forked from TrueCloudLab/distribution
50 lines
1.1 KiB
Go
50 lines
1.1 KiB
Go
|
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
|
||
|
|
}
|