Support tunnelling connections via ADB, as a connectivity fallback

Author: pimterry

app/src/main/java/tech/httptoolkit/android/MainActivity.kt

@@ -398,6 +398,7 @@ class MainActivity : AppCompatActivity(), CoroutineScope by MainScope() {
                 ProxyInfo(
                     listOf(lastProxy.ip),
                     lastProxy.port,
+                    null,
                     getCertificateFingerprint(lastProxy.certificate as X509Certificate)
                 )
             )

app/src/main/java/tech/httptoolkit/android/ProxyDetails.kt

@@ -27,6 +27,13 @@ data class ProxyInfo(
      */
     val port: Int,
 
+    /**
+     * A local tunnel port, with an ADB tunnel connected to the proxy. This is less good than a
+     * direct network connection, since it's dependent on the ADB server, but it's a useful fallback
+     * especially if the proxy computer has a firewall or the network blocks connections.
+     */
+    val localTunnelPort: Int?,
+
     /**
      * The expected PK hash of the proxy certificate. The certificate itself is obtained from the
      * proxy, as part of validating the connection. This hash is included in QR codes to

app/src/main/java/tech/httptoolkit/android/ProxySetup.kt

@@ -61,7 +61,19 @@ suspend fun getProxyConfig(proxyInfo: ProxyInfo): ProxyConfig {
 
             // Return with the first working proxy config (cert & address)
             // (or throw if all addresses are unreachable/invalid)
-            return@supervisorScope proxyTests.awaitFirst()
+            try {
+                return@supervisorScope proxyTests.awaitFirst()
+            } catch (e: Exception) {
+                if (proxyInfo.localTunnelPort == null) throw e;
+
+                // If all network connections fail, and we have a local ADB tunnel, fallback to
+                // using that connection instead.
+                return@supervisorScope testProxyAddress(
+                    "127.0.0.1",
+                    proxyInfo.localTunnelPort,
+                    proxyInfo.certFingerprint
+                )
+            }
         }
     }
 }