tidy up values into name, serviceName, serviceProto and packet generation

EXmDNS.cpp

@@ -2,15 +2,49 @@
 #include <Arduino.h>
 #include "EthernetInterface.h"
 #include "EXmDNS.h"
-#include "DIAG.h"
+
+// fixed values for mDNS
 static IPAddress mdnsMulticastIPAddr = IPAddress(224, 0, 0, 251);
 #define MDNS_SERVER_PORT 5353
 
+// dotToLen()
+// converts stings of form ".foo.barbar.x" to a string with the
+// dots replaced with lenght. So string above  would result in
+// "\x03foo\x06barbar\x01x" in C notation. If not NULL, *substr
+// will point to the beginning of the last component, in this
+// example that would be "\x01x".
+//
+static void dotToLen(char *str, char **substr) {
+  char *dotplace = NULL;
+  char *s;
+  byte charcount = 0;
+  for (s = str;/*see break*/ ; s++) {
+    if (*s == '.' || *s == '\0') {
+      // take care of accumulated
+      if (dotplace != NULL && charcount != 0) {
+	*dotplace = charcount;
+      }
+      if (*s == '\0')
+	break;
+      if (substr && *s == '.')
+	*substr = s;
+      // set new values
+      dotplace = s;
+      charcount = 0;
+    } else {
+      charcount++;
+    }
+  }
+}
+
 MDNS::MDNS(EthernetUDP& udp) {
   _udp = &udp;
 }
 MDNS::~MDNS() {
   _udp->stop();
+  if (_name) free(_name);
+  if (_serviceName) free(_serviceName);
+  if (_serviceProto) free(_serviceProto);
 }
 int MDNS::begin(const IPAddress& ip, char* name) {
   // if we were called very soon after the board was booted, we need to give the
@@ -21,56 +55,53 @@ int MDNS::begin(const IPAddress& ip, char* name) {
   //  delay(100);
   
   _ipAddress = ip;
-  _name = name;
+  _name = (char *)malloc(strlen(name +2));
+  byte n;
+  for(n = 0; n<strlen(name); n++)
+    _name[n+1] = name[n];
+  _name[n+1] = '\0';
+  _name[0] = '.';
+  dotToLen(_name, NULL);
   return _udp->beginMulticast(mdnsMulticastIPAddr, MDNS_SERVER_PORT);
 }
+
 int MDNS::addServiceRecord(const char* name, uint16_t port, MDNSServiceProtocol_t proto) {
   // we ignore proto, assume TCP
   _serviceName = (char *)malloc(strlen(name +2));
-  DIAG("name %d %s", strlen(name), name);
   byte n;
   for(n = 0; n<strlen(name); n++)
     _serviceName[n+1] = name[n];
   _serviceName[n+1] = '\0';
-  //strcpy(&_serviceName[1], name);
-  _serviceName[0] = (byte)strlen(name);
-  DIAG("sn %d", *_serviceName);
+  _serviceName[0] = '.';
+  _serviceProto = NULL; //to be filled in
+  dotToLen(_serviceName, &_serviceProto);
   _servicePort = port;
-  DIAG("Sevicename %d %s", strlen(_serviceName), _serviceName);
   return 1;
 }
 
 static char dns_rr_services[]   = "\x09_services\x07_dns-sd\x04_udp\x05local";
-static char dns_rr_withrottle[] = "\x0b_withrottle\x04_tcp\x05local";
-static char *dns_rr_tcplocal    = dns_rr_withrottle + dns_rr_withrottle[0] + 1; // jump over first record
+static char *dns_rr_tcplocal    = "\x04_tcp\x05local"; 
 static char *dns_rr_local       = dns_rr_tcplocal + dns_rr_tcplocal[0] + 1;
 
 typedef struct _DNSHeader_t 
 {
   uint16_t    xid;
-  uint16_t  flags;
-  /*
-  uint8_t     recursionDesired    : 1;
-  uint8_t     truncated           : 1;
-  uint8_t     authoritiveAnswer   : 1;
-  uint8_t     opCode              : 4;
-  uint8_t     queryResponse       : 1;
-  uint8_t     responseCode        : 4;
-  uint8_t     checkingDisabled    : 1;
-  uint8_t     authenticatedData   : 1;
-  uint8_t     zReserved           : 1;
-  uint8_t     recursionAvailable  : 1;
-  */
+  uint16_t  flags; // flags condensed
   uint16_t    queryCount;
   uint16_t    answerCount;
   uint16_t    authorityCount;
   uint16_t    additionalCount;
 } __attribute__((__packed__)) DNSHeader_t;
 
+//
+// MDNS::run()
+// This broadcasts whatever we got evey BROADCASTTIME seconds.
+// Why? Too much brokenness i all mDNS implementations available
+//
 void MDNS::run() {
-  static long int lastrun = 10000;
+  static long int lastrun = BROADCASTTIME * 1000UL;
   unsigned long int now = millis();
-  if (!(now - lastrun > 10000)) {
+  if (!(now - lastrun > BROADCASTTIME * 1000UL)) {
     return;
   }
   lastrun = now;
@@ -80,33 +111,39 @@ void MDNS::run() {
 
   // dns header
   dnsHeader.flags = lwip_htons(0x8400); // Response, authorative
-  dnsHeader.answerCount = lwip_htons(4 /*5*/);
+  dnsHeader.answerCount = lwip_htons(4 /*5 if TXT but we do not do that */);
   _udp->write((uint8_t*)&dnsHeader, sizeof(DNSHeader_t));
-  // rr #1
+
+  // rr #1, the PTR record from generic _services.x.local to service.x.local
   _udp->write((uint8_t*)dns_rr_services, sizeof(dns_rr_services));
+
   byte buf[10];
   buf[0] = 0x00;
   buf[1] = 0x0c;                           //PTR
   buf[2] = 0x00;
   buf[3] = 0x01;                           //IN
   *((uint32_t*)(buf+4)) = lwip_htonl(120); //TTL in sec
-  *((uint16_t*)(buf+8)) = lwip_htons(sizeof(dns_rr_withrottle));
-  _udp->write(buf, 10);
-  _udp->write(dns_rr_withrottle, sizeof(dns_rr_withrottle));
-  // rr #2
-  _udp->write(dns_rr_withrottle, sizeof(dns_rr_withrottle));
-  *((uint16_t*)(buf+8)) = lwip_htons(strlen(_serviceName) + sizeof(dns_rr_withrottle)); // recycle most of buf
+  *((uint16_t*)(buf+8)) = lwip_htons( _serviceProto[0] + 1 + strlen(dns_rr_tcplocal) + 1);
   _udp->write(buf, 10);
 
-  _udp->write(_serviceName, _serviceName[0]+1);
-  _udp->write(dns_rr_withrottle, sizeof(dns_rr_withrottle));
-  // rr #3
-  _udp->write(_serviceName, _serviceName[0]+1);
-  _udp->write(dns_rr_withrottle, sizeof(dns_rr_withrottle));
+  _udp->write(_serviceProto,_serviceProto[0]+1);
+  _udp->write(dns_rr_tcplocal, strlen(dns_rr_tcplocal)+1);
+
+  // rr #2, the PTR record from proto.x to name.proto.x
+  _udp->write(_serviceProto,_serviceProto[0]+1);
+  _udp->write(dns_rr_tcplocal, strlen(dns_rr_tcplocal)+1);
+  *((uint16_t*)(buf+8)) = lwip_htons(strlen(_serviceName) + strlen(dns_rr_tcplocal) + 1); // recycle most of buf
+  _udp->write(buf, 10);
+
+  _udp->write(_serviceName, strlen(_serviceName));
+  _udp->write(dns_rr_tcplocal, strlen(dns_rr_tcplocal)+1);
+  // rr #3, the SRV record for the service that points to local name
+  _udp->write(_serviceName, strlen(_serviceName));
+  _udp->write(dns_rr_tcplocal, strlen(dns_rr_tcplocal)+1);
 
   buf[1] = 0x21;                                  // recycle most of buf but here SRV
   buf[2] = 0x80;                                  // cache flush
-  *((uint16_t*)(buf+8)) = lwip_htons(strlen(_serviceName) + strlen(dns_rr_local) + 1 + 6);
+  *((uint16_t*)(buf+8)) = lwip_htons(strlen(_name) + strlen(dns_rr_local) + 1 + 6);
   _udp->write(buf, 10);
 
   byte srv[6];
@@ -116,11 +153,11 @@ void MDNS::run() {
   *((uint16_t*)(srv+4)) = lwip_htons(_servicePort);
   _udp->write(srv, 6);
   // target
-  _udp->write(_serviceName, _serviceName[0]+1);
+  _udp->write(_name, _name[0]+1);
   _udp->write(dns_rr_local, strlen(dns_rr_local)+1);
 
-  // rr #4
-  _udp->write(_serviceName, _serviceName[0]+1);
+  // rr #4, the A record for the name.local
+  _udp->write(_name, _name[0]+1);
   _udp->write(dns_rr_local, strlen(dns_rr_local)+1);
   
   buf[1] = 0x01;                                  // recycle most of buf but here A

EXmDNS.h

@@ -1,3 +1,6 @@
+
+#define BROADCASTTIME 15 //seconds
+
 typedef enum _MDNSServiceProtocol_t 
 {
   MDNSServiceTCP,
@@ -16,5 +19,6 @@ private:
   IPAddress _ipAddress;
   char* _name;
   char* _serviceName;
+  char* _serviceProto;
   int _servicePort;
 };

EthernetInterface.cpp

@@ -132,9 +132,8 @@ void EthernetInterface::setup()
   #ifdef DO_MDNS
     if (!mdns.begin(Ethernet.localIP(), WIFI_HOSTNAME))
       DIAG("mdns.begin fail"); // hostname
-    mdns.addServiceRecord(WIFI_HOSTNAME, IP_PORT, MDNSServiceTCP);
-  // Not sure if we need to run it once, but just in case!
-    mdns.run();
+    mdns.addServiceRecord(WIFI_HOSTNAME "._withrottle", IP_PORT, MDNSServiceTCP);
+    mdns.run(); // run it right away to get out info ASAP
   #endif  
   connected=true;    
 }