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Add captive dns server example
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cpq committed
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@@ -5,15 +5,6 @@
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#include "timer.h"
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#include "util.h"
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struct mg_dns_header {
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uint16_t transaction_id;
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uint16_t flags;
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uint16_t num_questions;
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uint16_t num_answers;
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uint16_t num_authority_prs;
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uint16_t num_other_prs;
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};
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struct dns_data {
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struct dns_data *next;
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struct mg_connection *c;
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@@ -39,73 +30,103 @@ void mg_resolve_cancel(struct mg_connection *c) {
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}
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}
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static size_t mg_dns_parse_name(const uint8_t *s, const uint8_t *e, size_t off,
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char *to, size_t tolen, int depth) {
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static size_t mg_dns_parse_name_depth(const uint8_t *s, size_t len, size_t ofs,
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char *to, size_t tolen, int depth) {
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size_t i = 0, j = 0;
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if (tolen > 0) to[0] = '\0';
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if (depth > 5) return 0;
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while (&s[off + i + 1] < e && s[off + i] > 0) {
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size_t n = s[off + i];
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if (n & 0xc0) {
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size_t ptr = (((n & 0x3f) << 8) | s[off + i + 1]) - 12; // 12 is hdr len
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if (&s[ptr + 1] < e && (s[ptr] & 0xc0) == 0) {
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mg_dns_parse_name(s, e, ptr, to, tolen, depth + 1);
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}
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while (ofs + i + 1 < len) {
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size_t n = s[ofs + i];
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if (n == 0) {
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i++;
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break;
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}
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if (&s[off + i + n + 1] >= e) break;
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if (j + n + 1 >= tolen) return 0; // Error - overflow
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if (j > 0) to[j++] = '.';
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memcpy(&to[j], &s[off + i + 1], n);
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if (n & 0xc0) {
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size_t ptr = (((n & 0x3f) << 8) | s[ofs + i + 1]); // 12 is hdr len
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if (ptr + 1 < len && (s[ptr] & 0xc0) == 0 &&
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mg_dns_parse_name_depth(s, len, ptr, to, tolen, depth + 1) == 0)
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return 0;
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i += 2;
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break;
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}
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if (ofs + i + n + 1 >= len) return 0;
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if (j > 0) {
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if (j < tolen) to[j] = '.';
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j++;
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}
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if (j + n < tolen) memcpy(&to[j], &s[ofs + i + 1], n);
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j += n;
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i += n + 1;
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to[j] = '\0'; // Zero-terminate this chunk
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// LOG(LL_DEBUG, ("-- %zu/%zu %zu %zu", i, e - s, j, n));
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if (j < tolen) to[j] = '\0'; // Zero-terminate this chunk
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}
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if (tolen > 0) to[tolen - 1] = '\0'; // Make sure make sure it is nul-term
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return i;
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}
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// txid flags numQ numA numAP numOP
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// 0000 00 01 81 80 00 01 00 01 00 00 00 00 07 63 65 73 .............ces
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// 0010 61 6e 74 61 03 63 6f 6d 00 00 01 00 01 c0 0c 00 anta.com........
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// 0020 01 00 01 00 00 02 57 00 04 94 fb 36 ec ......W....6.
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bool mg_dns_parse(const uint8_t *buf, size_t len, struct mg_dns_message *dm) {
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struct mg_dns_header *h = (struct mg_dns_header *) buf;
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const uint8_t *s = buf + sizeof(*h), *e = &buf[len];
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uint16_t atype, aclass;
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size_t i, j = 0, n;
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memset(dm, 0, sizeof(*dm));
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size_t mg_dns_parse_name(const uint8_t *s, size_t n, size_t ofs, char *dst,
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size_t dstlen) {
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return mg_dns_parse_name_depth(s, n, ofs, dst, dstlen, 0);
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}
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size_t mg_dns_parse_rr(const uint8_t *buf, size_t len, size_t ofs,
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bool is_question, struct mg_dns_rr *rr) {
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const struct mg_dns_header *h = (struct mg_dns_header *) buf;
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const uint8_t *s = buf + ofs, *e = &buf[len];
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memset(rr, 0, sizeof(*rr));
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if (len < sizeof(*h)) return 0; // Too small, headers dont fit
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if (len > 512) return 0; // Too large, we don't expect that
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if (s >= e) return 0; // Overflow
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if ((rr->nlen = mg_dns_parse_name(buf, len, ofs, NULL, 0)) == 0) return 0;
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// LOG(LL_INFO, ("%zu %zu %hu %d", ofs, len, rr->nlen, is_question));
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s += rr->nlen + 4;
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if (s > e) return 0;
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rr->atype = ((uint16_t) s[-4] << 8) | s[-3];
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rr->aclass = ((uint16_t) s[-2] << 8) | s[-1];
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if (is_question) return rr->nlen + 4;
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s += 6;
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if (s > e) return 0;
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rr->alen = ((uint16_t) s[-2] << 8) | s[-1];
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if (s + rr->alen > e) return 0;
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return rr->nlen + rr->alen + 10;
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}
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bool mg_dns_parse(const uint8_t *buf, size_t len, struct mg_dns_message *dm) {
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const struct mg_dns_header *h = (struct mg_dns_header *) buf;
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struct mg_dns_rr rr;
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size_t i, n, ofs = sizeof(*h);
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memset(dm, 0, sizeof(*dm));
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if (len < sizeof(*h)) return 0; // Too small, headers dont fit
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if (mg_ntohs(h->num_questions) > 1) return 0; // Sanity
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if (mg_ntohs(h->num_answers) > 10) return 0; // Sanity
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dm->txnid = mg_ntohs(h->transaction_id);
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dm->txnid = mg_ntohs(h->txnid);
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for (i = 0; i < mg_ntohs(h->num_questions); i++) {
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j += mg_dns_parse_name(s, e, j, dm->name, sizeof(dm->name), 0) + 5;
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// LOG(LL_INFO, ("QUE %zu %zu [%s]", i, j, dm->name));
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if ((n = mg_dns_parse_rr(buf, len, ofs, true, &rr)) == 0) return false;
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// LOG(LL_INFO, ("Q %zu %zu", ofs, n));
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ofs += n;
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}
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for (i = 0; i < mg_ntohs(h->num_answers); i++) {
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j += mg_dns_parse_name(s, e, j, dm->name, sizeof(dm->name), 0) + 9;
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if (&s[j] + 2 > e) break;
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atype = ((int) s[j - 8] << 8) | s[j - 7];
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aclass = ((int) s[j - 6] << 8) | s[j - 5];
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n = ((int) s[j] << 8) | s[j + 1];
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LOG(LL_VERBOSE_DEBUG, ("%s %d %hu %hu", dm->name, (int) n, atype, aclass));
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if (&s[j] + 2 + n > e) break;
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if (n == 4 && atype == 1 && aclass == 1) {
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// LOG(LL_INFO, ("A -- %zu %zu %s", ofs, n, dm->name));
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if ((n = mg_dns_parse_rr(buf, len, ofs, false, &rr)) == 0) return false;
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mg_dns_parse_name(buf, len, ofs, dm->name, sizeof(dm->name));
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LOG(LL_INFO, ("A %zu %zu %s", ofs, n, dm->name));
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ofs += n;
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if (rr.alen == 4 && rr.atype == 1 && rr.aclass == 1) {
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dm->addr.is_ip6 = false;
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memcpy(&dm->addr.ip, &s[j + 2], n);
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memcpy(&dm->addr.ip, &buf[ofs - 4], 4);
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dm->resolved = true;
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break; // Return success
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} else if (n == 16 && atype == 28 && aclass == 1) {
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} else if (rr.alen == 16 && rr.atype == 28 && rr.aclass == 1) {
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dm->addr.is_ip6 = true;
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memcpy(&dm->addr.ip6, &s[j + 2], n);
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memcpy(&dm->addr.ip6, &buf[ofs - 16], 16);
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dm->resolved = true;
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break; // Return success
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}
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j += 2 + n;
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}
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return true;
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}
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@@ -172,7 +193,7 @@ void mg_dns_send(struct mg_connection *c, const struct mg_str *name,
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} pkt;
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size_t i, n;
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memset(&pkt, 0, sizeof(pkt));
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pkt.header.transaction_id = mg_htons(txnid);
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pkt.header.txnid = mg_htons(txnid);
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pkt.header.flags = mg_htons(0x100);
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pkt.header.num_questions = mg_htons(1);
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for (i = n = 0; i < sizeof(pkt.data) - 5; i++) {
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@@ -14,6 +14,26 @@ struct mg_dns_message {
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char name[256]; // Host name
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};
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struct mg_dns_header {
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uint16_t txnid; // Transaction ID
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uint16_t flags;
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uint16_t num_questions;
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uint16_t num_answers;
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uint16_t num_authority_prs;
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uint16_t num_other_prs;
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};
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// DNS resource record
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struct mg_dns_rr {
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uint16_t nlen; // Name or pointer length
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uint16_t atype; // Address type
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uint16_t aclass; // Address class
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uint16_t alen; // Address length
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};
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void mg_resolve(struct mg_connection *, struct mg_str *, int);
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void mg_resolve_cancel(struct mg_connection *);
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bool mg_dns_parse(const uint8_t *buf, size_t len, struct mg_dns_message *);
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size_t mg_dns_parse_rr(const uint8_t *buf, size_t len, size_t ofs,
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bool is_question, struct mg_dns_rr *);
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size_t mg_dns_decode_name(const uint8_t *, size_t, size_t, char *, size_t);
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+1
-1
@@ -538,7 +538,7 @@ void mg_mgr_poll(struct mg_mgr *mgr, int ms) {
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c->is_resolving ? 'R' : 'r', c->is_closing ? 'C' : 'c'));
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if (c->is_resolving || c->is_closing) {
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// Do nothing
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} else if (c->is_listening) {
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} else if (c->is_listening && c->is_udp == 0) {
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if (c->is_readable) accept_conn(mgr, c);
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} else if (c->is_connecting) {
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if (c->is_readable || c->is_writable) connect_conn(c);
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