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 #include "interface.h"
  43
  44 static struct uloop_timeout cache_gc;
  45 struct avl_tree records, entries, hosts;
  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         avl_init(&records, avl_strcmp, true, NULL);
  97
  98         cache_gc.cb = cache_gc_timer;
  99         uloop_timeout_set(&cache_gc, 10000);
 100
 101         return 0;
 102 }
 103
 104 void cache_cleanup(void)
 105 {
 106         struct cache_record *r, *p;
 107         struct cache_entry *s, *t;
 108
 109         avl_for_each_element_safe(&records, r, avl, p)
 110                 cache_record_free(r);
 111
 112         avl_for_each_element_safe(&entries, s, avl, t)
 113                 cache_entry_free(s);
 114 }
 115
 116 void
 117 cache_scan(void)
 118 {
 119         struct cache_entry *s;
 120
 121         avl_for_each_element(&entries, s, avl)
 122                 dns_send_question(cur_iface, s->entry, TYPE_PTR);
 123 }
 124
 125 static struct cache_entry*
 126 cache_entry(struct uloop_fd *u, char *entry, int hlen, int ttl)
 127 {
 128         struct cache_entry *s;
 129         char *entry_buf;
 130         char *host_buf;
 131         char *type;
 132
 133         s = avl_find_element(&entries, entry, s, avl);
 134         if (s)
 135                 return s;
 136
 137         s = calloc_a(sizeof(*s),
 138                 &entry_buf, strlen(entry) + 1,
 139                 &host_buf, hlen ? hlen + 1 : 0);
 140
 141         s->avl.key = s->entry = strcpy(entry_buf, entry);
 142         s->time = time(NULL);
 143         s->ttl = ttl;
 144
 145         if (hlen)
 146                 s->host = strncpy(host_buf, s->entry, hlen);
 147
 148         type = strstr(entry_buf, "._");
 149         if (type)
 150                 type++;
 151         if (type)
 152                 s->avl.key = type;
 153         avl_insert(&entries, &s->avl);
 154
 155         if (!hlen)
 156                 dns_send_question(cur_iface, entry, TYPE_PTR);
 157
 158         return s;
 159 }
 160
 161 static struct cache_record*
 162 cache_record_find(char *record, int type, int port, int rdlength, uint8_t *rdata)
 163 {
 164         struct cache_record *l = avl_find_element(&records, record, l, avl);
 165
 166         if (!l)
 167                 return NULL;
 168
 169         while (l && !avl_is_last(&records, &l->avl) && !strcmp(l->record, record)) {
 170                 struct cache_record *r = l;
 171
 172                 l = avl_next_element(l, avl);
 173                 if (r->type != type)
 174                         continue;
 175
 176                 if (r->type == TYPE_TXT || (r->type == TYPE_SRV))
 177                         return r;
 178
 179                 if (r->port != port)
 180                         continue;
 181
 182                 if (r->rdlength != rdlength)
 183                         continue;
 184
 185                 if (!!r->rdata != !!rdata)
 186                         continue;
 187
 188                 if (!r->rdata || !rdata || memcmp(r->rdata, rdata, rdlength))
 189                         continue;
 190
 191                 return r;
 192         }
 193
 194         return NULL;
 195 }
 196
 197 int
 198 cache_host_is_known(char *record)
 199 {
 200         struct cache_record *l = avl_find_element(&records, record, l, avl);
 201
 202         if (!l)
 203                 return 0;
 204
 205         while (l && !avl_is_last(&records, &l->avl) && !strcmp(l->record, record)) {
 206                 struct cache_record *r = l;
 207
 208                 l = avl_next_element(l, avl);
 209                 if ((r->type != TYPE_A) && (r->type != TYPE_AAAA))
 210                         continue;
 211                 return 1;
 212         }
 213
 214         return 0;
 215 }
 216
 217 void
 218 cache_answer(struct uloop_fd *u, uint8_t *base, int blen, char *name, struct dns_answer *a, uint8_t *rdata)
 219 {
 220         struct dns_srv_data *dsd = (struct dns_srv_data *) rdata;
 221         struct cache_record *r;
 222         int port = 0, dlen = 0, tlen = 0, nlen, rdlength;
 223         char *p = NULL;
 224         char *name_buf;
 225         void *rdata_ptr, *txt_ptr;
 226         int host_len = 0;
 227
 228         if (!(a->class & CLASS_IN))
 229                 return;
 230
 231         nlen = strlen(name);
 232
 233         switch (a->type) {
 234         case TYPE_PTR:
 235                 if (a->rdlength < 2)
 236                         return;
 237
 238                 if (dn_expand(base, base + blen, rdata, rdata_buffer, MAX_DATA_LEN) < 0) {
 239                         perror("process_answer/dn_expand");
 240                         return;
 241                 }
 242
 243                 DBG(1, "A -> %s %s %s\n", dns_type_string(a->type), name, rdata_buffer);
 244
 245                 rdlength = strlen(rdata_buffer);
 246
 247                 if (strcmp(C_DNS_SD, name) != 0 &&
 248                     nlen + 1 < rdlength && !strcmp(rdata_buffer + rdlength - nlen, name))
 249                         host_len = rdlength - nlen - 1;
 250
 251                 cache_entry(u, rdata_buffer, host_len, a->ttl);
 252                 return;
 253
 254         case TYPE_SRV:
 255                 if (a->rdlength < 8)
 256                         return;
 257
 258                 port = be16_to_cpu(dsd->port);
 259                 break;
 260
 261         case TYPE_TXT:
 262                 rdlength = a->rdlength;
 263                 if (rdlength <= 2)
 264                         return;
 265
 266                 memcpy(rdata_buffer, &rdata[1], rdlength);
 267                 rdata_buffer[rdlength] = rdata_buffer[rdlength + 1] = '\0';
 268                 tlen = rdlength + 1;
 269                 p = &rdata_buffer[*rdata];
 270
 271                 do {
 272                         uint8_t v = *p;
 273
 274                         *p = '\0';
 275                         if (v)
 276                                 p += v + 1;
 277                 } while (*p);
 278                 break;
 279
 280         case TYPE_A:
 281                 cache_entry(u, name, strlen(name), a->ttl);
 282                 if (a->rdlength != 4)
 283                         return;
 284                 dlen = 4;
 285                 break;
 286
 287         case TYPE_AAAA:
 288                 cache_entry(u, name, strlen(name), a->ttl);
 289                 if (a->rdlength != 16)
 290                         return;
 291                 dlen = 16;
 292                 break;
 293
 294         default:
 295                 return;
 296         }
 297
 298         r = cache_record_find(name, a->type, port, dlen, rdata);
 299         if (r) {
 300                 if (!a->ttl) {
 301                         cache_record_free(r);
 302                         DBG(1, "D -> %s %s ttl:%d\n", dns_type_string(r->type), r->record, r->ttl);
 303                 } else {
 304                         r->ttl = a->ttl;
 305                         DBG(1, "A -> %s %s ttl:%d\n", dns_type_string(r->type), r->record, r->ttl);
 306                 }
 307                 return;
 308         }
 309
 310         if (!a->ttl)
 311                 return;
 312
 313         r = calloc_a(sizeof(*r),
 314                 &name_buf, strlen(name) + 1,
 315                 &txt_ptr, tlen,
 316                 &rdata_ptr, dlen);
 317
 318         r->avl.key = r->record = strcpy(name_buf, name);
 319         r->type = a->type;
 320         r->ttl = a->ttl;
 321         r->port = port;
 322         r->rdlength = dlen;
 323         r->time = time(NULL);
 324
 325         if (tlen)
 326                 r->txt = memcpy(txt_ptr, rdata_buffer, tlen);
 327
 328         if (dlen)
 329                 r->rdata = memcpy(rdata_ptr, rdata, dlen);
 330
 331         if (avl_insert(&records, &r->avl))
 332                 free(r);
 333         else
 334                 DBG(1, "A -> %s %s ttl:%d\n", dns_type_string(r->type), r->record, r->ttl);
 335 }