fix(vesktop): avoid DTLS stalls with multiple interfaces (#66)

* fix(vesktop): add WebRTC IP handling support

* fix(vesktop): constrain WebRTC interface selection

modules/applications/discord/home.nix

@@ -1,7 +1,19 @@
-_: {
+{
+  lib,
+  pkgs,
+  ...
+}: {
   programs.vesktop = {
     enable = true;
 
+    package =
+      if pkgs.stdenv.hostPlatform.isLinux then
+        pkgs.vesktop.overrideAttrs (old: {
+          patches = (old.patches or [ ]) ++ [ ./vesktop-webrtc-ip-handling-policy.patch ];
+        })
+      else
+        pkgs.vesktop;
+
     settings = {
       discordBranch = "stable";
 
@@ -16,6 +28,10 @@ _: {
 
       openLinksWithElectron = false;
 
+      # Keep WebRTC on interfaces used by the default route. Vesktop's default
+      # policy may select secondary private interfaces and stall at DTLS.
+      webRTCIPHandlingPolicy = "default_public_and_private_interfaces";
+
       spellCheckLanguages = [
         "ja-JP"
         "en-US"

modules/applications/discord/vesktop-webrtc-ip-handling-policy.patch

@@ -0,0 +1,36 @@
+diff --git a/src/main/index.ts b/src/main/index.ts
+index 2f4c399a4..0c81512a4 100644
+--- a/src/main/index.ts
++++ b/src/main/index.ts
+@@ -158,3 +158,15 @@ app.on("open-url", (_, url) => {
+ app.on("window-all-closed", () => {
+     if (process.platform !== "darwin") app.quit();
+ });
++
++// Sets the WebRTC IP handling policy for all current and future windows.
++// Switching to "default_public_and_private_interfaces" may fix calls stuck at "DTLS Connecting" when using VPNs, Tailscale, etc.
++// https://github.com/Vencord/Vesktop/issues/876
++app.on("web-contents-created", (_event, contents) => {
++    contents.setWebRTCIPHandlingPolicy(Settings.store.webRTCIPHandlingPolicy ?? "default");
++});
++Settings.addChangeListener("webRTCIPHandlingPolicy", () => {
++    for (const win of BrowserWindow.getAllWindows()) {
++        win.webContents.setWebRTCIPHandlingPolicy(Settings.store.webRTCIPHandlingPolicy ?? "default");
++    }
++});
+diff --git a/src/shared/settings.d.ts b/src/shared/settings.d.ts
+index 5b8fd6fff..b127f6def 100644
+--- a/src/shared/settings.d.ts
++++ b/src/shared/settings.d.ts
+@@ -9,6 +9,11 @@ import type { Rectangle } from "electron";
+ export interface Settings {
+     discordBranch?: "stable" | "canary" | "ptb";
+     transparencyOption?: "none" | "mica" | "tabbed" | "acrylic";
++    webRTCIPHandlingPolicy?:
++        | "default"
++        | "default_public_interface_only"
++        | "default_public_and_private_interfaces"
++        | "disable_non_proxied_udp";
+     tray?: boolean;
+     minimizeToTray?: boolean;
+     autoStartMinimized?: boolean;