Don,
Multicast group membership is per-interface, not per-port. If an
application binds to INADDR_ANY:9462 (UDP), it should receive any multicast
UDP packets sent to port 9462, whether or not that application did the join
for that multicast group. Similarly, if an application joins a group, but
never binds to a UDP port, the host should still answer, for example, ICMP
echo requests sent to that multicast address.
+-DLS
Don Hinton <dhinton@ieee.org>@vger.kernel.org on 11/07/2002 03:55:05 PM
Please respond to dhinton@ieee.org
Sent by: linux-net-owner@vger.kernel.org
To: linux-net@vger.kernel.org
cc:
Subject: [PATCH] (IPv4) multicast group filtering doesn't work if socket
only bound to a port
Hi:
The IPv4 stack, unlike IPv6, doesn't filter mcast groups for sockets only
bound to a port, but not an address, based on subscriptions. So even
if you only subscribe to a single group, but don't bind an address to the
socket, you'll receive all mcast dgrams delivered to the udp layer, i.e.,
all subscribed to groups no matter which application actually made the
subscription.
The following patch fixes the problem in a manner similar to the way the
IPv6 stack does it. It's against 2.4.19:
--- linux-2.4.19/net/ipv4/udp.c.old Wed Nov 6 19:16:03 2002
+++ linux-2.4.19/net/ipv4/udp.c Thu Nov 7 20:43:00 2002
@@ -82,6 +82,7 @@
#include <linux/mm.h>
#include <linux/config.h>
#include <linux/inet.h>
+#include <linux/igmp.h>
#include <linux/netdevice.h>
#include <net/snmp.h>
#include <net/ip.h>
@@ -267,6 +268,7 @@
int dif)
{
struct sock *s = sk;
+ struct ip_mc_socklist *mc;
unsigned short hnum = ntohs(loc_port);
for(; s; s = s->next) {
if ((s->num != hnum) ||
@@ -275,6 +277,14 @@
(s->rcv_saddr && s->rcv_saddr != loc_addr) ||
(s->bound_dev_if && s->bound_dev_if != dif))
continue;
+ else {
+ for (mc=s->protinfo.af_inet.mc_list; mc;
mc=mc->next) {
+ if (mc->multi.imr_multiaddr.s_addr ==
loc_addr)
+ break;
+ }
+ if (!mc)
+ continue;
+ }
break;
}
return s;
take care...
don
--
Don Hinton <dhinton @ ieee.org>
Software Engineer
P.O. Box 23524, Alexandria, Virginia 22304
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