Using the dummy0 interface for a local-only service to be broadcasted by Avahi
stgraber at ubuntu.com
Thu Dec 29 18:31:57 UTC 2016
On Thu, Dec 29, 2016 at 04:14:52PM -0200, Till Kamppeter wrote:
> On 12/29/2016 02:37 PM, Stéphane Graber wrote:
> > > How can I assign a different name to a dummy interface? Can I freely choose
> > > a name somehow, for example "ippusbxd"? Or have I to use "dummy1", "dummy2",
> > > ... (loading the dummy kernel module with an option to support more than one
> > > interface)?
> > root at castiana:~# ip link add ippusbxd type dummy
> > root at castiana:~# ip link set ippusbxd up
> > root at castiana:~# ifconfig ippusbxd
> > ippusbxd: flags=195<UP,BROADCAST,RUNNING,NOARP> mtu 1500
> > inet6 fe80::3004:2dff:feb6:b5c7 prefixlen 64 scopeid 0x20<link>
> > ether 32:04:2d:b6:b5:c7 txqueuelen 1000 (Ethernet)
> > RX packets 0 bytes 0 (0.0 B)
> > RX errors 0 dropped 0 overruns 0 frame 0
> > TX packets 2 bytes 140 (140.0 B)
> > TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
> > Which gets you your own dummy device with its IPv6 link-local address.
> Thank you very much. I copied and pasted the commands and got an ifconfig
> output similar to yours, only with different IP and MAC addresses and
> different values in the statistics.
> Then I tried to bind to the IPv6 IP address of this entry, on port 60000 and
> this did not work.
> Do I have to create an additional IP address? If yes, how? Do I have to run
> additional commands (route?)? Which ones?
Link-local addresses are slightly special in that they are indeed link local.
So you can't bind fe80::3004:2dff:feb6:b5c7 as you could in theory have
the same address on multiple interfaces. Instead, you need to tell
bind() what interface to bind on. This is typically indicated as
stgraber at castiana:~$ nc -l fe80::3004:2dff:feb6:b5c7 1234
nc: Invalid argument
^ Fails because the kernel doesn't know what interface you want.
stgraber at castiana:~$ nc -l fe80::3004:2dff:feb6:b5c7%ippusbxd 1234
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