Re: nslu2: two devices: one by default

[Michael Shuler <michael@pbandjelly.org>]

On 11/09/2009 11:23 AM, Xan wrote:
> En/na Lennart Sorensen ha escrit:
>> 'ethtool' or 'ip link' should be able to tell you if a link is up or
>> down.
>> A clever tool would subscribe to netlink and get notifications of link
>> state changes, but that probably isn't necesary.
>>
>>   
> I'm planned to write a daemon which change route table according with
> the ip link state of eth0. I have two alternatives: use ip link and see
> periodically the state of link of eth0 and use netlink. I think the best
> it's the second (in the first case I have to wait one hour or one
> minute.... for recover eth0 connection after plug).
> 
> Can you help me writting it?
> In the man page of netlink, we could follow:
> 
> The following example creates a NETLINK_ROUTE netlink socket which will
> listen to the RTMGRP_LINK (network interface create/delete/up/down
> events) and RTMGRP_IPV4_IFADDR (IPv4 addresses add/delete events) mul‐
> ticast groups.
> 
> struct sockaddr_nl sa;
> 
> memset(&sa, 0, sizeof(sa));
> snl.nl_family = AF_NETLINK;
> snl.nl_groups = RTMGRP_LINK | RTMGRP_IPV4_IFADDR;
> 
> fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
> bind(fd, (struct sockaddr*)&sa, sizeof(sa));
> 
> Is this that we want? Sorry but I'm not clear with this documentation.
> 
> I simply want script that:
> - get notification via netlink of up/down changes of eth0
> - run
> 
>     ip route del default via 10.200.16.1 dev eth0
>     ip route del 10.200.64.0/20 dev eth0  proto kernel  scope link  src
> 10.200.65.12
> 
> if eth0 link is down
> - and
>     ip route add 10.200.64.0/20 dev eth0  proto kernel  scope link  src
> 10.200.65.12
>     ip route add default via 10.200.16.1 dev eth0
> if it's come back.

I have not looked into the details of the issues you are having, and
have not actually used whereami scripts - but the whereami package
description looks to be very close to what you are looking for, and also
would seem to be the natural place to contribute features/functionality
to do what you want, if it does not already.  Just an observation.  :)

-- 
Kind regards,
Michael Shuler