import java.text.FieldPosition;
import java.util.ArrayList;
import java.util.List;
-import java.util.StringJoiner;
/**
* Defines basic data for DNS protocol based on RFC 1035.
public final int id;
public final int flags;
public final int rcode;
- private final int[] mSectionCount;
+ private final int[] mRecordCount;
/**
* Create a new DnsHeader from a positioned ByteBuffer.
* When this constructor returns, the reading position of the ByteBuffer has been
* advanced to the end of the DNS header record.
* This is meant to chain with other methods reading a DNS response in sequence.
- *
*/
DnsHeader(@NonNull ByteBuffer buf) throws BufferUnderflowException {
id = BitUtils.uint16(buf.getShort());
flags = BitUtils.uint16(buf.getShort());
rcode = flags & 0xF;
- mSectionCount = new int[NUM_SECTIONS];
+ mRecordCount = new int[NUM_SECTIONS];
for (int i = 0; i < NUM_SECTIONS; ++i) {
- mSectionCount[i] = BitUtils.uint16(buf.getShort());
+ mRecordCount[i] = BitUtils.uint16(buf.getShort());
}
}
/**
- * Get section count by section type.
+ * Get record count by type.
*/
- public int getSectionCount(int sectionType) {
- return mSectionCount[sectionType];
+ public int getRecordCount(int type) {
+ return mRecordCount[type];
}
}
- public class DnsSection {
+ /**
+ * It's used both for DNS questions and DNS resource records.
+ *
+ * DNS questions (No TTL/RDATA)
+ * DNS resource records (With TTL/RDATA)
+ */
+ public class DnsRecord {
private static final int MAXNAMESIZE = 255;
private static final int MAXLABELSIZE = 63;
private static final int MAXLABELCOUNT = 128;
private final DecimalFormat byteFormat = new DecimalFormat();
private final FieldPosition pos = new FieldPosition(0);
- private static final String TAG = "DnsSection";
+ private static final String TAG = "DnsRecord";
public final String dName;
public final int nsType;
public final int nsClass;
public final long ttl;
- private final byte[] mRR;
+ private final byte[] mRdata;
/**
- * Create a new DnsSection from a positioned ByteBuffer.
+ * Create a new DnsRecord from a positioned ByteBuffer.
*
- * The ByteBuffer must be in network byte order (which is the default).
- * Reads the passed ByteBuffer from its current position and decodes a DNS section.
+ * @param ByteBuffer input of record, must be in network byte order
+ * (which is the default).
+ * Reads the passed ByteBuffer from its current position and decodes a DNS record.
* When this constructor returns, the reading position of the ByteBuffer has been
* advanced to the end of the DNS header record.
* This is meant to chain with other methods reading a DNS response in sequence.
- *
*/
- DnsSection(int sectionType, @NonNull ByteBuffer buf)
+ DnsRecord(int recordType, @NonNull ByteBuffer buf)
throws BufferUnderflowException, ParseException {
dName = parseName(buf, 0 /* Parse depth */);
if (dName.length() > MAXNAMESIZE) {
- throw new ParseException("Parse name fail, name size is too long");
+ throw new ParseException(
+ "Parse name fail, name size is too long: " + dName.length());
}
nsType = BitUtils.uint16(buf.getShort());
nsClass = BitUtils.uint16(buf.getShort());
- if (sectionType != QDSECTION) {
+ if (recordType != QDSECTION) {
ttl = BitUtils.uint32(buf.getInt());
final int length = BitUtils.uint16(buf.getShort());
- mRR = new byte[length];
- buf.get(mRR);
+ mRdata = new byte[length];
+ buf.get(mRdata);
} else {
ttl = 0;
- mRR = null;
+ mRdata = null;
}
}
/**
- * Get a copy of rr.
+ * Get a copy of rdata.
*/
- @Nullable public byte[] getRR() {
- return (mRR == null) ? null : mRR.clone();
+ @Nullable
+ public byte[] getRR() {
+ return (mRdata == null) ? null : mRdata.clone();
}
/**
* Convert label from {@code byte[]} to {@code String}
*
- * It follows the same converting rule as native layer.
- * (See ns_name.c in libc)
- *
+ * Follows the same conversion rules of the native code (ns_name.c in libc)
*/
private String labelToString(@NonNull byte[] label) {
final StringBuffer sb = new StringBuffer();
int b = BitUtils.uint8(label[i]);
// Control characters and non-ASCII characters.
if (b <= 0x20 || b >= 0x7f) {
+ // Append the byte as an escaped decimal number, e.g., "\19" for 0x13.
sb.append('\\');
byteFormat.format(b, sb, pos);
} else if (b == '"' || b == '.' || b == ';' || b == '\\'
|| b == '(' || b == ')' || b == '@' || b == '$') {
+ // Append the byte as an escaped character, e.g., "\:" for 0x3a.
sb.append('\\');
sb.append((char) b);
} else {
+ // Append the byte as a character, e.g., "a" for 0x61.
sb.append((char) b);
}
}
private String parseName(@NonNull ByteBuffer buf, int depth) throws
BufferUnderflowException, ParseException {
- if (depth > MAXLABELCOUNT) throw new ParseException("Parse name fails, too many labels");
+ if (depth > MAXLABELCOUNT) {
+ throw new ParseException("Failed to parse name, too many labels");
+ }
final int len = BitUtils.uint8(buf.get());
final int mask = len & NAME_COMPRESSION;
if (0 == len) {
private static final String TAG = DnsPacket.class.getSimpleName();
protected final DnsHeader mHeader;
- protected final List<DnsSection>[] mSections;
+ protected final List<DnsRecord>[] mRecords;
public static class ParseException extends Exception {
public ParseException(String msg) {
throw new ParseException("Parse Header fail, bad input data", e);
}
- mSections = new ArrayList[NUM_SECTIONS];
+ mRecords = new ArrayList[NUM_SECTIONS];
for (int i = 0; i < NUM_SECTIONS; ++i) {
- final int count = mHeader.getSectionCount(i);
+ final int count = mHeader.getRecordCount(i);
if (count > 0) {
- mSections[i] = new ArrayList(count);
+ mRecords[i] = new ArrayList(count);
}
for (int j = 0; j < count; ++j) {
try {
- mSections[i].add(new DnsSection(i, buffer));
+ mRecords[i].add(new DnsRecord(i, buffer));
} catch (BufferUnderflowException e) {
- throw new ParseException("Parse section fail", e);
+ throw new ParseException("Parse record fail", e);
}
}
}
/**
* Dns resolver class for asynchronous dns querying
*
+ * Note that if a client sends a query with more than 1 record in the question section but
+ * the remote dns server does not support this, it may not respond at all, leading to a timeout.
+ *
*/
public final class DnsResolver {
private static final String TAG = "DnsResolver";
if (mHeader.rcode != 0) {
throw new ParseException("Response error, rcode:" + mHeader.rcode);
}
- if (mHeader.getSectionCount(ANSECTION) == 0) {
+ if (mHeader.getRecordCount(ANSECTION) == 0) {
throw new ParseException("No available answer");
}
- if (mHeader.getSectionCount(QDSECTION) == 0) {
+ if (mHeader.getRecordCount(QDSECTION) == 0) {
throw new ParseException("No question found");
}
- // Assume only one question per answer packet. (RFC1035)
- mQueryType = mSections[QDSECTION].get(0).nsType;
+ // Expect only one question in question section.
+ mQueryType = mRecords[QDSECTION].get(0).nsType;
}
public @NonNull List<InetAddress> getAddresses() {
final List<InetAddress> results = new ArrayList<InetAddress>();
- for (final DnsSection ansSec : mSections[ANSECTION]) {
+ for (final DnsRecord ansSec : mRecords[ANSECTION]) {
// Only support A and AAAA, also ignore answers if query type != answer type.
int nsType = ansSec.nsType;
if (nsType != mQueryType || (nsType != TYPE_A && nsType != TYPE_AAAA)) {
int qCount, int aCount, int nsCount, int arCount) {
assertEquals(header.id, id);
assertEquals(header.flags, flag);
- assertEquals(header.getSectionCount(DnsPacket.QDSECTION), qCount);
- assertEquals(header.getSectionCount(DnsPacket.ANSECTION), aCount);
- assertEquals(header.getSectionCount(DnsPacket.NSSECTION), nsCount);
- assertEquals(header.getSectionCount(DnsPacket.ARSECTION), arCount);
+ assertEquals(header.getRecordCount(DnsPacket.QDSECTION), qCount);
+ assertEquals(header.getRecordCount(DnsPacket.ANSECTION), aCount);
+ assertEquals(header.getRecordCount(DnsPacket.NSSECTION), nsCount);
+ assertEquals(header.getRecordCount(DnsPacket.ARSECTION), arCount);
}
- private void assertSectionParses(DnsPacket.DnsSection section, String dname,
+ private void assertRecordParses(DnsPacket.DnsRecord record, String dname,
int dtype, int dclass, int ttl, byte[] rr) {
- assertEquals(section.dName, dname);
- assertEquals(section.nsType, dtype);
- assertEquals(section.nsClass, dclass);
- assertEquals(section.ttl, ttl);
- assertTrue(Arrays.equals(section.getRR(), rr));
+ assertEquals(record.dName, dname);
+ assertEquals(record.nsType, dtype);
+ assertEquals(record.nsClass, dclass);
+ assertEquals(record.ttl, ttl);
+ assertTrue(Arrays.equals(record.getRR(), rr));
}
class TestDnsPacket extends DnsPacket {
public DnsHeader getHeader() {
return mHeader;
}
- public List<DnsSection> getSectionList(int secType) {
- return mSections[secType];
+ public List<DnsRecord> getRecordList(int secType) {
+ return mRecords[secType];
}
}
// Header part
assertHeaderParses(packet.getHeader(), 0x5566, 0x8180, 1, 1, 0, 0);
- // Section part
- List<DnsPacket.DnsSection> qdSectionList =
- packet.getSectionList(DnsPacket.QDSECTION);
- assertEquals(qdSectionList.size(), 1);
- assertSectionParses(qdSectionList.get(0), "www.google.com", 1, 1, 0, null);
+ // Record part
+ List<DnsPacket.DnsRecord> qdRecordList =
+ packet.getRecordList(DnsPacket.QDSECTION);
+ assertEquals(qdRecordList.size(), 1);
+ assertRecordParses(qdRecordList.get(0), "www.google.com", 1, 1, 0, null);
- List<DnsPacket.DnsSection> anSectionList =
- packet.getSectionList(DnsPacket.ANSECTION);
- assertEquals(anSectionList.size(), 1);
- assertSectionParses(anSectionList.get(0), "www.google.com", 1, 1, 0x12b,
+ List<DnsPacket.DnsRecord> anRecordList =
+ packet.getRecordList(DnsPacket.ANSECTION);
+ assertEquals(anRecordList.size(), 1);
+ assertRecordParses(anRecordList.get(0), "www.google.com", 1, 1, 0x12b,
new byte[]{ (byte) 0xac, (byte) 0xd9, (byte) 0xa1, (byte) 0x84 });
}
// Header part
assertHeaderParses(packet.getHeader(), 0x7722, 0x8180, 1, 1, 0, 0);
- // Section part
- List<DnsPacket.DnsSection> qdSectionList =
- packet.getSectionList(DnsPacket.QDSECTION);
- assertEquals(qdSectionList.size(), 1);
- assertSectionParses(qdSectionList.get(0), "www.google.com", 28, 1, 0, null);
+ // Record part
+ List<DnsPacket.DnsRecord> qdRecordList =
+ packet.getRecordList(DnsPacket.QDSECTION);
+ assertEquals(qdRecordList.size(), 1);
+ assertRecordParses(qdRecordList.get(0), "www.google.com", 28, 1, 0, null);
- List<DnsPacket.DnsSection> anSectionList =
- packet.getSectionList(DnsPacket.ANSECTION);
- assertEquals(anSectionList.size(), 1);
- assertSectionParses(anSectionList.get(0), "www.google.com", 28, 1, 0x37,
+ List<DnsPacket.DnsRecord> anRecordList =
+ packet.getRecordList(DnsPacket.ANSECTION);
+ assertEquals(anRecordList.size(), 1);
+ assertRecordParses(anRecordList.get(0), "www.google.com", 28, 1, 0x37,
new byte[]{ 0x24, 0x04, 0x68, 0x00, 0x40, 0x05, 0x08, 0x0d,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x20, 0x04 });
}
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