diff options
Diffstat (limited to 'slirp/dnssearch.c')
-rw-r--r-- | slirp/dnssearch.c | 314 |
1 files changed, 314 insertions, 0 deletions
diff --git a/slirp/dnssearch.c b/slirp/dnssearch.c new file mode 100644 index 0000000..4c9064e --- /dev/null +++ b/slirp/dnssearch.c @@ -0,0 +1,314 @@ +/* + * Domain search option for DHCP (RFC 3397) + * + * Copyright (c) 2012 Klaus Stengel + * + * Permission is hereby granted, free of charge, to any person obtaining a copy + * of this software and associated documentation files (the "Software"), to deal + * in the Software without restriction, including without limitation the rights + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell + * copies of the Software, and to permit persons to whom the Software is + * furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice shall be included in + * all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN + * THE SOFTWARE. + */ + +#include <stdlib.h> +#include <string.h> +#include <stdio.h> +#include <glib.h> +#include "slirp.h" + +static const uint8_t RFC3397_OPT_DOMAIN_SEARCH = 119; +static const uint8_t MAX_OPT_LEN = 255; +static const uint8_t OPT_HEADER_LEN = 2; +static const uint8_t REFERENCE_LEN = 2; + +struct compact_domain; + +typedef struct compact_domain { + struct compact_domain *self; + struct compact_domain *refdom; + uint8_t *labels; + size_t len; + size_t common_octets; +} CompactDomain; + +static size_t +domain_suffix_diffoff(const CompactDomain *a, const CompactDomain *b) +{ + size_t la = a->len, lb = b->len; + uint8_t *da = a->labels + la, *db = b->labels + lb; + size_t i, lm = (la < lb) ? la : lb; + + for (i = 0; i < lm; i++) { + da--; db--; + if (*da != *db) { + break; + } + } + return i; +} + +static int domain_suffix_ord(const void *cva, const void *cvb) +{ + const CompactDomain *a = cva, *b = cvb; + size_t la = a->len, lb = b->len; + size_t doff = domain_suffix_diffoff(a, b); + uint8_t ca = a->labels[la - doff]; + uint8_t cb = b->labels[lb - doff]; + + if (ca < cb) { + return -1; + } + if (ca > cb) { + return 1; + } + if (la < lb) { + return -1; + } + if (la > lb) { + return 1; + } + return 0; +} + +static size_t domain_common_label(CompactDomain *a, CompactDomain *b) +{ + size_t res, doff = domain_suffix_diffoff(a, b); + uint8_t *first_eq_pos = a->labels + (a->len - doff); + uint8_t *label = a->labels; + + while (*label && label < first_eq_pos) { + label += *label + 1; + } + res = a->len - (label - a->labels); + /* only report if it can help to reduce the packet size */ + return (res > REFERENCE_LEN) ? res : 0; +} + +static void domain_fixup_order(CompactDomain *cd, size_t n) +{ + size_t i; + + for (i = 0; i < n; i++) { + CompactDomain *cur = cd + i, *next = cd[i].self; + + while (!cur->common_octets) { + CompactDomain *tmp = next->self; /* backup target value */ + + next->self = cur; + cur->common_octets++; + + cur = next; + next = tmp; + } + } +} + +static void domain_mklabels(CompactDomain *cd, const char *input) +{ + uint8_t *len_marker = cd->labels; + uint8_t *output = len_marker; /* pre-incremented */ + const char *in = input; + char cur_chr; + size_t len = 0; + + if (cd->len == 0) { + goto fail; + } + cd->len++; + + do { + cur_chr = *in++; + if (cur_chr == '.' || cur_chr == '\0') { + len = output - len_marker; + if ((len == 0 && cur_chr == '.') || len >= 64) { + goto fail; + } + *len_marker = len; + + output++; + len_marker = output; + } else { + output++; + *output = cur_chr; + } + } while (cur_chr != '\0'); + + /* ensure proper zero-termination */ + if (len != 0) { + *len_marker = 0; + cd->len++; + } + return; + +fail: + g_warning("failed to parse domain name '%s'\n", input); + cd->len = 0; +} + +static void +domain_mkxrefs(CompactDomain *doms, CompactDomain *last, size_t depth) +{ + CompactDomain *i = doms, *target = doms; + + do { + if (i->labels < target->labels) { + target = i; + } + } while (i++ != last); + + for (i = doms; i != last; i++) { + CompactDomain *group_last; + size_t next_depth; + + if (i->common_octets == depth) { + continue; + } + + next_depth = -1; + for (group_last = i; group_last != last; group_last++) { + size_t co = group_last->common_octets; + if (co <= depth) { + break; + } + if (co < next_depth) { + next_depth = co; + } + } + domain_mkxrefs(i, group_last, next_depth); + + i = group_last; + if (i == last) { + break; + } + } + + if (depth == 0) { + return; + } + + i = doms; + do { + if (i != target && i->refdom == NULL) { + i->refdom = target; + i->common_octets = depth; + } + } while (i++ != last); +} + +static size_t domain_compactify(CompactDomain *domains, size_t n) +{ + uint8_t *start = domains->self->labels, *outptr = start; + size_t i; + + for (i = 0; i < n; i++) { + CompactDomain *cd = domains[i].self; + CompactDomain *rd = cd->refdom; + + if (rd != NULL) { + size_t moff = (rd->labels - start) + + (rd->len - cd->common_octets); + if (moff < 0x3FFFu) { + cd->len -= cd->common_octets - 2; + cd->labels[cd->len - 1] = moff & 0xFFu; + cd->labels[cd->len - 2] = 0xC0u | (moff >> 8); + } + } + + if (cd->labels != outptr) { + memmove(outptr, cd->labels, cd->len); + cd->labels = outptr; + } + outptr += cd->len; + } + return outptr - start; +} + +int translate_dnssearch(Slirp *s, const char **names) +{ + size_t blocks, bsrc_start, bsrc_end, bdst_start; + size_t i, num_domains, memreq = 0; + uint8_t *result = NULL, *outptr; + CompactDomain *domains = NULL; + const char **nameptr = names; + + while (*nameptr != NULL) { + nameptr++; + } + + num_domains = nameptr - names; + if (num_domains == 0) { + return -2; + } + + domains = g_malloc(num_domains * sizeof(*domains)); + + for (i = 0; i < num_domains; i++) { + size_t nlen = strlen(names[i]); + memreq += nlen + 2; /* 1 zero octet + 1 label length octet */ + domains[i].self = domains + i; + domains[i].len = nlen; + domains[i].common_octets = 0; + domains[i].refdom = NULL; + } + + /* reserve extra 2 header bytes for each 255 bytes of output */ + memreq += ((memreq + MAX_OPT_LEN - 1) / MAX_OPT_LEN) * OPT_HEADER_LEN; + result = g_malloc(memreq * sizeof(*result)); + + outptr = result; + for (i = 0; i < num_domains; i++) { + domains[i].labels = outptr; + domain_mklabels(domains + i, names[i]); + outptr += domains[i].len; + } + + if (outptr == result) { + g_free(domains); + g_free(result); + return -1; + } + + qsort(domains, num_domains, sizeof(*domains), domain_suffix_ord); + domain_fixup_order(domains, num_domains); + + for (i = 1; i < num_domains; i++) { + size_t cl = domain_common_label(domains + i - 1, domains + i); + domains[i - 1].common_octets = cl; + } + + domain_mkxrefs(domains, domains + num_domains - 1, 0); + memreq = domain_compactify(domains, num_domains); + + blocks = (memreq + MAX_OPT_LEN - 1) / MAX_OPT_LEN; + bsrc_end = memreq; + bsrc_start = (blocks - 1) * MAX_OPT_LEN; + bdst_start = bsrc_start + blocks * OPT_HEADER_LEN; + memreq += blocks * OPT_HEADER_LEN; + + while (blocks--) { + size_t len = bsrc_end - bsrc_start; + memmove(result + bdst_start, result + bsrc_start, len); + result[bdst_start - 2] = RFC3397_OPT_DOMAIN_SEARCH; + result[bdst_start - 1] = len; + bsrc_end = bsrc_start; + bsrc_start -= MAX_OPT_LEN; + bdst_start -= MAX_OPT_LEN + OPT_HEADER_LEN; + } + + g_free(domains); + s->vdnssearch = result; + s->vdnssearch_len = memreq; + return 0; +} |