mdns.c File Reference

mDNS service discovery implementation for ascii-chat More...

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Data Structures
struct	asciichat_mdns_t
	Internal mDNS context structure. More...

Macros
#define	MDNS_BUFFER_SIZE   (4 * 1024)
	mDNS packet buffer size (4KB should handle most service records)

Functions
asciichat_mdns_t *	asciichat_mdns_init (void)
	Initialize mDNS context.
void	asciichat_mdns_destroy (asciichat_mdns_t *mdns)
	Shutdown mDNS context and cleanup.
asciichat_error_t	asciichat_mdns_advertise (asciichat_mdns_t *mdns, const asciichat_mdns_service_t *service)
	Advertise a service on the local network.
asciichat_error_t	asciichat_mdns_unadvertise (asciichat_mdns_t *mdns, const char *service_name)
	Stop advertising a service.
asciichat_error_t	asciichat_mdns_query (asciichat_mdns_t *mdns, const char *service_type, asciichat_mdns_discovery_callback_fn callback, void *user_data)
	Query for services on the local network.
asciichat_error_t	asciichat_mdns_update (asciichat_mdns_t *mdns, int timeout_ms)
	Process pending mDNS events (must be called regularly)
int	asciichat_mdns_get_socket (asciichat_mdns_t *mdns)
	Get the socket file descriptor for integration with select/poll.

Detailed Description

mDNS service discovery implementation for ascii-chat

Wraps the mdns library (https://github.com/mjansson/mdns) with ascii-chat specific API. This implementation provides service advertisement and discovery for LAN-based sessions.

Definition in file network/mdns/mdns.c.

Macro Definition Documentation

MDNS_BUFFER_SIZE

#define MDNS_BUFFER_SIZE   (4 * 1024)

mDNS packet buffer size (4KB should handle most service records)

Definition at line 34 of file network/mdns/mdns.c.

Function Documentation

asciichat_mdns_advertise()

asciichat_error_t asciichat_mdns_advertise	(	asciichat_mdns_t *	mdns,
		const asciichat_mdns_service_t *	service
	)

Advertise a service on the local network.

Parameters

mdns	mDNS context
service	Service to advertise

Returns

ASCIICHAT_OK on success, error code otherwise

Note

The service structure should remain valid until unadvertised

Definition at line 85 of file network/mdns/mdns.c.

                                                                                                            {
  if (!mdns || !service) {
    return SET_ERRNO(ERROR_INVALID_PARAM, "mDNS context or service is NULL");
  }
 
  if (!service->name || !service->type || !service->host) {
    return SET_ERRNO(ERROR_INVALID_PARAM, "Service name, type, or host is NULL");
  }
 
  log_debug("Advertising mDNS service: %s (%s:%d)", service->name, service->host, service->port);
 
  /* TODO: Implement actual advertisement using mdns library
   * This will involve creating service records and sending announcements
   * The mdns library provides mdns_announce_* functions for this
   */
  return ASCIICHAT_OK;
}

References ASCIICHAT_OK, ERROR_INVALID_PARAM, asciichat_mdns_service_t::host, log_debug, asciichat_mdns_service_t::name, asciichat_mdns_service_t::port, SET_ERRNO, and asciichat_mdns_service_t::type.

Referenced by session_server_like_mdns_advertise().

asciichat_mdns_destroy()

void asciichat_mdns_destroy

(

asciichat_mdns_t *

mdns

)

Shutdown mDNS context and cleanup.

Parameters

mdns	Context to cleanup

Definition at line 71 of file network/mdns/mdns.c.

                                                    {
  if (!mdns) {
    return;
  }
 
  if (mdns->socket_fd >= 0) {
    mdns_socket_close(mdns->socket_fd);
  }
 
  SAFE_FREE(mdns->buffer);
  SAFE_FREE(mdns);
  log_debug("mDNS context shutdown");
}

References asciichat_mdns_t::buffer, log_debug, SAFE_FREE, and asciichat_mdns_t::socket_fd.

Referenced by discovery_mdns_query(), and session_server_like_run().

asciichat_mdns_get_socket()

int asciichat_mdns_get_socket

(

asciichat_mdns_t *

mdns

)

Get the socket file descriptor for integration with select/poll.

Parameters

mdns	mDNS context

Returns

Socket descriptor, or -1 on error

Note

Useful for integrating mDNS into existing event loops

Definition at line 289 of file network/mdns/mdns.c.

                                                      {
  if (!mdns) {
    return -1;
  }
  return mdns->socket_fd;
}

References asciichat_mdns_t::socket_fd.

asciichat_mdns_init()

asciichat_mdns_t * asciichat_mdns_init

(

void

)

Initialize mDNS context.

Returns

Opaque mDNS context, or NULL on error

Definition at line 36 of file network/mdns/mdns.c.

                                            {
  asciichat_mdns_t *mdns = SAFE_MALLOC(sizeof(asciichat_mdns_t), asciichat_mdns_t *);
  if (!mdns) {
    SET_ERRNO(ERROR_MEMORY, "Failed to allocate mDNS context");
    return NULL;
  }
 
  memset(mdns, 0, sizeof(asciichat_mdns_t));
 
  /* Allocate I/O buffer for mDNS packets */
  mdns->buffer = SAFE_MALLOC(MDNS_BUFFER_SIZE, uint8_t *);
  if (!mdns->buffer) {
    SAFE_FREE(mdns);
    SET_ERRNO(ERROR_MEMORY, "Failed to allocate mDNS buffer");
    return NULL;
  }
  mdns->buffer_capacity = MDNS_BUFFER_SIZE;
 
  /* Open IPv4 mDNS socket */
  mdns->socket_fd = mdns_socket_open_ipv4(NULL);
  if (mdns->socket_fd < 0) {
    SAFE_FREE(mdns->buffer);
    SAFE_FREE(mdns);
    SET_ERRNO(ERROR_NETWORK_BIND, "Failed to open mDNS socket");
    return NULL;
  }
 
  log_dev("mDNS context initialized (socket: %d, buffer: %zu bytes)", mdns->socket_fd, mdns->buffer_capacity);
 
  // Register mDNS context for debugging
  NAMED_REGISTER_CONTEXT(mdns, "asciichat_mdns", "mdns_context", NULL);
 
  return mdns;
}

References asciichat_mdns_t::buffer, asciichat_mdns_t::buffer_capacity, ERROR_MEMORY, ERROR_NETWORK_BIND, log_dev, MDNS_BUFFER_SIZE, NAMED_REGISTER_CONTEXT, SAFE_FREE, SAFE_MALLOC, SET_ERRNO, and asciichat_mdns_t::socket_fd.

Referenced by discovery_mdns_query(), and session_server_like_run().

asciichat_mdns_query()

asciichat_error_t asciichat_mdns_query	(	asciichat_mdns_t *	mdns,
		const char *	service_type,
		asciichat_mdns_discovery_callback_fn	callback,
		void *	user_data
	)

Query for services on the local network.

Parameters

mdns	mDNS context
service_type	Service type to query (e.g., "_ascii-chat._tcp.local")
callback	Function to call for each discovered service
user_data	User pointer passed to callback

Returns

ASCIICHAT_OK on success, error code otherwise

Definition at line 229 of file network/mdns/mdns.c.

                                                                                                       {
  if (!mdns || !service_type || !callback) {
    return SET_ERRNO(ERROR_INVALID_PARAM, "Invalid mDNS query parameters");
  }
 
  /* Validate service type is non-empty and has minimum length
   * Prevents underflow bug in mdns library when processing empty strings
   */
  size_t service_type_len = strlen(service_type);
  if (service_type_len == 0) {
    return SET_ERRNO(ERROR_INVALID_PARAM, "Service type cannot be empty");
  }
 
  mdns->callback = callback;
  mdns->callback_data = user_data;
 
  log_info("Starting mDNS query for: %s", service_type);
 
  /* Send PTR query for service type (one-shot query)
   * PTR query discovers all instances of a service type
   * mdns_query_send returns the query ID for response filtering
   */
  int query_id = mdns_query_send(mdns->socket_fd, MDNS_RECORDTYPE_PTR, service_type, service_type_len, mdns->buffer,
                                 mdns->buffer_capacity, 0);
 
  if (query_id < 0) {
    return SET_ERRNO(ERROR_NETWORK, "mDNS query send failed for %s (query_id=%d)", service_type, query_id);
  }
 
  mdns->query_id = (uint16_t)query_id;
  log_debug("mDNS query sent for service type: %s (query_id: %d)", service_type, query_id);
 
  return ASCIICHAT_OK;
}

References ASCIICHAT_OK, asciichat_mdns_t::buffer, asciichat_mdns_t::buffer_capacity, asciichat_mdns_t::callback, asciichat_mdns_t::callback_data, ERROR_INVALID_PARAM, ERROR_NETWORK, log_debug, log_info, asciichat_mdns_t::query_id, SET_ERRNO, and asciichat_mdns_t::socket_fd.

Referenced by discovery_mdns_query().

asciichat_mdns_unadvertise()

asciichat_error_t asciichat_mdns_unadvertise	(	asciichat_mdns_t *	mdns,
		const char *	service_name
	)

Stop advertising a service.

Parameters

mdns	mDNS context
service_name	Service instance name to unadvertise

Returns

ASCIICHAT_OK on success, error code otherwise

Definition at line 103 of file network/mdns/mdns.c.

                                                                                               {
  if (!mdns || !service_name) {
    return SET_ERRNO(ERROR_INVALID_PARAM, "mDNS context or service name is NULL");
  }
 
  log_info("Stopped advertising service: %s", service_name);
 
  /* TODO: Implement actual unadvertisement
   * This will involve sending goodbye records with TTL=0
   */
  return ASCIICHAT_OK;
}

References ASCIICHAT_OK, ERROR_INVALID_PARAM, log_info, and SET_ERRNO.

asciichat_mdns_update()

asciichat_error_t asciichat_mdns_update	(	asciichat_mdns_t *	mdns,
		int	timeout_ms
	)

Process pending mDNS events (must be called regularly)

This should be called from the main event loop to:

• Send advertisement packets
• Receive and parse query responses
• Invoke discovery callbacks

Parameters

mdns	mDNS context
timeout_ms	Maximum time to block (0 = non-blocking)

Returns

ASCIICHAT_OK on success, error code otherwise

Definition at line 265 of file network/mdns/mdns.c.

                                                                                {
  if (!mdns) {
    return SET_ERRNO(ERROR_INVALID_PARAM, "mDNS context is NULL");
  }
 
  /* Process incoming mDNS packets (responses from previous queries)
   * mdns_query_recv processes all records received since last call
   * The callback function (mdns_record_callback) is invoked for each record
   */
  int num_records =
      mdns_query_recv(mdns->socket_fd, mdns->buffer, mdns->buffer_capacity, mdns_record_callback, mdns, mdns->query_id);
 
  if (num_records < 0) {
    return SET_ERRNO(ERROR_NETWORK, "Failed to receive mDNS query responses");
  }
 
  if (num_records > 0) {
    log_debug("Processed %d mDNS records", num_records);
  }
 
  (void)timeout_ms;
  return ASCIICHAT_OK;
}

References ASCIICHAT_OK, asciichat_mdns_t::buffer, asciichat_mdns_t::buffer_capacity, ERROR_INVALID_PARAM, ERROR_NETWORK, log_debug, asciichat_mdns_t::query_id, SET_ERRNO, and asciichat_mdns_t::socket_fd.

Referenced by discovery_mdns_query().