ripd: improve passive interface

Hi tech,

The passive keyword in ripd.conf ensures, that no RIP packets are
processed on the given interface.

Other RIP implementation advertise the prefixes from a passive interface.
ospfd and ospf6d also advertise prefixes from passive interfaces

This diff implements that behaviour for ripd.

OK?

Remi


--- usr.sbin/ripd/ripd.c
+++ usr.sbin/ripd/ripd.c
@@ -461,6 +461,14 @@ rip_redistribute(struct kroute *kr)
 	if (kr->flags & F_RIPD_INSERTED)
 		return (1);
 
+	/* redistribute prefixes from passive interfaces */
+	if (kr->flags & F_CONNECTED) {
+		struct iface *iface = if_find_index(kr->ifindex);
+
+		if (iface != NULL && iface->passive)
+			return (1);
+	}
+
 	/* only allow 0.0.0.0/0 via REDIST_DEFAULT */
 	if (kr->prefix.s_addr == INADDR_ANY && kr->netmask.s_addr == INADDR_ANY)
 		is_default = 1;

--- usr.sbin/ripd/ripd.conf.5
+++ usr.sbin/ripd/ripd.conf.5
@@ -221,7 +221,8 @@ when the interface state is going down.
 The demotion counter will be decreased when the interface
 state is active again.
 .It Ic passive
-Prevent transmission and reception of RIP packets on this interface.
+Prevent transmission and reception of RIP packets on this interface 
+and advertise all prefixes configured on this interface.
 .El
 .Sh FILES
 .Bl -tag -width /etc/examples/ripd.conf -compact