Subject: Re: drvspec ioctl question
To: Andrew Brown <>
From: Kyunghwan Kim <>
List: tech-net
Date: 10/22/2001 23:17:44
On Mon, Oct 22, 2001 at 09:14:45AM -0400, Andrew Brown wrote:
> SIOCSDRVSPEC is handled by the default case which calls
> 		error = ((*so->so_proto->pr_usrreq)(so, PRU_CONTROL,
> 		    (struct mbuf *)cmd, (struct mbuf *)data,
> 		    (struct mbuf *)ifp, p));
> where pr_usrreq(), in a call to manipulate a bridge device, will be a
> udp socket, that means udp_usrreq() in netinet/udp_usrreq.c, which
> does this:
> 	if (req == PRU_CONTROL)
> 		return (in_control(so, (long)m, (caddr_t)nam,
> 		    (struct ifnet *)control, p));

Oh, I see. That's why ioctl is associated with socket file 
descriptor which is SOCK_DGRAM type.

> in_control() in netinet/in.c has a default case near the bottom of a
> long switch that does this:
>                 error = (*ifp->if_ioctl)(ifp, cmd, data);
> and that's how bridge_ioctl() gets called.

Thank you for clarification.

Kyunghwan Kim