text: /*-
   * Copyright (c) 1982, 1986, 1993
   *	The Regents of the University of California.  All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 4. Neither the name of the University nor the names of its contributors
   *    may be used to endorse or promote products derived from this software
   *    without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   *
   *	From: @(#)if_loop.c	8.1 (Berkeley) 6/10/93
   * $FreeBSD: releng/9.3/sys/net/if_disc.c 191148 2009-04-16 20:30:28Z kmacy $
   */
  
  /*
   * Discard interface driver for protocol testing and timing.
   * (Based on the loopback.)
   */
  
  #include <sys/param.h>
  #include <sys/systm.h>
  #include <sys/kernel.h>
  #include <sys/malloc.h>
  #include <sys/module.h>
  #include <sys/mbuf.h>
  #include <sys/socket.h>
  #include <sys/sockio.h>
  
  #include <net/if.h>
  #include <net/if_clone.h>
  #include <net/if_types.h>
  #include <net/route.h>
  #include <net/bpf.h>
  
  #include "opt_inet.h"
  #include "opt_inet6.h"
  
  #ifdef TINY_DSMTU
  #define	DSMTU	(1024+512)
  #else
  #define DSMTU	65532
  #endif
  
  #define DISCNAME	"disc"
  
  struct disc_softc {
  	struct ifnet *sc_ifp;
  };
  
  static int	discoutput(struct ifnet *, struct mbuf *,
  		    struct sockaddr *, struct route *);
  static void	discrtrequest(int, struct rtentry *, struct rt_addrinfo *);
  static int	discioctl(struct ifnet *, u_long, caddr_t);
  static int	disc_clone_create(struct if_clone *, int, caddr_t);
  static void	disc_clone_destroy(struct ifnet *);
  
  static MALLOC_DEFINE(M_DISC, DISCNAME, "Discard interface");
  
  IFC_SIMPLE_DECLARE(disc, 0);
  
  static int
  disc_clone_create(struct if_clone *ifc, int unit, caddr_t params)
  {
  	struct ifnet		*ifp;
  	struct disc_softc	*sc;
  
  	sc = malloc(sizeof(struct disc_softc), M_DISC, M_WAITOK | M_ZERO);
  	ifp = sc->sc_ifp = if_alloc(IFT_LOOP);
  	if (ifp == NULL) {
  		free(sc, M_DISC);
  		return (ENOSPC);
  	}
  
  	ifp->if_softc = sc;
  	if_initname(ifp, ifc->ifc_name, unit);
  	ifp->if_mtu = DSMTU;
  	/*
  	 * IFF_LOOPBACK should not be removed from disc's flags because
  	 * it controls what PF-specific routes are magically added when
  	 * a network address is assigned to the interface.  Things just
  	 * won't work as intended w/o such routes because the output
  	 * interface selection for a packet is totally route-driven.
  	 * A valid alternative to IFF_LOOPBACK can be IFF_BROADCAST or
  	 * IFF_POINTOPOINT, but it would result in different properties
  	 * of the interface.
  	 */
  	ifp->if_flags = IFF_LOOPBACK | IFF_MULTICAST;
  	ifp->if_drv_flags = IFF_DRV_RUNNING;
  	ifp->if_ioctl = discioctl;
  	ifp->if_output = discoutput;
  	ifp->if_hdrlen = 0;
  	ifp->if_addrlen = 0;
  	ifp->if_snd.ifq_maxlen = 20;
  	if_attach(ifp);
  	bpfattach(ifp, DLT_NULL, sizeof(u_int32_t));
  
  	return (0);
  }
  
  static void
  disc_clone_destroy(struct ifnet *ifp)
  {
  	struct disc_softc	*sc;
  
  	sc = ifp->if_softc;
  
  	bpfdetach(ifp);
  	if_detach(ifp);
  	if_free(ifp);
  
  	free(sc, M_DISC);
  }
  
  static int
  disc_modevent(module_t mod, int type, void *data)
  {
  
  	switch (type) {
  	case MOD_LOAD:
  		if_clone_attach(&disc_cloner);
  		break;
  	case MOD_UNLOAD:
  		if_clone_detach(&disc_cloner);
  		break;
  	default:
  		return (EOPNOTSUPP);
  	}
  	return (0);
  }
  
  static moduledata_t disc_mod = {
  	"if_disc",
  	disc_modevent,
  	NULL
  };
  
  DECLARE_MODULE(if_disc, disc_mod, SI_SUB_PSEUDO, SI_ORDER_ANY);
  
  static int
  discoutput(struct ifnet *ifp, struct mbuf *m, struct sockaddr *dst,
      struct route *ro)
  {
  	u_int32_t af;
  
  	M_ASSERTPKTHDR(m);
  
  	/* BPF writes need to be handled specially. */
  	if (dst->sa_family == AF_UNSPEC) {
  		bcopy(dst->sa_data, &af, sizeof(af));
  		dst->sa_family = af;
  	}
  
  	if (bpf_peers_present(ifp->if_bpf)) {
  		u_int af = dst->sa_family;
  		bpf_mtap2(ifp->if_bpf, &af, sizeof(af), m);
  	}
  	m->m_pkthdr.rcvif = ifp;
  
  	ifp->if_opackets++;
  	ifp->if_obytes += m->m_pkthdr.len;
  
  	m_freem(m);
  	return (0);
  }
  
  /* ARGSUSED */
  static void
  discrtrequest(int cmd, struct rtentry *rt, struct rt_addrinfo *info)
  {
  	RT_LOCK_ASSERT(rt);
  	rt->rt_rmx.rmx_mtu = DSMTU;
  }
  
  /*
   * Process an ioctl request.
   */
  static int
  discioctl(struct ifnet *ifp, u_long cmd, caddr_t data)
  {
  	struct ifaddr *ifa;
  	struct ifreq *ifr = (struct ifreq *)data;
  	int error = 0;
  
  	switch (cmd) {
  
  	case SIOCSIFADDR:
  		ifp->if_flags |= IFF_UP;
  		ifa = (struct ifaddr *)data;
  		if (ifa != 0)
  			ifa->ifa_rtrequest = discrtrequest;
  		/*
  		 * Everything else is done at a higher level.
  		 */
  		break;
  
  	case SIOCADDMULTI:
  	case SIOCDELMULTI:
  		if (ifr == 0) {
  			error = EAFNOSUPPORT;		/* XXX */
  			break;
  		}
  		switch (ifr->ifr_addr.sa_family) {
  
  #ifdef INET
  		case AF_INET:
  			break;
  #endif
  #ifdef INET6
  		case AF_INET6:
  			break;
  #endif
  
  		default:
  			error = EAFNOSUPPORT;
  			break;
  		}
  		break;
  
  	case SIOCSIFMTU:
  		ifp->if_mtu = ifr->ifr_mtu;
  		break;
  
  	default:
  		error = EINVAL;
  	}
  	return (error);
  }
  