Babel: Log the reason when refusing to run on an interface

The babel protocol code checks whether iface supports multicast, and
whether it has a link-local address assigned. However, it doesn not give
any feedback if any of those checks fail, it just silently ignores the
interface. Fix this by explicitly logging when multicast check fails.

Based on patch from Toke Høiland-Jørgensen, thanks!

1 files changed, 19 insertions, 9 deletions

diff --git a/proto/babel/babel.c b/proto/babel/babel.c
index 4b6b9d7f..25d8e330 100644
--- a/proto/babel/babel.c
+++ b/proto/babel/babel.c
@@ -1639,6 +1639,20 @@ babel_remove_iface(struct babel_proto *p, struct babel_iface *ifa)
   rfree(ifa->pool); /* contains ifa itself, locks, socket, etc */
 }
 
+static int
+iface_is_valid(struct babel_proto *p, struct iface *iface)
+{
+  if (!(iface->flags & IF_MULTICAST))
+  {
+    log(L_ERR "%s: Interface %s does not support multicast",
+	p->p.name, iface->name);
+
+    return 0;
+  }
+
+  return 1;
+}
+
 static void
 babel_if_notify(struct proto *P, unsigned flags, struct iface *iface)
 {
@@ -1658,16 +1672,13 @@ babel_if_notify(struct proto *P, unsigned flags, struct iface *iface)
     if (!(iface->flags & IF_UP))
       return;
 
-    /* We only speak multicast */
-    if (!(iface->flags & IF_MULTICAST))
-      return;
-
     /* Ignore ifaces without link-local address */
     if (!iface->llv6)
       return;
 
     struct babel_iface_config *ic = (void *) iface_patt_find(&cf->iface_list, iface, NULL);
-    if (ic)
+
+    if (ic && iface_is_valid(p, iface))
       babel_add_iface(p, iface, ic);
 
     return;
@@ -1736,10 +1747,6 @@ babel_reconfigure_ifaces(struct babel_proto *p, struct babel_config *cf)
     if (!(iface->flags & IF_UP))
       continue;
 
-    /* Ignore non-multicast ifaces */
-    if (!(iface->flags & IF_MULTICAST))
-      continue;
-
     /* Ignore ifaces without link-local address */
     if (!iface->llv6)
       continue;
@@ -1747,6 +1754,9 @@ babel_reconfigure_ifaces(struct babel_proto *p, struct babel_config *cf)
     struct babel_iface *ifa = babel_find_iface(p, iface);
     struct babel_iface_config *ic = (void *) iface_patt_find(&cf->iface_list, iface, NULL);
 
+    if (ic && iface_is_valid(p, iface))
+      ic = NULL;
+
     if (ifa && ic)
     {
       if (babel_reconfigure_iface(p, ifa, ic))