Add system stack

internal/clashtcpip/ipv6.go

@@ -0,0 +1,141 @@
+package clashtcpip
+
+import (
+	"encoding/binary"
+	"net/netip"
+)
+
+const (
+	versTCFL = 0
+
+	IPv6PayloadLenOffset = 4
+
+	IPv6NextHeaderOffset = 6
+	hopLimit             = 7
+	v6SrcAddr            = 8
+	v6DstAddr            = v6SrcAddr + IPv6AddressSize
+
+	IPv6FixedHeaderSize = v6DstAddr + IPv6AddressSize
+)
+
+const (
+	versIHL        = 0
+	tos            = 1
+	ipVersionShift = 4
+	ipIHLMask      = 0x0f
+	IPv4IHLStride  = 4
+)
+
+type IPv6Packet []byte
+
+const (
+	IPv6MinimumSize = IPv6FixedHeaderSize
+
+	IPv6AddressSize = 16
+
+	IPv6Version = 6
+
+	IPv6MinimumMTU = 1280
+)
+
+func (b IPv6Packet) PayloadLength() uint16 {
+	return binary.BigEndian.Uint16(b[IPv6PayloadLenOffset:])
+}
+
+func (b IPv6Packet) HopLimit() uint8 {
+	return b[hopLimit]
+}
+
+func (b IPv6Packet) NextHeader() byte {
+	return b[IPv6NextHeaderOffset]
+}
+
+func (b IPv6Packet) Protocol() IPProtocol {
+	return b.NextHeader()
+}
+
+func (b IPv6Packet) Payload() []byte {
+	return b[IPv6MinimumSize:][:b.PayloadLength()]
+}
+
+func (b IPv6Packet) SourceIP() netip.Addr {
+	addr, _ := netip.AddrFromSlice(b[v6SrcAddr:][:IPv6AddressSize])
+	return addr
+}
+
+func (b IPv6Packet) DestinationIP() netip.Addr {
+	addr, _ := netip.AddrFromSlice(b[v6DstAddr:][:IPv6AddressSize])
+	return addr
+}
+
+func (IPv6Packet) Checksum() uint16 {
+	return 0
+}
+
+func (b IPv6Packet) TOS() (uint8, uint32) {
+	v := binary.BigEndian.Uint32(b[versTCFL:])
+	return uint8(v >> 20), v & 0xfffff
+}
+
+func (b IPv6Packet) SetTOS(t uint8, l uint32) {
+	vtf := (6 << 28) | (uint32(t) << 20) | (l & 0xfffff)
+	binary.BigEndian.PutUint32(b[versTCFL:], vtf)
+}
+
+func (b IPv6Packet) SetPayloadLength(payloadLength uint16) {
+	binary.BigEndian.PutUint16(b[IPv6PayloadLenOffset:], payloadLength)
+}
+
+func (b IPv6Packet) SetSourceIP(addr netip.Addr) {
+	if addr.Is6() {
+		copy(b[v6SrcAddr:][:IPv6AddressSize], addr.AsSlice())
+	}
+}
+
+func (b IPv6Packet) SetDestinationIP(addr netip.Addr) {
+	if addr.Is6() {
+		copy(b[v6DstAddr:][:IPv6AddressSize], addr.AsSlice())
+	}
+}
+
+func (b IPv6Packet) SetHopLimit(v uint8) {
+	b[hopLimit] = v
+}
+
+func (b IPv6Packet) SetNextHeader(v byte) {
+	b[IPv6NextHeaderOffset] = v
+}
+
+func (b IPv6Packet) SetProtocol(p IPProtocol) {
+	b.SetNextHeader(p)
+}
+
+func (b IPv6Packet) DecTimeToLive() {
+	b[hopLimit] = b[hopLimit] - uint8(1)
+}
+
+func (IPv6Packet) SetChecksum(uint16) {
+}
+
+func (IPv6Packet) ResetChecksum() {
+}
+
+func (b IPv6Packet) PseudoSum() uint32 {
+	sum := Sum(b[v6SrcAddr:IPv6FixedHeaderSize])
+	sum += uint32(b.Protocol())
+	sum += uint32(b.PayloadLength())
+	return sum
+}
+
+func (b IPv6Packet) Valid() bool {
+	return len(b) >= IPv6MinimumSize && len(b) >= int(b.PayloadLength())+IPv6MinimumSize
+}
+
+func IPVersion(b []byte) int {
+	if len(b) < versIHL+1 {
+		return -1
+	}
+	return int(b[versIHL] >> ipVersionShift)
+}
+
+var _ IP = (*IPv6Packet)(nil)