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