cache.c

   1 /*
   2  * Copyright (C) 2014 John Crispin <blogic@openwrt.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU Lesser General Public License version 2.1
   6  * as published by the Free Software Foundation
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  */
  13
  14 #define _GNU_SOURCE
  15 #include <sys/types.h>
  16 #include <sys/stat.h>
  17
  18 #include <fcntl.h>
  19 #include <time.h>
  20 #include <stdio.h>
  21 #include <string.h>
  22 #include <unistd.h>
  23 #include <sys/types.h>
  24 #include <sys/socket.h>
  25 #include <netinet/in.h>
  26 #include <arpa/inet.h>
  27 #include <arpa/nameser.h>
  28 #include <resolv.h>
  29 #include <time.h>
  30
  31 #include <libubox/usock.h>
  32 #include <libubox/uloop.h>
  33 #include <libubox/avl-cmp.h>
  34 #include <libubox/blobmsg_json.h>
  35 #include <libubox/kvlist.h>
  36 #include <libubus.h>
  37
  38 #include "cache.h"
  39 #include "util.h"
  40 #include "dns.h"
  41 #include "interface.h"
  42
  43 static struct uloop_timeout cache_gc;
  44 struct avl_tree entries;
  45 static AVL_TREE(records, avl_strcmp, true, NULL);
  46
  47 static void
  48 cache_record_free(struct cache_record *r)
  49 {
  50         DBG(2, "%s %s\n", dns_type_string(r->type), r->record);
  51         avl_delete(&records, &r->avl);
  52         free(r);
  53 }
  54
  55 static void
  56 cache_entry_free(struct cache_entry *s)
  57 {
  58         DBG(2, "%s\n", s->entry);
  59         avl_delete(&entries, &s->avl);
  60         free(s);
  61 }
  62
  63 static int
  64 cache_is_expired(time_t t, uint32_t ttl)
  65 {
  66         if (time(NULL) - t >= ttl)
  67                 return 1;
  68
  69         return 0;
  70 }
  71
  72 static void
  73 cache_gc_timer(struct uloop_timeout *timeout)
  74 {
  75         struct cache_record *r, *p;
  76         struct cache_entry *s, *t;
  77
  78         avl_for_each_element_safe(&records, r, avl, p)
  79                 if (cache_is_expired(r->time, r->ttl))
  80                         cache_record_free(r);
  81
  82         avl_for_each_element_safe(&entries, s, avl, t) {
  83                 if (!s->host)
  84                         continue;
  85                 if (cache_is_expired(s->time, s->ttl))
  86                         cache_entry_free(s);
  87         }
  88
  89         uloop_timeout_set(timeout, 10000);
  90 }
  91
  92 int
  93 cache_init(void)
  94 {
  95         avl_init(&entries, avl_strcmp, true, NULL);
  96
  97         cache_gc.cb = cache_gc_timer;
  98         uloop_timeout_set(&cache_gc, 10000);
  99
 100         return 0;
 101 }
 102
 103 void cache_cleanup(void)
 104 {
 105         struct cache_record *r, *p;
 106         struct cache_entry *s, *t;
 107
 108         avl_for_each_element_safe(&records, r, avl, p)
 109                 cache_record_free(r);
 110
 111         avl_for_each_element_safe(&entries, s, avl, t)
 112                 cache_entry_free(s);
 113 }
 114
 115 void
 116 cache_scan(void)
 117 {
 118         struct interface *iface;
 119         struct cache_entry *s;
 120
 121         vlist_for_each_element(&interfaces, iface, node)
 122                 avl_for_each_element(&entries, s, avl)
 123                         dns_send_question(iface, s->entry, TYPE_PTR, 1);
 124 }
 125
 126 static struct cache_entry*
 127 cache_entry(struct interface *iface, char *entry, int hlen, int ttl)
 128 {
 129         struct cache_entry *s, *t;
 130         char *entry_buf;
 131         char *host_buf;
 132         char *type;
 133
 134         avl_for_each_element_safe(&entries, s, avl, t)
 135                 if (!strcmp(s->entry, entry))
 136                         return s;
 137
 138         s = calloc_a(sizeof(*s),
 139                 &entry_buf, strlen(entry) + 1,
 140                 &host_buf, hlen ? hlen + 1 : 0);
 141
 142         s->avl.key = s->entry = strcpy(entry_buf, entry);
 143         s->time = time(NULL);
 144         s->ttl = ttl;
 145
 146         if (hlen)
 147                 s->host = strncpy(host_buf, s->entry, hlen);
 148
 149         type = strstr(entry_buf, "._");
 150         if (type)
 151                 type++;
 152         if (type)
 153                 s->avl.key = type;
 154         avl_insert(&entries, &s->avl);
 155
 156         if (!hlen)
 157                 dns_send_question(iface, entry, TYPE_PTR, !iface->multicast);
 158
 159         return s;
 160 }
 161
 162 static struct cache_record*
 163 cache_record_find(char *record, int type, int port, int rdlength, uint8_t *rdata)
 164 {
 165         struct cache_record *l = avl_find_element(&records, record, l, avl);
 166
 167         if (!l)
 168                 return NULL;
 169
 170         while (l && l->record && !strcmp(l->record, record)) {
 171                 struct cache_record *r = l;
 172
 173                 l = avl_next_element(l, avl);
 174                 if (r->type != type)
 175                         continue;
 176
 177                 if (r->type == TYPE_TXT || (r->type == TYPE_SRV))
 178                         return r;
 179
 180                 if (r->port != port)
 181                         continue;
 182
 183                 if (r->rdlength != rdlength)
 184                         continue;
 185
 186                 if (!!r->rdata != !!rdata)
 187                         continue;
 188
 189                 if (!r->rdata || !rdata || memcmp(r->rdata, rdata, rdlength))
 190                         continue;
 191
 192                 return r;
 193         }
 194
 195         return NULL;
 196 }
 197
 198 int
 199 cache_host_is_known(char *record)
 200 {
 201         struct cache_record *l = avl_find_element(&records, record, l, avl);
 202
 203         if (!l)
 204                 return 0;
 205
 206         while (l && !avl_is_last(&records, &l->avl) && !strcmp(l->record, record)) {
 207                 struct cache_record *r = l;
 208
 209                 l = avl_next_element(l, avl);
 210                 if ((r->type != TYPE_A) && (r->type != TYPE_AAAA))
 211                         continue;
 212                 return 1;
 213         }
 214
 215         return 0;
 216 }
 217
 218 void
 219 cache_answer(struct interface *iface, uint8_t *base, int blen, char *name, struct dns_answer *a, uint8_t *rdata)
 220 {
 221         struct dns_srv_data *dsd = (struct dns_srv_data *) rdata;
 222         struct cache_record *r;
 223         int port = 0, dlen = 0, tlen = 0, nlen, rdlength;
 224         char *p = NULL;
 225         char *name_buf;
 226         void *rdata_ptr, *txt_ptr;
 227         int host_len = 0;
 228         static char *rdata_buffer = (char *) mdns_buf;
 229
 230         if (!(a->class & CLASS_IN))
 231                 return;
 232
 233         nlen = strlen(name);
 234
 235         switch (a->type) {
 236         case TYPE_PTR:
 237                 if (a->rdlength < 2)
 238                         return;
 239
 240                 if (dn_expand(base, base + blen, rdata, rdata_buffer, MAX_DATA_LEN) < 0) {
 241                         perror("process_answer/dn_expand");
 242                         return;
 243                 }
 244
 245                 DBG(1, "A -> %s %s %s\n", dns_type_string(a->type), name, rdata_buffer);
 246
 247                 rdlength = strlen(rdata_buffer);
 248
 249                 if (strcmp(C_DNS_SD, name) != 0 &&
 250                     nlen + 1 < rdlength && !strcmp(rdata_buffer + rdlength - nlen, name))
 251                         host_len = rdlength - nlen - 1;
 252
 253                 cache_entry(iface, rdata_buffer, host_len, a->ttl);
 254                 return;
 255
 256         case TYPE_SRV:
 257                 if (a->rdlength < 8)
 258                         return;
 259
 260                 port = be16_to_cpu(dsd->port);
 261                 break;
 262
 263         case TYPE_TXT:
 264                 rdlength = a->rdlength;
 265                 if (rdlength <= 2)
 266                         return;
 267
 268                 memcpy(rdata_buffer, &rdata[1], rdlength);
 269                 rdata_buffer[rdlength] = rdata_buffer[rdlength + 1] = '\0';
 270                 tlen = rdlength + 1;
 271                 p = &rdata_buffer[*rdata];
 272
 273                 do {
 274                         uint8_t v = *p;
 275
 276                         *p = '\0';
 277                         if (v && p + v < &rdata_buffer[rdlength])
 278                                 p += v + 1;
 279                 } while (*p);
 280                 break;
 281
 282         case TYPE_A:
 283                 cache_entry(iface, name, strlen(name), a->ttl);
 284                 if (a->rdlength != 4)
 285                         return;
 286                 dlen = 4;
 287                 break;
 288
 289         case TYPE_AAAA:
 290                 cache_entry(iface, name, strlen(name), a->ttl);
 291                 if (a->rdlength != 16)
 292                         return;
 293                 dlen = 16;
 294                 break;
 295
 296         default:
 297                 return;
 298         }
 299
 300         r = cache_record_find(name, a->type, port, dlen, rdata);
 301         if (r) {
 302                 if (!a->ttl) {
 303                         DBG(1, "D -> %s %s ttl:%d\n", dns_type_string(r->type), r->record, r->ttl);
 304                         r->time = time(0) + 1 - r->ttl;
 305                 } else {
 306                         r->ttl = a->ttl;
 307                         DBG(1, "A -> %s %s ttl:%d\n", dns_type_string(r->type), r->record, r->ttl);
 308                 }
 309                 return;
 310         }
 311
 312         if (!a->ttl)
 313                 return;
 314
 315         r = calloc_a(sizeof(*r),
 316                 &name_buf, strlen(name) + 1,
 317                 &txt_ptr, tlen,
 318                 &rdata_ptr, dlen);
 319
 320         r->avl.key = r->record = strcpy(name_buf, name);
 321         r->type = a->type;
 322         r->ttl = a->ttl;
 323         r->port = port;
 324         r->rdlength = dlen;
 325         r->time = time(NULL);
 326
 327         if (tlen)
 328                 r->txt = memcpy(txt_ptr, rdata_buffer, tlen);
 329
 330         if (dlen)
 331                 r->rdata = memcpy(rdata_ptr, rdata, dlen);
 332
 333         if (avl_insert(&records, &r->avl))
 334                 free(r);
 335         else
 336                 DBG(1, "A -> %s %s ttl:%d\n", dns_type_string(r->type), r->record, r->ttl);
 337 }
 338
 339 void
 340 cache_dump_records(struct blob_buf *buf, const char *name)
 341 {
 342         struct cache_record *r, *last, *next;
 343         const char *txt;
 344         char buffer[INET6_ADDRSTRLEN];
 345
 346         last = avl_last_element(&records, last, avl);
 347         for (r = avl_find_element(&records, name, r, avl); r; r = next) {
 348                 switch (r->type) {
 349                 case TYPE_TXT:
 350                         if (r->txt && strlen(r->txt)) {
 351                                 txt = r->txt;
 352                                 do {
 353                                         blobmsg_add_string(buf, "txt", txt);
 354                                         txt = &txt[strlen(txt) + 1];
 355                                 } while (*txt);
 356                         }
 357                         break;
 358
 359                 case TYPE_SRV:
 360                         if (r->port)
 361                                 blobmsg_add_u32(buf, "port", r->port);
 362                         break;
 363
 364                 case TYPE_A:
 365                         if ((r->rdlength == 4) && inet_ntop(AF_INET, r->rdata, buffer, INET6_ADDRSTRLEN))
 366                                 blobmsg_add_string(buf, "ipv4", buffer);
 367                         break;
 368
 369                 case TYPE_AAAA:
 370                         if ((r->rdlength == 16) && inet_ntop(AF_INET6, r->rdata, buffer, INET6_ADDRSTRLEN))
 371                                 blobmsg_add_string(buf, "ipv6", buffer);
 372                         break;
 373                 }
 374
 375                 if (r == last)
 376                         break;
 377
 378                 next = avl_next_element(r, avl);
 379                 if (strcmp(r->record, next->record) != 0)
 380                         break;
 381         }
 382 }