[j-nsp] JunOS interop problems with RFC5549

[Brian Rak]

I'm running into an issue where JunOS will not accept BGP updates 
containing a MP_REACH_NLRI attribute with a 32 byte nexthop.  As soon as 
I send one, the session gets closed and the following logged:

rpd[16187]: bgp_read_v4_update:12111: NOTIFICATION sent to 
fe80::ae1f:6bff:fe8a:435d (External AS 64555): code 3 (Update Message 
Error) subcode 9 (error with optional attribute)
rpd[16187]: Received malformed update from fe80::ae1f:6bff:fe8a:435d 
(External AS 64555)
rpd[16187]:   Family inet-unicast, prefix 0.0.0.0/0
rpd[16187]:   Malformed Attribute MP_REACH(14) flag 0x80 length 42.

The other end of the BGP session is a Cumulus router (or a linux machine 
running FRR).  If I patch that end to only send 16 byte nexthops, JunOS 
accepts the route and seems to work just fine.

RFC5549 states:

 >   o  Length of Next Hop Address = 16 or 32
 >   o  Next Hop Address = IPv6 address of next hop (potentially followed
       by the link-local IPv6 address of the next hop).  This field is to
       be constructed as per Section 3 of [RFC2545].

It seems like JunOS does not fully respect the RFC here, and only 
accepts 16 byte next hops.

Has anyone else run into this?