Klaus Stengel | 63d2960 | 2012-10-27 19:53:39 +0200 | [diff] [blame] | 1 | /* |
| 2 | * Domain search option for DHCP (RFC 3397) |
| 3 | * |
| 4 | * Copyright (c) 2012 Klaus Stengel |
| 5 | * |
| 6 | * Permission is hereby granted, free of charge, to any person obtaining a copy |
| 7 | * of this software and associated documentation files (the "Software"), to deal |
| 8 | * in the Software without restriction, including without limitation the rights |
| 9 | * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell |
| 10 | * copies of the Software, and to permit persons to whom the Software is |
| 11 | * furnished to do so, subject to the following conditions: |
| 12 | * |
| 13 | * The above copyright notice and this permission notice shall be included in |
| 14 | * all copies or substantial portions of the Software. |
| 15 | * |
| 16 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| 17 | * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| 18 | * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL |
| 19 | * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
| 20 | * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, |
| 21 | * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN |
| 22 | * THE SOFTWARE. |
| 23 | */ |
| 24 | |
Peter Maydell | 7df7482 | 2016-01-29 17:49:59 +0000 | [diff] [blame] | 25 | #include "qemu/osdep.h" |
Klaus Stengel | 63d2960 | 2012-10-27 19:53:39 +0200 | [diff] [blame] | 26 | #include "slirp.h" |
| 27 | |
| 28 | static const uint8_t RFC3397_OPT_DOMAIN_SEARCH = 119; |
| 29 | static const uint8_t MAX_OPT_LEN = 255; |
| 30 | static const uint8_t OPT_HEADER_LEN = 2; |
| 31 | static const uint8_t REFERENCE_LEN = 2; |
| 32 | |
| 33 | struct compact_domain; |
| 34 | |
| 35 | typedef struct compact_domain { |
| 36 | struct compact_domain *self; |
| 37 | struct compact_domain *refdom; |
| 38 | uint8_t *labels; |
| 39 | size_t len; |
| 40 | size_t common_octets; |
| 41 | } CompactDomain; |
| 42 | |
| 43 | static size_t |
| 44 | domain_suffix_diffoff(const CompactDomain *a, const CompactDomain *b) |
| 45 | { |
| 46 | size_t la = a->len, lb = b->len; |
| 47 | uint8_t *da = a->labels + la, *db = b->labels + lb; |
| 48 | size_t i, lm = (la < lb) ? la : lb; |
| 49 | |
| 50 | for (i = 0; i < lm; i++) { |
| 51 | da--; db--; |
| 52 | if (*da != *db) { |
| 53 | break; |
| 54 | } |
| 55 | } |
| 56 | return i; |
| 57 | } |
| 58 | |
| 59 | static int domain_suffix_ord(const void *cva, const void *cvb) |
| 60 | { |
| 61 | const CompactDomain *a = cva, *b = cvb; |
| 62 | size_t la = a->len, lb = b->len; |
| 63 | size_t doff = domain_suffix_diffoff(a, b); |
| 64 | uint8_t ca = a->labels[la - doff]; |
| 65 | uint8_t cb = b->labels[lb - doff]; |
| 66 | |
| 67 | if (ca < cb) { |
| 68 | return -1; |
| 69 | } |
| 70 | if (ca > cb) { |
| 71 | return 1; |
| 72 | } |
| 73 | if (la < lb) { |
| 74 | return -1; |
| 75 | } |
| 76 | if (la > lb) { |
| 77 | return 1; |
| 78 | } |
| 79 | return 0; |
| 80 | } |
| 81 | |
| 82 | static size_t domain_common_label(CompactDomain *a, CompactDomain *b) |
| 83 | { |
| 84 | size_t res, doff = domain_suffix_diffoff(a, b); |
| 85 | uint8_t *first_eq_pos = a->labels + (a->len - doff); |
| 86 | uint8_t *label = a->labels; |
| 87 | |
| 88 | while (*label && label < first_eq_pos) { |
| 89 | label += *label + 1; |
| 90 | } |
| 91 | res = a->len - (label - a->labels); |
| 92 | /* only report if it can help to reduce the packet size */ |
| 93 | return (res > REFERENCE_LEN) ? res : 0; |
| 94 | } |
| 95 | |
| 96 | static void domain_fixup_order(CompactDomain *cd, size_t n) |
| 97 | { |
| 98 | size_t i; |
| 99 | |
| 100 | for (i = 0; i < n; i++) { |
| 101 | CompactDomain *cur = cd + i, *next = cd[i].self; |
| 102 | |
| 103 | while (!cur->common_octets) { |
| 104 | CompactDomain *tmp = next->self; /* backup target value */ |
| 105 | |
| 106 | next->self = cur; |
| 107 | cur->common_octets++; |
| 108 | |
| 109 | cur = next; |
| 110 | next = tmp; |
| 111 | } |
| 112 | } |
| 113 | } |
| 114 | |
| 115 | static void domain_mklabels(CompactDomain *cd, const char *input) |
| 116 | { |
| 117 | uint8_t *len_marker = cd->labels; |
| 118 | uint8_t *output = len_marker; /* pre-incremented */ |
| 119 | const char *in = input; |
| 120 | char cur_chr; |
| 121 | size_t len = 0; |
| 122 | |
| 123 | if (cd->len == 0) { |
| 124 | goto fail; |
| 125 | } |
| 126 | cd->len++; |
| 127 | |
| 128 | do { |
| 129 | cur_chr = *in++; |
| 130 | if (cur_chr == '.' || cur_chr == '\0') { |
| 131 | len = output - len_marker; |
| 132 | if ((len == 0 && cur_chr == '.') || len >= 64) { |
| 133 | goto fail; |
| 134 | } |
| 135 | *len_marker = len; |
| 136 | |
| 137 | output++; |
| 138 | len_marker = output; |
| 139 | } else { |
| 140 | output++; |
| 141 | *output = cur_chr; |
| 142 | } |
| 143 | } while (cur_chr != '\0'); |
| 144 | |
| 145 | /* ensure proper zero-termination */ |
| 146 | if (len != 0) { |
| 147 | *len_marker = 0; |
| 148 | cd->len++; |
| 149 | } |
| 150 | return; |
| 151 | |
| 152 | fail: |
| 153 | g_warning("failed to parse domain name '%s'\n", input); |
| 154 | cd->len = 0; |
| 155 | } |
| 156 | |
| 157 | static void |
| 158 | domain_mkxrefs(CompactDomain *doms, CompactDomain *last, size_t depth) |
| 159 | { |
| 160 | CompactDomain *i = doms, *target = doms; |
| 161 | |
| 162 | do { |
| 163 | if (i->labels < target->labels) { |
| 164 | target = i; |
| 165 | } |
| 166 | } while (i++ != last); |
| 167 | |
| 168 | for (i = doms; i != last; i++) { |
| 169 | CompactDomain *group_last; |
| 170 | size_t next_depth; |
| 171 | |
| 172 | if (i->common_octets == depth) { |
| 173 | continue; |
| 174 | } |
| 175 | |
| 176 | next_depth = -1; |
| 177 | for (group_last = i; group_last != last; group_last++) { |
| 178 | size_t co = group_last->common_octets; |
| 179 | if (co <= depth) { |
| 180 | break; |
| 181 | } |
| 182 | if (co < next_depth) { |
| 183 | next_depth = co; |
| 184 | } |
| 185 | } |
| 186 | domain_mkxrefs(i, group_last, next_depth); |
| 187 | |
| 188 | i = group_last; |
| 189 | if (i == last) { |
| 190 | break; |
| 191 | } |
| 192 | } |
| 193 | |
| 194 | if (depth == 0) { |
| 195 | return; |
| 196 | } |
| 197 | |
| 198 | i = doms; |
| 199 | do { |
| 200 | if (i != target && i->refdom == NULL) { |
| 201 | i->refdom = target; |
| 202 | i->common_octets = depth; |
| 203 | } |
| 204 | } while (i++ != last); |
| 205 | } |
| 206 | |
| 207 | static size_t domain_compactify(CompactDomain *domains, size_t n) |
| 208 | { |
| 209 | uint8_t *start = domains->self->labels, *outptr = start; |
| 210 | size_t i; |
| 211 | |
| 212 | for (i = 0; i < n; i++) { |
| 213 | CompactDomain *cd = domains[i].self; |
| 214 | CompactDomain *rd = cd->refdom; |
| 215 | |
| 216 | if (rd != NULL) { |
| 217 | size_t moff = (rd->labels - start) |
| 218 | + (rd->len - cd->common_octets); |
| 219 | if (moff < 0x3FFFu) { |
| 220 | cd->len -= cd->common_octets - 2; |
| 221 | cd->labels[cd->len - 1] = moff & 0xFFu; |
| 222 | cd->labels[cd->len - 2] = 0xC0u | (moff >> 8); |
| 223 | } |
| 224 | } |
| 225 | |
| 226 | if (cd->labels != outptr) { |
| 227 | memmove(outptr, cd->labels, cd->len); |
| 228 | cd->labels = outptr; |
| 229 | } |
| 230 | outptr += cd->len; |
| 231 | } |
| 232 | return outptr - start; |
| 233 | } |
| 234 | |
| 235 | int translate_dnssearch(Slirp *s, const char **names) |
| 236 | { |
| 237 | size_t blocks, bsrc_start, bsrc_end, bdst_start; |
| 238 | size_t i, num_domains, memreq = 0; |
| 239 | uint8_t *result = NULL, *outptr; |
| 240 | CompactDomain *domains = NULL; |
| 241 | const char **nameptr = names; |
| 242 | |
| 243 | while (*nameptr != NULL) { |
| 244 | nameptr++; |
| 245 | } |
| 246 | |
| 247 | num_domains = nameptr - names; |
| 248 | if (num_domains == 0) { |
| 249 | return -2; |
| 250 | } |
| 251 | |
| 252 | domains = g_malloc(num_domains * sizeof(*domains)); |
| 253 | |
| 254 | for (i = 0; i < num_domains; i++) { |
| 255 | size_t nlen = strlen(names[i]); |
| 256 | memreq += nlen + 2; /* 1 zero octet + 1 label length octet */ |
| 257 | domains[i].self = domains + i; |
| 258 | domains[i].len = nlen; |
| 259 | domains[i].common_octets = 0; |
| 260 | domains[i].refdom = NULL; |
| 261 | } |
| 262 | |
| 263 | /* reserve extra 2 header bytes for each 255 bytes of output */ |
Laurent Vivier | 8069568 | 2016-05-31 18:36:01 +0200 | [diff] [blame] | 264 | memreq += DIV_ROUND_UP(memreq, MAX_OPT_LEN) * OPT_HEADER_LEN; |
Klaus Stengel | 63d2960 | 2012-10-27 19:53:39 +0200 | [diff] [blame] | 265 | result = g_malloc(memreq * sizeof(*result)); |
| 266 | |
| 267 | outptr = result; |
| 268 | for (i = 0; i < num_domains; i++) { |
| 269 | domains[i].labels = outptr; |
| 270 | domain_mklabels(domains + i, names[i]); |
| 271 | outptr += domains[i].len; |
| 272 | } |
| 273 | |
| 274 | if (outptr == result) { |
| 275 | g_free(domains); |
| 276 | g_free(result); |
| 277 | return -1; |
| 278 | } |
| 279 | |
| 280 | qsort(domains, num_domains, sizeof(*domains), domain_suffix_ord); |
| 281 | domain_fixup_order(domains, num_domains); |
| 282 | |
| 283 | for (i = 1; i < num_domains; i++) { |
| 284 | size_t cl = domain_common_label(domains + i - 1, domains + i); |
| 285 | domains[i - 1].common_octets = cl; |
| 286 | } |
| 287 | |
| 288 | domain_mkxrefs(domains, domains + num_domains - 1, 0); |
| 289 | memreq = domain_compactify(domains, num_domains); |
| 290 | |
Laurent Vivier | 8069568 | 2016-05-31 18:36:01 +0200 | [diff] [blame] | 291 | blocks = DIV_ROUND_UP(memreq, MAX_OPT_LEN); |
Klaus Stengel | 63d2960 | 2012-10-27 19:53:39 +0200 | [diff] [blame] | 292 | bsrc_end = memreq; |
| 293 | bsrc_start = (blocks - 1) * MAX_OPT_LEN; |
| 294 | bdst_start = bsrc_start + blocks * OPT_HEADER_LEN; |
| 295 | memreq += blocks * OPT_HEADER_LEN; |
| 296 | |
| 297 | while (blocks--) { |
| 298 | size_t len = bsrc_end - bsrc_start; |
| 299 | memmove(result + bdst_start, result + bsrc_start, len); |
| 300 | result[bdst_start - 2] = RFC3397_OPT_DOMAIN_SEARCH; |
| 301 | result[bdst_start - 1] = len; |
| 302 | bsrc_end = bsrc_start; |
| 303 | bsrc_start -= MAX_OPT_LEN; |
| 304 | bdst_start -= MAX_OPT_LEN + OPT_HEADER_LEN; |
| 305 | } |
| 306 | |
| 307 | g_free(domains); |
| 308 | s->vdnssearch = result; |
| 309 | s->vdnssearch_len = memreq; |
| 310 | return 0; |
| 311 | } |