9pfs: fix crash when fsdev is missing
[qemu.git] / slirp / dnssearch.c
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
25 #include "qemu/osdep.h"
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 */
264 memreq += DIV_ROUND_UP(memreq, MAX_OPT_LEN) * OPT_HEADER_LEN;
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
291 blocks = DIV_ROUND_UP(memreq, MAX_OPT_LEN);
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 }