Dedupe Docker DNS hostnames

Not a big deal, but this does dedupe the
http-toolkit-host.docker.internal address that's used in every single
container, and in the process avoids some warnings if that's used
directly somewhere (and probably in other cases too).

Author: pimterry

src/dns-server.ts

@@ -37,17 +37,18 @@ class DnsServer extends dns2.UDPServer {
 
     private hostMaps: {
         [sourceId: string]: {
-            [host: string]: string[] | undefined
+            [host: string]: Set<string> | undefined
         }
     } = {};
 
-    setSourceHosts(sourceId: string, hosts: { [hostname: string]: string[] }) {
+    setSourceHosts(sourceId: string, hosts: { [hostname: string]: Set<string> }) {
         this.hostMaps[sourceId] = hosts;
     }
 
-    private getHostAddresses(hostname: string) {
+    private getHostAddresses(hostname: string): Set<string> {
         return _.flatMap(this.hostMaps, (hostMap) => hostMap[hostname])
-            .filter(h => !!h) as string[];
+            .filter(h => !!h)
+            .reduce<Set<string>>((result, set) => new Set([...result!, ...set!]), new Set());
     }
 
     handleQuery(request: dns2.DnsRequest, sendResponse: (response: dns2.DnsResponse) => void) {
@@ -59,7 +60,7 @@ class DnsServer extends dns2.UDPServer {
 
         const answers = this.getHostAddresses(question.name);
 
-        if (answers.length > 1) {
+        if (answers.size > 1) {
             console.log(`Multiple hosts in internal DNS for hostname ${question.name}: ${answers}`);
         }
 

src/interceptors/docker/docker-networking.ts

@@ -135,7 +135,7 @@ class DockerNetworkMonitor {
         private docker: Docker,
         private proxyPort: number,
         private dockerEventStream: NodeJS.ReadableStream,
-        private updateCallback: (aliases: { [hostname: string]: string[] }) => void
+        private updateCallback: (aliases: { [hostname: string]: Set<string> }) => void
     ) {
         dockerEventStream.on('data', this.onEvent);
 
@@ -174,10 +174,10 @@ class DockerNetworkMonitor {
         // Merge the sets for the same hostname in multiple networks together, to create
         // a single mapping from hostnames to all possible addresses. This isn't great,
         // but hopefully in practice there will be few or zero conflicts regardless.
-        return _.assignWith<{ [hostname: string]: string [] }>({},
+        return _.assignWith<{ [hostname: string]: Set<string> }>({},
             ...Object.values(this.aliasMappings),
-            (existingIps: string[] = [], nextIps: Set<string> = new Set()) => {
-                return [...existingIps, ...nextIps.values()];
+            (existingIps: Set<string> = new Set(), nextIps: Set<string> = new Set()) => {
+                return new Set([...existingIps, ...nextIps]);
             }
         );
     }