contrib/dhcp-3.0/common/tr.c

   1 /* tr.c
   2
   3    token ring interface support
   4    Contributed in May of 1999 by Andrew Chittenden */
   5
   6 /*
   7  * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
   8  * Copyright (c) 1996-2003 by Internet Software Consortium
   9  *
  10  * Permission to use, copy, modify, and distribute this software for any
  11  * purpose with or without fee is hereby granted, provided that the above
  12  * copyright notice and this permission notice appear in all copies.
  13  *
  14  * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
  15  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  16  * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
  17  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  18  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  19  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
  20  * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  21  *
  22  *   Internet Systems Consortium, Inc.
  23  *   950 Charter Street
  24  *   Redwood City, CA 94063
  25  *   <info@isc.org>
  26  *   http://www.isc.org/
  27  */
  28
  29 #ifndef lint
  30 static char copyright[] =
  31 "$Id: tr.c,v 1.7.2.2 2004/06/10 17:59:21 dhankins Exp $ Copyright (c) 2004 Internet Systems Consortium.  All rights reserved.\n";
  32 #endif /* not lint */
  33
  34 #include "dhcpd.h"
  35
  36 #if defined (HAVE_TR_SUPPORT) && \
  37         (defined (PACKET_ASSEMBLY) || defined (PACKET_DECODING))
  38 #include "includes/netinet/ip.h"
  39 #include "includes/netinet/udp.h"
  40 #include "includes/netinet/if_ether.h"
  41 #include "netinet/if_tr.h"
  42 #include <sys/time.h>
  43
  44 /*
  45  * token ring device handling subroutines.  These are required as token-ring
  46  * does not have a simple on-the-wire header but requires the use of
  47  * source routing
  48  */
  49
  50 static int insert_source_routing PROTO ((struct trh_hdr *trh, struct interface_info* interface));
  51 static void save_source_routing PROTO ((struct trh_hdr *trh, struct interface_info* interface));
  52 static void expire_routes PROTO ((void));
  53
  54 /*
  55  * As we keep a list of interesting routing information only, a singly
  56  * linked list is all we need
  57  */
  58 struct routing_entry {
  59         struct routing_entry *next;
  60         unsigned char addr[TR_ALEN];
  61         unsigned char iface[5];
  62         __u16 rcf;                      /* route control field */
  63         __u16 rseg[8];                  /* routing registers */
  64         unsigned long access_time;      /* time we last used this entry */
  65 };
  66
  67 static struct routing_entry *routing_info = NULL;
  68
  69 static int routing_timeout = 10;
  70 static struct timeval routing_timer;
  71
  72 void assemble_tr_header (interface, buf, bufix, to)
  73         struct interface_info *interface;
  74         unsigned char *buf;
  75         unsigned *bufix;
  76         struct hardware *to;
  77 {
  78         struct trh_hdr *trh;
  79         int hdr_len;
  80         struct trllc *llc;
  81
  82
  83         /* set up the token header */
  84         trh = (struct trh_hdr *) &buf[*bufix];
  85         if (interface -> hw_address.hlen - 1 == sizeof (trh->saddr))
  86                 memcpy (trh->saddr, &interface -> hw_address.hbuf [1],
  87                                     sizeof (trh->saddr));
  88         else
  89                 memset (trh->saddr, 0x00, sizeof (trh->saddr));
  90
  91         if (to && to -> hlen == 7) /* XXX */
  92                 memcpy (trh->daddr, &to -> hbuf [1], sizeof trh->daddr);
  93         else
  94                 memset (trh->daddr, 0xff, sizeof (trh->daddr));
  95
  96         hdr_len = insert_source_routing (trh, interface);
  97
  98         trh->ac = AC;
  99         trh->fc = LLC_FRAME;
 100
 101         /* set up the llc header for snap encoding after the tr header */
 102         llc = (struct trllc *)(buf + *bufix + hdr_len);
 103         llc->dsap = EXTENDED_SAP;
 104         llc->ssap = EXTENDED_SAP;
 105         llc->llc = UI_CMD;
 106         llc->protid[0] = 0;
 107         llc->protid[1] = 0;
 108         llc->protid[2] = 0;
 109         llc->ethertype = htons(ETHERTYPE_IP);
 110
 111         hdr_len += sizeof(struct trllc);
 112
 113         *bufix += hdr_len;
 114 }
 115
 116
 117 static unsigned char tr_broadcast[6] = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };
 118
 119 /*
 120  * decoding the token header is a bit complex as you can see here. It is
 121  * further complicated by the linux kernel stripping off some valuable
 122  * information (see comment below) even though we've asked for the raw
 123  * packets.
 124  */
 125 ssize_t decode_tr_header (interface, buf, bufix, from)
 126         struct interface_info *interface;
 127         unsigned char *buf;
 128         unsigned bufix;
 129         struct hardware *from;
 130 {
 131         struct trh_hdr *trh = (struct trh_hdr *) buf + bufix;
 132         struct trllc *llc;
 133         struct ip *ip;
 134         struct udphdr *udp;
 135         unsigned int route_len = 0;
 136         ssize_t hdr_len;
 137         struct timeval now;
 138
 139         /* see whether any source routing information has expired */
 140         gettimeofday(&now, NULL);
 141
 142         if (routing_timer.tv_sec == 0)
 143                 routing_timer.tv_sec = now.tv_sec + routing_timeout;
 144         else if ((now.tv_sec - routing_timer.tv_sec) > 0)
 145                 expire_routes();
 146
 147         /* the kernel might have stripped off the source
 148          * routing bit. We try a heuristic to determine whether
 149          * this is the case and put it back on if so
 150          */
 151         route_len = (ntohs(trh->rcf) & TR_RCF_LEN_MASK) >> 8;
 152         llc = (struct trllc *)(buf + bufix + sizeof(struct trh_hdr)-TR_MAXRIFLEN+route_len);
 153         if (llc->dsap == EXTENDED_SAP
 154                         && llc->ssap == EXTENDED_SAP
 155                         && llc->llc == UI_CMD
 156                         && llc->protid[0] == 0
 157                         && llc->protid[1] == 0
 158                         && llc->protid[2] == 0) {
 159                 /* say there is source routing information present */
 160                 trh->saddr[0] |= TR_RII;
 161         }
 162
 163         if (trh->saddr[0] & TR_RII)
 164                 route_len = (ntohs(trh->rcf) & TR_RCF_LEN_MASK) >> 8;
 165         else
 166                 route_len = 0;
 167
 168         hdr_len = sizeof (struct trh_hdr) - TR_MAXRIFLEN + route_len;
 169
 170         /* now filter out unwanted packets: this is based on the packet
 171          * filter code in bpf.c */
 172         llc = (struct trllc *)(buf + bufix + hdr_len);
 173         ip = (struct ip *) (llc + 1);
 174         udp = (struct udphdr *) ((unsigned char*) ip + IP_HL (ip));
 175
 176         /* make sure it is a snap encoded, IP, UDP, unfragmented packet sent
 177          * to our port */
 178         if (llc->dsap != EXTENDED_SAP
 179                         || ntohs(llc->ethertype) != ETHERTYPE_IP
 180                         || ip->ip_p != IPPROTO_UDP
 181                         || (ntohs (ip->ip_off) & IP_OFFMASK) != 0
 182                         || udp->uh_dport != local_port)
 183                 return -1;
 184
 185         /* only save source routing information for packets from valued hosts */
 186         save_source_routing(trh, interface);
 187
 188         return hdr_len + sizeof (struct trllc);
 189 }
 190
 191 /* insert_source_routing inserts source route information into the token ring
 192  * header
 193  */
 194 static int insert_source_routing (trh, interface)
 195         struct trh_hdr *trh;
 196         struct interface_info* interface;
 197 {
 198         struct routing_entry *rover;
 199         struct timeval now;
 200         unsigned int route_len = 0;
 201
 202         gettimeofday(&now, NULL);
 203
 204         /* single route broadcasts as per rfc 1042 */
 205         if (memcmp(trh->daddr, tr_broadcast,TR_ALEN) == 0) {
 206                 trh->saddr[0] |= TR_RII;
 207                 trh->rcf = ((sizeof(trh->rcf)) << 8) & TR_RCF_LEN_MASK;
 208                 trh->rcf |= (TR_RCF_FRAME2K | TR_RCF_LIMITED_BROADCAST);
 209                 trh->rcf = htons(trh->rcf);
 210         } else {
 211                 /* look for a routing entry */
 212                 for (rover = routing_info; rover != NULL; rover = rover->next) {
 213                         if (memcmp(rover->addr, trh->daddr, TR_ALEN) == 0)
 214                                 break;
 215                 }
 216
 217                 if (rover != NULL) {
 218                         /* success: route that frame */
 219                         if ((rover->rcf & TR_RCF_LEN_MASK) >> 8) {
 220                                 __u16 rcf = rover->rcf;
 221                                 memcpy(trh->rseg,rover->rseg,sizeof(trh->rseg));
 222                                 rcf ^= TR_RCF_DIR_BIT;
 223                                 rcf &= ~TR_RCF_BROADCAST_MASK;
 224                                 trh->rcf = htons(rcf);
 225                                 trh->saddr[0] |= TR_RII;
 226                         }
 227                         rover->access_time = now.tv_sec;
 228                 } else {
 229                         /* we don't have any routing information so send a
 230                          * limited broadcast */
 231                         trh->saddr[0] |= TR_RII;
 232                         trh->rcf = ((sizeof(trh->rcf)) << 8) & TR_RCF_LEN_MASK;
 233                         trh->rcf |= (TR_RCF_FRAME2K | TR_RCF_LIMITED_BROADCAST);
 234                         trh->rcf = htons(trh->rcf);
 235                 }
 236         }
 237
 238         /* return how much of the header we've actually used */
 239         if (trh->saddr[0] & TR_RII)
 240                 route_len = (ntohs(trh->rcf) & TR_RCF_LEN_MASK) >> 8;
 241         else
 242                 route_len = 0;
 243
 244         return sizeof (struct trh_hdr) - TR_MAXRIFLEN + route_len;
 245 }
 246
 247 /*
 248  * save any source routing information
 249  */
 250 static void save_source_routing(trh, interface)
 251         struct trh_hdr *trh;
 252         struct interface_info *interface;
 253 {
 254         struct routing_entry *rover;
 255         struct timeval now;
 256         unsigned char saddr[TR_ALEN];
 257         __u16 rcf = 0;
 258
 259         gettimeofday(&now, NULL);
 260
 261         memcpy(saddr, trh->saddr, sizeof(saddr));
 262         saddr[0] &= 0x7f;   /* strip off source routing present flag */
 263
 264         /* scan our table to see if we've got it */
 265         for (rover = routing_info; rover != NULL; rover = rover->next) {
 266                 if (memcmp(&rover->addr[0], &saddr[0], TR_ALEN) == 0)
 267                         break;
 268         }
 269
 270         /* found an entry so update it with fresh information */
 271         if (rover != NULL) {
 272                 if ((trh->saddr[0] & TR_RII) &&
 273                     ((ntohs(trh->rcf) & TR_RCF_LEN_MASK) >> 8) > 2) {
 274                         rcf = ntohs(trh->rcf);
 275                         rcf &= ~TR_RCF_BROADCAST_MASK;
 276                         memcpy(rover->rseg, trh->rseg, sizeof(rover->rseg));
 277                 }
 278                 rover->rcf = rcf;
 279                 rover->access_time = now.tv_sec;
 280                 return;     /* that's all folks */
 281         }
 282
 283         /* no entry found, so create one */
 284         rover = dmalloc (sizeof (struct routing_entry), MDL);
 285         if (rover == NULL) {
 286                 fprintf(stderr,
 287                         "%s: unable to save source routing information\n",
 288                         __FILE__);
 289                 return;
 290         }
 291
 292         memcpy(rover->addr, saddr, sizeof(rover->addr));
 293         memcpy(rover->iface, interface->name, 5);
 294         rover->access_time = now.tv_sec;
 295         if (trh->saddr[0] & TR_RII) {
 296                 if (((ntohs(trh->rcf) & TR_RCF_LEN_MASK) >> 8) > 2) {
 297                         rcf = ntohs(trh->rcf);
 298                         rcf &= ~TR_RCF_BROADCAST_MASK;
 299                         memcpy(rover->rseg, trh->rseg, sizeof(rover->rseg));
 300                 }
 301                 rover->rcf = rcf;
 302         }
 303
 304         /* insert into list */
 305         rover->next = routing_info;
 306         routing_info = rover;
 307
 308         return;
 309 }
 310
 311 /*
 312  * get rid of old routes
 313  */
 314 static void expire_routes()
 315 {
 316         struct routing_entry *rover;
 317         struct routing_entry **prover = &routing_info;
 318         struct timeval now;
 319
 320         gettimeofday(&now, NULL);
 321
 322         while((rover = *prover) != NULL) {
 323                 if ((now.tv_sec - rover->access_time) > routing_timeout) {
 324                         *prover = rover->next;
 325                         dfree (rover, MDL);
 326                 } else
 327                         prover = &rover->next;
 328         }
 329
 330         /* Reset the timer */
 331         routing_timer.tv_sec = now.tv_sec + routing_timeout;
 332         routing_timer.tv_usec = now.tv_usec;
 333 }
 334
 335 #endif