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7.0 refactor
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cpq committed
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@@ -0,0 +1,205 @@
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#include "dns.h"
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#include "log.h"
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#include "private.h"
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#include "str.h"
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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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unsigned long expire;
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uint16_t txnid;
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};
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static void mg_dns_free(struct dns_data **head, struct dns_data *d) {
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LIST_DELETE(struct dns_data, head, d);
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// LOG(LL_INFO, ("--> %p %p %d", d, d->c, d->c->fd));
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free(d);
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}
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void mg_resolve_cancel(struct mg_mgr *mgr, struct mg_connection *c) {
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struct dns_data *tmp, *d, **head;
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head = mgr->dnsc == NULL ? NULL : (struct dns_data **) &mgr->dnsc->pfn_data;
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for (d = head == NULL ? NULL : *head; d != NULL; d = tmp) {
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tmp = d->next;
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if (d->c == c) mg_dns_free(head, d);
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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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size_t i = 0, j = 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 && depth < 5) {
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j = mg_dns_parse_name(s, e, ptr, to, tolen, depth + 1);
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}
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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 > 0 && j < tolen) to[j++] = '.';
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if (j + n < tolen) memcpy(&to[j], &s[off + i + 1], n);
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j += n;
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i += n + 1;
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}
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if (j < tolen) to[j] = '\0'; // Zero-terminate the name
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to[tolen - 1] = '\0'; // Just in case
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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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int 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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size_t i, j, n, ok = 0;
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if (len < sizeof(*h)) return ok;
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for (i = j = 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 [%s]", name));
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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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// LOG(LL_DEBUG, ("NAME %s", name));
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if (&s[j] + 2 > e) break;
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n = ((int) s[j] << 8) | s[j + 1];
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if (&s[j] + 2 + n > e) break;
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if (n == 4) {
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dm->txnid = mg_ntohs(h->transaction_id);
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memcpy(&dm->ipaddr, &s[j + 2], 4);
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ok = 1;
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break;
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}
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j += 2 + n;
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}
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return ok;
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}
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static void dns_cb(struct mg_connection *c, int ev, void *ev_data,
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void *fn_data) {
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struct dns_data *d, *tmp, **head = (struct dns_data **) &c->pfn_data;
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if (ev == MG_EV_POLL) {
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unsigned long now = *(unsigned long *) ev_data;
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for (d = (struct dns_data *) fn_data; d != NULL; d = tmp) {
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tmp = d->next;
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// LOG(LL_DEBUG, ("%lu %lu dns poll", d->expire, now));
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if (now > d->expire) mg_error(d->c, "DNS timeout");
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}
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} else if (ev == MG_EV_READ) {
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struct mg_dns_message dm;
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int resolved = 0;
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if (mg_dns_parse(c->recv.buf, c->recv.len, &dm)) {
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for (d = (struct dns_data *) c->pfn_data; d != NULL; d = tmp) {
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tmp = d->next;
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// LOG(LL_INFO, ("d %p %p", d, tmp));
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if (dm.txnid != d->txnid) continue;
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if (d->c->is_resolving) {
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d->c->is_resolving = 0;
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d->c->peer.ip = dm.ipaddr;
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mg_connect_resolved(d->c);
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mg_dns_free(head, d);
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} else {
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LOG(LL_ERROR, ("%p already resolved", d->c->fd));
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}
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resolved = 1;
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}
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}
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if (!resolved) LOG(LL_ERROR, ("stray DNS reply"));
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c->recv.len = 0;
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} else if (ev == MG_EV_CLOSE) {
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for (d = *head; d != NULL; d = tmp) {
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tmp = d->next;
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mg_dns_free(head, d);
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}
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}
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}
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void mg_dns_send(struct mg_connection *c, const struct mg_str *name,
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uint16_t txnid) {
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struct {
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struct mg_dns_header header;
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uint8_t data[256];
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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.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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if (name->ptr[i] == '.' || i >= name->len) {
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pkt.data[n] = (uint8_t)(i - n);
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memcpy(&pkt.data[n + 1], name->ptr + n, i - n);
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n = i + 1;
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}
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if (i >= name->len) break;
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}
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memcpy(&pkt.data[n], "\x00\x00\x01\x00\x01", 5); // A query
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n += 5;
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mg_send(c, &pkt, sizeof(pkt.header) + n);
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#if 0
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// Immediately after A query, send AAAA query. Whatever reply comes first,
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// we'll use it. Note: we cannot send two queries in a single packet.
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// https://stackoverflow.com/questions/4082081/requesting-a-and-aaaa-records-in-single-dns-query
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pkt.data[n - 3] = 0x1c; // AAAA query
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mg_send(c, &pkt, sizeof(pkt.header) + n);
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#endif
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}
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void mg_resolve(struct mg_mgr *mgr, struct mg_connection *c,
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struct mg_str *name, int ms) {
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struct dns_data *d = NULL;
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int resolved = mg_aton(name->ptr, &c->peer.ip);
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// Try to parse name as IP address
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if (mg_vcmp(name, "localhost") == 0) {
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resolved = 1;
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c->peer.ip = mg_htonl(0x7f000001);
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}
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if (resolved) {
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// name is an IP address, do not fire name resolution
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mg_connect_resolved(c);
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} else {
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// name is not an IP, send DNS resolution request
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if (mgr->dnsc == NULL) {
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const char *srv = mgr->dnsserver ? mgr->dnsserver : "udp://8.8.8.8:53";
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mgr->dnsc = mg_connect(mgr, srv, NULL, NULL);
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if (mgr->dnsc != NULL) {
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mgr->dnsc->pfn = dns_cb;
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// mgr->dnsc->is_hexdumping = 1;
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snprintf(mgr->dnsc->label, sizeof(mgr->dnsc->label), "%s", "RESOLVER");
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}
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}
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if (mgr->dnsc == NULL) {
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mg_error(c, "resolver");
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} else if ((d = (struct dns_data *) calloc(1, sizeof(*d))) == NULL) {
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mg_error(c, "resolve OOM");
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} else {
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struct dns_data **head = (struct dns_data **) &mgr->dnsc->pfn_data;
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d->txnid = *head ? (*head)->txnid + 1 : 1;
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d->next = *head;
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*head = d;
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d->expire = mg_millis() + ms;
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d->c = c;
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c->is_resolving = 1;
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LOG(LL_DEBUG, ("%p resolving %.*s, txnid %hu", c->fd, (int) name->len,
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name->ptr, d->txnid));
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mg_dns_send(mgr->dnsc, name, d->txnid);
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}
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}
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}
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