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