Old AS path maching supposes thath AS number appears
only once in AS path, but that is not true. It also
contains some bugs related to AS path sets.
New code does not use any assumptions about semantic
structure of AS path. It is asymptotically slower than
the old code, but on real paths it is not significant.
It also allows '?' for matching one arbitrary AS number.
AS4 optional attribute errors were handled by session
drop (according to BGP RFC). This patch implements
error handling according to new BGP AS4 draft (*)
- ignoring invalid AS4 optional attributes.
(*) http://www.ietf.org/internet-drafts/draft-chen-rfc4893bis-02.txt
- Old MED handling was completely different from behavior
specified in RFCs - for example they havn't been propagated
to neighboring areas.
- Update tie-breaking according to RFC 4271.
- Change default value for 'default bgp_med' configuration
option according to RFC 4271.
Added real comparison of BGP routes (inspired by the Cisco one).
Default local preference and default MED are now settable.
Defined filter keywords for all BGP attributes we know.
