Naive timeout for DNS resolution using a thread per request

DNSTimeoutInterceptor.java

    /**
     * Based on http://stackoverflow.com/questions/693997/how-to-set-httpresponse-timeout-for-android-in-java/31643186#31643186
     * as per https://github.com/square/okhttp/issues/95
     */
    private static class DNSTimeoutInterceptor implements Interceptor {
        long mTimeoutMillis;

        public DNSTimeoutInterceptor(long timeoutMillis) {
            mTimeoutMillis = timeoutMillis;
        }

        @Override
        public Response intercept(final Chain chain) throws IOException {
            Request request = chain.request();
            Log.SplitTimer timer = (request.tag() instanceof RequestTag ? ((RequestTag) request.tag()).getTimer() : null);

            // underlying call should timeout after 2 tries of 5s:  https://android.googlesource.com/platform/bionic/+/android-5.1.1_r38/libc/dns/include/resolv_private.h#137
            // could use our own Dns implementation that falls back to public DNS servers:  https://garage.easytaxi.com/tag/dns-android-okhttp/
            if (!DNSResolver.isDNSReachable(request.url().host(), mTimeoutMillis)) {
                throw new UnknownHostException("DNS timeout");
            }
            return chain.proceed(request);
        }

        private static class DNSResolver implements Runnable {
            private String mDomain;
            private InetAddress mAddress;

            public static boolean isDNSReachable(String domain, long timeoutMillis) {
                try {
                    DNSResolver dnsRes = new DNSResolver(domain);

                    Thread t = new Thread(dnsRes, "DNSResolver");
                    t.start();
                    t.join(timeoutMillis);
                    return dnsRes.get() != null;
                }  catch(Exception e)  {
                    return false;
                }
            }

            public DNSResolver(String domain) {
                this.mDomain = domain;
            }

            public void run() {
                try {
                    InetAddress addr = InetAddress.getByName(mDomain);
                    set(addr);
                } catch (UnknownHostException e) {
                }
            }

            public synchronized void set(InetAddress inetAddr) {
                this.mAddress = inetAddr;
            }
            public synchronized InetAddress get() {
                return mAddress;
            }
        }
    }