Re: C and/or ioctl question

[James Morris <jmorris@xxxxxxxxxxxxxxxx>]

On 8 Aug 2001, Stephen Waters wrote:

> hi, I've been studying the net-tools ifconfig implementation a bit in my
> efforts to better learn C and ioctl for Linux.
>

> int main () {
>    struct ifconf ifc;
>    int skfd;
>    skfd = socket(AF_INET, SOCK_DGRAM, 0);
>    if (ioctl(skfd, SIOCGIFCONF, &ifc) < 0) {


You need to set up the ifconf structure first and allocate enough memory
in it for a payload of ifreq structures to be returned from the kernel.

Have a look at if_readconf() in net-tools/lib/interface.c


- James
-- 
James Morris
<jmorris@xxxxxxxxxxxxxxxx>