[avahi] Broadcast IP address and no host name

[Till Kamppeter]

Hi,

I have a machine with several network interfaces (lo, dummy0, eth0, 
virbr0, ...).

The dummy0 is set up like this:

sudo modprobe dummy
sudo ifconfig dummy0 10.0.0.1 netmask 255.255.255.0 multicast

Then ifconfig gives this:

----------
dummy0: flags=4291<UP,BROADCAST,RUNNING,NOARP,MULTICAST>  mtu 1500
         inet 10.0.0.1  netmask 255.255.255.0  broadcast 10.0.0.255
         inet6 fe80::243f:c8ff:fe47:e4c2  prefixlen 64  scopeid 0x20<link>
         ether 26:3f:c8:47:e4:c2  txqueuelen 1000  (Ethernet)
         RX packets 0  bytes 0 (0.0 B)
         RX errors 0  dropped 0  overruns 0  frame 0
         TX packets 631  bytes 488318 (488.3 KB)
         TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

enx00051bb07395: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
         inet 192.168.0.15  netmask 255.255.255.0  broadcast 192.168.0.255
         inet6 fe80::205:1bff:feb0:7395  prefixlen 64  scopeid 0x20<link>
         inet6 2804:14c:5ba8:8b97::5  prefixlen 128  scopeid 0x0<global>
         inet6 2804:14c:5ba8:8b97:205:1bff:feb0:7395  prefixlen 64 
scopeid 0x0<global>
         ether 00:05:1b:b0:73:95  txqueuelen 1000  (Ethernet)
         RX packets 269444  bytes 294040282 (294.0 MB)
         RX errors 2  dropped 0  overruns 0  frame 0
         TX packets 179144  bytes 25171845 (25.1 MB)
         TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

eth0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
         ether 54:ee:75:39:35:2c  txqueuelen 1000  (Ethernet)
         RX packets 0  bytes 0 (0.0 B)
         RX errors 0  dropped 0  overruns 0  frame 0
         TX packets 0  bytes 0 (0.0 B)
         TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
         device interrupt 20  memory 0xf0500000-f0520000

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
         inet 127.0.0.1  netmask 255.0.0.0
         inet6 ::1  prefixlen 128  scopeid 0x10<host>
         loop  txqueuelen 1  (Local Loopback)
         RX packets 241623  bytes 79247221 (79.2 MB)
         RX errors 0  dropped 0  overruns 0  frame 0
         TX packets 241623  bytes 79247221 (79.2 MB)
         TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

virbr0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
         inet 192.168.122.1  netmask 255.255.255.0  broadcast 
192.168.122.255
         ether fe:54:00:bc:d2:60  txqueuelen 1000  (Ethernet)
         RX packets 37468  bytes 3107560 (3.1 MB)
         RX errors 0  dropped 0  overruns 0  frame 0
         TX packets 62801  bytes 86995841 (86.9 MB)
         TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

vnet0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
         inet6 fe80::fc54:ff:febc:d260  prefixlen 64  scopeid 0x20<link>
         ether fe:54:00:bc:d2:60  txqueuelen 1000  (Ethernet)
         RX packets 37468  bytes 3632112 (3.6 MB)
         RX errors 0  dropped 0  overruns 0  frame 0
         TX packets 66808  bytes 87498217 (87.4 MB)
         TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

----------

Now I broadcast a service (an IPP printer) as follows:

   avahi_entry_group_add_service_strlst(bonjour_data->ipp_ref,
				       (interface ?
					(int)if_nametoindex(interface) :
					AVAHI_IF_UNSPEC),
				       AVAHI_PROTO_UNSPEC, 0,
				       dnssd_name,
				       "_ipp._tcp", NULL, NULL, port,
				       ipp_txt);

Where the variable "interface" is set to "enx00051bb07395" to broadcast 
only to my wired Ethernet interface with IP 192.168.0.15. "port" is set 
to 60000 as my IPP printer is bound to port 60000 (the standard port 631 
is already in use by CUPS).

In avahi-discover I have an entry under

enx00051bb07395 -> local -> Internet Printer

with the "Address" set to "till-x1carbon.local/192.168.0.15:60000" 
showing my host name, my interface's IP and the port.

I can talk to the printer via 192.168.0.15:60000 but I cannot talk to it 
via till-x1carbon.local:60000. When I do

ping till-x1carbon.local

it associates the name till-x1carbon.local to the IP 10.0.0.1 of dummy0, 
which is probably the cause of the problem. Calling the name leads to 
the wrong IP.

Now utilities of CUPS show the printers as 
ipp://till-x1carbon.local:60000/ipp/print making the host name being used.

Now I want to know whether I can modify the Avahi broadcast so that it 
does not use the host name any more, so that the "Adress" in 
avahi-discover is something like "192.168.0.15/192.168.0.15:60000", not 
containing the name and the CUPS tools are forced to display

ipp://192.168.0.15:60000/ipp/print

then. Is this possible?

    Till