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Constify rtentry of if_output

We no longer need to change rtentry below if_output.

The change makes it clear where rtentries are changed (or not)
and helps forthcoming locking (os psrefing) rtentries.

/*      $NetBSD: if_atm.c,v 1.38 2016/04/28 00:16:56 ozaki-r Exp $       */

/*
 * Copyright (c) 1996 Charles D. Cranor and Washington University.
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
 */

/*
 * IP <=> ATM address resolution.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: if_atm.c,v 1.38 2016/04/28 00:16:56 ozaki-r Exp $");

#ifdef _KERNEL_OPT
#include "opt_inet.h"
#include "opt_natm.h"
#endif

#if defined(INET) || defined(INET6)

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/kernel.h>
#include <sys/errno.h>
#include <sys/ioctl.h>
#include <sys/syslog.h>
#include <sys/proc.h>

#include <net/if.h>
#include <net/if_dl.h>
#include <net/route.h>
#include <net/if_atm.h>

#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/in_var.h>
#include <netinet/ip.h>
#include <netinet/if_atm.h>

#ifdef NATM
#include <netnatm/natm.h>
#endif


/*
 * atm_rtrequest: handle ATM rt request (in support of generic code)
 *   inputs: "req" = request code
 *           "rt" = route entry
 *           "sa" = sockaddr
 */

void
atm_rtrequest(int req, struct rtentry *rt, const struct rt_addrinfo *info)
{
	struct sockaddr *gate = rt->rt_gateway;
	struct atm_pseudoioctl api;
#ifdef NATM
	const struct sockaddr_in *sin;
	struct natmpcb *npcb = NULL;
	const struct atm_pseudohdr *aph;
#endif
	const struct ifnet *ifp = rt->rt_ifp;
	uint8_t namelen = strlen(ifp->if_xname);
	uint8_t addrlen = ifp->if_addrlen;

	if (rt->rt_flags & RTF_GATEWAY)   /* link level requests only */
		return;

	switch (req) {

	case RTM_ADD:

		/*
		 * route added by a command (e.g. ifconfig, route, arp...).
		 *
		 * first check to see if this is not a host route, in which
		 * case we are being called via "ifconfig" to set the address.
		 */

		if ((rt->rt_flags & RTF_HOST) == 0) {
			union {
				struct sockaddr sa;
				struct sockaddr_dl sdl;
				struct sockaddr_storage ss;
			} u;

			sockaddr_dl_init(&u.sdl, sizeof(u.ss),
			    ifp->if_index, ifp->if_type,
			    NULL, namelen, NULL, addrlen);
			rt_setgate(rt, &u.sa);
			gate = rt->rt_gateway;
			break;
		}

		if (gate->sa_family != AF_LINK ||
		    gate->sa_len < sockaddr_dl_measure(namelen, addrlen)) {
			log(LOG_DEBUG, "atm_rtrequest: bad gateway value\n");
			break;
		}

#ifdef DIAGNOSTIC
		if (rt->rt_ifp->if_ioctl == NULL) panic("atm null ioctl");
#endif

#ifdef NATM
		/*
		 * let native ATM know we are using this VCI/VPI
		 * (i.e. reserve it)
		 */
		sin = satocsin(rt_getkey(rt));
		if (sin->sin_family != AF_INET)
			goto failed;
		aph = (const struct atm_pseudohdr *)CLLADDR(satosdl(gate));
		npcb = npcb_add(NULL, rt->rt_ifp, ATM_PH_VCI(aph),
						ATM_PH_VPI(aph));
		if (npcb == NULL)
			goto failed;
		npcb->npcb_flags |= NPCB_IP;
		npcb->ipaddr.s_addr = sin->sin_addr.s_addr;
		/* XXX: move npcb to llinfo when ATM ARP is ready */
		rt->rt_llinfo = (void *) npcb;
#endif
		/*
		 * let the lower level know this circuit is active
		 */
		memcpy(&api.aph, CLLADDR(satocsdl(gate)), sizeof(api.aph));
		api.rxhand = NULL;
		if (rt->rt_ifp->if_ioctl(rt->rt_ifp, SIOCATMENA, &api) != 0) {
			printf("atm: couldn't add VC\n");
			goto failed;
		}

		satosdl(gate)->sdl_type = rt->rt_ifp->if_type;
		satosdl(gate)->sdl_index = rt->rt_ifp->if_index;

		break;

failed:
#ifdef NATM
		if (npcb) {
			npcb_free(npcb, NPCB_DESTROY);
			rt->rt_llinfo = NULL;
		}
#endif
		rtrequest(RTM_DELETE, rt_getkey(rt), NULL,
			rt_mask(rt), 0, NULL);
		break;

	case RTM_DELETE:

		/*
		 * tell the lower layer to disable this circuit
		 */

		memcpy(&api.aph, CLLADDR(satocsdl(gate)), sizeof(api.aph));
		api.rxhand = NULL;
		(void)rt->rt_ifp->if_ioctl(rt->rt_ifp, SIOCATMDIS, &api);

		break;
	}
}

/*
 * atmresolve:
 *   inputs:
 *     [1] "rt" = the link level route to use (or null if need to look one up)
 *     [2] "m" = mbuf containing the data to be sent
 *     [3] "dst" = sockaddr_in (IP) address of dest.
 *   output:
 *     [4] "desten" = ATM pseudo header which we will fill in VPI/VCI info
 *   return:
 *     0 == resolve FAILED; note that "m" gets m_freem'd in this case
 *     1 == resolve OK; desten contains result
 *
 *   XXX: will need more work if we wish to support ATMARP in the kernel,
 *   but this is enough for PVCs entered via the "route" command.
 */

int
atmresolve(const struct rtentry *rt0, struct mbuf *m, const struct sockaddr *dst,
    struct atm_pseudohdr *desten /* OUT */)
{
	const struct sockaddr_dl *sdl;
	struct rtentry *rt = NULL;

	if (m->m_flags & (M_BCAST|M_MCAST)) {
		log(LOG_INFO, "atmresolve: BCAST/MCAST packet detected/dumped\n");
		goto bad;
	}

	if (rt0 == NULL) {
		rt = RTALLOC1(dst, 0);
		if (rt == NULL)
			goto bad; /* failed */
		if ((rt->rt_flags & RTF_GATEWAY) != 0 ||
		    /* XXX: are we using LLINFO? */
		    rt->rt_gateway->sa_family != AF_LINK) {
			rtfree(rt);
			goto bad;
		}
	}

	/*
	 * note that rt_gateway is a sockaddr_dl which contains the
	 * atm_pseudohdr data structure for this route.   we currently
	 * don't need any rt_llinfo info (but will if we want to support
	 * ATM ARP [c.f. if_ether.c]).
	 */

	sdl = satocsdl((rt ? rt : rt0)->rt_gateway);

	/*
	 * Check the address family and length is valid, the address
	 * is resolved; otherwise, try to resolve.
	 */

	if (sdl->sdl_family == AF_LINK && sdl->sdl_alen == sizeof(*desten)) {
		memcpy(desten, CLLADDR(sdl), sdl->sdl_alen);
		if (rt != NULL)
			rtfree(rt);
		return (1);	/* ok, go for it! */
	}

	if (rt != NULL)
		rtfree(rt);

	/*
	 * we got an entry, but it doesn't have valid link address
	 * info in it (it is prob. the interface route, which has
	 * sdl_alen == 0).    dump packet.  (fall through to "bad").
	 */

bad:
	m_freem(m);
	return (0);
}
#endif /* INET */