Hi,
if you can't use devinet_ioctl() directly because of userspace copying,
just copy the code from devinet_ioctl() over or parts of them...
Not really a nice way, but a working one.
Bye
Am Mi, den 16.06.2004 schrieb Bhaskar-ROCSYS um 13:24:
> Hi
> Thanks for the reply. I followed the same and found out that the
> function devinet_ioctl() function does the configuration changes. This
> function is defined in /usr/src/linux/net/ipv4/devinet.c
>
> But if you the code it copies the contents from user space memory to
> kernel space (copy_from_user). It would mean that I cannot call this
> function from kernel space, as the buffer I would be passing would
> definitely be in kernel space.
>
> I cannot even use get_fs() and set_fs() (using get_ds()) and continue
> calling the function because it is not always true that my module will
> always be initated in process context.
>
> Please comment if I am wrong.
>
> Regards
> bhaskar
> On Wed, 2004-06-16 at 16:12, Jan Hudec wrote:
> > On Wed, Jun 16, 2004 at 11:58:15 +0530, Bhaskar-ROCSYS wrote:
> > > Hi all,
> > >
> > > Is there any way to create a dynamic interface from kernel space.
> > >
> > > Is it possible to change the parameters of an interface from kernel
> > > space?
> > >
> > > All these can be done by using ifconfig. But I want to do it from
> > > kernel space.
> > > I want to change the IP address from kernel space and change the IP
> > > address. I have written a small code to do this but i am not able to
> > > see the effect.
> >
> > ifconfig obviously runs in userspace. So it can't touch the kernel
> > varaibles. So it has to communicate the data somehow. Look how it works
> > (strace will suffice -- you just need to know the syscalls it calls).
> > Then read the code of those syscalls until you get past the
> > copy_from_user stuff and basic sanity-checiking. Then call the function
> > that does the works.
> >
> > > The code I had written is:
> >
> > > [...]
> > > int init_module()
> > > {
> > > struct in_device *in_dev;
> > > struct in_ifaddr **ifap = NULL;
> > > struct in_ifaddr *ifa = NULL;
> > > struct net_device *dev;
> > >
> > > if((dev = __dev_get_by_name("eth0")) == NULL)
> > > {
> > > printk("<1>Cannot get info for eth0\n");
> > > return -1;
> > > }
> > >
> > > if((in_dev = __in_dev_get(dev))!= NULL)
> > > {
> > > for (ifap=&in_dev->ifa_list; (ifa=*ifap) != NULL; ifap=&ifa->ifa_next)
> > > {
> > > if ((strcmp("eth0", ifa->ifa_label) == 0))
> > > break; /* found */
> > > }
> > > }
> > > if(ifa)
> > > {
> > > ifa->ifa_local = htonl(0xac100f63);
> > >
> > > ifa->ifa_prefixlen = 24;
> > > ifa->ifa_mask = inet_make_mask(ifa->ifa_prefixlen);
> > > if ((dev->flags&IFF_BROADCAST) && ifa->ifa_prefixlen <
> > > 31)
> > > ifa->ifa_broadcast =
> > > ifa->ifa_address|~ifa->ifa_mask;
> > > }
> > > else printk("<1>Could not find the device\n");
> > >
> > > return 0;
> > > }
> > >
> > > The changes are made but when I am trying to send packet its failing.
> > >
> > > Is there any other way to change the interface parameters from kernel
> > > space ?
> >
> > It's likely harder than just changing the value. There might be other
> > data structures, that need updating. Just read the code used by ifconfig
> > to set it and call it or do the same.
> >
> > -------------------------------------------------------------------------------
> > Jan 'Bulb' Hudec <bulb@ucw.cz>
>
>
>
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> Kernelnewbies: Help each other learn about the Linux kernel.
> Archive: http://mail.nl.linux.org/kernelnewbies/
> FAQ: http://kernelnewbies.org/faq/
>
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