How programatically in C do I get/set the default route or gateway address of eth0

jroberts5477 · 09-14-2006, 04:03 PM

I am trying to write code in C to get and set the default route or gateway address on a specific piece of hardware. I have tried many different things, but nothing seems to work. The closest way that looks close to me is using RTNetlink, however I'm not sure if that even works. When I use RTNetlink, I get a gateway address to return, however it is always 0.0.0.0. Any help would be great.

fuzzyash · 09-15-2006, 09:26 AM

To find out what the current address is you could use "/sbin/ifconfig eth0" & write something to filter out the IP number. This will "get" the address for you but what do you mean by :

Quote:

set the default route or gateway address on a specific piece of hardware.

What do you want to "set"? What do you mean by setting it on a specific piece of hardware?

If you can use bash instead of C you can use the following line to get the current IP of eth0 :

Code:

/sbin/ifconfig eth0 | /bin/awk /eth0/'{next}//{split($0,a,":");split(a[2],a," ");print a[1];exit}'

It does exactly what I mentioned above in that it filters the IP out from the command "/sbin/ifconfig eth0"

jroberts5477 · 09-15-2006, 01:11 PM

I have multiple network adapters and for eth0 I want to programmatically set the gateway address for that interface. I can set the IP address, Subnet Mask, and broadcast address with ioctl(), but do not know how to, in C code, find and set the gateway.