If no SRV record found when no port specifiec, look for A record. (#125)

* If no SRV record found when no port specifiec, look for A record.

* update log statement to info level

lib/regbot.js

@@ -204,17 +204,32 @@ class Regbot {
         }));
 
         // for reg trunks, create ephemeral set of IP addresses for inbound gateways
-        if (this.trunk_type === 'reg' && !isValidIPv4(this.ipv4)) {
+        if (this.trunk_type === 'reg') {
           this.addresses = [];
-          if (this.port) {
-            const addrs = await dnsResolverA(this.logger, this.ipv4);
-            this.addresses.push(...addrs);
+          if (isValidIPv4(this.ipv4)) {
+            this.addresses.push(this.ipv4);
           }
           else {
-            const addrs = await dnsResolverSrv(this.logger, this.ipv4, this.transport);
-            this.addresses.push(...addrs);
+            if (this.port) {
+              const addrs = await dnsResolverA(this.logger, this.ipv4);
+              this.addresses.push(...addrs);
+            }
+            else {
+              const addrs = await dnsResolverSrv(this.logger, this.ipv4, this.transport);
+              if (addrs.length) {
+                this.addresses.push(...addrs);
+              } else {
+                this.logger.info({ipv4: this.ipv4, transport: this.transport},
+                  'No SRV addresses found for reg-gateway');
+                const addrsARecord = await dnsResolverA(this.logger, this.ipv4);
+                if (addrsARecord.length) {
+                  this.addresses.push(...addrsARecord);
+                } else {
+                  this.logger.info({ipv4: this.ipv4}, 'No A record found for reg-gateway');
+                }
+              }
+            }
           }
-
           if (this.addresses.length) {
             try {
               await Promise.all(