[mpls-linux-devel] Problem with netlink use by MPLS

[Vincent U. <vin...@im...>]

Hi,

I reported a crash in this thread:
http://sourceforge.net/mailarchive/forum.php?thread_id=3D7071062&forum_id=
=3D5051

After some debugging, we think we found the problem. Here's what's
happening:

 * tcpdump/ethereal/etc. call getifaddrs() to get the the list of
   interfaces
 * in glibc >=3D 2.3.3, getifaddrs() uses netlink to find the
   informations. It opens a netlink socket with the NETLINK_ROUTE family
   and send RTM_GETLINK and RTM_GETADDR requests for every protocol
   (AF_UNSPEC)
 * MPLS uses the NETLINK_ROUTE family and overrides the RTM_* types with
   its own types. For example, RTM_GETADDR is overrided by
   MPLS_RTM_GETILM.
 * when the kernel receives the RTM_GETADDR requests for every protocol,
   it uses the rtnelink_links[] table to find the table for each
   protocol that determines what function is called. For MPLS, this
   table is mpls_rtnetlink_table. Thus, when a RTM_GETADDR request for
   every protocol is sent, the MPLS_RTM_GETILM callback is called and
   returns some data.
 * as this data is not expected (it's not a link and it's not an
   adresse), the libc abort().

There are two problems here :
 * MPLS overrides the meaning of RTM_* when it shouldn't. I don't think
   this is easily fixable since the number of RTM_* types is limited and
   there is not enough space left for MPLS.
 * MPLS uses NETLINK_ROUTE. It should really use a new netlink family,
   for example NETLINK_MPLS. I don't think this will be hard to do. It
   probably involves copying some code from net/core/rtnetlink.c in
   net/mpls/mpls_netlink.c

We'll try to make a patch to add NETLINK_MPLS.

Vincent

--=20
Les gens heureux ne sont pas press=C3=A9s.