diff options
Diffstat (limited to 'dhcp.c')
| -rw-r--r-- | dhcp.c | 97 |
1 files changed, 94 insertions, 3 deletions
@@ -45,7 +45,6 @@ struct opt { static struct opt opts[255] = { [1] = { 0, 4, { 0 }, 0, { 0 }, }, /* Mask */ [3] = { 0, 4, { 0 }, 0, { 0 }, }, /* Router */ - [6] = { 0, 4, { 0 }, 0, { 0 }, }, /* DNS */ [51] = { 0, 4, { 0xff, 0xff, 0xff, 0xff }, 0, { 0 }, }, /* Lease time */ [53] = { 0, 1, { 0 }, 0, { 0 }, }, /* Type */ #define DHCPDISCOVER 1 @@ -155,6 +154,92 @@ static int fill(struct msg *m) } /** + * opt_dns_search_dup_ptr() - Look for possible domain name compression pointer + * @buf: Current option buffer with existing labels + * @cmp: Portion of domain name being added + * @len: Length of current option buffer + * + * Return: offset to corresponding compression pointer if any, -1 if not found + */ +static int opt_dns_search_dup_ptr(unsigned char *buf, char *cmp, size_t len) +{ + unsigned int i; + + for (i = 0; i < len; i++) { + if (buf[i] == 0 && + len - i - 1 >= strlen(cmp) && + !memcmp(buf + i + 1, cmp, strlen(cmp))) + return i; + + if ((buf[i] & 0xc0) == 0xc0 && + len - i - 2 >= strlen(cmp) && + !memcmp(buf + i + 2, cmp, strlen(cmp))) + return i + 1; + } + + return -1; +} + +/** + * opt_set_dns_search() - Fill data and set length for Domain Search option + * @c: Execution context + * @max_len: Maximum total length of option buffer + */ +static void opt_set_dns_search(struct ctx *c, size_t max_len) +{ + char buf[NS_MAXDNAME]; + int i; + + opts[119].slen = 0; + + for (i = 0; i < 255; i++) + max_len -= opts[i].slen; + + for (i = 0; *c->dns_search[i].n; i++) { + unsigned int n; + int dup = -1; + char *p; + + buf[0] = 0; + for (p = c->dns_search[i].n, n = 1; *p; p++) { + if (*p == '.') { + /* RFC 1035 4.1.4 Message compression */ + dup = opt_dns_search_dup_ptr(opts[119].s, p + 1, + opts[119].slen); + + if (dup >= 0) { + buf[n++] = '\xc0'; + buf[n++] = dup; + break; + } else { + buf[n++] = '.'; + } + } else { + buf[n++] = *p; + } + } + + /* The compression pointer is also an end of label */ + if (dup < 0) + buf[n++] = 0; + + if (n >= max_len) + break; + + memcpy(opts[119].s + opts[119].slen, buf, n); + opts[119].slen += n; + max_len -= n; + } + + for (i = 0; i < opts[119].slen; i++) { + if (!opts[119].s[i] || opts[119].s[i] == '.') { + opts[119].s[i] = strcspn((char *)opts[119].s + i + 1, + ".\xc0"); + } + } +} + +/** * dhcp() - Check if this is a DHCP message, reply as needed * @c: Execution context * @len: Total L2 packet length @@ -213,10 +298,16 @@ int dhcp(struct ctx *c, struct ethhdr *eh, size_t len) m->yiaddr = c->addr4; *(unsigned long *)opts[1].s = c->mask4; *(unsigned long *)opts[3].s = c->gw4; - *(unsigned long *)opts[6].s = c->dns4; *(unsigned long *)opts[54].s = c->gw4; - uh->len = htons(len = offsetof(struct msg, o) + fill(m)); + for (i = 0, opts[6].slen = 0; c->dns4[i]; i++) { + ((uint32_t *)opts[6].s)[i] = c->dns4[i]; + opts[6].slen += sizeof(uint32_t); + } + + opt_set_dns_search(c, sizeof(m->o)); + + uh->len = htons(len = offsetof(struct msg, o) + fill(m) + sizeof(*uh)); uh->check = 0; uh->source = htons(67); uh->dest = htons(68); |