filter

var (

	// CaptureLengthFixed denotes a simple fixed snaplen strategy
	CaptureLengthFixed = func(snaplen int) CaptureLengthStrategy {
		return func(*link.Link) int {
			return snaplen
		}
	}

	// CaptureLengthMinimalIPv4Header indicates that the minimal necessary length to
	// facilitate IPv4 layer analysis should be chosen
	CaptureLengthMinimalIPv4Header = func(l *link.Link) int {
		return int(l.Type.IPHeaderOffset()) + ipv4.HeaderLen
	}

	// CaptureLengthMinimalIPv6Header indicates that the minimal necessary length to
	// facilitate IPv6 layer analysis should be chosen
	CaptureLengthMinimalIPv6Header = func(l *link.Link) int {
		return int(l.Type.IPHeaderOffset()) + ipv6.HeaderLen
	}

	// CaptureLengthMinimalIPv4Transport indicates that the minimal necessary length to
	// facilitate IPv4 transport layer analysis should be chosen
	CaptureLengthMinimalIPv4Transport = func(l *link.Link) int {
		return int(l.Type.IPHeaderOffset()) + ipv4.HeaderLen + 14
	}

	// CaptureLengthMinimalIPv6Transport indicates that the minimal necessary length to
	// facilitate IPv6 transport layer analysis should be chosen
	CaptureLengthMinimalIPv6Transport = func(l *link.Link) int {
		return int(l.Type.IPHeaderOffset()) + ipv6.HeaderLen + 14
	}
)

var BpfInstructionsNoLimit = func(snapLen int, ignoreVLANs bool, extraInstr ...bpf.RawInstruction) (res []bpf.RawInstruction) {
	if snapLen == 0 {
		snapLen = defaultSnapLen
	}
	nExtra := uint8(len(extraInstr))

	if ignoreVLANs {
		res = []bpf.RawInstruction{
			{Op: opLDW, Jt: 0x0, Jf: 0x0, K: regVLanT},
			{Op: opJEQ, Jt: 0x0, Jf: 0x1 + nExtra, K: 0x0},
		}
	}

	if nExtra > 0 {
		res = append(res, extraInstr...)
	}

	res = append(res, []bpf.RawInstruction{
		{Op: opRET, Jt: 0x0, Jf: 0x0, K: uint32(snapLen)},
		{Op: opRET, Jt: 0x0, Jf: 0x0, K: 0x0},
	}...)

	return
}