Subject: Re: [PATCH] [RFC] C/R: inet4 and inet6 unicast routes (v2)

From: Dan Smith <[email-masked]>
Date: Mon, 03 May 2010 07:21:02 -0700

j> The problem as i see it (with all net structures not just routes -
j> i was equally pessimistic when i saw those other net structure
j> checkpoint/restore changes) is you are faced with a herculean
j> high-maintainance effort...  You have a separate piece of code
j> which populates structures that _you_ maintain for attributes that
j> are defined elsewhere by other people.  Nobody adding a new
j> attribute that is very important to route restoration for example
j> is likely to change your code. Unless you tie the two together (so
j> changing one forces the coder to change the other).  And once
j> people deploy kernels it is hard to change. Historically (for
j> pragmatic reasons) such rich interfaces sit in user space - much
j> easier to update user space.

The benefits of doing what we can in userspace are well-understood and
arguing for doing so where it makes sense is, of course, a good idea.

However, it seems to me that the rtnl interface provides us a
reasonable layer of isolation between us and such changes.  Am I
wrong?  The rtnl messages appear to be rather generic and timeless,
and in most cases have a significant amount of flexibility with
respect to allowing advanced attributes to be ignored (which implies
taking the default).

In many other areas of C/R we're not so lucky and don't have a
well-defined interface for dumping that information out of the
kernel...

-- 
Dan Smith
IBM Linux Technology Center
email: [email-masked]