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