/// <summary>
/// Parses a resource record from the packet passed.
/// </summary>
/// <param name="message">The message containing the record being parsed.</param>
/// <param name="packet">The raw DNS message packet.</param>
/// <param name="offset">
/// The current offset in the packet. Returns as the offset of the first byte
/// after the record.
/// </param>
/// <returns>The resource record or <c>null</c> if there was an error.</returns>
public static DnsRR Parse(DnsMessage message, byte[] packet, ref int offset)
{
string qname;
DnsRRType rrtype;
DnsRR rr;
int savePos;
// Peek the qname and record type
savePos = offset;
if (!message.ReadName(packet, ref offset, out qname))
{
return(null);
}
rrtype = (DnsRRType)Helper.ReadInt16(packet, ref offset);
offset = savePos;
switch (rrtype)
{
case DnsRRType.A:
rr = new A_RR();
break;
case DnsRRType.CNAME:
rr = new CNAME_RR();
break;
case DnsRRType.NS:
rr = new NS_RR();
break;
case DnsRRType.MX:
rr = new MX_RR();
break;
case DnsRRType.SOA:
rr = new SOA_RR();
break;
default:
rr = new DnsRR();
break;
}
if (!rr.Read(message, packet, ref offset))
{
return(null);
}
return(rr);
}
/// <summary>
/// This method parses the resource record from the packet beginning
/// at the offset passed.
/// </summary>
/// <param name="message">The message containing the record being parsed.</param>
/// <param name="packet">The packet buffer.</param>
/// <param name="offset">
/// The offset in the packet where the record is located.
/// This parameter will return set to the offset of the first
/// byte after the parsed record.
/// </param>
/// <returns>True on success.</returns>
public bool Read(DnsMessage message, byte[] packet, ref int offset)
{
if (!message.ReadName(packet, ref offset, out rname))
{
return(false);
}
rrtype = (DnsRRType)Helper.ReadInt16(packet, ref offset);
qclass = (DnsQClass)Helper.ReadInt16(packet, ref offset);
ttl = Helper.ReadInt32(packet, ref offset);
return(ReadData(message, packet, ref offset));
}
/// <summary>
/// This method parses the resource record's (including its
/// length from the packet beginning at the offset passed.
/// </summary>
/// <param name="message">The message containing the record being parsed.</param>
/// <param name="packet">The packet buffer.</param>
/// <param name="offset">
/// The offset in the packet where the data will be read.
/// This parameter will return set to the offset of the first
/// byte after the parsed data.
/// </param>
/// <returns>True on success.</returns>
protected override bool ReadData(DnsMessage message, byte[] packet, ref int offset)
{
int pos;
int cb;
cb = Helper.ReadInt16(packet, ref offset);
pos = offset;
if (!message.ReadName(packet, ref offset, out cname))
{
return(false);
}
return(pos + cb == offset);
}