On 15/03/16 17:03, Ben Greear wrote:
I want to use wget on multi-homed machines, and I use routing rules to
route pkts
out specific interfaces based on the source IP.
So, I need to be able to bind to a local IP address, including for the
resolver logic,
which is why I want to use libcares.
To test, I think it would be sufficient to put two IPs on a port
(1.1.1.1, 1.1.1.2), and then
use cmd-line args to choose one or the other. Sniff and watch for
proper source address.
For DNS servers, have 1.1.1.3 and 1.1.1.4 be specified. Sniff and
watch to see that the
resolver destination IP is as specified. This should be completely
independent of whatever
is in /etc/resolv.conf, etc.
I (and others) have patched libcares and curl in the past to handle
all of this,
so I know libcares can do it. I think the main work is to handle new
cmd-line
arguments, pass appropriate info to libcares, and make wget use
libcares for it's
resolve logic.
Thanks,
Ben
I think it's ok to add a --bind parameter to wget to choose the
interface for download, but I don't think it should use a different
resolver just for this.
You _could_ change the libc nameservers from the application by changing
_res.nsaddr_list after res_init(). It may be a bit fragile, but should
work fine. And even better than changing each application, I would
recommend you to create a simple LD_PRELOAD library that overrides
res_init() & friends, and allows you to specify the target dns server
with an environment variable. It's a pity there's no RESOLV_CONF var
similar to RESOLV_HOST_CONF, for using a separate /etc/resolv.conf.
Best regards
