commit 3a75e74c76cef8daa7944159b016c4ee7c56e568
author Mike Ryan <mikeryan@isi.edu> Wed Dec 01 11:16:47 2010 -0800
committer Michael S. Tsirkin <mst@redhat.com> Thu Dec 09 12:45:50 2010 +0200
tree 9b3b7f9f45c49a3d29d6bfb3b0d553b525942191
parent 138b38b61bf92d4e9588acf934e532499c94e185

net/sock: option to specify local address

Add an option to specify the host IP to send multicast packets from,
when using a multicast socket for networking. The option takes an IP
address and sets the IP_MULTICAST_IF socket option, which causes the
packets to use that IP's interface as an egress.

This is useful if the host machine has several interfaces with several
virtual networks across disparate interfaces.

Signed-off-by: Mike Ryan <mikeryan@ISI.EDU>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

qemu-options.hx

diff --git a/qemu-options.hx b/qemu-options.hx
index 4d99a58..accd16a 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -1061,8 +1061,9 @@
 #endif
     "-net socket[,vlan=n][,name=str][,fd=h][,listen=[host]:port][,connect=host:port]\n"
     "                connect the vlan 'n' to another VLAN using a socket connection\n"
-    "-net socket[,vlan=n][,name=str][,fd=h][,mcast=maddr:port]\n"
+    "-net socket[,vlan=n][,name=str][,fd=h][,mcast=maddr:port[,localaddr=addr]]\n"
     "                connect the vlan 'n' to multicast maddr and port\n"
+    "                use 'localaddr=addr' to specify the host address to send packets from\n"
 #ifdef CONFIG_VDE
     "-net vde[,vlan=n][,name=str][,sock=socketpath][,port=n][,group=groupname][,mode=octalmode]\n"
     "                connect the vlan 'n' to port 'n' of a vde switch running\n"
@@ -1256,7 +1257,7 @@
                -net socket,connect=127.0.0.1:1234
 @end example
 
-@item -net socket[,vlan=@var{n}][,name=@var{name}][,fd=@var{h}] [,mcast=@var{maddr}:@var{port}]
+@item -net socket[,vlan=@var{n}][,name=@var{name}][,fd=@var{h}][,mcast=@var{maddr}:@var{port}[,localaddr=@var{addr}]]
 
 Create a VLAN @var{n} shared with another QEMU virtual
 machines using a UDP multicast socket, effectively making a bus for
@@ -1296,6 +1297,12 @@
 /path/to/linux ubd0=/path/to/root_fs eth0=mcast
 @end example
 
+Example (send packets from host's 1.2.3.4):
+@example
+qemu linux.img -net nic,macaddr=52:54:00:12:34:56 \
+               -net socket,mcast=239.192.168.1:1102,localaddr=1.2.3.4
+@end example
+
 @item -net vde[,vlan=@var{n}][,name=@var{name}][,sock=@var{socketpath}] [,port=@var{n}][,group=@var{groupname}][,mode=@var{octalmode}]
 Connect VLAN @var{n} to PORT @var{n} of a vde switch running on host and
 listening for incoming connections on @var{socketpath}. Use GROUP @var{groupname}