nhrpd/nhrp_shortcut.c

   1 /* NHRP shortcut related functions
   2  * Copyright (c) 2014-2015 Timo Teräs
   3  *
   4  * This file is free software: you may copy, redistribute and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation, either version 2 of the License, or
   7  * (at your option) any later version.
   8  */
   9
  10 #include "nhrpd.h"
  11 #include "table.h"
  12 #include "memory.h"
  13 #include "thread.h"
  14 #include "log.h"
  15 #include "nhrp_protocol.h"
  16
  17 DEFINE_MTYPE_STATIC(NHRPD, NHRP_SHORTCUT, "NHRP shortcut")
  18
  19 static struct route_table *shortcut_rib[AFI_MAX];
  20
  21 static int nhrp_shortcut_do_purge(struct thread *t);
  22 static void nhrp_shortcut_delete(struct nhrp_shortcut *s);
  23 static void nhrp_shortcut_send_resolution_req(struct nhrp_shortcut *s);
  24
  25 static void nhrp_shortcut_check_use(struct nhrp_shortcut *s)
  26 {
  27         char buf[PREFIX_STRLEN];
  28
  29         if (s->expiring && s->cache && s->cache->used) {
  30                 debugf(NHRP_DEBUG_ROUTE, "Shortcut %s used and expiring",
  31                         prefix2str(s->p, buf, sizeof buf));
  32                 nhrp_shortcut_send_resolution_req(s);
  33         }
  34 }
  35
  36 static int nhrp_shortcut_do_expire(struct thread *t)
  37 {
  38         struct nhrp_shortcut *s = THREAD_ARG(t);
  39
  40         s->t_timer = NULL;
  41         THREAD_TIMER_ON(master, s->t_timer, nhrp_shortcut_do_purge, s, s->holding_time/3);
  42         s->expiring = 1;
  43         nhrp_shortcut_check_use(s);
  44
  45         return 0;
  46 }
  47
  48 static void nhrp_shortcut_cache_notify(struct notifier_block *n, unsigned long cmd)
  49 {
  50         struct nhrp_shortcut *s = container_of(n, struct nhrp_shortcut, cache_notifier);
  51
  52         switch (cmd) {
  53         case NOTIFY_CACHE_UP:
  54                 if (!s->route_installed) {
  55                         nhrp_route_announce(1, s->type, s->p, NULL, &s->cache->remote_addr, 0);
  56                         s->route_installed = 1;
  57                 }
  58                 break;
  59         case NOTIFY_CACHE_USED:
  60                 nhrp_shortcut_check_use(s);
  61                 break;
  62         case NOTIFY_CACHE_DOWN:
  63         case NOTIFY_CACHE_DELETE:
  64                 if (s->route_installed) {
  65                         nhrp_route_announce(0, NHRP_CACHE_INVALID, s->p, NULL, NULL, 0);
  66                         s->route_installed = 0;
  67                 }
  68                 if (cmd == NOTIFY_CACHE_DELETE)
  69                         nhrp_shortcut_delete(s);
  70                 break;
  71         }
  72 }
  73
  74 static void nhrp_shortcut_update_binding(struct nhrp_shortcut *s, enum nhrp_cache_type type, struct nhrp_cache *c, int holding_time)
  75 {
  76         s->type = type;
  77         if (c != s->cache) {
  78                 if (s->cache) {
  79                         nhrp_cache_notify_del(s->cache, &s->cache_notifier);
  80                         s->cache = NULL;
  81                 }
  82                 s->cache = c;
  83                 if (s->cache) {
  84                         nhrp_cache_notify_add(s->cache, &s->cache_notifier, nhrp_shortcut_cache_notify);
  85                         if (s->cache->route_installed) {
  86                                 /* Force renewal of Zebra announce on prefix change */
  87                                 s->route_installed = 0;
  88                                 nhrp_shortcut_cache_notify(&s->cache_notifier, NOTIFY_CACHE_UP);
  89                         }
  90                 }
  91                 if (!s->cache || !s->cache->route_installed)
  92                         nhrp_shortcut_cache_notify(&s->cache_notifier, NOTIFY_CACHE_DOWN);
  93         }
  94         if (s->type == NHRP_CACHE_NEGATIVE && !s->route_installed) {
  95                 nhrp_route_announce(1, s->type, s->p, NULL, NULL, 0);
  96                 s->route_installed = 1;
  97         } else if (s->type == NHRP_CACHE_INVALID && s->route_installed) {
  98                 nhrp_route_announce(0, NHRP_CACHE_INVALID, s->p, NULL, NULL, 0);
  99                 s->route_installed = 0;
 100         }
 101
 102         THREAD_OFF(s->t_timer);
 103         if (holding_time) {
 104                 s->expiring = 0;
 105                 s->holding_time = holding_time;
 106                 THREAD_TIMER_ON(master, s->t_timer, nhrp_shortcut_do_expire, s, 2*holding_time/3);
 107         }
 108 }
 109
 110 static void nhrp_shortcut_delete(struct nhrp_shortcut *s)
 111 {
 112         struct route_node *rn;
 113         afi_t afi = family2afi(PREFIX_FAMILY(s->p));
 114         char buf[PREFIX_STRLEN];
 115
 116         THREAD_OFF(s->t_timer);
 117         nhrp_reqid_free(&nhrp_packet_reqid, &s->reqid);
 118
 119         debugf(NHRP_DEBUG_ROUTE, "Shortcut %s purged",
 120                 prefix2str(s->p, buf, sizeof buf));
 121
 122         nhrp_shortcut_update_binding(s, NHRP_CACHE_INVALID, NULL, 0);
 123
 124         /* Delete node */
 125         rn = route_node_lookup(shortcut_rib[afi], s->p);
 126         if (rn) {
 127                 XFREE(MTYPE_NHRP_SHORTCUT, rn->info);
 128                 rn->info = NULL;
 129                 route_unlock_node(rn);
 130                 route_unlock_node(rn);
 131         }
 132 }
 133
 134 static int nhrp_shortcut_do_purge(struct thread *t)
 135 {
 136         struct nhrp_shortcut *s = THREAD_ARG(t);
 137         s->t_timer = NULL;
 138         nhrp_shortcut_delete(s);
 139         return 0;
 140 }
 141
 142 static struct nhrp_shortcut *nhrp_shortcut_get(struct prefix *p)
 143 {
 144         struct nhrp_shortcut *s;
 145         struct route_node *rn;
 146         char buf[PREFIX_STRLEN];
 147         afi_t afi = family2afi(PREFIX_FAMILY(p));
 148
 149         if (!shortcut_rib[afi])
 150                 return 0;
 151
 152         rn = route_node_get(shortcut_rib[afi], p);
 153         if (!rn->info) {
 154                 s = rn->info = XCALLOC(MTYPE_NHRP_SHORTCUT, sizeof(struct nhrp_shortcut));
 155                 s->type = NHRP_CACHE_INVALID;
 156                 s->p = &rn->p;
 157
 158                 debugf(NHRP_DEBUG_ROUTE, "Shortcut %s created",
 159                         prefix2str(s->p, buf, sizeof buf));
 160         } else {
 161                 s = rn->info;
 162                 route_unlock_node(rn);
 163         }
 164         return s;
 165 }
 166
 167 static void nhrp_shortcut_recv_resolution_rep(struct nhrp_reqid *reqid, void *arg)
 168 {
 169         struct nhrp_packet_parser *pp = arg;
 170         struct nhrp_shortcut *s = container_of(reqid, struct nhrp_shortcut, reqid);
 171         struct nhrp_shortcut *ps;
 172         struct nhrp_extension_header *ext;
 173         struct nhrp_cie_header *cie;
 174         struct nhrp_cache *c = NULL;
 175         union sockunion *proto, cie_proto, *nbma, *nbma_natoa, cie_nbma, nat_nbma;
 176         struct prefix prefix, route_prefix;
 177         struct zbuf extpl;
 178         char bufp[PREFIX_STRLEN], buf[3][SU_ADDRSTRLEN];
 179         int holding_time = pp->if_ad->holdtime;
 180
 181         nhrp_reqid_free(&nhrp_packet_reqid, &s->reqid);
 182         THREAD_OFF(s->t_timer);
 183         THREAD_TIMER_ON(master, s->t_timer, nhrp_shortcut_do_purge, s, 1);
 184
 185         if (pp->hdr->type != NHRP_PACKET_RESOLUTION_REPLY) {
 186                 if (pp->hdr->type == NHRP_PACKET_ERROR_INDICATION &&
 187                     pp->hdr->u.error.code == NHRP_ERROR_PROTOCOL_ADDRESS_UNREACHABLE) {
 188                         debugf(NHRP_DEBUG_COMMON, "Shortcut: Resolution: Protocol address unreachable");
 189                         nhrp_shortcut_update_binding(s, NHRP_CACHE_NEGATIVE, NULL, holding_time);
 190                 } else {
 191                         debugf(NHRP_DEBUG_COMMON, "Shortcut: Resolution failed");
 192                 }
 193                 return;
 194         }
 195
 196         /* Parse extensions */
 197         memset(&nat_nbma, 0, sizeof nat_nbma);
 198         while ((ext = nhrp_ext_pull(&pp->extensions, &extpl)) != NULL) {
 199                 switch (htons(ext->type) & ~NHRP_EXTENSION_FLAG_COMPULSORY) {
 200                 case NHRP_EXTENSION_NAT_ADDRESS:
 201                         nhrp_cie_pull(&extpl, pp->hdr, &nat_nbma, &cie_proto);
 202                         break;
 203                 }
 204         }
 205
 206         /* Minor sanity check */
 207         prefix2sockunion(s->p, &cie_proto);
 208         if (!sockunion_same(&cie_proto, &pp->dst_proto)) {
 209                 debugf(NHRP_DEBUG_COMMON, "Shortcut: Warning dst_proto altered from %s to %s",
 210                         sockunion2str(&cie_proto, buf[0], sizeof buf[0]),
 211                         sockunion2str(&pp->dst_proto, buf[1], sizeof buf[1]));
 212         }
 213
 214         /* One or more CIEs should be given as reply, we support only one */
 215         cie = nhrp_cie_pull(&pp->payload, pp->hdr, &cie_nbma, &cie_proto);
 216         if (!cie || cie->code != NHRP_CODE_SUCCESS) {
 217                 debugf(NHRP_DEBUG_COMMON, "Shortcut: CIE code %d", cie ? cie->code : -1);
 218                 return;
 219         }
 220
 221         proto = sockunion_family(&cie_proto) != AF_UNSPEC ? &cie_proto : &pp->dst_proto;
 222         if (cie->holding_time)
 223                 holding_time = htons(cie->holding_time);
 224
 225         prefix = *s->p;
 226         prefix.prefixlen = cie->prefix_length;
 227
 228         /* Sanity check prefix length */
 229         if (prefix.prefixlen >= 8*prefix_blen(&prefix)) {
 230                 prefix.prefixlen = 8*prefix_blen(&prefix);
 231         } else if (nhrp_route_address(NULL, &pp->dst_proto, &route_prefix, NULL) == NHRP_ROUTE_NBMA_NEXTHOP) {
 232                 if (prefix.prefixlen < route_prefix.prefixlen)
 233                         prefix.prefixlen = route_prefix.prefixlen;
 234         }
 235
 236         debugf(NHRP_DEBUG_COMMON, "Shortcut: %s is at proto %s cie-nbma %s nat-nbma %s cie-holdtime %d",
 237                 prefix2str(&prefix, bufp, sizeof bufp),
 238                 sockunion2str(proto, buf[0], sizeof buf[0]),
 239                 sockunion2str(&cie_nbma, buf[1], sizeof buf[1]),
 240                 sockunion2str(&nat_nbma, buf[2], sizeof buf[2]),
 241                 htons(cie->holding_time));
 242
 243         /* Update cache entry for the protocol to nbma binding */
 244         if (sockunion_family(&nat_nbma) != AF_UNSPEC) {
 245                 nbma = &nat_nbma;
 246                 nbma_natoa = &cie_nbma;
 247         } else {
 248                 nbma = &cie_nbma;
 249                 nbma_natoa = NULL;
 250         }
 251         if (sockunion_family(nbma)) {
 252                 c = nhrp_cache_get(pp->ifp, proto, 1);
 253                 if (c) {
 254                         nhrp_cache_update_binding(
 255                                         c, NHRP_CACHE_CACHED, holding_time,
 256                                         nhrp_peer_get(pp->ifp, nbma),
 257                                         htons(cie->mtu), nbma_natoa);
 258                 }
 259         }
 260
 261         /* Update shortcut entry for subnet to protocol gw binding */
 262         if (c && !sockunion_same(proto, &pp->dst_proto)) {
 263                 ps = nhrp_shortcut_get(&prefix);
 264                 if (ps) {
 265                         ps->addr = s->addr;
 266                         nhrp_shortcut_update_binding(ps, NHRP_CACHE_CACHED, c, holding_time);
 267                 }
 268         }
 269
 270         debugf(NHRP_DEBUG_COMMON, "Shortcut: Resolution reply handled");
 271 }
 272
 273 static void nhrp_shortcut_send_resolution_req(struct nhrp_shortcut *s)
 274 {
 275         struct zbuf *zb;
 276         struct nhrp_packet_header *hdr;
 277         struct interface *ifp;
 278         struct nhrp_interface *nifp;
 279         struct nhrp_peer *peer;
 280
 281         if (nhrp_route_address(NULL, &s->addr, NULL, &peer) != NHRP_ROUTE_NBMA_NEXTHOP)
 282                 return;
 283
 284         if (s->type == NHRP_CACHE_INVALID || s->type == NHRP_CACHE_NEGATIVE)
 285                 s->type = NHRP_CACHE_INCOMPLETE;
 286
 287         ifp = peer->ifp;
 288         nifp = ifp->info;
 289
 290         /* Create request */
 291         zb = zbuf_alloc(1500);
 292         hdr = nhrp_packet_push(zb, NHRP_PACKET_RESOLUTION_REQUEST,
 293                 &nifp->nbma, &nifp->afi[family2afi(sockunion_family(&s->addr))].addr, &s->addr);
 294         hdr->u.request_id = htonl(nhrp_reqid_alloc(&nhrp_packet_reqid, &s->reqid, nhrp_shortcut_recv_resolution_rep));
 295         hdr->flags = htons(NHRP_FLAG_RESOLUTION_SOURCE_IS_ROUTER |
 296                            NHRP_FLAG_RESOLUTION_AUTHORATIVE |
 297                            NHRP_FLAG_RESOLUTION_SOURCE_STABLE);
 298
 299         /* RFC2332 - One or zero CIEs, if CIE is present contains:
 300          *  - Prefix length: widest acceptable prefix we accept (if U set, 0xff)
 301          *  - MTU: MTU of the source station
 302          *  - Holding Time: Max time to cache the source information
 303          * */
 304         /* FIXME: Send holding time, and MTU */
 305
 306         nhrp_ext_request(zb, hdr, ifp);
 307
 308         /* Cisco NAT detection extension */
 309         hdr->flags |= htons(NHRP_FLAG_RESOLUTION_NAT);
 310         nhrp_ext_push(zb, hdr, NHRP_EXTENSION_NAT_ADDRESS);
 311
 312         nhrp_packet_complete(zb, hdr);
 313
 314         nhrp_peer_send(peer, zb);
 315         nhrp_peer_unref(peer);
 316         zbuf_free(zb);
 317 }
 318
 319 void nhrp_shortcut_initiate(union sockunion *addr)
 320 {
 321         struct prefix p;
 322         struct nhrp_shortcut *s;
 323
 324         sockunion2hostprefix(addr, &p);
 325         s = nhrp_shortcut_get(&p);
 326         if (s && s->type != NHRP_CACHE_INCOMPLETE) {
 327                 s->addr = *addr;
 328                 THREAD_OFF(s->t_timer);
 329                 THREAD_TIMER_ON(master, s->t_timer, nhrp_shortcut_do_purge, s, 30);
 330                 nhrp_shortcut_send_resolution_req(s);
 331         }
 332 }
 333
 334 void nhrp_shortcut_init(void)
 335 {
 336         shortcut_rib[AFI_IP] = route_table_init();
 337         shortcut_rib[AFI_IP6] = route_table_init();
 338 }
 339
 340 void nhrp_shortcut_terminate(void)
 341 {
 342         route_table_finish(shortcut_rib[AFI_IP]);
 343         route_table_finish(shortcut_rib[AFI_IP6]);
 344 }
 345
 346 void nhrp_shortcut_foreach(afi_t afi, void (*cb)(struct nhrp_shortcut *, void *), void *ctx)
 347 {
 348         struct route_table *rt = shortcut_rib[afi];
 349         struct route_node *rn;
 350         route_table_iter_t iter;
 351
 352         if (!rt) return;
 353
 354         route_table_iter_init(&iter, rt);
 355         while ((rn = route_table_iter_next(&iter)) != NULL) {
 356                 if (rn->info) cb(rn->info, ctx);
 357         }
 358         route_table_iter_cleanup(&iter);
 359 }
 360
 361 struct purge_ctx {
 362         const struct prefix *p;
 363         int deleted;
 364 };
 365
 366 void nhrp_shortcut_purge(struct nhrp_shortcut *s, int force)
 367 {
 368         THREAD_OFF(s->t_timer);
 369         nhrp_reqid_free(&nhrp_packet_reqid, &s->reqid);
 370
 371         if (force) {
 372                 /* Immediate purge on route with draw or pending shortcut */
 373                 THREAD_TIMER_MSEC_ON(master, s->t_timer, nhrp_shortcut_do_purge, s, 5);
 374         } else {
 375                 /* Soft expire - force immediate renewal, but purge
 376                  * in few seconds to make sure stale route is not
 377                  * used too long. In practice most purges are caused
 378                  * by hub bgp change, but target usually stays same.
 379                  * This allows to keep nhrp route up, and to not
 380                  * cause temporary rerouting via hubs causing latency
 381                  * jitter. */
 382                 THREAD_TIMER_MSEC_ON(master, s->t_timer, nhrp_shortcut_do_purge, s, 3000);
 383                 s->expiring = 1;
 384                 nhrp_shortcut_check_use(s);
 385         }
 386 }
 387
 388 static void nhrp_shortcut_purge_prefix(struct nhrp_shortcut *s, void *ctx)
 389 {
 390         struct purge_ctx *pctx = ctx;
 391
 392         if (prefix_match(pctx->p, s->p))
 393                 nhrp_shortcut_purge(s, pctx->deleted || !s->cache);
 394 }
 395
 396 void nhrp_shortcut_prefix_change(const struct prefix *p, int deleted)
 397 {
 398         struct purge_ctx pctx = {
 399                 .p = p,
 400                 .deleted = deleted,
 401         };
 402         nhrp_shortcut_foreach(family2afi(PREFIX_FAMILY(p)), nhrp_shortcut_purge_prefix, &pctx);
 403 }
 404