DnsNameResolver does not resolve property A+CNAME answer, close AsyncHttpClient#1193

Author: slandelle

netty-bp/codec-dns/src/main/java/io/netty/handler/codec/dns/DefaultDnsRecordDecoder.java

@@ -90,7 +90,7 @@ protected DnsRecord decodeRecord(
 
         if (type == DnsRecordType.PTR) {
             in.setIndex(offset, offset + length);
-            return new DefaultDnsPtrRecord(name, dnsClass, timeToLive, decodeName(in));
+            return new DefaultDnsPtrRecord(name, dnsClass, timeToLive, decodeName0(in));
         }
         return new DefaultDnsRawRecord(
                 name, type, dnsClass, timeToLive, in.duplicate().setIndex(offset, offset + length).retain());
@@ -104,7 +104,19 @@ protected DnsRecord decodeRecord(
      * @param in the byte buffer containing the DNS packet
      * @return the domain name for an entry
      */
-    protected String decodeName(ByteBuf in) {
+    protected String decodeName0(ByteBuf in) {
+        return decodeName(in);
+    }
+
+    /**
+     * Retrieves a domain name given a buffer containing a DNS packet. If the
+     * name contains a pointer, the position of the buffer will be set to
+     * directly after the pointer's index after the name has been read.
+     *
+     * @param in the byte buffer containing the DNS packet
+     * @return the domain name for an entry
+     */
+    public static String decodeName(ByteBuf in) {
         int position = -1;
         int checked = 0;
         final int end = in.writerIndex();

netty-bp/resolver-dns/src/main/java/io/netty/resolver/dns/DnsNameResolverContext.java

@@ -20,6 +20,7 @@
 import io.netty.buffer.ByteBufHolder;
 import io.netty.channel.AddressedEnvelope;
 import io.netty.channel.socket.InternetProtocolFamily;
+import io.netty.handler.codec.CorruptedFrameException;
 import io.netty.handler.codec.dns.DefaultDnsQuestion;
 import io.netty.handler.codec.dns.DefaultDnsRecordDecoder;
 import io.netty.handler.codec.dns.DnsResponseCode;
@@ -29,7 +30,6 @@
 import io.netty.handler.codec.dns.DnsRecord;
 import io.netty.handler.codec.dns.DnsRecordType;
 import io.netty.handler.codec.dns.DnsResponse;
-import io.netty.util.CharsetUtil;
 import io.netty.util.ReferenceCountUtil;
 import io.netty.util.concurrent.Future;
 import io.netty.util.concurrent.FutureListener;
@@ -412,25 +412,23 @@ private void finishResolve() {
         final int tries = maxAllowedQueries - allowedQueries;
         final StringBuilder buf = new StringBuilder(64);
 
-        buf.append("failed to resolve ");
-        buf.append(hostname);
-
+        buf.append("failed to resolve '")
+           .append(hostname).append('\'');
         if (tries > 1) {
-            buf.append(" after ");
-            buf.append(tries);
-            if (trace != null) {
-                buf.append(" queries:");
-                buf.append(trace);
+            if (tries < maxAllowedQueries) {
+                buf.append(" after ")
+                   .append(tries)
+                   .append(" queries ");
             } else {
-                buf.append(" queries");
-            }
-        } else {
-            if (trace != null) {
-                buf.append(':');
-                buf.append(trace);
+                buf.append(". Exceeded max queries per resolve ")
+                .append(maxAllowedQueries)
+                .append(' ');
             }
         }
-
+        if (trace != null) {
+            buf.append(':')
+               .append(trace);
+        }
         final UnknownHostException cause = new UnknownHostException(buf.toString());
 
         resolveCache.cache(hostname, cause, parent.ch.eventLoop());
@@ -440,53 +438,15 @@ private void finishResolve() {
     protected abstract boolean finishResolve(
             InternetProtocolFamily f, List<DnsCacheEntry> resolvedEntries);
 
-    /**
-     * Adapted from {@link DefaultDnsRecordDecoder#decodeName(ByteBuf)}.
-     */
-    static String decodeDomainName(ByteBuf buf) {
-        buf.markReaderIndex();
+    static String decodeDomainName(ByteBuf in) {
+        in.markReaderIndex();
         try {
-            int position = -1;
-            int checked = 0;
-            final int end = buf.writerIndex();
-            final StringBuilder name = new StringBuilder(buf.readableBytes() << 1);
-            for (int len = buf.readUnsignedByte(); buf.isReadable() && len != 0; len = buf.readUnsignedByte()) {
-                boolean pointer = (len & 0xc0) == 0xc0;
-                if (pointer) {
-                    if (position == -1) {
-                        position = buf.readerIndex() + 1;
-                    }
-
-                    final int next = (len & 0x3f) << 8 | buf.readUnsignedByte();
-                    if (next >= end) {
-                        // Should not happen.
-                        return null;
-                    }
-                    buf.readerIndex(next);
-
-                    // check for loops
-                    checked += 2;
-                    if (checked >= end) {
-                        // Name contains a loop; give up.
-                        return null;
-                    }
-                } else {
-                    name.append(buf.toString(buf.readerIndex(), len, CharsetUtil.UTF_8)).append('.');
-                    buf.skipBytes(len);
-                }
-            }
-
-            if (position != -1) {
-                buf.readerIndex(position);
-            }
-
-            if (name.length() == 0) {
-                return null;
-            }
-
-            return name.substring(0, name.length() - 1);
+            return DefaultDnsRecordDecoder.decodeName(in);
+        } catch (CorruptedFrameException e) {
+            // In this case we just return null.
+            return null;
         } finally {
-            buf.resetReaderIndex();
+            in.resetReaderIndex();
         }
     }