From a3062085827db3115961eacd9d945ac202728174 Mon Sep 17 00:00:00 2001
From: Ondrej Zajicek <santiago@crfreenet.org>
Date: Wed, 13 Jan 2010 14:53:33 +0100
Subject: Comment update.

---
 proto/ospf/iface.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/proto/ospf/iface.c b/proto/ospf/iface.c
index 25a9822..b90ab9f 100644
--- a/proto/ospf/iface.c
+++ b/proto/ospf/iface.c
@@ -69,11 +69,14 @@ ospf_open_socket(struct ospf_iface *ifa, int mc)
   ipsk->dport = OSPF_PROTO;
 
 #ifdef OSPFv2
-  /* FIXME - why there is IPA_NONE on multicast sockets ? */
-  if (mc)
-    ipsk->saddr = IPA_NONE;
-  else
-    ipsk->saddr = ifa->iface->addr->ip;
+  /*
+   * In Linux IPv4, binding a raw socket to an IP address of an iface causes
+   * that the socket does not receive multicast packets, as they have
+   * different (multicast) destination IP address.
+   *
+   * We want such filter in the vlink (non-mc) socket.
+   */
+  ipsk->saddr = mc ? IPA_NONE : ifa->iface->addr->ip;
 #else /* OSPFv3 */
   ipsk->saddr = ifa->lladdr;
 #endif
-- 
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