}                return;                }            /*             * Update timer for interface route on which the message arrived.             * If none is found and the sender is the other end of a              * point-to-point link that isn't registered in the routing              * tables, add or restore that route.             */            if ((rt = rtfind(from)) &&                (rt->rt_state & (RTS_INTERFACE | RTS_REMOTE)))                {                rt->rt_timer = 0;                if (rt->inKernel)                     ripRouteAgeUpdate (rt); /* Update age for IP group MIB. */                }            else if ((ifp = ripIfWithDstAddr(from, NULL)) &&                     (rt == 0 || rt->rt_metric >= ifp->int_metric))                addrouteforif(ifp);            /*              * NOTE: The preceding rtfind() routine will not detect a              * match for updates from a router on the same supernet with              * a different class-based network number than the local             * interfaces. (For instance, it will not reset the route              * timer for 192.168.254.0/23 when an update is received              * from 192.168.255.x/23 if the local interface has the              * address 192.168.254.x/23. This omission has no effect              * because the timer for an interface route is never              * incremented. The return value of 0 will not cause an             * incorrect call to addrouteforif() because the search in             *  ripIfWithDstAddr will always fail in this situation.             */            /*             * Reset the pointer to validate the interface from which the             * message arrived. Updates are accepted from routers directly              * connected via broadcast or point-to-point networks.             */            ifp = pErrorIfp;    /* Results of ripIfLookup on source address. */            if ( (ifp->int_flags &                     (IFF_BROADCAST | IFF_POINTOPOINT | IFF_REMOTE)) == 0 ||                ifp->int_flags & IFF_PASSIVE)                {                /* Error: source does not use a directly-connected network. */                if (memcmp(from, &badfrom, sizeof(badfrom)) != 0)                    {                    if (routedDebug)                        logMsg ("packet from unknown router, %s\n",                             (int)(*afswitch[from->sa_family].af_format)(from),                                0, 0, 0, 0, 0);                    badfrom = *from;                    }                pErrorIfp->ifStat.rip2IfStatRcvBadPackets++;                return;                }            /*             * At this point, the source address and port number of the              * response have been checked. It is from another host on a              * directly connected network and was sent to the correct port.              * Begin processing the datagram by ignoring the initial data              * (command, version, and two unused bytes) and leading              * authentication header, if any.             */            size = size - ((char *)n - (char *)rip);            /* Now start processing actual route entries. */            for (; size > 0; size -= sizeof (struct netinfo), n++)                {                if (size < sizeof (struct netinfo))                    break;                n->rip_dst.sa_family =                    ntohs(osa(n->rip_dst)->sa_family);                n->rip_dst.sa_len = sizeof(n->rip_dst);                n->rip_metric = ntohl(n->rip_metric);                /* Ignore any entry with an unknown address family. */                if (n->rip_dst.sa_family >= AF_MAX ||                    (afp = &afswitch[n->rip_dst.sa_family])->af_hash ==                    (int (*)())0)                    {                    if (routedDebug)                        logMsg("route in unsupported address family %d from %s"                               "(af %d)\n", n->rip_dst.sa_family,                                (int)(*afswitch[from->sa_family].af_format)                               (from), from->sa_family, 0, 0, 0);                    pErrorIfp->ifStat.rip2IfStatRcvBadRoutes++;                    continue;                    }                 /*                   * Ignore an entry if the unused fields are not zero.                  * (These fields are only unused in version 1 updates).                  */                if (rip->rip_vers == 1)                    {                    if ( ((RIP2PKT *)n)->tag != 0)                        {                        pErrorIfp->ifStat.rip2IfStatRcvBadRoutes++;                        continue;                        }                    if ( ((RIP2PKT *)n)->subnet != 0)                        {                        pErrorIfp->ifStat.rip2IfStatRcvBadRoutes++;                        continue;                        }                    if ( ((RIP2PKT *)n)->gateway != 0)                        {                        pErrorIfp->ifStat.rip2IfStatRcvBadRoutes++;                        continue;                        }                    }                /*                  * Ignore any entry with an inappropriate address.                 * The receiving interface is used to detect broadcast                 * addresses if no netmask is present in the route update.                 */                if ( ((*afp->af_checkhost)(&n->rip_dst, ifp)) == 0)                    {                    if (routedDebug)                        logMsg ("bad host in route from %s (af %d)\n",                             (int)(*afswitch[from->sa_family].af_format)(from),                                from->sa_family, 0, 0, 0, 0);                    pErrorIfp->ifStat.rip2IfStatRcvBadRoutes++;                    continue;                    }                if ((n->rip_metric == 0) ||                    ((unsigned) n->rip_metric > HOPCNT_INFINITY))                    {                    if (memcmp(from, &badfrom2,                               sizeof(badfrom2)) != 0)                        {                        if (routedDebug)                            logMsg ("bad metric (%d) from %s\n", n->rip_metric,                             (int)(*afswitch[from->sa_family].af_format)(from),                                    0, 0, 0, 0);                        badfrom2 = *from;                        }                    pErrorIfp->ifStat.rip2IfStatRcvBadRoutes++;                    continue;                    }                rt = rtlookup (&n->rip_dst);                /*                  * Do not allow a route learnt from other protocols to be                 * replaced                 */                if (rt && ((rt->rt_state & RTS_OTHER) != 0))                    continue;                                if (rt == 0 ||                    (rt->rt_state & (RTS_INTERNAL|RTS_INTERFACE)) ==                    (RTS_INTERNAL|RTS_INTERFACE))                    {                    /*                     * If we're hearing a logical network route                     * back from a peer to which we sent it,                     * ignore it.                     */                    if (rt && rt->rt_state & RTS_SUBNET &&                        (*afp->af_sendroute)(rt, from, ifp))                        {                        pErrorIfp->ifStat.rip2IfStatRcvBadRoutes++;                        continue;                        }                    /*                     * Adjust metric according to incoming interface.                     */                    if ((unsigned)n->rip_metric < HOPCNT_INFINITY)                        {                        /*                         * Look for an equivalent route that                         * includes this one before adding                         * this route.                         */                        rt = rtfind(&n->rip_dst);                        if ((rt && equal(from, &rt->rt_router)) &&                            (rt->rt_metric <= n->rip_metric))                            continue;                        n->rip_metric += ifp->int_metric;                        if (rip->rip_vers < 2)                            {                            rtadd (&n->rip_dst, from, n->rip_metric,                                    0, NULL, M2_ipRouteProto_rip, 0,                                   ((struct sockaddr_in *)from)->                                    sin_addr.s_addr, pErrorIfp);                            }                        else                            {                            ripSplitPacket (ifp, (struct sockaddr_in *)from,                                             &n->rip_dst, &gateway, &netmask,                                            &tag);                            if (((struct sockaddr_in *)&netmask)->                                sin_addr.s_addr == -1)                                {                                pErrorIfp->ifStat.rip2IfStatRcvBadRoutes++;                                continue;                                }                            /*                             * RFC 1723, Section 3.4: check to see that the                              * gateway is directly reachable. If not, treat                              * that value as 0.0.0.0 by using the originator                              * as the gateway.                             */                            if ((((struct sockaddr_in *)&gateway)->                                 sin_addr.s_addr &                                  htonl (ifp->int_subnetmask)) !=                                 (((struct sockaddr_in *)&ifp->int_addr)->                                 sin_addr.s_addr &                                  htonl (ifp->int_subnetmask)))                                {                                ((struct sockaddr_in *)&gateway)->                                    sin_addr.s_addr =                                     ((struct sockaddr_in *)from)->                                    sin_addr.s_addr;                                }                            rtadd(&n->rip_dst, &gateway, n->rip_metric, 0,                                  &netmask, M2_ipRouteProto_rip, tag,                                  ((struct sockaddr_in *)from)->                                  sin_addr.s_addr, pErrorIfp);                            }                        changes++;                        }                    continue;                    }                /*                 * Update if from gateway and different,                 * shorter, or equivalent but old route                 * is getting stale.                 */                /*                 * If this was a pre-existinng route then we can                 * update it to be "infinite" and should.                 * ANVL 7.13.                 */                origMetric = n->rip_metric;                if ((unsigned) n->rip_metric < HOPCNT_INFINITY)                    n->rip_metric += ifp->int_metric;                if (n->rip_metric > HOPCNT_INFINITY)                    {                    pErrorIfp->ifStat.rip2IfStatRcvBadRoutes++;                    continue;                    }                if (rip->rip_vers > 1)                    {                    ripSplitPacket(ifp, (struct sockaddr_in *)from,                                    &n->rip_dst, &gateway, &netmask,                                   &tag);                    if (((struct sockaddr_in *)&netmask)->                        sin_addr.s_addr == -1)                        {                        pErrorIfp->ifStat.rip2IfStatRcvBadRoutes++;                        continue;                        }                    /*                     * RFC 1723, Section 3.4: check to see that the                      * gateway is directly reachable. If not, treat                      * that value as 0.0.0.0 by using the originator                      * as the gateway.                     */                    if ((((struct sockaddr_in *)&gateway)->sin_addr.s_addr &                          htonl (ifp->int_subnetmask)) !=                         (((struct sockaddr_in *)&ifp->int_addr)->                         sin_addr.s_addr & htonl (ifp->int_subnetmask)))                        {                        ((struct sockaddr_in *)&gateway)->sin_addr.s_addr =                             ((struct sockaddr_in *)from)->sin_addr.s_addr;                        }                    }                /*                 * We are making an assumption here that the address                 * is an internet address (4 bytes long). Since we currently                 * support only the AF_INET family its OK, but if that                 * changes, the following check will need to be changed                 * accordingly                 */                if (((struct sockaddr_in *)from)->sin_addr.s_addr ==                    rt->rt_orgrouter)