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 <asm/byteorder.h>
  28 #include <arpa/nameser.h>
  29 #include <resolv.h>
  30 #include <time.h>
  31
  32 #include <libubox/usock.h>
  33 #include <libubox/uloop.h>
  34 #include <libubox/avl-cmp.h>
  35 #include <libubox/blobmsg_json.h>
  36 #include <libubox/kvlist.h>
  37 #include <libubus.h>
  38
  39 #include "cache.h"
  40 #include "util.h"
  41 #include "dns.h"
  42
  43 static struct uloop_timeout cache_gc;
  44 struct avl_tree records, entries, hosts;
  45 static struct blob_buf b;
  46
  47 static struct kvlist types;
  48
  49 static void
  50 cache_record_free(struct cache_record *r, int rem)
  51 {
  52         DBG(2, "%s %s\n", dns_type_string(r->type), r->record);
  53         if (rem)
  54                 avl_delete(&records, &r->avl);
  55         if (r->record)
  56                 free(r->record);
  57         if (r->rdata)
  58                 free(r->rdata);
  59         if (r->txt)
  60                 free(r->txt);
  61         free(r);
  62 }
  63
  64 static void
  65 cache_entry_free(struct cache_entry *s)
  66 {
  67         DBG(2, "%s\n", s->entry);
  68         avl_delete(&entries, &s->avl);
  69         if (s->host)
  70                 free(s->host);
  71         if (s->entry)
  72                 free(s->entry);
  73         free(s);
  74 }
  75
  76 static int
  77 cache_is_expired(time_t t, uint32_t ttl)
  78 {
  79         if (time(NULL) - t >= ttl)
  80                 return 1;
  81
  82         return 0;
  83 }
  84
  85 static void
  86 cache_gc_timer(struct uloop_timeout *timeout)
  87 {
  88         struct cache_record *r, *p;
  89         struct cache_entry *s, *t;
  90
  91         avl_for_each_element_safe(&records, r, avl, p)
  92                 if (cache_is_expired(r->time, r->ttl))
  93                         cache_record_free(r, 1);
  94
  95         avl_for_each_element_safe(&entries, s, avl, t) {
  96                 if (!s->host)
  97                         continue;
  98                 if (cache_is_expired(s->time, s->ttl))
  99                         cache_entry_free(s);
 100         }
 101
 102         uloop_timeout_set(timeout, 10000);
 103 }
 104
 105 static void
 106 cache_load_services(void)
 107 {
 108         struct blob_attr *cur;
 109         int rem;
 110
 111         blob_buf_init(&b, 0);
 112
 113         if (!blobmsg_add_json_from_file(&b, "/lib/mdns/service-types"))
 114                 return;
 115
 116         blob_for_each_attr(cur, b.head, rem)
 117                 kvlist_set(&types, blobmsg_name(cur), blobmsg_get_string(cur));
 118 }
 119
 120 char*
 121 cache_lookup_name(const char *key)
 122 {
 123         return kvlist_get(&types, key);
 124 }
 125
 126 int
 127 cache_init(void)
 128 {
 129         kvlist_init(&types, kvlist_strlen);
 130         avl_init(&entries, avl_strcmp, true, NULL);
 131         avl_init(&records, avl_strcmp, true, NULL);
 132
 133         cache_gc.cb = cache_gc_timer;
 134         uloop_timeout_set(&cache_gc, 10000);
 135         cache_load_services();
 136
 137         return 0;
 138 }
 139
 140 void cache_cleanup(void)
 141 {
 142         struct cache_record *r, *p;
 143         struct cache_entry *s, *t;
 144
 145         avl_for_each_element_safe(&records, r, avl, p)
 146                 cache_record_free(r, 1);
 147
 148         avl_for_each_element_safe(&entries, s, avl, t)
 149                 cache_entry_free(s);
 150 }
 151
 152 void
 153 cache_scan(void)
 154 {
 155         struct cache_entry *s;
 156
 157         avl_for_each_element(&entries, s, avl)
 158                 dns_send_question(&listener, s->entry, TYPE_PTR);
 159 }
 160
 161 static struct cache_entry*
 162 cache_find_entry(char *entry)
 163 {
 164         struct cache_entry *s;
 165
 166         avl_for_each_element(&entries, s, avl)
 167                 if (!strcmp(s->entry, entry))
 168                         return s;
 169         return NULL;
 170 }
 171
 172 static struct cache_entry*
 173 cache_entry(struct uloop_fd *u, char *entry, int hlen, int ttl)
 174 {
 175         struct cache_entry *s;
 176         char *type;
 177
 178         s = cache_find_entry(entry);
 179         if (s)
 180                 return s;
 181
 182         s = malloc(sizeof(struct cache_entry));
 183         memset(s, 0, sizeof(struct cache_entry));
 184         s->avl.key = s->entry = strdup(entry);
 185         s->time = time(NULL);
 186         s->ttl = ttl;
 187
 188         if (hlen)
 189                 s->host = strndup(s->entry, hlen);
 190         type = strstr(s->entry, "._");
 191         if (type)
 192                 type++;
 193         if (type)
 194                 s->avl.key = type;
 195         avl_insert(&entries, &s->avl);
 196
 197         if (!hlen)
 198                 dns_send_question(u, entry, TYPE_PTR);
 199
 200         return s;
 201 }
 202
 203 static struct cache_record*
 204 cache_record_find(char *record, int type, int port, int rdlength, uint8_t *rdata)
 205 {
 206         struct cache_record *l = avl_find_element(&records, record, l, avl);
 207
 208         if (!l)
 209                 return NULL;
 210
 211         while (l && !avl_is_last(&records, &l->avl) && !strcmp(l->record, record)) {
 212                 struct cache_record *r = l;
 213
 214                 l = avl_next_element(l, avl);
 215                 if (r->type != type)
 216                         continue;
 217
 218                 if (r->type == TYPE_TXT || (r->type == TYPE_SRV))
 219                         return r;
 220
 221                 if (r->port != port)
 222                         continue;
 223
 224                 if (r->rdlength != rdlength)
 225                         continue;
 226
 227                 if (!!r->rdata != !!rdata)
 228                         continue;
 229
 230                 if (!r->rdata || !rdata || memcmp(r->rdata, rdata, rdlength))
 231                         continue;
 232
 233                 return r;
 234         }
 235
 236         return NULL;
 237 }
 238
 239 int
 240 cache_host_is_known(char *record)
 241 {
 242         struct cache_record *l = avl_find_element(&records, record, l, avl);
 243
 244         if (!l)
 245                 return 0;
 246
 247         while (l && !avl_is_last(&records, &l->avl) && !strcmp(l->record, record)) {
 248                 struct cache_record *r = l;
 249
 250                 l = avl_next_element(l, avl);
 251                 if ((r->type != TYPE_A) && (r->type != TYPE_AAAA))
 252                         continue;
 253                 return 1;
 254         }
 255
 256         return 0;
 257 }
 258
 259 void
 260 cache_answer(struct uloop_fd *u, uint8_t *base, int blen, char *name, struct dns_answer *a, uint8_t *rdata)
 261 {
 262         struct dns_srv_data *dsd = (struct dns_srv_data *) rdata;
 263         struct cache_record *r;
 264         int port = 0, dlen = 0, tlen = 0, nlen, rdlength;
 265         char *p = NULL;
 266
 267         if (!(a->class & CLASS_IN))
 268                 return;
 269
 270         nlen = strlen(name);
 271
 272         switch (a->type) {
 273         case TYPE_PTR:
 274                 if (a->rdlength < 2)
 275                         return;
 276
 277                 if (dn_expand(base, base + blen, rdata, rdata_buffer, MAX_DATA_LEN) < 0) {
 278                         perror("process_answer/dn_expand");
 279                         return;
 280                 }
 281
 282                 DBG(1, "A -> %s %s %s\n", dns_type_string(a->type), name, rdata_buffer);
 283
 284                 rdlength = strlen(rdata_buffer);
 285
 286                 if (!strcmp(C_DNS_SD, name)) {
 287                         cache_entry(u, rdata_buffer, 0, a->ttl);
 288                         return;
 289                 }
 290
 291                 if ((rdlength < nlen) && (rdlength - nlen - 1 > 0))
 292                         return;
 293
 294                 cache_entry(u, rdata_buffer, rdlength - nlen - 1, a->ttl);
 295                 return;
 296
 297         case TYPE_SRV:
 298                 if (a->rdlength < 8)
 299                         return;
 300
 301                 port = be16_to_cpu(dsd->port);
 302                 break;
 303
 304         case TYPE_TXT:
 305                 rdlength = a->rdlength;
 306                 if (rdlength <= 2)
 307                         return;
 308
 309                 memcpy(rdata_buffer, &rdata[1], rdlength);
 310                 rdata_buffer[rdlength] = rdata_buffer[rdlength + 1] = '\0';
 311                 tlen = rdlength + 1;
 312                 p = &rdata_buffer[*rdata];
 313
 314                 do {
 315                         uint8_t v = *p;
 316
 317                         *p = '\0';
 318                         if (v)
 319                                 p += v + 1;
 320                 } while (*p);
 321                 break;
 322
 323         case TYPE_A:
 324                 cache_entry(u, name, strlen(name), a->ttl);
 325                 if (a->rdlength != 4)
 326                         return;
 327                 dlen = 4;
 328                 break;
 329
 330         case TYPE_AAAA:
 331                 cache_entry(u, name, strlen(name), a->ttl);
 332                 if (a->rdlength != 16)
 333                         return;
 334                 dlen = 16;
 335                 break;
 336
 337         default:
 338                 return;
 339         }
 340
 341         r = cache_record_find(name, a->type, port, dlen, rdata);
 342         if (r) {
 343                 if (!a->ttl) {
 344                         cache_record_free(r, 1);
 345                         DBG(1, "D -> %s %s ttl:%d\n", dns_type_string(r->type), r->record, r->ttl);
 346                 } else {
 347                         r->ttl = a->ttl;
 348                         DBG(1, "A -> %s %s ttl:%d\n", dns_type_string(r->type), r->record, r->ttl);
 349                 }
 350                 return;
 351         }
 352
 353         if (!a->ttl)
 354                 return;
 355
 356         r = malloc(sizeof(struct cache_record));
 357         memset(r, 0, sizeof(struct cache_record));
 358         r->avl.key = r->record = strdup(name);
 359         r->type = a->type;
 360         r->ttl = a->ttl;
 361         r->port = port;
 362         r->rdlength = dlen;
 363         r->time = time(NULL);
 364
 365         if (tlen) {
 366                 r->txt = malloc(tlen);
 367                 if (r->txt)
 368                         memcpy(r->txt, rdata_buffer, tlen);
 369         }
 370
 371         if (dlen) {
 372                 r->rdata = malloc(dlen);
 373                 if (!r->rdata) {
 374                         cache_record_free(r, 0);
 375                         return;
 376                 }
 377                 memcpy(r->rdata, rdata, dlen);
 378         }
 379
 380         if (avl_insert(&records, &r->avl))
 381                 cache_record_free(r, 0);
 382         else
 383                 DBG(1, "A -> %s %s ttl:%d\n", dns_type_string(r->type), r->record, r->ttl);
 384 }