Restore legacy behaviour for fallback hostname

Author: milhnl

wled00/cfg.cpp

@@ -57,14 +57,14 @@ bool deserializeConfig(JsonObject doc, bool fromFS) {
 #endif
 
   JsonObject id = doc["id"];
+  getStringFromJson(serverDescription, id["name"], sizeof(serverDescription));
   // legacy behaviour
   getStringFromJson(hostName, id[F("mdns")], sizeof(hostName));
   if (strlen(hostName) == 0) {
     mDNSenabled = false; // if no host name is set, disable mDNS
-    sprintf_P(hostName, PSTR("wled-%.*s"), 6, escapedMac.c_str() + 6);
+    prepareHostname(hostName, sizeof(hostName)-1);
   }
 
-  getStringFromJson(serverDescription, id["name"], sizeof(serverDescription));
 #ifndef WLED_DISABLE_ALEXA
   getStringFromJson(alexaInvocationName, id[F("inv")], sizeof(alexaInvocationName));
 #endif

wled00/fcn_declare.h

@@ -389,6 +389,7 @@ size_t printSetFormValue(Print& settingsScript, const char* key, int val);
 size_t printSetFormValue(Print& settingsScript, const char* key, const char* val);
 size_t printSetFormIndex(Print& settingsScript, const char* key, int index);
 size_t printSetClassElementHTML(Print& settingsScript, const char* key, const int index, const char* val);
+void prepareHostname(char* hostname, size_t maxLen = 32);
 [[gnu::pure]] bool isAsterisksOnly(const char* str, byte maxLen);
 bool requestJSONBufferLock(uint8_t moduleID=255);
 void releaseJSONBufferLock();

wled00/set.cpp

@@ -64,7 +64,7 @@ void handleSettingsSet(AsyncWebServerRequest *request, byte subPage)
     }
 
     strlcpy(hostName, request->arg(F("CM")).c_str(), sizeof(hostName));
-    if (strlen(hostName) == 0) sprintf_P(hostName, PSTR("wled-%.*s"), 6, escapedMac.c_str() + 6); // hostname must not be empty
+    if (strlen(hostName) == 0) prepareHostname(hostName, sizeof(hostName)-1);
     #ifdef ARDUINO_ARCH_ESP32
       #ifdef WLED_USE_ETHERNET
     ETH.setHostname(hostName);

wled00/util.cpp

@@ -123,6 +123,30 @@ size_t printSetClassElementHTML(Print& settingsScript, const char* key, const in
   return settingsScript.printf_P(PSTR("d.getElementsByClassName(\"%s\")[%d].innerHTML=\"%s\";"), key, index, val);
 }
 
+// prepare a unique hostname based on the last 6 digits of the MAC address
+// if no mDNS name or serverDescription is set, otherwise use cmDNS or serverDescription
+// the hostname will be at most 24 characters long, starting with "wled-"
+// and containing only alphanumeric characters and hyphens
+// the hostname will not end with a hyphen and will be null-terminated
+void prepareHostname(char* hostname, size_t maxLen)
+{
+  // create a unique hostname based on the last 6 digits of the MAC address if no serverDescription is set
+  sprintf_P(hostname, PSTR("wled-%*s"), 6, escapedMac.c_str() + 6);
+  const char *pC = serverDescription;  // use serverDescription, this method is not called if hostName is set
+  unsigned pos = 5;             // keep "wled-" from unique name
+  while (*pC && pos < maxLen) { // while !null and not over length
+    if (isalnum(*pC)) {         // if the current char is alpha-numeric append it to the hostname
+      hostname[pos++] = *pC;
+    } else if (*pC == ' ' || *pC == '_' || *pC == '-' || *pC == '+' || *pC == '!' || *pC == '?' || *pC == '*') {
+      hostname[pos++] = '-';
+    }
+    // else do nothing - no leading hyphens and do not include hyphens for all other characters.
+    pC++;
+  }
+  // last character must not be hyphen
+  while (pos > 4 && hostname[pos-1] == '-') pos--;
+  hostname[pos] = '\0'; // terminate string (leave at least "wled")
+}
 
 bool isAsterisksOnly(const char* str, byte maxLen)
 {

wled00/wled.cpp

@@ -424,7 +424,7 @@ void WLED::setup()
   escapedMac.toLowerCase();
 
   // generate host name if no compile time default is set
-  if (strcmp(hostName, DEFAULT_MDNS_NAME) == 0) sprintf_P(hostName, PSTR("wled-%.*s"), 6, escapedMac.c_str() + 6);
+  if (strcmp(hostName, DEFAULT_MDNS_NAME) == 0) prepareHostname(hostName, sizeof(hostName)-1);
   WLED_SET_AP_SSID(); // otherwise it is empty on first boot until config is saved
   multiWiFi.push_back(WiFiConfig(CLIENT_SSID,CLIENT_PASS)); // initialise vector with default WiFi