BGP: Add option 'next hop prefer global'

Add BGP channel option 'next hop prefer global' that modifies BGP
recursive next hop resolution to use global next hop IPv6 address instead
of link-local next hop IPv6 address for immediate next hop of received
routes.

1 files changed, 14 insertions, 0 deletions

diff --git a/doc/bird.sgml b/doc/bird.sgml
index 648b4a1c..3dc1e294 100644
--- a/doc/bird.sgml
+++ b/doc/bird.sgml
@@ -2911,6 +2911,20 @@ be used in explicit configuration.
 	BGP session (if acceptable), or the preferred address of an associated
 	interface.
 
+	<tag><label id="bgp-next-hop-prefer">next hop prefer global</tag>
+	Prefer global IPv6 address to link-local IPv6 address for immediate next
+	hops of received routes. For IPv6 routes, the Next Hop attribute may
+	contain both a global IP address and a link-local IP address. For IBGP
+	sessions, the global IP address is resolved (<ref id="bgp-gateway"
+	name="gateway recursive">) through an IGP routing table
+	(<ref id="bgp-igp-table" name="igp table">) to get an immediate next
+	hop. If the resulting IGP route is a direct route (i.e., the next hop is
+	a direct neighbor), then the link-local IP address from the Next Hop
+	attribute is used as the immediate next hop. This option change it to
+	use the global IP address instead. Note that even with this option
+	enabled a route may end with a link-local immediate next hop when the
+	IGP route has one. Default: disabled.
+
 	<tag><label id="bgp-gateway">gateway direct|recursive</tag>
 	For received routes, their <cf/gw/ (immediate next hop) attribute is
 	computed from received <cf/bgp_next_hop/ attribute. This option