source: rtems/cpukit/libnetworking/net/route.c @ 4c672b93

/*
 * Copyright (c) 1980, 1986, 1991, 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.
 *
 *      @(#)route.c     8.2 (Berkeley) 11/15/93
 *      $Id$
 */

#include "opt_mrouting.h"

#include <sys/param.h>
#include <sys/queue.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/domain.h>
#include <sys/protosw.h>
#include <sys/ioctl.h>

#include <net/if.h>
#include <net/route.h>
#include <net/raw_cb.h>

#include <netinet/in.h>
#include <netinet/in_var.h>
#include <netinet/ip_mroute.h>

#define SA(p) ((struct sockaddr *)(p))

struct route_cb route_cb;
static struct rtstat rtstat;
struct radix_node_head *rt_tables[AF_MAX+1];

static int      rttrash;                /* routes not in table but not freed */

static void rt_maskedcopy(struct sockaddr *,
            struct sockaddr *, struct sockaddr *);
static void rtable_init(struct radix_node_head **);

/* compare two sockaddr structures */
#define sa_equal(a1, a2) (bcmp((a1), (a2), (a1)->sa_len) == 0)

static void
rtable_init(struct radix_node_head **table)
{
        struct domain *dom;
        for (dom = domains; dom; dom = dom->dom_next)
                if (dom->dom_rtattach)
                        dom->dom_rtattach((void *)&table[dom->dom_family],
                            dom->dom_rtoffset);
}

void
route_init(void)
{
        rn_init();      /* initialize all zeroes, all ones, mask table */
        rtable_init(rt_tables);
}

/*
 * Packet routing routines.
 */
void
rtalloc(struct route *ro)
{
        if (ro->ro_rt && ro->ro_rt->rt_ifp && (ro->ro_rt->rt_flags & RTF_UP))
                return;                          /* XXX */
        ro->ro_rt = rtalloc1(&ro->ro_dst, 1, 0UL);
}

void
rtalloc_ign(struct route *ro, u_long ignore)
{
        if (ro->ro_rt && ro->ro_rt->rt_ifp && (ro->ro_rt->rt_flags & RTF_UP))
                return;                          /* XXX */
        ro->ro_rt = rtalloc1(&ro->ro_dst, 1, ignore);
}

/*
 * Look up the route that matches the address given
 * Or, at least try.. Create a cloned route if needed.
 */
struct rtentry *
rtalloc1(struct sockaddr *dst, int report, u_long ignflags)
{
        struct radix_node_head *rnh = rt_tables[dst->sa_family];
        struct rtentry *rt;
        struct radix_node *rn;
        struct rtentry *newrt;
        struct rt_addrinfo info;
        u_long nflags;
        int  s = splnet();
        int err = 0, msgtype = RTM_MISS;

        newrt = NULL;
        /*
         * Look up the address in the table for that Address Family
         */
        if (rnh && (rn = rnh->rnh_matchaddr((caddr_t)dst, rnh)) &&
            ((rn->rn_flags & RNF_ROOT) == 0)) {
                /*
                 * If we find it and it's not the root node, then
                 * get a refernce on the rtentry associated.
                 */
                newrt = rt = (struct rtentry *)rn;
                nflags = rt->rt_flags & ~ignflags;
                if (report && (nflags & (RTF_CLONING | RTF_PRCLONING))) {
                        /*
                         * We are apparently adding (report = 0 in delete).
                         * If it requires that it be cloned, do so.
                         * (This implies it wasn't a HOST route.)
                         */
                        err = rtrequest(RTM_RESOLVE, dst, SA(0),
                                              SA(0), 0, &newrt);
                        if (err) {
                                /*
                                 * If the cloning didn't succeed, maybe
                                 * what we have will do. Return that.
                                 */
                                newrt = rt;
                                rt->rt_refcnt++;
                                goto miss;
                        }
                        if ((rt = newrt) && (rt->rt_flags & RTF_XRESOLVE)) {
                                /*
                                 * If the new route specifies it be 
                                 * externally resolved, then go do that.
                                 */
                                msgtype = RTM_RESOLVE;
                                goto miss;
                        }
                } else
                        rt->rt_refcnt++;
        } else {
                /*
                 * Either we hit the root or couldn't find any match,
                 * Which basically means
                 * "caint get there frm here"
                 */
                rtstat.rts_unreach++;
        miss:   if (report) {
                        /*
                         * If required, report the failure to the supervising
                         * Authorities.
                         * For a delete, this is not an error. (report == 0)
                         */
                        bzero(&info, sizeof(info));
                        info.rti_info[RTAX_DST] = dst;
                        rt_missmsg(msgtype, &info, 0, err);
                }
        }
        splx(s);
        return (newrt);
}

/*
 * Remove a reference count from an rtentry.
 * If the count gets low enough, take it out of the routing table
 */
void
rtfree(struct rtentry *rt)
{
        register struct radix_node_head *rnh =
                rt_tables[rt_key(rt)->sa_family];
        register struct ifaddr *ifa;

        if (rt == 0 || rnh == 0)
                panic("rtfree");
        rt->rt_refcnt--;
        if(rnh->rnh_close && rt->rt_refcnt == 0) {
                rnh->rnh_close((struct radix_node *)rt, rnh);
        }
        if (rt->rt_refcnt <= 0 && (rt->rt_flags & RTF_UP) == 0) {
                if (rt->rt_nodes->rn_flags & (RNF_ACTIVE | RNF_ROOT))
                        panic ("rtfree 2");
                rttrash--;
                if (rt->rt_refcnt < 0) {
                        printf("rtfree: %p not freed (neg refs)\n", rt);
                        return;
                }
                ifa = rt->rt_ifa;
                IFAFREE(ifa);
                if (rt->rt_parent) {
                        RTFREE(rt->rt_parent);
                }
                Free(rt_key(rt));
                Free(rt);
        }
}

void
ifafree(ifa)
        register struct ifaddr *ifa;
{
        if (ifa == NULL)
                panic("ifafree");
        if (ifa->ifa_refcnt == 0)
                free(ifa, M_IFADDR);
        else
                ifa->ifa_refcnt--;
}

/*
 * Force a routing table entry to the specified
 * destination to go through the given gateway.
 * Normally called as a result of a routing redirect
 * message from the network layer.
 *
 * N.B.: must be called at splnet
 *
 */
void
rtredirect(struct sockaddr *dst, 
        struct sockaddr *gateway, 
        struct sockaddr *netmask, 
        int flags,
        struct sockaddr *src,
        struct rtentry **rtp)
{
        struct rtentry *rt;
        int error = 0;
        short *stat = NULL;
        struct rt_addrinfo info;
        struct ifaddr *ifa;

        /* verify the gateway is directly reachable */
        if ((ifa = ifa_ifwithnet(gateway)) == NULL) {
                error = ENETUNREACH;
                goto out;
        }
        rt = rtalloc1(dst, 0, 0UL);
        /*
         * If the redirect isn't from our current router for this dst,
         * it's either old or wrong.  If it redirects us to ourselves,
         * we have a routing loop, perhaps as a result of an interface
         * going down recently.
         */
#define equal(a1, a2) (bcmp((caddr_t)(a1), (caddr_t)(a2), (a1)->sa_len) == 0)
        if (!(flags & RTF_DONE) && rt &&
             (!equal(src, rt->rt_gateway) || rt->rt_ifa != ifa))
                error = EINVAL;
        else if (ifa_ifwithaddr(gateway))
                error = EHOSTUNREACH;
        if (error)
                goto done;
        /*
         * Create a new entry if we just got back a wildcard entry
         * or the the lookup failed.  This is necessary for hosts
         * which use routing redirects generated by smart gateways
         * to dynamically build the routing tables.
         */
        if ((rt == 0) || (rt_mask(rt) && rt_mask(rt)->sa_len < 2))
                goto create;
        /*
         * Don't listen to the redirect if it's
         * for a route to an interface.
         */
        if (rt->rt_flags & RTF_GATEWAY) {
                if (((rt->rt_flags & RTF_HOST) == 0) && (flags & RTF_HOST)) {
                        /*
                         * Changing from route to net => route to host.
                         * Create new route, rather than smashing route to net.
                         */
                create:
                        flags |=  RTF_GATEWAY | RTF_DYNAMIC;
                        error = rtrequest((int)RTM_ADD, dst, gateway,
                                    netmask, flags,
                                    (struct rtentry **)0);
                        stat = &rtstat.rts_dynamic;
                } else {
                        /*
                         * Smash the current notion of the gateway to
                         * this destination.  Should check about netmask!!!
                         */
                        rt->rt_flags |= RTF_MODIFIED;
                        flags |= RTF_MODIFIED;
                        stat = &rtstat.rts_newgateway;
                        rt_setgate(rt, rt_key(rt), gateway);
                }
        } else
                error = EHOSTUNREACH;
done:
        if (rt) {
                if (rtp && !error)
                        *rtp = rt;
                else
                        rtfree(rt);
        }
out:
        if (error)
                rtstat.rts_badredirect++;
        else if (stat != NULL)
                (*stat)++;
        bzero(&info, sizeof(info));
        info.rti_info[RTAX_DST] = dst;
        info.rti_info[RTAX_GATEWAY] = gateway;
        info.rti_info[RTAX_NETMASK] = netmask;
        info.rti_info[RTAX_AUTHOR] = src;
        rt_missmsg(RTM_REDIRECT, &info, flags, error);
}

/*
* Routing table ioctl interface.
*/
int
rtioctl(req, data, p)
        int req;
        caddr_t data;
        struct proc *p;
{
#ifdef INET
        /* Multicast goop, grrr... */
#ifdef MROUTING
        return mrt_ioctl(req, data);
#else
        return mrt_ioctl(req, data, p);
#endif
#else /* INET */
        return ENXIO;
#endif /* INET */
}

struct ifaddr *
ifa_ifwithroute(int flags, struct sockaddr *dst, struct sockaddr *gateway)
{
        register struct ifaddr *ifa;
        if ((flags & RTF_GATEWAY) == 0) {
                /*
                 * If we are adding a route to an interface,
                 * and the interface is a pt to pt link
                 * we should search for the destination
                 * as our clue to the interface.  Otherwise
                 * we can use the local address.
                 */
                ifa = NULL;
                if (flags & RTF_HOST) {
                        ifa = ifa_ifwithdstaddr(dst);
                }
                if (ifa == NULL)
                        ifa = ifa_ifwithaddr(gateway);
        } else {
                /*
                 * If we are adding a route to a remote net
                 * or host, the gateway may still be on the
                 * other end of a pt to pt link.
                 */
                ifa = ifa_ifwithdstaddr(gateway);
        }
        if (ifa == 0)
                ifa = ifa_ifwithnet(gateway);
        if (ifa == 0) {
                struct rtentry *rt = rtalloc1(dst, 0, 0UL);
                if (rt == 0)
                        return (0);
                rt->rt_refcnt--;
                if ((ifa = rt->rt_ifa) == 0)
                        return (0);
        }
        if (ifa->ifa_addr->sa_family != dst->sa_family) {
                struct ifaddr *oifa = ifa;
                ifa = ifaof_ifpforaddr(dst, ifa->ifa_ifp);
                if (ifa == 0)
                        ifa = oifa;
        }
        return (ifa);
}

#define ROUNDUP(a) (a>0 ? (1 + (((a) - 1) | (sizeof(long) - 1))) : sizeof(long))

static int rt_fixdelete(struct radix_node *, void *);
static int rt_fixchange(struct radix_node *, void *);

struct rtfc_arg {
        struct rtentry *rt0;
        struct radix_node_head *rnh;
};

/*
 * Do appropriate manipulations of a routing tree given
 * all the bits of info needed
 */
int
rtrequest(int req,
        struct sockaddr *dst,
        struct sockaddr *gateway,
        struct sockaddr *netmask,
        int flags,
        struct rtentry **ret_nrt)
{
        int s = splnet(); int error = 0;
        register struct rtentry *rt;
        register struct radix_node *rn;
        register struct radix_node_head *rnh;
        struct ifaddr *ifa;
        struct sockaddr *ndst;
#define senderr(x) { error = x ; goto bad; }

        /*
         * Find the correct routing tree to use for this Address Family
         */
        if ((rnh = rt_tables[dst->sa_family]) == 0)
                senderr(ESRCH);
        /*
         * If we are adding a host route then we don't want to put
         * a netmask in the tree
         */
        if (flags & RTF_HOST)
                netmask = 0;
        switch (req) {
        case RTM_DELETE:
                /*
                 * Remove the item from the tree and return it.
                 * Complain if it is not there and do no more processing.
                 */
                if ((rn = rnh->rnh_deladdr(dst, netmask, rnh)) == 0)
                        senderr(ESRCH);
                if (rn->rn_flags & (RNF_ACTIVE | RNF_ROOT))
                        panic ("rtrequest delete");
                rt = (struct rtentry *)rn;

                /*
                 * Now search what's left of the subtree for any cloned
                 * routes which might have been formed from this node.
                 */
                if ((rt->rt_flags & RTF_PRCLONING) && netmask) {
                        rnh->rnh_walktree_from(rnh, dst, netmask,
                                               rt_fixdelete, rt);
                }

                /*
                 * Remove any external references we may have.
                 * This might result in another rtentry being freed if
                 * we held it's last reference.
                 */
                if (rt->rt_gwroute) {
                        rt = rt->rt_gwroute;
                        RTFREE(rt);
                        (rt = (struct rtentry *)rn)->rt_gwroute = 0;
                }

                /*
                 * NB: RTF_UP must be set during the search above,
                 * because we might delete the last ref, causing
                 * rt to get freed prematurely.
                 */
                rt->rt_flags &= ~RTF_UP;

                /* 
                 * If there is llinfo or similar associated with the 
                 * route, give the interface a chance to deal with it..
                 */
                if ((ifa = rt->rt_ifa) && ifa->ifa_rtrequest)
                        ifa->ifa_rtrequest(RTM_DELETE, rt, SA(0));
                rttrash++;
                /*
                 * If the caller wants it, then it can have it, but it's up to it
                 * to free the rtentry as we won't be doing it.
                 */
                if (ret_nrt)
                        *ret_nrt = rt;
                else if (rt->rt_refcnt <= 0) {
                        rt->rt_refcnt++; /* make a 1->0 transition */
                        rtfree(rt);
                }
                break;

        case RTM_RESOLVE:
                if (ret_nrt == 0 || (rt = *ret_nrt) == 0)
                        senderr(EINVAL);
                ifa = rt->rt_ifa;
                flags = rt->rt_flags &
                    ~(RTF_CLONING | RTF_PRCLONING | RTF_STATIC);
                flags |= RTF_WASCLONED;
                gateway = rt->rt_gateway;
                if ((netmask = rt->rt_genmask) == 0)
                        flags |= RTF_HOST;
                goto makeroute;

        case RTM_ADD:
                if ((flags & RTF_GATEWAY) && !gateway)
                        panic("rtrequest: GATEWAY but no gateway");

                if ((ifa = ifa_ifwithroute(flags, dst, gateway)) == 0)
                        senderr(ENETUNREACH);

        makeroute:
                R_Malloc(rt, struct rtentry *, sizeof(*rt));
                if (rt == 0)
                        senderr(ENOBUFS);
                Bzero(rt, sizeof(*rt));
                rt->rt_flags = RTF_UP | flags;
                if ((error = rt_setgate(rt, dst, gateway))) {
                        Free(rt);
                        senderr(error);
                }
                ndst = rt_key(rt);
                if (netmask) {
                        rt_maskedcopy(dst, ndst, netmask);
                } else
                        Bcopy(dst, ndst, dst->sa_len);

                /*
                 * This moved from below so that rnh->rnh_addaddr() can
                 * examine the ifa and ifp if it so desires.
                 */
                ifa->ifa_refcnt++;
                rt->rt_ifa = ifa;
                rt->rt_ifp = ifa->ifa_ifp;

                rn = rnh->rnh_addaddr((caddr_t)ndst, (caddr_t)netmask,
                                        rnh, rt->rt_nodes);
                if (rn == 0) {
                        struct rtentry *rt2;
                        /*
                         * Uh-oh, we already have one of these in the tree.
                         * We do a special hack: if the route that's already
                         * there was generated by the protocol-cloning
                         * mechanism, then we just blow it away and retry
                         * the insertion of the new one.
                         */
                        rt2 = rtalloc1(dst, 0, RTF_PRCLONING);
                        if (rt2 && rt2->rt_parent) {
                                rtrequest(RTM_DELETE, 
                                          (struct sockaddr *)rt_key(rt2),
                                          rt2->rt_gateway,
                                          rt_mask(rt2), rt2->rt_flags, 0);
                                RTFREE(rt2);
                                rn = rnh->rnh_addaddr((caddr_t)ndst,
                                                      (caddr_t)netmask,
                                                      rnh, rt->rt_nodes);
                        } else if (rt2) {
                                RTFREE(rt2);
                        }
                }

                if (rn == 0) {
                        if (rt->rt_gwroute)
                                rtfree(rt->rt_gwroute);
                        if (rt->rt_ifa) {
                                IFAFREE(rt->rt_ifa);
                        }
                        Free(rt_key(rt));
                        Free(rt);
                        senderr(EEXIST);
                }
                rt->rt_parent = 0;

                if (req == RTM_RESOLVE) {
                        rt->rt_rmx = (*ret_nrt)->rt_rmx; /* copy metrics */
                        if ((*ret_nrt)->rt_flags & RTF_PRCLONING) {
                                rt->rt_parent = (*ret_nrt);
                                (*ret_nrt)->rt_refcnt++;
                        }
                }
                if (ifa->ifa_rtrequest)
                        ifa->ifa_rtrequest(req, rt, SA(ret_nrt ? *ret_nrt : 0));
                /*
                 * We repeat the same procedure from rt_setgate() here because
                 * it doesn't fire when we call it there because the node
                 * hasn't been added to the tree yet.
                 */
                if (!(rt->rt_flags & RTF_HOST) && rt_mask(rt) != 0) {
                        struct rtfc_arg arg;
                        arg.rnh = rnh;
                        arg.rt0 = rt;
                        rnh->rnh_walktree_from(rnh, rt_key(rt), rt_mask(rt),
                                               rt_fixchange, &arg);
                }

                if (ret_nrt) {
                        *ret_nrt = rt;
                        rt->rt_refcnt++;
                }
                break;
        }
bad:
        splx(s);
        return (error);
}

/*
 * Called from rtrequest(RTM_DELETE, ...) to fix up the route's ``family''
 * (i.e., the routes related to it by the operation of cloning).  This
 * routine is iterated over all potential former-child-routes by way of
 * rnh->rnh_walktree_from() above, and those that actually are children of
 * the late parent (passed in as VP here) are themselves deleted.
 */
static int
rt_fixdelete(struct radix_node *rn, void *vp)
{
        struct rtentry *rt = (struct rtentry *)rn;
        struct rtentry *rt0 = vp;

        if (rt->rt_parent == rt0 && !(rt->rt_flags & RTF_PINNED)) {
                return rtrequest(RTM_DELETE, rt_key(rt),
                                 (struct sockaddr *)0, rt_mask(rt),
                                 rt->rt_flags, (struct rtentry **)0);
        }
        return 0;
}

/*
 * This routine is called from rt_setgate() to do the analogous thing for
 * adds and changes.  There is the added complication in this case of a
 * middle insert; i.e., insertion of a new network route between an older
 * network route and (cloned) host routes.  For this reason, a simple check
 * of rt->rt_parent is insufficient; each candidate route must be tested
 * against the (mask, value) of the new route (passed as before in vp)
 * to see if the new route matches it.  Unfortunately, this has the obnoxious
 * property of also triggering for insertion /above/ a pre-existing network
 * route and clones.  Sigh.  This may be fixed some day.
 *
 * XXX - it may be possible to do fixdelete() for changes and reserve this
 * routine just for adds.  I'm not sure why I thought it was necessary to do
 * changes this way.
 */
#ifdef DEBUG
int rtfcdebug = 0;
#endif

static int
rt_fixchange(struct radix_node *rn, void *vp)
{
        struct rtentry *rt = (struct rtentry *)rn;
        struct rtfc_arg *ap = vp;
        struct rtentry *rt0 = ap->rt0;
        struct radix_node_head *rnh = ap->rnh;
        u_char *xk1, *xm1, *xk2;
        int i, len;

#ifdef DEBUG
        if (rtfcdebug)
                printf("rt_fixchange: rt %p, rt0 %p\n", rt, rt0);
#endif

        if (!rt->rt_parent || (rt->rt_flags & RTF_PINNED)) {
#ifdef DEBUG
                if(rtfcdebug) printf("no parent or pinned\n");
#endif
                return 0;
        }

        if (rt->rt_parent == rt0) {
#ifdef DEBUG
                if(rtfcdebug) printf("parent match\n");
#endif
                return rtrequest(RTM_DELETE, rt_key(rt),
                                 (struct sockaddr *)0, rt_mask(rt),
                                 rt->rt_flags, (struct rtentry **)0);
        }

        /*
         * There probably is a function somewhere which does this...
         * if not, there should be.
         */
        len = imin(((struct sockaddr *)rt_key(rt0))->sa_len,
                   ((struct sockaddr *)rt_key(rt))->sa_len);

        xk1 = (u_char *)rt_key(rt0);
        xm1 = (u_char *)rt_mask(rt0);
        xk2 = (u_char *)rt_key(rt);

        for (i = rnh->rnh_treetop->rn_offset; i < len; i++) {
                if ((xk2[i] & xm1[i]) != xk1[i]) {
#ifdef DEBUG
                        if(rtfcdebug) printf("no match\n");
#endif
                        return 0;
                }
        }

        /*
         * OK, this node is a clone, and matches the node currently being
         * changed/added under the node's mask.  So, get rid of it.
         */
#ifdef DEBUG
        if(rtfcdebug) printf("deleting\n");
#endif
        return rtrequest(RTM_DELETE, rt_key(rt), (struct sockaddr *)0,
                         rt_mask(rt), rt->rt_flags, (struct rtentry **)0);
}

int
rt_setgate(rt0, dst, gate)
        struct rtentry *rt0;
        struct sockaddr *dst, *gate;
{
        caddr_t new, old;
        int dlen = ROUNDUP(dst->sa_len), glen = ROUNDUP(gate->sa_len);
        register struct rtentry *rt = rt0;
        struct radix_node_head *rnh = rt_tables[dst->sa_family];

        /*
         * A host route with the destination equal to the gateway
         * will interfere with keeping LLINFO in the routing
         * table, so disallow it.
         */
        if (((rt0->rt_flags & (RTF_HOST|RTF_GATEWAY|RTF_LLINFO)) ==
                                        (RTF_HOST|RTF_GATEWAY)) &&
            (dst->sa_len == gate->sa_len) &&
            (bcmp(dst, gate, dst->sa_len) == 0)) {
                /*
                 * The route might already exist if this is an RTM_CHANGE
                 * or a routing redirect, so try to delete it.
                 */
                if (rt_key(rt0))
                        rtrequest(RTM_DELETE, (struct sockaddr *)rt_key(rt0),
                            rt0->rt_gateway, rt_mask(rt0), rt0->rt_flags, 0);
                return EADDRNOTAVAIL;
        }

        if (rt->rt_gateway == 0 || glen > ROUNDUP(rt->rt_gateway->sa_len)) {
                old = (caddr_t)rt_key(rt);
                R_Malloc(new, caddr_t, dlen + glen);
                if (new == 0)
                        return ENOBUFS;
                rt->rt_nodes->rn_key = new;
        } else {
                new = rt->rt_nodes->rn_key;
                old = 0;
        }
        Bcopy(gate, (rt->rt_gateway = (struct sockaddr *)(new + dlen)), glen);
        if (old) {
                Bcopy(dst, new, dlen);
                Free(old);
        }
        if (rt->rt_gwroute) {
                rt = rt->rt_gwroute; RTFREE(rt);
                rt = rt0; rt->rt_gwroute = 0;
        }
        /*
         * Cloning loop avoidance:
         * In the presence of protocol-cloning and bad configuration,
         * it is possible to get stuck in bottomless mutual recursion
         * (rtrequest rt_setgate rtalloc1).  We avoid this by not allowing
         * protocol-cloning to operate for gateways (which is probably the
         * correct choice anyway), and avoid the resulting reference loops
         * by disallowing any route to run through itself as a gateway.
         * This is obviuosly mandatory when we get rt->rt_output().
         */
        if (rt->rt_flags & RTF_GATEWAY) {
                rt->rt_gwroute = rtalloc1(gate, 1, RTF_PRCLONING);
                if (rt->rt_gwroute == rt) {
                        RTFREE(rt->rt_gwroute);
                        rt->rt_gwroute = 0;
                        return EDQUOT; /* failure */
                }
        }

        /*
         * This isn't going to do anything useful for host routes, so
         * don't bother.  Also make sure we have a reasonable mask
         * (we don't yet have one during adds).
         */
        if (!(rt->rt_flags & RTF_HOST) && rt_mask(rt) != 0) {
                struct rtfc_arg arg;
                arg.rnh = rnh;
                arg.rt0 = rt;
                rnh->rnh_walktree_from(rnh, rt_key(rt), rt_mask(rt),
                                       rt_fixchange, &arg);
        }

        return 0;
}

static void
rt_maskedcopy(src, dst, netmask)
        struct sockaddr *src, *dst, *netmask;
{
        register u_char *cp1 = (u_char *)src;
        register u_char *cp2 = (u_char *)dst;
        register u_char *cp3 = (u_char *)netmask;
        u_char *cplim = cp2 + *cp3;
        u_char *cplim2 = cp2 + *cp1;

        *cp2++ = *cp1++; *cp2++ = *cp1++; /* copies sa_len & sa_family */
        cp3 += 2;
        if (cplim > cplim2)
                cplim = cplim2;
        while (cp2 < cplim)
                *cp2++ = *cp1++ & *cp3++;
        if (cp2 < cplim2)
                bzero(cp2, (unsigned)(cplim2 - cp2));
}

/*
 * Set up a routing table entry, normally
 * for an interface.
 */
int
rtinit(ifa, cmd, flags)
        register struct ifaddr *ifa;
        int cmd, flags;
{
        register struct rtentry *rt;
        register struct sockaddr *dst;
        register struct sockaddr *deldst;
        struct mbuf *m = 0;
        struct rtentry *nrt = 0;
        int error;

        dst = flags & RTF_HOST ? ifa->ifa_dstaddr : ifa->ifa_addr;
        /*
         * If it's a delete, check that if it exists, it's on the correct
         * interface or we might scrub a route to another ifa which would
         * be confusing at best and possibly worse.
         */
        if (cmd == RTM_DELETE) {
                /* 
                 * It's a delete, so it should already exist..
                 * If it's a net, mask off the host bits
                 * (Assuming we have a mask)
                 */
                if ((flags & RTF_HOST) == 0 && ifa->ifa_netmask) {
                        m = m_get(M_WAIT, MT_SONAME);
                        deldst = mtod(m, struct sockaddr *);
                        rt_maskedcopy(dst, deldst, ifa->ifa_netmask);
                        dst = deldst;
                }
                /*
                 * Get an rtentry that is in the routing tree and
                 * contains the correct info. (if this fails we can't get there).
                 * We set "report" to FALSE so that if it doesn't exist,
                 * it doesn't report an error or clone a route, etc. etc.
                 */
                rt = rtalloc1(dst, 0, 0UL);
                if (rt) {
                        /*
                         * Ok so we found the rtentry. it has an extra reference
                         * for us at this stage. we won't need that so
                         * lop that off now.
                         */
                        rt->rt_refcnt--;
                        if (rt->rt_ifa != ifa) {
                                /*
                                 * If the interface in the rtentry doesn't match
                                 * the interface we are using, then we don't
                                 * want to delete it, so return an error.
                                 * This seems to be the only point of 
                                 * this whole RTM_DELETE clause.
                                 */
                                if (m)
                                        (void) m_free(m);
                                return (flags & RTF_HOST ? EHOSTUNREACH
                                                        : ENETUNREACH);
                        }
                }
                /* XXX */
#if 0
                else {
                        /* 
                         * One would think that as we are deleting, and we know
                         * it doesn't exist, we could just return at this point
                         * with an "ELSE" clause, but apparently not..
                         */
                        return (flags & RTF_HOST ? EHOSTUNREACH
                                                        : ENETUNREACH);
                }
#endif
        }
        /*
         * Do the actual request
         */
        error = rtrequest(cmd, dst, ifa->ifa_addr, ifa->ifa_netmask,
                        flags | ifa->ifa_flags, &nrt);
        if (m)
                (void) m_free(m);
        /*
         * If we are deleting, and we found an entry, then
         * it's been removed from the tree.. now throw it away.
         */
        if (cmd == RTM_DELETE && error == 0 && (rt = nrt)) {
                /*
                 * notify any listenning routing agents of the change
                 */
                rt_newaddrmsg(cmd, ifa, error, nrt);
                if (rt->rt_refcnt <= 0) {
                        rt->rt_refcnt++; /* need a 1->0 transition to free */
                        rtfree(rt);
                }
        }

        /*
         * We are adding, and we have a returned routing entry.
         * We need to sanity check the result.
         */
        if (cmd == RTM_ADD && error == 0 && (rt = nrt)) {
                /*
                 * We just wanted to add it.. we don't actually need a reference
                 */
                rt->rt_refcnt--;
                /*
                 * If it came back with an unexpected interface, then it must 
                 * have already existed or something. (XXX)
                 */
                if (rt->rt_ifa != ifa) {
                        printf("rtinit: wrong ifa (%p) was (%p)\n", ifa,
                                rt->rt_ifa);
                        /*
                         * Ask that the route we got back be removed
                         * from the routing tables as we are trying
                         * to supersede it.
                         */
                        if (rt->rt_ifa->ifa_rtrequest)
                            rt->rt_ifa->ifa_rtrequest(RTM_DELETE, rt, SA(0));
                        /* 
                         * Remove the referenve to the it's ifaddr.
                         */
                        IFAFREE(rt->rt_ifa);
                        /*
                         * And substitute in references to the ifaddr
                         * we are adding.
                         */
                        rt->rt_ifa = ifa;
                        rt->rt_ifp = ifa->ifa_ifp;
                        ifa->ifa_refcnt++;
                        /*
                         * Now add it to the routing table
                         * XXX could we have just left it?
                         * as it might have been in the right place..
                         */
                        if (ifa->ifa_rtrequest)
                            ifa->ifa_rtrequest(RTM_ADD, rt, SA(0));
                }
                /*
                 * notify any listenning routing agents of the change
                 */
                rt_newaddrmsg(cmd, ifa, error, nrt);
        }
        return (error);
}