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Merge pull request #3643 from cesanta/mdns
Add SD query and response to mDNS
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10 files changed
+444
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@@ -228,16 +228,16 @@ static void dns_cb(struct mg_connection *c, int ev, void *ev_data) {
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}
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}
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static bool mg_dns_send(struct mg_connection *c, const struct mg_str *name,
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uint16_t txnid, bool ipv6) {
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struct {
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static bool dns_send(struct mg_connection *c, const struct mg_str *name,
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unsigned int rtype, uint16_t txnid, uint16_t flags) {
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struct { // RFC-1035 4.1.2
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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.txnid = mg_htons(txnid);
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pkt.header.flags = mg_htons(0x100);
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pkt.header.flags = mg_htons(flags);
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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->buf[i] == '.' || i >= name->len) {
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@@ -247,14 +247,19 @@ static bool mg_dns_send(struct mg_connection *c, const struct mg_str *name,
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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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memset(&pkt.data[n], 0, 5); // nul, QTYPE, QCLASS
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pkt.data[n + 2] = (uint8_t) rtype; // QTYPE = rtype, only 0-255 supported
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pkt.data[n + 4] = 1; // QCLASS = IN
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n += 5;
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if (ipv6) pkt.data[n - 3] = 0x1c; // AAAA query
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// memcpy(&pkt.data[n], "\xc0\x0c\x00\x1c\x00\x01", 6); // AAAA query
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// n += 6;
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return mg_send(c, &pkt, sizeof(pkt.header) + n);
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}
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static bool mg_dns_send(struct mg_connection *c, const struct mg_str *name,
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uint16_t txnid, bool ipv6) {
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return dns_send(c, name, ipv6 ? MG_DNS_RTYPE_AAAA : MG_DNS_RTYPE_A, txnid,
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0x100); // RD
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}
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bool mg_dnsc_init(struct mg_mgr *mgr, struct mg_dns *dnsc);
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bool mg_dnsc_init(struct mg_mgr *mgr, struct mg_dns *dnsc) {
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if (dnsc->url == NULL) {
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@@ -574,43 +579,149 @@ static void handle_mdns_query(struct mg_connection *c) {
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}
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}
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static size_t srvtoname(char *svc) {
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char *dot = strchr(svc, '.');
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if (dot == NULL) return 0;
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*dot = '\0';
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return (size_t) (dot - svc);
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}
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#define MG_MAX_MDNS_RECORDS 8
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// Condense one useful mDNS/DNS-SD chain from a response datagram into a single
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// MG_EV_MDNS_RESP event. A/AAAA as the first supported record are terminal
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// address answers (AAAA currently ignored). For PTR/SRV/TXT, subsequent
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// records are attached only when their label matches the service instance, or
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// the SRV target for address records.
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// Some devices send SRV/TXT as extra Answer RRs instead of Additional RRs, so
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// both sections are parsed as one chain.
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static void handle_mdns_response(struct mg_connection *c) {
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struct mg_dns_header *rh = (struct mg_dns_header *) c->recv.buf;
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struct mg_dns_rr rr;
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size_t n;
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// Parse first response, offset 12 is header size
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n = mg_dns_parse_rr(c->recv.buf, c->recv.len, 12, false, &rr);
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MG_VERBOSE(("mDNS response parsed, result=%d", (int) n));
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if (n > 0) {
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// RFC-6762 Appendix C, RFC2181 11: m(n + 1-63), max 255 + 0x0
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char name[256];
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uint8_t name_len;
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struct mg_mdns_resp resp;
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memset(&resp, 0, sizeof(resp));
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if (rh->num_answers > mg_htons(1)) MG_DEBUG(("ignoring > 1 answers"));
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mg_dns_parse_name(c->recv.buf, c->recv.len, 12, name, sizeof(name));
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name_len = (uint8_t) strlen(name);
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MG_VERBOSE(("RR %u %u %s", (unsigned int) rr.atype,
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(unsigned int) rr.aclass, name));
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if (rr.alen == 4 && rr.atype == MG_DNS_RTYPE_A &&
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(rr.aclass & 0x7FFF) == 1) {
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resp.addr.is_ip6 = false;
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memcpy(resp.addr.addr.ip, (char *) (rh + 1) + n - 4, 4);
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MG_DEBUG(("A response from %.*s = %M", name_len, name, mg_print_ip,
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&resp.addr));
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// } else if (rr.alen == 16 && rr.atype == MG_DNS_RTYPE_AAAA &&
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// (rr.aclass & 0x7FFF) == 1) {
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// resp.addr.is_ip6 = true;
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// memcpy(resp.addr.addr.ip, (char *)(rh + 1) + n - 16], 16);
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// MG_DEBUG(("AAAA response from %.*s = %M", name_len, name,
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// mg_print_ip, &resp.addr));
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} else {
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return;
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}
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resp.name = mg_str_n(name, name_len);
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resp.rr = &rr;
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mg_call(c, MG_EV_MDNS_RESP, &resp);
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struct mg_dns_rr rr, rr_[5]; // A, PTR, SRV, TXT, AAAA, in that order
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struct mg_mdns_resp resp;
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size_t n, i, num, answers, roff_[5], roff = 12; // offset 12 is header size
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// RFC-6762 Appendix C, RFC2181 11: m(n + 1-63), max 255 + 0x0
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char name[256], srvcproto[256], instance[256], host[256];
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uint16_t atype = 0;
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answers = mg_ntohs(rh->num_answers);
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num = answers + mg_ntohs(rh->num_other_prs);
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if (answers == 0) return;
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MG_VERBOSE(("mDNS response: %u answer, %u additional", (unsigned) answers,
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(unsigned) (num - answers)));
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if (num > MG_MAX_MDNS_RECORDS) {
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num = MG_MAX_MDNS_RECORDS;
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MG_DEBUG(("ignoring > %u records", MG_MAX_MDNS_RECORDS));
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}
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memset(roff_, 0, sizeof(roff_));
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memset(&rr_, 0, sizeof(rr_));
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memset(&resp, 0, sizeof(resp));
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instance[0] = host[0] = '\0';
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for (i = 0; i < num; i++) { // First Answer RR is primary; the rest must match it
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n = mg_dns_parse_rr(c->recv.buf, c->recv.len, roff, false, &rr);
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MG_VERBOSE(("mDNS record parsed, result=%u", n));
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if (n == 0) return;
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if (mg_dns_parse_name(c->recv.buf, c->recv.len, roff, name, sizeof(name)) == 0) return;
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MG_VERBOSE(("RR %u %u %s", (unsigned int) rr.atype, (unsigned int) rr.aclass, name));
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if (rr.alen == 4 && rr.atype == MG_DNS_RTYPE_A && (rr.aclass & 0x7FFF) == 1 &&
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(i == 0 || (host[0] != '\0' && strcmp(name, host) == 0) ||
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(host[0] == '\0' && instance[0] != '\0' && strcmp(name, instance) == 0))) {
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if (rr_[0].atype != 0) break;
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if (i == 0) atype = rr.atype;
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resp.name = mg_str(name);
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resp.addr.is_ip6 = false;
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memcpy(resp.addr.addr.ip, c->recv.buf + roff + n - 4, 4);
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MG_VERBOSE(("A record"));
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roff_[0] = roff, rr_[0] = rr;
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if (atype == MG_DNS_RTYPE_A) break;
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} else if (rr.alen == 16 && rr.atype == MG_DNS_RTYPE_AAAA && (rr.aclass & 0x7FFF) == 1 &&
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(i == 0 || (host[0] != '\0' && strcmp(name, host) == 0) ||
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(host[0] == '\0' && instance[0] != '\0' && strcmp(name, instance) == 0))) {
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# if 0
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if (rr_[4].atype != 0) break;
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resp.addr.is_ip6 = true;
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if (i == 0) atype = rr.atype;
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resp.name = mg_str(name);
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memcpy(resp.addr.addr.ip, c->recv.buf + roff + n - 16, 16);
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MG_VERBOSE(("AAAA record"));
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roff_[4] = roff, rr_[4] = rr;
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if (atype == MG_DNS_RTYPE_AAAA) break;
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#else
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MG_VERBOSE(("ignored AAAA record"));
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#endif
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} else if (rr.atype == MG_DNS_RTYPE_PTR && (rr.aclass & 0x7FFF) == 1 && i == 0) {
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if (rr_[1].atype != 0) break;
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atype = rr.atype;
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if (mg_dns_parse_name(c->recv.buf, c->recv.len, roff + rr.nlen + 10,
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instance, sizeof(instance)) == 0) return;
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MG_VERBOSE(("PTR record"));
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roff_[1] = roff, rr_[1] = rr;
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} else if (rr.atype == MG_DNS_RTYPE_SRV && rr.alen >= 6 && (rr.aclass & 0x7FFF) == 1 &&
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(i == 0 || (instance[0] != '\0' && strcmp(name, instance) == 0))) {
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if (rr_[2].atype != 0) break;
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if (i == 0) atype = rr.atype;
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resp.sd.port = MG_LOAD_BE16(c->recv.buf + roff + rr.nlen + 14);
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resp.addr.port = mg_htons(resp.sd.port);
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if (instance[0] == '\0') mg_snprintf(instance, sizeof(instance), "%s", name);
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if (mg_dns_parse_name(c->recv.buf, c->recv.len, roff + rr.nlen + 16,
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host, sizeof(host)) == 0) return;
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MG_VERBOSE(("SRV record"));
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roff_[2] = roff, rr_[2] = rr;
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} else if (rr.atype == MG_DNS_RTYPE_TXT && (rr.aclass & 0x7FFF) == 1 &&
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(i == 0 || (instance[0] != '\0' && strcmp(name, instance) == 0))) {
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if (rr_[3].atype != 0) break;
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if (i == 0) atype = rr.atype;
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if (instance[0] == '\0') mg_snprintf(instance, sizeof(instance), "%s", name);
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resp.sd.txt = mg_str_n((char *) c->recv.buf + roff + rr.nlen + 10, rr.alen);
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MG_VERBOSE(("TXT record"));
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roff_[3] = roff, rr_[3] = rr;
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}
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roff += n;
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if (i == 0 && atype == 0) return;
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}
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if (atype == MG_DNS_RTYPE_A) {
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resp.rr = &rr_[0];
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MG_DEBUG(("A response from %s = %M", name, mg_print_ip, &resp.addr));
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#if 0
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} else if (atype == MG_DNS_RTYPE_AAAA) {
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resp.rr = &rr_[4];
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MG_DEBUG(("AAAA response from %s = %M", name, mg_print_ip6, resp.addr.addr.ip));
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#endif
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} else if (atype == MG_DNS_RTYPE_PTR) {
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size_t len;
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resp.rr = &rr_[1];
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if (mg_dns_parse_name(c->recv.buf, c->recv.len, roff_[1], srvcproto,
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sizeof(srvcproto)) == 0) return;
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len = strlen(srvcproto);
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if (len <= 6) return;
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resp.sd.srvcproto = mg_str_n(srvcproto, len - 6); // remove .local
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if (host[0] != '\0') {
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resp.name = mg_str(host);
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} else if (rr_[0].atype == 0) {
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mg_snprintf(name, sizeof(name), "%s", instance);
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resp.name = mg_str_n(name, srvtoname(name));
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} else {
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if (mg_dns_parse_name(c->recv.buf, c->recv.len, roff_[0], name,
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sizeof(name)) == 0) return;
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resp.name = mg_str(name);
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}
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MG_DEBUG(("PTR response for %s from %s", srvcproto, name));
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} else if (atype == MG_DNS_RTYPE_SRV || atype == MG_DNS_RTYPE_TXT) {
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size_t len, name_len;
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resp.rr = atype == MG_DNS_RTYPE_SRV ? &rr_[2] : &rr_[3];
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if (mg_dns_parse_name(c->recv.buf, c->recv.len,
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atype == MG_DNS_RTYPE_SRV ? roff_[2] : roff_[3],
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srvcproto, sizeof(srvcproto)) == 0)
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return;
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len = strlen(srvcproto);
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name_len = srvtoname(srvcproto);
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if (name_len == 0 || len <= name_len + 7) return; // remove .local
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resp.sd.srvcproto = mg_str_n(srvcproto + name_len + 1, len - name_len - 7);
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resp.name = mg_str_n(srvcproto, name_len);
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MG_DEBUG(("%s response for %s from %s", atype == MG_DNS_RTYPE_SRV ? "SRV" : "TXT", srvcproto, name));
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} else {
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return;
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}
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mg_call(c, MG_EV_MDNS_RESP, &resp);
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}
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static void handle_mdns_record(struct mg_connection *c) {
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@@ -684,8 +795,7 @@ struct mg_connection *mg_mdns_listen(struct mg_mgr *mgr, mg_event_handler_t fn,
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static bool mdns_query(struct mg_connection *c, struct mg_str *name,
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unsigned int rtype) {
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mg_multicast_restore(c, (uint8_t *) &c->loc);
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(void) rtype;
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return mg_dns_send(c, name, 0, false);
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return dns_send(c, name, rtype, 0, 0); // RFC-6762 18.1 id = 0, 18.6 RD = 0
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}
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bool mg_mdns_query(struct mg_connection *c, const char *name,
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@@ -60,11 +60,12 @@ struct mg_mdns_req {
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bool is_unicast; // True if the client requested a unicast (QU) response
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};
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// ev_data for MG_EV_MDNS_RESP, carrying the resolved address from an mDNS response.
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// ev_data for MG_EV_MDNS_RESP, carrying address/data from a mDNS response
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struct mg_mdns_resp {
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struct mg_dns_rr *rr; // Resource record from the response
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struct mg_dns_rr *rr; // Resource record from the response (1st in chain)
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struct mg_str name; // Resolved hostname, without the .local suffix
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struct mg_addr addr; // Resolved IP address
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struct mg_dnssd_record sd; // Service Discovery data
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};
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// Parses a DNS query or response from buf/len into dm. Returns true on success.
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