Add support for PTR queries

Author: Mygod

Diff for: core/build.gradle.kts

@@ -87,7 +87,7 @@ dependencies {
     api("com.google.firebase:firebase-config-ktx:19.1.4")
     api("com.google.firebase:firebase-crashlytics:17.0.0")
     api("com.jakewharton.timber:timber:4.7.1")
-    api("dnsjava:dnsjava:3.0.2")
+    api("dnsjava:dnsjava:3.1.0")
     api("org.jetbrains.kotlinx:kotlinx-coroutines-android:$coroutinesVersion")
     api("org.jetbrains.kotlinx:kotlinx-coroutines-play-services:$coroutinesVersion")
     kapt("androidx.room:room-compiler:$roomVersion")

Diff for: core/src/main/java/com/github/shadowsocks/net/DnsResolverCompat.kt

@@ -70,6 +70,7 @@ sealed class DnsResolverCompat {
 
         fun prepareDnsResponse(request: Message) = Message(request.header.id).apply {
             header.setFlag(Flags.QR.toInt())    // this is a response
+            header.setFlag(Flags.RA.toInt())    // recursion available
             if (request.header.getFlag(Flags.RD.toInt())) header.setFlag(Flags.RD.toInt())
             request.question?.also { addRecord(it, Section.QUESTION) }
         }
@@ -135,11 +136,22 @@ sealed class DnsResolverCompat {
             val isIpv6 = when (val type = question?.type) {
                 Type.A -> false
                 Type.AAAA -> true
+                Type.PTR -> {
+                    val ip = try {
+                        ReverseMap.fromName(question.name)
+                    } catch (e: IOException) {
+                        throw UnsupportedOperationException(e)  // unrecognized PTR name
+                    }
+                    // Android does not provide a PTR lookup API for Network prior to Android 10
+                    val hostname = Name.fromString(GlobalScope.async(unboundedIO) { ip.hostName }.await())
+                    return prepareDnsResponse(request).apply {
+                        addRecord(PTRRecord(question.name, DClass.IN, TTL, hostname), Section.ANSWER)
+                    }.toWire()
+                }
                 else -> throw UnsupportedOperationException("Unsupported query type $type")
             }
             val host = question.name.canonicalize().toString(true)
             return prepareDnsResponse(request).apply {
-                header.setFlag(Flags.RA.toInt())   // recursion available
                 for (address in hostResolver(host).asIterable().run {
                     if (isIpv6) filterIsInstance<Inet6Address>() else filterIsInstance<Inet4Address>()
                 }) addRecord(when (address) {

Diff for: core/src/main/rust/shadowsocks-rust

@@ -14,7 +14,7 @@ androidExtensions.isExperimental = true
 
 dependencies {
     implementation("androidx.browser:browser:1.2.0")
-    implementation("androidx.constraintlayout:constraintlayout:2.0.0-beta5")
+    implementation("androidx.constraintlayout:constraintlayout:2.0.0-beta6")
     implementation("androidx.lifecycle:lifecycle-runtime-ktx:$lifecycleVersion")
     implementation("com.google.android.gms:play-services-vision:20.0.0")
     implementation("com.google.firebase:firebase-ads:19.1.0")