bgpd: add 'bgp bestpath as-path multipath-relax'

Compute multipath in BGP based on AS_PATH hop count match. If the knob
is turned on, it is not required to have an exact match of AS_PATHs
(provided other multipath conditions are met, of course).

Signed-off-by: Pradosh Mohapatra <pmohapat at cumulusnetworks.com>
Reviewed-by: Dinesh G Dutt <ddutt at cumulusnetworks.com>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
diff --git a/doc/bgpd.texi b/doc/bgpd.texi
index dd37d3e..24028d6 100644
--- a/doc/bgpd.texi
+++ b/doc/bgpd.texi
@@ -124,6 +124,12 @@
 decision process.
 @end deffn
 
+@deffn {BGP} {bgp bestpath as-path multipath-relax} {}
+This command specifies that BGP decision process should consider paths
+of equal AS_PATH length candidates for multipath computation. Without
+the knob, the entire AS_PATH must match for multipath computation.
+@end deffn
+
 @node BGP route flap dampening
 @subsection BGP route flap dampening