Bug 741786

Created attachment 525215 [details]
patch

Description of problem:
Adding an alias entry to dhclient.conf leads to dhclient-script overwriting the a newly bound ip address with the alias address when address is configured with initscripts (untested with NetworkManager).

Version-Release number of selected component (if applicable):
dhclient-4.2.1-11.P1
iproute-2.6.38.1-4
initscripts-9.30-2

How reproducible:
Always with an alias configured in dhclient.conf
Add an entry for an alias to dhclient.conf on an interface configured for dhcp via initscripts.

Steps to Reproduce:
1. Configure an interface for dhcp in initscripts, eg: ifcfg-em1

  File: ifcfg-em1
    DEVICE=em1
    BOOTPROTO=dhcp
    ONBOOT=yes
    NM_CONTROLLED=no

  File: ifcfg-em1:0
    DEVICE=em1:0
    ONPARENT=yes
    IPADDR=192.168.100.2
    NETMASK=255.255.255.0
    NM_CONTROLLED=no

2. Add an entry for alias for the interface in dhclient.conf, eg:

  File: dhclient.conf
  alias {
    interface "em1";
    fixed-address 192.168.100.2;
    option subnet-mask 255.255.255.0;
    option broadcast-address 192.168.100.255;
  }

3. Bring the interface up: # ifup em1

  
Actual results:

  Only alias address is present on device after bind, eg:

  # ip addr show dev em1
  1: em: <BROADCAST,MULTICAST,UP,LOWER_UP> ...
    inet 192.168.100.2/24 scope global em1

Expected results:

  Both alias and newly bound address should be on link, with alias correctly labeled.

  # ip addr show dev em1
  1: em: <BROADCAST,MULTICAST,UP,LOWER_UP> ...
    inet 10.0.10.121/24 brd 255.255.255.255 scope global em1
    inet 192.168.100.2/24 brd 192.168.100.255 scope global em1:0

Additional info:

It appears that the script is performing a flush on ${interface}:0, however iproute2 will flush the device, not the alias, removing the existing bound address.

When configured with initscripts, aliases such as "${interface}:0" are created with ifconfig which uses labels to distinguish the alias address from the primary address on the interface.  To flush just the labeled address, the correct syntax is:

  # ip addr flush dev ${interface} label ${interface}:0

There appears to be numerous errors in dhclient-script with respect to aliases, with the script using the "dev ${interface}:0" syntax rather than "dev ${interface} label ${interface}:0"

In addition, there appears to be a few places where dhclient-script sets the link down when it appears to actually just wish to purge the alias address.

Also, the alias address is set without using the "broadcast ${alias_broadcast_address}" clause.

I've attached a patch to dhclient-script with some proposed fixes, including:
  1. label the alias using the ${interface}:0 label
  2. add "broadcast ${alias_broadcast_address}" clause where appropriate
  3. correct syntax of "dev ${interface}:0" clauses where appropriate
  4. replace alias link down with flush on the alias label