[Bug report] Unable to remove 'default' routes using the CLI tools

[Tony Cheneau]

Hello,

I just ran a git-bisect and can new affirm that the issue has been 
introduced with commit a2207c7beb80050671d209650aaaeba429658e49 (just 
before version 3.2.15). I joined a patch, that disable the issue for 
now, but I don't believe it should be applied to the tree, as it does 
not fix the real problem. Unfortunately, I don't have time or in-depth 
knowledge of the code to actually fix the issue properly.

Please note that I was only interested in the "route" submodule, so it 
is the only one I tested. It could also affect some other submodules 
(given previous commits seem to affect similar portions of the code in 
those others submodules).

I'd be interested to know if I'm the only one having this issue.

Regards,
Tony

P.-S.: I cc'ed Roopa, because both of us had a private email exchange 
about this topic.

Le 2013-02-05 23:43, Tony Cheneau a écrit :
> Hello,
>
> For my own purposes, I'm building a bunch of python wrappers around
> libraries exposed by CLI tools (that is the functions exposed in the
> netlink/cli directory). To be more precise, I'm using cython to glue
> the libnl C code within a python wrapper. While performing my tests, 
> I
> found out a odd behavior when playing with default routes: I could 
> not
> always remove them. To me, it qualifies as a bug, but it might be an
> intended behavior. This issue is also present with the 
> nl-route-delete
> binary, so I'll use this tool for my bug report. Finally, I must add
> that I'm using the current git tree tip.
>
> So, first step is to add multiple default routes (lines starting with
> # are indicates the command I inputted):
> # ./nl-route-add  -d default -n via=10.0.0.3,dev=eth0
> Added inet default via 10.0.0.3 dev eth0
> # ./nl-route-add  -d default -n via=10.0.0.2,dev=eth0
> Added inet default via 10.0.0.2 dev eth0
> # ./nl-route-add  -d default -n via=10.0.0.1,dev=eth0
> Added inet default via 10.0.0.1 dev eth0
>
> Then I try listing current routes:
> # ./nl-route-list|grep default
> inet default table main type unicast via 10.0.20.200 dev eth0
> inet6 default table unspec type unreachable via dev lo
>
> I find it weird enough that the route does not show up. Only the
> initial route to my default gateway shows up (it was set before I run
> any of the previous commands).
> However, if I try adding a route again, I obtain the following
> message (that would indicate that the previous commands went 
> through):
> # ./nl-route-add  -d default -n via=10.0.0.1,dev=eth0
> Error: Unable to add route: Object exists
>
> Now, this is the part that motivates me to write this bug report, if
> I try to remove the default routes using symmetrical command
> "nl-route-delete", I obtain the following:
> # ./nl-route-delete  -d default -n via=10.0.0.3,dev=eth0
> Deleted 0 routes
> # ./nl-route-delete  -d default -n via=10.0.0.2,dev=eth0
> Deleted 0 routes
> # ./nl-route-delete  -d default -n via=10.0.0.1,dev=eth0
> Deleted 0 routes
>
> However, if I remove the next-hop selector, it works (I omitted the
> part when I removed my default gateway, because I lost connection on
> this one and could not retrieve the output):
> # ./nl-route-delete -d default
> Deleted inet default table main type unicast via 10.0.0.3 dev eth0
> Deleted 1 routes
> # ./nl-route-delete -d default
> Deleted inet default table main type unicast via 10.0.0.2 dev eth0
> Deleted 1 routes
> # ./nl-route-delete -d default
> Deleted inet default table main type unicast via 10.0.0.1 dev eth0
> Deleted 1 routes
>
> It also works if I reverse the ordering when removing routes (when no
> default gateway is set):
> # ./nl-route-add  -d default -n via=10.0.0.3,dev=eth0
> Added inet default via 10.0.0.3 dev eth0
> # ./nl-route-add  -d default -n via=10.0.0.2,dev=eth0
> Added inet default via 10.0.0.2 dev eth0
> # ./nl-route-add  -d default -n via=10.0.0.1,dev=eth0
> Added inet default via 10.0.0.1 dev eth0
> # ./nl-route-delete  -d default -n via=10.0.0.1,dev=eth0
> Deleted 0 routes
> # ./nl-route-delete  -d default -n via=10.0.0.3
> Deleted inet default table main type unicast via 10.0.0.3 dev eth0
> Deleted 1 routes
> # ./nl-route-delete  -d default -n via=10.0.0.2
> Deleted inet default table main type unicast via 10.0.0.2 dev eth0
> Deleted 1 routes
> # ./nl-route-delete  -d default -n via=10.0.0.1
> Deleted inet default table main type unicast via 10.0.0.1 dev eth0
> Deleted 1 routes
>
> The same phenomena seems to occur when using IPv6 addresses.
>
> (As a side note, I wanted to add that I'm aware of the various python
> bindings existing for libnl, but, to the best of my knowledge, none 
> of
> them seems to control the netlink "route" sub-system that I need.)
>
> Regards,
> Tony Cheneau
>
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