1 /* $NetBSD: dns_rr.c,v 1.1.1.2 2011/03/02 19:32:10 tron Exp $ */ 2 3 /*++ 4 /* NAME 5 /* dns_rr 3 6 /* SUMMARY 7 /* resource record memory and list management 8 /* SYNOPSIS 9 /* #include <dns.h> 10 /* 11 /* DNS_RR *dns_rr_create(qname, rname, type, class, ttl, preference, 12 /* data, data_len) 13 /* const char *qname; 14 /* const char *rname; 15 /* unsigned short type; 16 /* unsigned short class; 17 /* unsigned int ttl; 18 /* unsigned preference; 19 /* const char *data; 20 /* size_t data_len; 21 /* 22 /* void dns_rr_free(list) 23 /* DNS_RR *list; 24 /* 25 /* DNS_RR *dns_rr_copy(record) 26 /* DNS_RR *record; 27 /* 28 /* DNS_RR *dns_rr_append(list, record) 29 /* DNS_RR *list; 30 /* DNS_RR *record; 31 /* 32 /* DNS_RR *dns_rr_sort(list, compar) 33 /* DNS_RR *list 34 /* int (*compar)(DNS_RR *, DNS_RR *); 35 /* 36 /* int dns_rr_compare_pref_ipv6(DNS_RR *a, DNS_RR *b) 37 /* DNS_RR *list 38 /* DNS_RR *list 39 /* 40 /* int dns_rr_compare_pref_ipv4(DNS_RR *a, DNS_RR *b) 41 /* DNS_RR *list 42 /* DNS_RR *list 43 /* 44 /* int dns_rr_compare_pref_any(DNS_RR *a, DNS_RR *b) 45 /* DNS_RR *list 46 /* DNS_RR *list 47 /* 48 /* DNS_RR *dns_rr_shuffle(list) 49 /* DNS_RR *list; 50 /* 51 /* DNS_RR *dns_rr_remove(list, record) 52 /* DNS_RR *list; 53 /* DNS_RR *record; 54 /* DESCRIPTION 55 /* The routines in this module maintain memory for DNS resource record 56 /* information, and maintain lists of DNS resource records. 57 /* 58 /* dns_rr_create() creates and initializes one resource record. 59 /* The \fIqname\fR field specifies the query name. 60 /* The \fIrname\fR field specifies the reply name. 61 /* \fIpreference\fR is used for MX records; \fIdata\fR is a null 62 /* pointer or specifies optional resource-specific data; 63 /* \fIdata_len\fR is the amount of resource-specific data. 64 /* 65 /* dns_rr_free() releases the resource used by of zero or more 66 /* resource records. 67 /* 68 /* dns_rr_copy() makes a copy of a resource record. 69 /* 70 /* dns_rr_append() appends a resource record to a (list of) resource 71 /* record(s). 72 /* A null input list is explicitly allowed. 73 /* 74 /* dns_rr_sort() sorts a list of resource records into ascending 75 /* order according to a user-specified criterion. The result is the 76 /* sorted list. 77 /* 78 /* dns_rr_compare_pref_XXX() are dns_rr_sort() helpers to sort 79 /* records by their MX preference and by their address family. 80 /* 81 /* dns_rr_shuffle() randomly permutes a list of resource records. 82 /* 83 /* dns_rr_remove() removes the specified record from the specified list. 84 /* The updated list is the result value. 85 /* The record MUST be a list member. 86 /* LICENSE 87 /* .ad 88 /* .fi 89 /* The Secure Mailer license must be distributed with this software. 90 /* AUTHOR(S) 91 /* Wietse Venema 92 /* IBM T.J. Watson Research 93 /* P.O. Box 704 94 /* Yorktown Heights, NY 10598, USA 95 /*--*/ 96 97 /* System library. */ 98 99 #include <sys_defs.h> 100 #include <string.h> 101 #include <stdlib.h> 102 103 /* Utility library. */ 104 105 #include <msg.h> 106 #include <mymalloc.h> 107 #include <myrand.h> 108 109 /* DNS library. */ 110 111 #include "dns.h" 112 113 /* dns_rr_create - fill in resource record structure */ 114 115 DNS_RR *dns_rr_create(const char *qname, const char *rname, 116 ushort type, ushort class, 117 unsigned int ttl, unsigned pref, 118 const char *data, size_t data_len) 119 { 120 DNS_RR *rr; 121 122 rr = (DNS_RR *) mymalloc(sizeof(*rr) + data_len - 1); 123 rr->qname = mystrdup(qname); 124 rr->rname = mystrdup(rname); 125 rr->type = type; 126 rr->class = class; 127 rr->ttl = ttl; 128 rr->pref = pref; 129 if (data && data_len > 0) 130 memcpy(rr->data, data, data_len); 131 rr->data_len = data_len; 132 rr->next = 0; 133 return (rr); 134 } 135 136 /* dns_rr_free - destroy resource record structure */ 137 138 void dns_rr_free(DNS_RR *rr) 139 { 140 if (rr) { 141 if (rr->next) 142 dns_rr_free(rr->next); 143 myfree(rr->qname); 144 myfree(rr->rname); 145 myfree((char *) rr); 146 } 147 } 148 149 /* dns_rr_copy - copy resource record */ 150 151 DNS_RR *dns_rr_copy(DNS_RR *src) 152 { 153 ssize_t len = sizeof(*src) + src->data_len - 1; 154 DNS_RR *dst; 155 156 /* 157 * Combine struct assignment and data copy in one block copy operation. 158 */ 159 dst = (DNS_RR *) mymalloc(len); 160 memcpy((char *) dst, (char *) src, len); 161 dst->qname = mystrdup(src->qname); 162 dst->rname = mystrdup(src->rname); 163 dst->next = 0; 164 return (dst); 165 } 166 167 /* dns_rr_append - append resource record to list */ 168 169 DNS_RR *dns_rr_append(DNS_RR *list, DNS_RR *rr) 170 { 171 if (list == 0) { 172 list = rr; 173 } else { 174 list->next = dns_rr_append(list->next, rr); 175 } 176 return (list); 177 } 178 179 /* dns_rr_compare_pref_ipv6 - compare records by preference, ipv6 preferred */ 180 181 int dns_rr_compare_pref_ipv6(DNS_RR *a, DNS_RR *b) 182 { 183 if (a->pref != b->pref) 184 return (a->pref - b->pref); 185 #ifdef HAS_IPV6 186 if (a->type == b->type) /* 200412 */ 187 return 0; 188 if (a->type == T_AAAA) 189 return (-1); 190 if (b->type == T_AAAA) 191 return (+1); 192 #endif 193 return 0; 194 } 195 196 /* dns_rr_compare_pref_ipv4 - compare records by preference, ipv4 preferred */ 197 198 int dns_rr_compare_pref_ipv4(DNS_RR *a, DNS_RR *b) 199 { 200 if (a->pref != b->pref) 201 return (a->pref - b->pref); 202 #ifdef HAS_IPV6 203 if (a->type == b->type) 204 return 0; 205 if (a->type == T_AAAA) 206 return (+1); 207 if (b->type == T_AAAA) 208 return (-1); 209 #endif 210 return 0; 211 } 212 213 /* dns_rr_compare_pref_any - compare records by preference, protocol-neutral */ 214 215 int dns_rr_compare_pref_any(DNS_RR *a, DNS_RR *b) 216 { 217 if (a->pref != b->pref) 218 return (a->pref - b->pref); 219 return 0; 220 } 221 222 /* dns_rr_compare_pref - binary compatibility helper after name change */ 223 224 int dns_rr_compare_pref(DNS_RR *a, DNS_RR *b) 225 { 226 return (dns_rr_compare_pref_ipv6(a, b)); 227 } 228 229 /* dns_rr_sort_callback - glue function */ 230 231 static int (*dns_rr_sort_user) (DNS_RR *, DNS_RR *); 232 233 static int dns_rr_sort_callback(const void *a, const void *b) 234 { 235 DNS_RR *aa = *(DNS_RR **) a; 236 DNS_RR *bb = *(DNS_RR **) b; 237 238 return (dns_rr_sort_user(aa, bb)); 239 } 240 241 /* dns_rr_sort - sort resource record list */ 242 243 DNS_RR *dns_rr_sort(DNS_RR *list, int (*compar) (DNS_RR *, DNS_RR *)) 244 { 245 int (*saved_user) (DNS_RR *, DNS_RR *); 246 DNS_RR **rr_array; 247 DNS_RR *rr; 248 int len; 249 int i; 250 251 /* 252 * Save state and initialize. 253 */ 254 saved_user = dns_rr_sort_user; 255 dns_rr_sort_user = compar; 256 257 /* 258 * Build linear array with pointers to each list element. 259 */ 260 for (len = 0, rr = list; rr != 0; len++, rr = rr->next) 261 /* void */ ; 262 rr_array = (DNS_RR **) mymalloc(len * sizeof(*rr_array)); 263 for (len = 0, rr = list; rr != 0; len++, rr = rr->next) 264 rr_array[len] = rr; 265 266 /* 267 * Sort by user-specified criterion. 268 */ 269 qsort((char *) rr_array, len, sizeof(*rr_array), dns_rr_sort_callback); 270 271 /* 272 * Fix the links. 273 */ 274 for (i = 0; i < len - 1; i++) 275 rr_array[i]->next = rr_array[i + 1]; 276 rr_array[i]->next = 0; 277 list = rr_array[0]; 278 279 /* 280 * Cleanup. 281 */ 282 myfree((char *) rr_array); 283 dns_rr_sort_user = saved_user; 284 return (list); 285 } 286 287 /* dns_rr_shuffle - shuffle resource record list */ 288 289 DNS_RR *dns_rr_shuffle(DNS_RR *list) 290 { 291 DNS_RR **rr_array; 292 DNS_RR *rr; 293 int len; 294 int i; 295 int r; 296 297 /* 298 * Build linear array with pointers to each list element. 299 */ 300 for (len = 0, rr = list; rr != 0; len++, rr = rr->next) 301 /* void */ ; 302 rr_array = (DNS_RR **) mymalloc(len * sizeof(*rr_array)); 303 for (len = 0, rr = list; rr != 0; len++, rr = rr->next) 304 rr_array[len] = rr; 305 306 /* 307 * Shuffle resource records. 308 */ 309 for (i = 0; i < len; i++) { 310 r = myrand() % len; 311 rr = rr_array[i]; 312 rr_array[i] = rr_array[r]; 313 rr_array[r] = rr; 314 } 315 316 /* 317 * Fix the links. 318 */ 319 for (i = 0; i < len - 1; i++) 320 rr_array[i]->next = rr_array[i + 1]; 321 rr_array[i]->next = 0; 322 list = rr_array[0]; 323 324 /* 325 * Cleanup. 326 */ 327 myfree((char *) rr_array); 328 return (list); 329 } 330 331 /* dns_rr_remove - remove record from list, return new list */ 332 333 DNS_RR *dns_rr_remove(DNS_RR *list, DNS_RR *record) 334 { 335 if (list == 0) 336 msg_panic("dns_rr_remove: record not found"); 337 338 if (list == record) { 339 list = record->next; 340 record->next = 0; 341 dns_rr_free(record); 342 } else { 343 list->next = dns_rr_remove(list->next, record); 344 } 345 return (list); 346 } 347