Re: [lwip-users] Setting the netif hostname without using DHCP

[David Empson]

Simon Goldschmidt <address@hidden> wrote:
>  Karthik Vadambacheri Manian wrote:
> > Basically I want to ping from a unix box not a windows box. I tried
> > setting NETBIOS_LWIP_NAME but as you said it works for windows only.
> > So without using DHCP in LWIP is there a way to set the hostname which
> > I can ping from another m/c?
> The question isn't if there is a way in lwIP to set a hostname, the
> question is how can you make your unix box know the name. And as far as I
> know, the only portable way under unixes is DNS. You could configure your
> local network's DNS server to translate names into addresses, but that's
> not what you want, I guess. BTW, using DHCP for that also only works if
> the DHCP- and DNS-server work together and are allowed (by the admin) to
> take hostnames suggested by clients.
>
> Another method would be mDNS, but that's not available yet for lwIP
> (although there's a task for that on savannah, already) and you need
> special software for unix, too.

If SAMBA is installed on the unix machine, you can use the 'nmblookup'
command to look up a NetBIOS name.

I don't know if later versions are any better, but the one I have (supplied
with Mac OS X 10.6, Samba version 3.0.28a-apple) doesn't have any options to
tidy up its output in a way which allows it to be easily used in conjunction 
with
other commands, so you need to do some postprocessing with other tools.

Its normal output looks like this, if it finds the name on the first
available network interface:

% nmblookup foo
querying name on 192.168.0.255
192.168.0.17 foo<00>

If it can't find the name, it does this:

% nmblookup foo
querying name on 192.168.0.255
querying name on 172.16.191.255
name_query failed to find name foo


If you assume the name lookup will be successful, this trick can be used to
extract the IP address:

% nmblookup foo | tail -1 | sed 's/ .*//'
192.168.0.17

(tail -1 gets the last line, and sed with that argument strips off 
everything on the line
beginning with the first space.)

If the name is not found, it returns

% nmblookup bar | tail -1 | sed 's/ .*//'
name_query

I'm sure a more seasoned unix shell scripter can turn this into an alias
with a parameter, or come up with a tidier way to extract the first "word"
from the last line of the output of nmblookup.

You can combine the command with another one by using backticks:

% ping `nmblookup foo | tail -1 | sed 's/ .*//'`
PING 192.168.0.17 (192.168.0.17): 56 data bytes
64 bytes from 192.168.0.17: icmp_seq=0 ttl=128 time=0.528 ms
64 bytes from 192.168.0.17: icmp_seq=1 ttl=128 time=0.598 ms
64 bytes from 192.168.0.17: icmp_seq=2 ttl=128 time=0.572 ms
^C
--- 192.168.0.17 ping statistics ---
3 packets transmitted, 3 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 0.528/0.566/0.598/0.029 ms

(A failed lookup will attempt to ping 'name_query', which isn't likely to
achieve much.)