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[mdns]: Add support for mdns service discovery #967

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81 changes: 78 additions & 3 deletions components/mdns/mdns_querier.c
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Original file line number Diff line number Diff line change
Expand Up @@ -248,8 +248,23 @@ mdns_search_once_t *mdns_priv_query_find_from(mdns_search_once_t *s, mdns_name_t
return s;
}

if (type == MDNS_TYPE_PTR && type == s->type && !strcasecmp(name->service, s->service) && !strcasecmp(name->proto, s->proto)) {
return s;
if (type == MDNS_TYPE_PTR && type == s->type) {
// Special handling for _services._dns-sd._udp queries
// When querying _services._dns-sd._udp, the search has service="_services._dns-sd" and proto="_udp"
// But the parsed PTR name has host="_services", service="_dns-sd", proto="_udp"
if ((name->host[0] && !strcasecmp(name->host, "_services"))
&& (name->service[0] && !strcasecmp(name->service, "_dns-sd"))
&& (name->proto[0] && !strcasecmp(name->proto, "_udp"))
&& (name->domain[0] && !strcasecmp(name->domain, MDNS_UTILS_DEFAULT_DOMAIN))) {
// Check if this search is for _services._dns-sd._udp
if (s->service && s->proto &&
!strcasecmp(s->service, "_services._dns-sd") &&
!strcasecmp(s->proto, "_udp")) {
return s;
}
} else if (!strcasecmp(name->service, s->service) && !strcasecmp(name->proto, s->proto)) {
return s;
}
}

s = s->next;
Expand Down Expand Up @@ -288,6 +303,64 @@ static mdns_tx_packet_t *create_search_packet(mdns_search_once_t *search, mdns_i
q->proto = search->proto;
q->domain = MDNS_UTILS_DEFAULT_DOMAIN;
q->own_dynamic_memory = false;

// Special handling for _services._dns-sd._udp queries
// The service parameter is "_services._dns-sd" which needs to be split into two labels:
// host="_services" and service="_dns-sd"
if (search->service && strchr(search->service, '.')) {
char *dot = strchr(search->service, '.');
if (dot && dot > search->service) {
// Split: first part becomes host, second part becomes service
size_t host_len = dot - search->service;
size_t service_len = strlen(dot + 1);
if (host_len < MDNS_NAME_BUF_LEN && service_len < MDNS_NAME_BUF_LEN && host_len > 0 && service_len > 0) {
// Allocate temporary buffers for all fields that will be freed
size_t proto_len = search->proto ? strlen(search->proto) : 0;
size_t domain_len = strlen(MDNS_UTILS_DEFAULT_DOMAIN);
char *host_part = mdns_mem_malloc(host_len + 1);
char *service_part = mdns_mem_malloc(service_len + 1);
char *proto_part = NULL;
char *domain_part = mdns_mem_malloc(domain_len + 1);

// Only allocate proto_part if proto exists
if (proto_len > 0) {
proto_part = mdns_mem_malloc(proto_len + 1);
}

// Check if all required allocations succeeded
bool alloc_ok = host_part && service_part && domain_part && (!proto_len || proto_part);

if (alloc_ok) {
memcpy(host_part, search->service, host_len);
host_part[host_len] = '\0';
memcpy(service_part, dot + 1, service_len);
service_part[service_len] = '\0';
if (proto_part && search->proto) {
memcpy(proto_part, search->proto, proto_len);
proto_part[proto_len] = '\0';
}
memcpy(domain_part, MDNS_UTILS_DEFAULT_DOMAIN, domain_len);
domain_part[domain_len] = '\0';

q->host = host_part;
q->service = service_part;
// If proto exists, we must have allocated proto_part (checked in alloc_ok)
// Set to NULL if proto doesn't exist so cleanup can safely free NULL
q->proto = proto_part ? proto_part : NULL;
q->domain = domain_part;
q->own_dynamic_memory = true; // Mark that we need to free these
} else {
// If allocation fails, free what we got and fall back to original strings
mdns_mem_free(host_part);
mdns_mem_free(service_part);
mdns_mem_free(proto_part);
mdns_mem_free(domain_part);
// q->host, q->service, q->proto, q->domain remain pointing to original values
}
}
}
}

queueToEnd(mdns_out_question_t, packet->questions, q);

if (search->type == MDNS_TYPE_PTR) {
Expand Down Expand Up @@ -763,7 +836,9 @@ esp_err_t mdns_query_generic(const char *name, const char *service, const char *

esp_err_t mdns_query(const char *name, const char *service_type, const char *proto, uint16_t type, uint32_t timeout, size_t max_results, mdns_result_t **results)
{
return mdns_query_generic(name, service_type, proto, type, type != MDNS_TYPE_PTR, timeout, max_results, results);
// PTR queries should be multicast, all other types should be unicast
mdns_query_transmission_type_t transmission_type = (type == MDNS_TYPE_PTR) ? MDNS_QUERY_MULTICAST : MDNS_QUERY_UNICAST;
return mdns_query_generic(name, service_type, proto, type, transmission_type, timeout, max_results, results);
}

esp_err_t mdns_query_ptr(const char *service, const char *proto, uint32_t timeout, size_t max_results, mdns_result_t **results)
Expand Down
11 changes: 10 additions & 1 deletion components/mdns/tests/host_test/main/main.c
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
/*
* SPDX-FileCopyrightText: 2022-2024 Espressif Systems (Shanghai) CO LTD
* SPDX-FileCopyrightText: 2022-2025 Espressif Systems (Shanghai) CO LTD
*
* SPDX-License-Identifier: Unlicense OR CC0-1.0
*/
Expand Down Expand Up @@ -93,6 +93,15 @@ static void mdns_test_app(esp_netif_t *interface)
ESP_LOGI(TAG, "mdns hostname set to: [%s]", CONFIG_TEST_HOSTNAME);
ESP_ERROR_CHECK(mdns_register_netif(interface));
ESP_ERROR_CHECK(mdns_netif_action(interface, MDNS_EVENT_ENABLE_IP4 /*| MDNS_EVENT_ENABLE_IP6 */ | MDNS_EVENT_IP4_REVERSE_LOOKUP | MDNS_EVENT_IP6_REVERSE_LOOKUP));
/// here we query for _services._dns-sd._udp
mdns_result_t *results = NULL;
esp_err_t err = mdns_query_ptr("_services._dns-sd", "_udp", 2000, 1, &results);
if (err) {
ESP_LOGE(TAG, "Query Failed: %x", (err));
// return;
}
ESP_LOGI(TAG, "Query PTR: _services._dns-sd._udp results: %p", results);
mdns_query_results_free(results);

#ifdef CONFIG_TEST_CONSOLE
esp_console_repl_t *repl = NULL;
Expand Down
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