From 7144c9ca46f092da33a4e051bbce8f973a3bd8c4 Mon Sep 17 00:00:00 2001
From: Radu Carpa <radu.carpa@cern.ch>
Date: Tue, 17 Jan 2023 18:13:37 +0100
Subject: Filter: Allow setting the 'onlink' route attribute in filters

Add static route attribute to set onlink flag for route next hop. Can be
used to build a dynamically routed IP-in-IP overlay network. Usage:

     ifname = "tunl0";
     onlink = true;
     gw = bgp_next_hop;
---
 doc/bird.sgml | 8 ++++++++
 1 file changed, 8 insertions(+)

(limited to 'doc')

diff --git a/doc/bird.sgml b/doc/bird.sgml
index 50657ebf..001fcbd4 100644
--- a/doc/bird.sgml
+++ b/doc/bird.sgml
@@ -1816,6 +1816,14 @@ Common route attributes are:
 	creation/removal. Zero is returned for routes with undefined outgoing
 	interfaces. Read-only.
 
+	<tag><label id="rta-onlink"><m/bool/ onlink</tag>
+	Onlink flag means that the specified nexthop is accessible on the
+	interface regardless of IP prefixes configured on the interface.
+	The attribute can be used to configure such next hops by first setting
+	<cf/onlink = true/ and <cf/ifname/, and then setting <cf/gw/. Possible
+	use case for setting this flag is to automatically build overlay IP-IP
+	networks on linux.
+
 	<tag><label id="rta-weight"><m/int/ weight</tag>
 	Multipath weight of route next hops. Valid values are 1-256. Reading
 	returns the weight of the first next hop, setting it sets weights of all
-- 
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