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
  46 static void
  47 cache_record_free(struct cache_record *r)
  48 {
  49         DBG(2, "%s %s\n", dns_type_string(r->type), r->record);
  50         avl_delete(&records, &r->avl);
  51         free(r);
  52 }
  53
  54 static void
  55 cache_entry_free(struct cache_entry *s)
  56 {
  57         DBG(2, "%s\n", s->entry);
  58         avl_delete(&entries, &s->avl);
  59         free(s);
  60 }
  61
  62 static int
  63 cache_is_expired(time_t t, uint32_t ttl)
  64 {
  65         if (time(NULL) - t >= ttl)
  66                 return 1;
  67
  68         return 0;
  69 }
  70
  71 static void
  72 cache_gc_timer(struct uloop_timeout *timeout)
  73 {
  74         struct cache_record *r, *p;
  75         struct cache_entry *s, *t;
  76
  77         avl_for_each_element_safe(&records, r, avl, p)
  78                 if (cache_is_expired(r->time, r->ttl))
  79                         cache_record_free(r);
  80
  81         avl_for_each_element_safe(&entries, s, avl, t) {
  82                 if (!s->host)
  83                         continue;
  84                 if (cache_is_expired(s->time, s->ttl))
  85                         cache_entry_free(s);
  86         }
  87
  88         uloop_timeout_set(timeout, 10000);
  89 }
  90
  91 int
  92 cache_init(void)
  93 {
  94         avl_init(&entries, avl_strcmp, true, NULL);
  95         avl_init(&records, 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 cache_entry *s;
 119
 120         avl_for_each_element(&entries, s, avl)
 121                 dns_send_question(&listener, s->entry, TYPE_PTR);
 122 }
 123
 124 static struct cache_entry*
 125 cache_entry(struct uloop_fd *u, char *entry, int hlen, int ttl)
 126 {
 127         struct cache_entry *s;
 128         char *entry_buf;
 129         char *host_buf;
 130         char *type;
 131
 132         s = avl_find_element(&entries, entry, s, avl);
 133         if (s)
 134                 return s;
 135
 136         s = calloc_a(sizeof(*s),
 137                 &entry_buf, strlen(entry) + 1,
 138                 &host_buf, hlen ? hlen + 1 : 0);
 139
 140         s->avl.key = s->entry = strcpy(entry_buf, entry);
 141         s->time = time(NULL);
 142         s->ttl = ttl;
 143
 144         if (hlen)
 145                 s->host = strncpy(host_buf, s->entry, hlen);
 146
 147         type = strstr(entry_buf, "._");
 148         if (type)
 149                 type++;
 150         if (type)
 151                 s->avl.key = type;
 152         avl_insert(&entries, &s->avl);
 153
 154         if (!hlen)
 155                 dns_send_question(u, entry, TYPE_PTR);
 156
 157         return s;
 158 }
 159
 160 static struct cache_record*
 161 cache_record_find(char *record, int type, int port, int rdlength, uint8_t *rdata)
 162 {
 163         struct cache_record *l = avl_find_element(&records, record, l, avl);
 164
 165         if (!l)
 166                 return NULL;
 167
 168         while (l && !avl_is_last(&records, &l->avl) && !strcmp(l->record, record)) {
 169                 struct cache_record *r = l;
 170
 171                 l = avl_next_element(l, avl);
 172                 if (r->type != type)
 173                         continue;
 174
 175                 if (r->type == TYPE_TXT || (r->type == TYPE_SRV))
 176                         return r;
 177
 178                 if (r->port != port)
 179                         continue;
 180
 181                 if (r->rdlength != rdlength)
 182                         continue;
 183
 184                 if (!!r->rdata != !!rdata)
 185                         continue;
 186
 187                 if (!r->rdata || !rdata || memcmp(r->rdata, rdata, rdlength))
 188                         continue;
 189
 190                 return r;
 191         }
 192
 193         return NULL;
 194 }
 195
 196 int
 197 cache_host_is_known(char *record)
 198 {
 199         struct cache_record *l = avl_find_element(&records, record, l, avl);
 200
 201         if (!l)
 202                 return 0;
 203
 204         while (l && !avl_is_last(&records, &l->avl) && !strcmp(l->record, record)) {
 205                 struct cache_record *r = l;
 206
 207                 l = avl_next_element(l, avl);
 208                 if ((r->type != TYPE_A) && (r->type != TYPE_AAAA))
 209                         continue;
 210                 return 1;
 211         }
 212
 213         return 0;
 214 }
 215
 216 void
 217 cache_answer(struct uloop_fd *u, uint8_t *base, int blen, char *name, struct dns_answer *a, uint8_t *rdata)
 218 {
 219         struct dns_srv_data *dsd = (struct dns_srv_data *) rdata;
 220         struct cache_record *r;
 221         int port = 0, dlen = 0, tlen = 0, nlen, rdlength;
 222         char *p = NULL;
 223         char *name_buf;
 224         void *rdata_ptr, *txt_ptr;
 225         int host_len = 0;
 226
 227         if (!(a->class & CLASS_IN))
 228                 return;
 229
 230         nlen = strlen(name);
 231
 232         switch (a->type) {
 233         case TYPE_PTR:
 234                 if (a->rdlength < 2)
 235                         return;
 236
 237                 if (dn_expand(base, base + blen, rdata, rdata_buffer, MAX_DATA_LEN) < 0) {
 238                         perror("process_answer/dn_expand");
 239                         return;
 240                 }
 241
 242                 DBG(1, "A -> %s %s %s\n", dns_type_string(a->type), name, rdata_buffer);
 243
 244                 rdlength = strlen(rdata_buffer);
 245
 246                 if (strcmp(C_DNS_SD, name) != 0 &&
 247                     nlen + 1 < rdlength && !strcmp(rdata_buffer + rdlength - nlen, name))
 248                         host_len = rdlength - nlen - 1;
 249
 250                 cache_entry(u, rdata_buffer, host_len, a->ttl);
 251                 return;
 252
 253         case TYPE_SRV:
 254                 if (a->rdlength < 8)
 255                         return;
 256
 257                 port = be16_to_cpu(dsd->port);
 258                 break;
 259
 260         case TYPE_TXT:
 261                 rdlength = a->rdlength;
 262                 if (rdlength <= 2)
 263                         return;
 264
 265                 memcpy(rdata_buffer, &rdata[1], rdlength);
 266                 rdata_buffer[rdlength] = rdata_buffer[rdlength + 1] = '\0';
 267                 tlen = rdlength + 1;
 268                 p = &rdata_buffer[*rdata];
 269
 270                 do {
 271                         uint8_t v = *p;
 272
 273                         *p = '\0';
 274                         if (v)
 275                                 p += v + 1;
 276                 } while (*p);
 277                 break;
 278
 279         case TYPE_A:
 280                 cache_entry(u, name, strlen(name), a->ttl);
 281                 if (a->rdlength != 4)
 282                         return;
 283                 dlen = 4;
 284                 break;
 285
 286         case TYPE_AAAA:
 287                 cache_entry(u, name, strlen(name), a->ttl);
 288                 if (a->rdlength != 16)
 289                         return;
 290                 dlen = 16;
 291                 break;
 292
 293         default:
 294                 return;
 295         }
 296
 297         r = cache_record_find(name, a->type, port, dlen, rdata);
 298         if (r) {
 299                 if (!a->ttl) {
 300                         cache_record_free(r);
 301                         DBG(1, "D -> %s %s ttl:%d\n", dns_type_string(r->type), r->record, r->ttl);
 302                 } else {
 303                         r->ttl = a->ttl;
 304                         DBG(1, "A -> %s %s ttl:%d\n", dns_type_string(r->type), r->record, r->ttl);
 305                 }
 306                 return;
 307         }
 308
 309         if (!a->ttl)
 310                 return;
 311
 312         r = calloc_a(sizeof(*r),
 313                 &name_buf, strlen(name) + 1,
 314                 &txt_ptr, tlen,
 315                 &rdata_ptr, dlen);
 316
 317         r->avl.key = r->record = strcpy(name_buf, name);
 318         r->type = a->type;
 319         r->ttl = a->ttl;
 320         r->port = port;
 321         r->rdlength = dlen;
 322         r->time = time(NULL);
 323
 324         if (tlen)
 325                 r->txt = memcpy(txt_ptr, rdata_buffer, tlen);
 326
 327         if (dlen)
 328                 r->rdata = memcpy(rdata_ptr, rdata, dlen);
 329
 330         if (avl_insert(&records, &r->avl))
 331                 free(r);
 332         else
 333                 DBG(1, "A -> %s %s ttl:%d\n", dns_type_string(r->type), r->record, r->ttl);
 334 }