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package dns
// https://datatracker.ietf.org/doc/html/rfc5395
type Header struct {
ID uint16
Flags uint16
QDCount uint16
ANCount uint16
NSCount uint16
ARCount uint16
}
// https://datatracker.ietf.org/doc/html/rfc2929#section-2
// Flags has 16-bit Field. Each hexadecima value below indicates
// which items are active.
// Example 0 0000 0 0 0 0 000 0 0 000, so if only AA is active, then
// Example 1 0000 0 0 0 0 000 0 0 000, is 0x8000
// Query and Response
func (h *Header) QR() bool { return h.Flags&0x8000 != 0 }
// Opcode has 4-bit (14 -- 11)
func (h *Header) OpCode() uint8 { return uint8((h.Flags >> 11) & 0xF) }
// Authoritative Answer
func (h *Header) AA() bool { return h.Flags&0x0400 != 0 }
// Truncation
func (h *Header) TC() bool { return h.Flags&0x0200 != 0 }
// Recursion Desired
func (h *Header) RD() bool { return h.Flags&0x0100 != 0 }
// Recursion Available
func (h *Header) RA() bool { return h.Flags&0x0080 != 0 }
// Mutator Flags
func (h *Header) SetQR(v bool) { h.set(0x8000, v) }
func (h *Header) SetOpCode(v uint8) {
h.Flags = (h.Flags &^ (0xF << 11)) |
((uint16(v) & 0xF) << 11)
}
func (h *Header) SetAA(v bool) { h.set(0x0400, v) }
func (h *Header) SetTC(v bool) { h.set(0x0200, v) }
func (h *Header) SetRD(v bool) { h.set(0x0100, v) }
func (h *Header) SetRA(v bool) { h.set(0x0080, v) }
func (h *Header) SetZ(v uint8) { h.Flags = (h.Flags &^ (0x7 << 4)) | ((uint16(v) & 0x7) << 4) }
func (h *Header) SetAD(v bool) { h.set(0x0020, v) }
func (h *Header) SetCD(v bool) { h.set(0x0010, v) }
func (h *Header) SetRCode(v uint8) { h.Flags = (h.Flags &^ 0xF) | (uint16(v) & 0xF) }
func (h *Header) set(mask uint16, v bool) {
if v {
h.Flags |= mask
} else {
h.Flags &^= mask
}
}
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