Re: NM does not completely handle default route

[Gene Czarcinski <gene czarc net>]

On Saturday 10 October 2009 17:32:42 Gene Czarcinski wrote:
> OK, this is a followup to a lot of my previous email about NM handling the
> default route when a system has multiple NICs.
> 
> I have closed out my BZ report for Fedora 11 as WONTFIX --
> https://bugzilla.redhat.com/show_bug.cgi?id=523875 -- and have opened a new
> report against rawhide --
>  https://bugzilla.redhat.com/show_bug.cgi?id=528281
> 
> I do not expect that this problem will be fixed in time for F12 GA but hope
> that it can be fixed post GA.
> 
> I have been poking around the NM source code mainly with grep and gedit.  I
> believe it is possible/practical to fix things with any big re-write (which
>  I believe is neither practical or desirable). [sure is a lot of code]  I
>  mainly looked at how GATEWAYDEV=, GATEWAY=, and ONBOOT= (and their
> ~/.gconf/system/networking/ counterparts) where handled.
> 
> Some characteristics/constraints --
> 
> 1.  Having a system with one or more NICs and no default route is a valid
> configuration and should (must?) be supported by NM.
> 
> 2. Regardless of having a default route or not, some connections should
>  never be the default route (the intent, I believe, of the current
>  implementation).
> 
> 3.  Having GATEWAYDEV=xxx in /etc/sysconfig/network will cause all NICs
>  other than xxx to be marked as "never-default".  This is and should
>  continue to be supported.
> 
> 4. Only if a NIC is marked as NOT for all users can I mark it for
>  "connection only" (never-default).  This needs to be fixed.  I should be
>  able to mark a NIC which is available to all users (an ifcfg-xxx system
>  configuration in /etc/sysconfig/network-scripts/) as a "connection only"
>  (never-default) NIC.
> 
> 5.  I should be able to mark a NIC as the default route device.  I think
>  this is needed for completeness but am not sure it is really required.
> 
> 6.  If two or more NICs with static IPs are configured with different
>  default route, I do not care ... this is a mis-configuration.
> 
> 7.  The problem is not really with NICs that have static IPs but with those
> that use dhcp where each dhcp server supplies a default route.

Oops ... I sent this partial message instead of saving the draft.  To continue 
...

8. system-config-network currently has a problem with GATEWAYDEV=xxx being in 
the /etc/sysconfig/network file and will delete it if you use s-c-n to change 
the NIC system configuration files.  Any solution needs to avoid this problem.
---------------------------------------------
What I propose is also something Dan mentioned ... add a new option/parameter 
to the ifcfg-xxx file.  I tried adding "FOOBARBS=yes" to the file and this is 
left alone by system-config-network and ignored by NM.  

So, I propose adding a new option/parameter such as "DEFAULTGW=yes|no" to the 
system configuration file.

Upon loading the file (in ifcfg-rh/reader.c), if DEFAULTGW=no is specified, then 
mark that connection as "never-default".

When saving the file (applying updates), if the connection is "never-default", 
then set DEFAULTGW=no.  

A small problem occurs when I am changing a connection definition for "never-
default" to allowing it for default.  For now, I propose that a connection 
which is NOT "never-default" (that is, never-default is false in 
~/.gconf/...), then we should set DEFAULTGW=? for now.

As an initial attempt at a fix, I think this may be "good enough".  Yes, having 
DEFAULTGW=yes have some meaning may be useful but ... ???.  As described, I 
think this will only involve ifcfg-rh/reader.c and ifcfg-rh/writer.c.

The patch to implement this should be fairly simple and I am going to give it 
a try.


Before I go too far on this ... any comments??

Gene