From: Jens David (gplkqit.weiersbwbm@nraef.org)
Date: Wed Jan 24 2001 - 18:50:47 EET
> On Wed, 24 Jan 2001, Jens David wrote:
> >
> > In fact it might be better to just fix the kernel this time.
> > The fix is pretty self contained and consists only of the ax25_gifconf function.
> > See af_ax25.c at the end.
> > Whoever maintains the old stuff should just copy-and-paste it out and fix
> > the stupid thing once for all. It will save a lot of time necessary to answer
> > the questions.
>
> Tried that once. It broke traceroute IIRC. I'm not convinced the
> ax25_gifconf returns what it is supposed to. I tried asking people about
> what it should do (including Alan) but no-one seemed interested.
Huh?
Isn't that fairly obvious?
See net/core/dev.c:
/*
* Perform a SIOCGIFCONF call. This structure will change
* size eventually, and there is nothing I can do about it.
* Thus we will need a 'compatibility mode'.
*/
static int dev_ifconf(char *arg)
{
blablabla
done = gifconf_list[i](dev, NULL, 0);
blablabla
}
...
/* Protocol dependent address dumping routines */
static gifconf_func_t * gifconf_list [NPROTO];
int register_gifconf(unsigned int family, gifconf_func_t * gifconf)
{
if (family>=NPROTO)
return -EINVAL;
gifconf_list[family] = gifconf;
return 0;
}
Now, if an interface is an IP-capable interface the IP protocol
does the job. Since Linux 2.0 or something however, not every
interface does necessarily need to be an IP interface. If it
has an IP address assigned, net/ipv4 takes over the job of
paining out the ifconf structure:
static int
inet_gifconf(struct device *dev, char *buf, int len)
{
... paint out structure ...
}
__initfunc(void devinet_init(void))
{
register_gifconf(PF_INET, inet_gifconf);
...
}
The SIOCGIFCONF ioctl() is expected to return a list if active
interfaces. It is used in ifconfig and several ax.25 tools. If
no function is registered to return at least the interface name,
the interface basically does not exist in the list and thus the
tool fails.
If your traceroute can't cope with non-IP interfaces it is severely
broken and needs to be fixed, though.
-- Jens
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