Capabilities: [100] Advanced Error Reporting
     Capabilities: [13c] Device Serial Number 00-00-54-9f-35-09-8f-68
     Capabilities: [150] Power Budgeting <?>
     Capabilities: [160] Virtual Channel
     Kernel driver in use: tg3
    --
    01:00.1 0200: 14e4:165f
     Subsystem: 1028:1f5b
     Flags: bus master, fast devsel, latency 0, IRQ 45
     Memory at 91b00000 (64-bit, prefetchable) [size=64K]
     Memory at 91b10000 (64-bit, prefetchable) [size=64K]
     Memory at 91b20000 (64-bit, prefetchable) [size=64K]
     Expansion ROM at 91bc0000 [disabled] [size=256K]
     Capabilities: [48] Power Management version 3
     Capabilities: [50] Vital Product Data
     Capabilities: [58] MSI: Enable- Count=1/8 Maskable- 64bit+
     Capabilities: [a0] MSI-X: Enable- Count=17 Masked-
     Capabilities: [ac] Express Endpoint, MSI 00
     Capabilities: [100] Advanced Error Reporting
     Capabilities: [13c] Device Serial Number 00-00-54-9f-35-09-8f-69
     Capabilities: [150] Power Budgeting <?>
     Capabilities: [160] Virtual Channel
     Kernel driver in use: tg3
    --
    02:00.0 0200: 14e4:165f
     Subsystem: 1028:1f5b
     Flags: bus master, fast devsel, latency 0, IRQ 40
     Memory at 91a30000 (64-bit, prefetchable) [size=64K]
     Memory at 91a40000 (64-bit, prefetchable) [size=64K]
     Memory at 91a50000 (64-bit, prefetchable) [size=64K]
     Expansion ROM at 91a80000 [disabled] [size=256K]
     Capabilities: [48] Power Management version 3
     Capabilities: [50] Vital Product Data
     Capabilities: [58] MSI: Enable- Count=1/8 Maskable- 64bit+
     Capabilities: [a0] MSI-X: Enable- Count=17 Masked-
     Capabilities: [ac] Express Endpoint, MSI 00
     Capabilities: [100] Advanced Error Reporting
     Capabilities: [13c] Device Serial Number 00-00-54-9f-35-09-8f-6a
     Capabilities: [150] Power Budgeting <?>
     Capabilities: [160] Virtual Channel
     Kernel driver in use: tg3
    --
    02:00.1 0200: 14e4:165f
     Subsystem: 1028:1f5b
     Flags: bus master, fast devsel, latency 0, IRQ 44
     Memory at 91a00000 (64-bit, prefetchable) [size=64K]
     Memory at 91a10000 (64-bit, prefetchable) [size=64K]
     Memory at 91a20000 (64-bit, prefetchable) [size=64K]
     Expansion ROM at 91ac0000 [disabled] [size=256K]
     Capabilities: [48] Power Management version 3
     Capabilities: [50] Vital Product Data
     Capabilities: [58] MSI: Enable- Count=1/8 Maskable- 64bit+
     Capabilities: [a0] MSI-X: Enable- Count=17 Masked-
     Capabilities: [ac] Express Endpoint, MSI 00
     Capabilities: [100] Advanced Error Reporting
     Capabilities: [13c] Device Serial Number 00-00-54-9f-35-09-8f-6b
     Capabilities: [150] Power Budgeting <?>
     Capabilities: [160] Virtual Channel
     Kernel driver in use: tg3

-----

Description: Ubuntu 14.04.2 LTS
Release: 14.04

[James Thomas Moon (jtm-moon-forum-user+launchpad)]

To clarify ahead of time, this bug is similar but not the same as https://bugs.launchpad.net/ubuntu/+source/biosdevname/+bug/1284043

This does appear to a form of this forum post observation http://www.linuxquestions.org/questions/linux-networking-3/etc-udev-rules-d-70-persistent-net-rules-and-%27ip-link%27-rename-946670/

[Martin Pitt (pitti)]

This got fixed in 219-6, and thus in 15.04.

[Martin Pitt (pitti)]

Uploaded to SRU review queue.

[Chris J Arges (arges)]

Hello James, or anyone else affected,

Accepted systemd into trusty-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/systemd/204-5ubuntu20.15 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, and change the tag from verification-needed to verification-done. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed. In either case, details of your testing will help us make a better decision.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance!

[Launchpad Janitor (janitor)]

This bug was fixed in the package systemd - 204-5ubuntu20.15

---------------
systemd (204-5ubuntu20.15) trusty; urgency=medium

  * Avoid writing duplicate entries in 70-persistent-net.rules by double
    checking if the new udev rule has already been written for the given
    interface. This happens if multiple add events are generated before
    the write_net_rules script returns and udevd renames the interface.
  * write_net_rules: Escape '{' and '}' characters as well, to make this work
    with busybox grep. (LP: #1470399)

 -- Louis Bouchard <email address hidden> Mon, 05 Oct 2015 12:34:41 +0200

[Chris J Arges (arges)]

The verification of the Stable Release Update for systemd has completed successfully and the package has now been released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.

[James Thomas Moon (jtm-moon-forum-user+launchpad)]

> Hello James, or anyone else affected,
> ...
> Please help us by testing this new package

I'm sorry, but the machine on which this occurred cannot be modified for this testing. And I don't have access to a machine with a similar NIC.
Thanks for fixing this. Sorry I can't help re-test this.