Bug#367264: mapping clause now useless; please remove

[EspeonEefi <espeoneefi@eep.dnsalias.org>]

Package: netcfg
Severity: normal

A bit of history for reference can be found in bug #340935 .

If the interface set up should be brought up upon detection by a 
hotplugging mechanism, netcfg inserts the following clause into the 
generated /etc/network/interfaces file:

# This is a list of hotpluggable network interfaces.
# They will be activated automatically by the hotplug subsystem.
mapping eth0
	script grep
	map eth0

(This is written by netcfg_write_common() in netcfg-common.c.)

Now, I believe this is cruft code left over from the old hotplugging 
system. I believe that the way it used to work was that you would have 
something like...

# This is a list of hotpluggable network interfaces.
# They will be activated automatically by the hotplug subsystem.
mapping hotplug
	script grep
	map eth0
	map eth2

Then, when the first network was hotplugged, hotplug would go

ifup eth0=hotplug

ifup would look through /etc/network/interfaces looking for the 
definition of the logical interface hotplug. It would find the mapping 
clause and would proceed to call the script named by the script 
definition with the physical interface as the argument and it would send 
the lines marked by map to its standard input. That is, it would see 
hotplug was a mapping logical interface, it would call

grep eth0

and write to grep's standard input

eth0
eth2

At this point, grep would return the line

eth0

which ifup would use then as the logical interface to bring up the 
physical eth0 as. (That is, ifup would transform ifup eth0=hotplug into 
ifup eth0=eth0.)

Note that the same thing would be done for eth2.

Note however, that upon hotplugging the second network card, physical 
interface eth1, ifup eth1=hotplug would get nothing back from grep. ifup 
would take this as a sign that eth1 should not be brought up under the 
current conditions.

(This is why the comment says that the mapping clause is there to 
contain a list of hotpluggable interfaces.)

Unfortunately, all of this was lost in the fix to shift to allow-hotplug 
to mark hotpluggable interfaces (see the bug referenced above). Now 
we're left with netcfg putting a totally useless mapping clause with an 
utterly confusing associated comment into the default installed 
/etc/network/interfaces...

-- System Information:
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