[bird_radv] Add option to include MTU in RAs.

type/__bird_radv/man.rst

@@ -15,12 +15,17 @@ autoconfigure IPv6 hosts, this type is a rudimentary implementation to generate
 configuration for Bird to do so.
 
 
-REQUIRED MULTIPLE PARAMETERS
-----------------------------
+REQUIRED PARAMETERS
+-------------------
 interface
   The interfaces to activate the protocol on. RAs will be sent using the
   prefixes configured on these interfaces.
 
+OPTIONAL PARAMETERS
+-------------------
+mtu
+  An optional MTU setting to include in the router advertisements.
+
 
 OPTIONAL MULTIPLE PARAMETERS
 ----------------------------
@@ -41,6 +46,7 @@ EXAMPLES
 
     __bird_radv datacenter \
         --interface eth1 \
+        --mtu 9000 \
         --route ::/0 \
         --ns 2001:DB8:cafe::4 \
         --ns 2001:DB8:cafe::14 \

type/__bird_radv/manifest

@@ -55,6 +55,12 @@ then
 	DNSSL=$(sed -e 's/^/\tdnssl "/' -e 's/$/";/' "${__object:?}/parameter/dnssl")
 fi
 
+MTU=
+if [ -f "${__object:?}/parameter/mtu" ];
+then
+	MTU=$(cat "${__object:?}/parameter/mtu")
+fi
+
 __file "${confdir:?}/radv-${__object_id:?}.conf" \
 	--mode 0640 --owner root --group bird \
 	--source - << EOF
@@ -71,7 +77,9 @@ protocol radv ${__object_id:?} {
 	propagate routes ${have_routes:?};
 	ipv6 { table radv_routes; export all; };
 
-$(sed -e 's/^/\tinterface "/' -e 's/$/";/' "${__object:?}/parameter/interface")
+	interface "$(cat "${__object:?}/parameter/interface")" {
+	$MTU
+	};
 
 $RDNS
 

type/__bird_radv/parameter/optional

@@ -0,0 +1 @@
+mtu