Lightweight way to resolve DNS SRV records on Android

Question

What is the most resource-efficient way to do SRV record lookups on Android, e.g. in an XMPP client like yaxim?

I am aware of:

• JNDI, which is part of JavaSE but not in Android
• dnsjava, which adds 800 KByte of class files (580KByte after ProGuard, so it will probably be hard to separate the files only needed for SRV lookup)
• native tools like dig, nslookup, etc., which, when compiled statically, have a footprint similar to dnsjava and in addition make your app native-code dependant

I have read Querying the DNS service records to find the hostname and TCP/IP, but it only lists JNDI and dnsjava.

For sure I am not the first one to encounter this problem and there must be some lightweight DNS SRV resolver in Java :-)

Edit: bonus points for providing DNSSEC verification / DANE certificate querying.

Answer 1

Stumbled over this question. Since there was no accepted answer and dnsjava has been sort of ruled out in question, already, I took this question to Google once again and stumbled over minidns. It supports DNSSEC, comes with a separate API for querying SRV records and I was successful in integrating it with an Android application prototype.

In my app/build.gradle I was adding this:

dependencies {
    implementation "org.minidns:minidns-hla:0.3.2"
}

After that I was capable of implementing a query like this using Kotlin:

package com.example.app

import android.os.AsyncTask
import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity

import kotlinx.android.synthetic.main.activity_main.*
import android.util.Log
import org.minidns.hla.ResolverApi
import java.io.IOException


class MainActivity : AppCompatActivity() {
    private val serviceName = "_mysrv._tcp.example.com"

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        FetchSrvRecord().execute(serviceName)
    }

    inner class FetchSrvRecord() : AsyncTask<String, Int, String>() {
        override fun doInBackground(names: Array<String>): String {
            try {
                val result = ResolverApi.INSTANCE.resolveSrv(names[0])
                if (result.wasSuccessful()) {
                    val srvRecords = result.sortedSrvResolvedAddresses
                    for (record in srvRecords) {
                        return "https://" + record.srv.target.toString()
                    }
                }
            } catch (e: IOException) {
                Log.e("PoC", "failed IO", e)
            } catch (e: Throwable) {
                Log.e("PoC", "failed", e)
            }

            return "https://example.com"
        }

        override fun onPostExecute(url: String) {
            super.onPostExecute(url);

            Log.d("PoC", "got $url");
        }
    }
}

I'm not that familiar with Java/Android there was no obviously available file I could find as output of compiling that library so can't tell the library's impact on your apk's size.