mDNS : implement service subtype to the LwIP mDNS application

src/apps/mdns/mdns.c

@@ -2507,12 +2507,14 @@ mdns_resp_netif_active(struct netif *netif)
  * @param txt_fn Callback to get TXT data. Will be called each time a TXT reply is created to
  *               allow dynamic replies.
  * @param txt_data Userdata pointer for txt_fn
+ * @param subTypes table contanins all subtypes of the service
+ * param subtypes_nbr the number of the subtypes linked to that service, it should be <=MDNS_MAX_SERVICES_SUBTYPES
  * @return service_id if the service was added to the netif, an err_t otherwise
  */
 s8_t
-mdns_resp_add_service(struct netif *netif, const char *name, const char *service, enum mdns_sd_proto proto, u16_t port, service_get_txt_fn_t txt_fn, void *txt_data)
+mdns_resp_add_service(struct netif *netif, const char *name, const char *service, enum mdns_sd_proto proto, u16_t port, service_get_txt_fn_t txt_fn, void *txt_data, char **subTypes,  u8_t subtypes_nbr )
 {
-  u8_t slot;
+  u8_t slot,i;
   struct mdns_service *srv;
   struct mdns_host *mdns;
 
@@ -2537,10 +2539,13 @@ mdns_resp_add_service(struct netif *netif, const char *name, const char *service
 
   MEMCPY(&srv->name, name, LWIP_MIN(MDNS_LABEL_MAXLEN, strlen(name)));
   MEMCPY(&srv->service, service, LWIP_MIN(MDNS_LABEL_MAXLEN, strlen(service)));
+  for(i=0;i<LWIP_MIN(subtypes_nbr,MDNS_MAX_SERVICES_SUBTYPES);i++)
+      MEMCPY(&srv->subTypes[i], subTypes[i], LWIP_MIN(MDNS_LABEL_MAXLEN, strlen(subTypes[i])));
   srv->txt_fn = txt_fn;
   srv->txt_userdata = txt_data;
   srv->proto = (u16_t)proto;
   srv->port = port;
+  srv->subtypes_nbr = subtypes_nbr;
 
   mdns->services[slot] = srv;
 

src/apps/mdns/mdns_domain.c

@@ -632,4 +632,30 @@ mdns_write_domain(struct mdns_outpacket *outpkt, struct mdns_domain *domain)
   return ERR_OK;
 }
 
+/**
+ * Build domain name for a subtype service
+ * @param domain Where to write the domain name
+ * @param service The service struct, containing service name, type and protocol
+ * @param include_name Whether to include the service name in the domain
+ * @return ERR_OK if domain was written. If service name is included,
+ *         \<subType\>.\<_sub\>.\<type\>.\<proto\>.local. will be written, otherwise \<type\>.\<proto\>.local.
+ *         An err_t is returned on error.
+ */
+err_t
+mdns_build_subtype_service_domain(struct mdns_domain *domain, struct mdns_service *service, int subTypes_index)
+{
+  err_t res;
+  LWIP_UNUSED_ARG(res);
+  memset(domain, 0, sizeof(struct mdns_domain));
+  res = mdns_domain_add_label(domain, service->subTypes[subTypes_index], strlen(service->subTypes[subTypes_index]));
+  LWIP_ERROR("mdns_build_service_domain: Failed to add label", (res == ERR_OK), return res);
+  res = mdns_domain_add_label(domain, "_sub", 4);
+  LWIP_ERROR("mdns_build_service_domain: Failed to add label", (res == ERR_OK), return res);
+  res = mdns_domain_add_label(domain, service->service, (u8_t)strlen(service->service));
+  LWIP_ERROR("mdns_build_service_domain: Failed to add label", (res == ERR_OK), return res);
+  res = mdns_domain_add_label(domain, dnssd_protos[service->proto], (u8_t)strlen(dnssd_protos[service->proto]));
+  LWIP_ERROR("mdns_build_service_domain: Failed to add label", (res == ERR_OK), return res);
+  return mdns_add_dotlocal(domain);
+}
+
 #endif /* LWIP_MDNS_RESPONDER */

src/apps/mdns/mdns_out.c

@@ -54,7 +54,7 @@
 
 /* Function prototypes */
 static void mdns_clear_outmsg(struct mdns_outmsg *outmsg);
-
+static err_t mdns_add_service_subtype_ptr_answer(struct mdns_outpacket *reply, struct mdns_outmsg *msg, struct mdns_service *service);
 /**
  * Call user supplied function to setup TXT data
  * @param service The service to build TXT record for
@@ -660,6 +660,8 @@ mdns_create_outpacket(struct netif *netif, struct mdns_outmsg *msg,
 
     if (msg->serv_replies[i] & REPLY_SERVICE_NAME_PTR) {
       res = mdns_add_servicename_ptr_answer(outpkt, msg, service);
+      /*if a subtype is used, that following function write answer of the subtype service PTR RR to outpacket*/
+      res = mdns_add_service_subtype_ptr_answer(outpkt, msg, service);
       if (res != ERR_OK) {
         return res;
       }
@@ -1160,4 +1162,39 @@ mdns_send_request(struct mdns_request *req, struct netif *netif, const ip_addr_t
 }
 #endif
 
+/** Write an all subtype services ->  PTR RR to outpacket */
+static err_t
+mdns_add_service_subtype_ptr_answer(struct mdns_outpacket *reply, struct mdns_outmsg *msg,
+                                struct mdns_service *service)
+{
+  err_t res = ERR_OK;
+  u8_t subtyes_index;
+  u32_t ttl = MDNS_TTL_4500;
+  struct mdns_domain service_type, sub_service;
+  for(subtyes_index=0;subtyes_index < LWIP_MIN(service->subtypes_nbr,MDNS_MAX_SERVICES_SUBTYPES); subtyes_index++)
+  {
+    res =mdns_build_subtype_service_domain(&sub_service, service,subtyes_index);
+    res =mdns_build_service_domain(&service_type, service, 1);
+  /* When answering to a legacy querier, we need to repeat the question and
+   * limit the ttl to the short legacy ttl */
+  if(msg->legacy_query) {
+    /* Repeating the question only needs to be done for the question asked
+     * (max one question), not for the additional records. */
+    if(reply->questions < 1) {
+      LWIP_DEBUGF(MDNS_DEBUG, ("MDNS: Add question for legacy query\n"));
+      res = mdns_add_question(reply, &sub_service, DNS_RRTYPE_PTR, DNS_RRCLASS_IN, 0);
+      if (res != ERR_OK) {
+        return res;
+      }
+      reply->questions = 1;
+    }
+    /* ttl of legacy answer may not be greater then 10 seconds */
+    ttl = MDNS_TTL_10;
+  }
+  LWIP_DEBUGF(MDNS_DEBUG, ("MDNS: Responding with service type PTR record\n"));
+  res =mdns_add_answer(reply, &sub_service, DNS_RRTYPE_PTR, DNS_RRCLASS_IN,
+                         0, ttl, NULL, 0, &service_type);
+  }
+  return res;
+}
 #endif /* LWIP_MDNS_RESPONDER */

src/include/lwip/apps/mdns.h

@@ -112,7 +112,7 @@ err_t mdns_resp_remove_netif(struct netif *netif);
 err_t mdns_resp_rename_netif(struct netif *netif, const char *hostname);
 int mdns_resp_netif_active(struct netif *netif);
 
-s8_t  mdns_resp_add_service(struct netif *netif, const char *name, const char *service, enum mdns_sd_proto proto, u16_t port, service_get_txt_fn_t txt_fn, void *txt_userdata);
+s8_t  mdns_resp_add_service(struct netif *netif, const char *name, const char *service, enum mdns_sd_proto proto, u16_t port, service_get_txt_fn_t txt_fn, void *txt_data, char **subTypes,  u8_t subtypes_nbr );
 err_t mdns_resp_del_service(struct netif *netif, u8_t slot);
 err_t mdns_resp_rename_service(struct netif *netif, u8_t slot, const char *name);
 

src/include/lwip/apps/mdns_domain.h

@@ -70,7 +70,7 @@ err_t mdns_build_request_domain(struct mdns_domain *domain, struct mdns_request
 #endif
 u16_t mdns_compress_domain(struct pbuf *pbuf, u16_t *offset, struct mdns_domain *domain);
 err_t mdns_write_domain(struct mdns_outpacket *outpkt, struct mdns_domain *domain);
-
+err_t mdns_build_subtype_service_domain(struct mdns_domain *domain, struct mdns_service *service, int subTypes_index);
 #endif /* LWIP_MDNS_RESPONDER */
 
 #ifdef __cplusplus

src/include/lwip/apps/mdns_opts.h

@@ -52,12 +52,14 @@
  * transport. IGMP is needed for IPv4 multicast.
  */
 #ifndef LWIP_MDNS_RESPONDER
-#define LWIP_MDNS_RESPONDER             0
+#define LWIP_MDNS_RESPONDER             1
 #endif /* LWIP_MDNS_RESPONDER */
 
 /** The maximum number of services per netif */
 #ifndef MDNS_MAX_SERVICES
 #define MDNS_MAX_SERVICES               1
+/** The maximum number of subtypes per service */
+#define MDNS_MAX_SERVICES_SUBTYPES      4
 #endif
 
 /** The minimum delay between probes in ms. RFC 6762 require 250ms.

src/include/lwip/apps/mdns_priv.h

@@ -98,14 +98,18 @@ struct mdns_service {
   char name[MDNS_LABEL_MAXLEN + 1];
   /** Type of service, like '_http' */
   char service[MDNS_LABEL_MAXLEN + 1];
-  /** Callback function and userdata
-   * to update txtdata buffer */
+  /** SubType of service, like '_printer' */
+  char subTypes[MDNS_MAX_SERVICES_SUBTYPES][MDNS_LABEL_MAXLEN + 1];
+  /** Callback function and userdata/*
+   /* to update txtdata buffer */
   service_get_txt_fn_t txt_fn;
   void *txt_userdata;
   /** Protocol, TCP or UDP */
   u16_t proto;
   /** Port of the service */
   u16_t port;
+  /** Number of the subtypes of a service */
+  u16_t subtypes_nbr;
 };
 
 /** mDNS output packet */