TUN-528: Move cloudflared into a separate repo

vendor/github.com/miekg/dns/rawmsg.go

@@ -0,0 +1,49 @@
+package dns
+
+import "encoding/binary"
+
+// rawSetRdlength sets the rdlength in the header of
+// the RR. The offset 'off' must be positioned at the
+// start of the header of the RR, 'end' must be the
+// end of the RR.
+func rawSetRdlength(msg []byte, off, end int) bool {
+	l := len(msg)
+Loop:
+	for {
+		if off+1 > l {
+			return false
+		}
+		c := int(msg[off])
+		off++
+		switch c & 0xC0 {
+		case 0x00:
+			if c == 0x00 {
+				// End of the domainname
+				break Loop
+			}
+			if off+c > l {
+				return false
+			}
+			off += c
+
+		case 0xC0:
+			// pointer, next byte included, ends domainname
+			off++
+			break Loop
+		}
+	}
+	// The domainname has been seen, we at the start of the fixed part in the header.
+	// Type is 2 bytes, class is 2 bytes, ttl 4 and then 2 bytes for the length.
+	off += 2 + 2 + 4
+	if off+2 > l {
+		return false
+	}
+	//off+1 is the end of the header, 'end' is the end of the rr
+	//so 'end' - 'off+2' is the length of the rdata
+	rdatalen := end - (off + 2)
+	if rdatalen > 0xFFFF {
+		return false
+	}
+	binary.BigEndian.PutUint16(msg[off:], uint16(rdatalen))
+	return true
+}