Re: [patch] NM does not completely handle default route

[Gene Czarcinski <gene czarc net>]

On Sunday 11 October 2009 14:44:06 Gene Czarcinski wrote:
> On Saturday 10 October 2009 17:56:36 Gene Czarcinski wrote:
> > 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.
> 
> Attached is a proposed patch to "correct" the default route with system
>  config (ifcfg-xxx) files.
> 
> I decided to follow the general approach used in the existing code which
> creates the "never-default" attribute for a NIC/connection.
> 
> The only changes are to ifcfg-rh/reader.c and ifcfg-rh/writer.c.  This
>  change creates a new option/parameter for the ifcfg-xxx file in
>  /etc/sysconfig/network- scripts/:  NM_NEVER_DEFAULT=xxx
> 
> On input (reader.c), if NM_NEVER_DEFAULT=yes in the ifcfg-xxx file or
> GATWAYDEV=xxx in /etc/sysconfig/network indicate that this device should
>  never have the default route then never-default is set to true, otherwise
>  it is false.
> 
> On output:
> 
> If never-default is true, then NM_NEVER_DEFAULT=yes is added/changed in the
> ifcfg-xxx file.
> 
> If never-default is false and NM_NEVER_DEFAULT= is in the ifcfg-xxx file,
>  it is changed to NM_NEVER_DEFAULT=no.
> 
> If never-default is false and NM_NEVER_DEFAULT= does not exist in the
>  ifcfg- xxx file, nothing is changed.
> 
> The GATEWAYDEV= code in reader.c remains.  However, consideration should be
> given to deleting the code since 1) it is poorly documented and 2) it is
> unnecessary with this patch.
> 
> The addition is NM_NEVER_DEFAULT= is compatible with system-config-network
> whereas GATEWAYDEV= is not compatible.

Some additional info ...

1. The patch was built against the latest NetworkManager from rawhide 
(git20091002).

2. Since this seems to work fine on F12, I thought I would give a shot at F11.  
The patch applies with no changes on the latest NetworkManager updatre 
(git20090708).

3. On F11 (as compared to F12), the update does nothing!  Not only that but 
GATEWAYDEV= does not do anything either.  I tried adding NM_NEVER_DEFAULT=yes 
manually (with vi) and it does not recognize it ... or, at least, it has no 
effect.  NM_NEVER_DEFAULT is also not set to "no" if the box is unchecked 
either.

4.  I can set the DHCP Client ID and turn ONBOOT on and of but nothing happens 
with "never-default".

5.  "never-default" does work is I change the connection to be a "private" 
connection (no available to all users).

Strange!?

Gene