[cmaster-next] Bug in zebra_mpls

[Renato Westphal]

On Mon, Dec 12, 2016 at 11:18 AM, Bingen Eguzkitza <bingen at voltanet.io> wrote:
> Adding Renato too, as he might be interested in.
>
> On Mon, Dec 12, 2016 at 2:16 PM, Bingen Eguzkitza <bingen at voltanet.io>
> wrote:
>>
>> Hi,
>>
>> Fredi and Marc here found a bug that was causing Zebra to segfault. Find
>> attached a patch for it.

I'm ok with this patch in the sense that it's an useful safeguard to have.

But I can't see how this was causing a segfault to you.

NHLFE entries are never removed directly. Instead of that, we always
set the NHLFE_FLAG_DELETED flag and call lsp_processq_add(). Then the
Quagga's workqueue guarantees that lsp_process() is called before
lsp_processq_del(), which is where nhlfe_del() is called. With that
said, it's impossible to have an invalid 'lsp->best_nhlfe' pointer in
lsp_process().

There's one other case where nhlfe_del() is called directly which is
when the NHLFE_FLAG_INSTALLED flag is not set. But in this case the
NHLFE entry will never be best NHLFE entry from the corresponding LSP.

Finally, the lines introduced by your patch are not consistent in
style with the rest of code (GNU style). Please resubmit a new version
with this fixed.
-- 
Renato Westphal