|
| 1 | +package tun |
| 2 | + |
| 3 | +import ( |
| 4 | + "net/netip" |
| 5 | + "sync" |
| 6 | + |
| 7 | + "github.com/sagernet/sing-tun/internal/gtcpip/checksum" |
| 8 | + "github.com/sagernet/sing-tun/internal/gtcpip/header" |
| 9 | +) |
| 10 | + |
| 11 | +type NatMapping struct { |
| 12 | + access sync.RWMutex |
| 13 | + sessions map[DirectRouteSession]DirectRouteContext |
| 14 | + ipRewrite bool |
| 15 | +} |
| 16 | + |
| 17 | +func NewNatMapping(ipRewrite bool) *NatMapping { |
| 18 | + return &NatMapping{ |
| 19 | + sessions: make(map[DirectRouteSession]DirectRouteContext), |
| 20 | + ipRewrite: ipRewrite, |
| 21 | + } |
| 22 | +} |
| 23 | + |
| 24 | +func (m *NatMapping) CreateSession(session DirectRouteSession, context DirectRouteContext) { |
| 25 | + if m.ipRewrite { |
| 26 | + session.Source = netip.Addr{} |
| 27 | + } |
| 28 | + m.access.Lock() |
| 29 | + m.sessions[session] = context |
| 30 | + m.access.Unlock() |
| 31 | +} |
| 32 | + |
| 33 | +func (m *NatMapping) DeleteSession(session DirectRouteSession) { |
| 34 | + if m.ipRewrite { |
| 35 | + session.Source = netip.Addr{} |
| 36 | + } |
| 37 | + m.access.Lock() |
| 38 | + delete(m.sessions, session) |
| 39 | + m.access.Unlock() |
| 40 | +} |
| 41 | + |
| 42 | +func (m *NatMapping) WritePacket(packet []byte) (bool, error) { |
| 43 | + var routeSession DirectRouteSession |
| 44 | + switch header.IPVersion(packet) { |
| 45 | + case header.IPv4Version: |
| 46 | + ipHdr := header.IPv4(packet) |
| 47 | + routeSession.Source = ipHdr.DestinationAddr() |
| 48 | + routeSession.Destination = ipHdr.SourceAddr() |
| 49 | + case header.IPv6Version: |
| 50 | + ipHdr := header.IPv6(packet) |
| 51 | + routeSession.Source = ipHdr.DestinationAddr() |
| 52 | + routeSession.Destination = ipHdr.SourceAddr() |
| 53 | + default: |
| 54 | + return false, nil |
| 55 | + } |
| 56 | + m.access.RLock() |
| 57 | + context, loaded := m.sessions[routeSession] |
| 58 | + m.access.RUnlock() |
| 59 | + if !loaded { |
| 60 | + return false, nil |
| 61 | + } |
| 62 | + return true, context.WritePacket(packet) |
| 63 | +} |
| 64 | + |
| 65 | +type NatWriter struct { |
| 66 | + inet4Address netip.Addr |
| 67 | + inet6Address netip.Addr |
| 68 | +} |
| 69 | + |
| 70 | +func NewNatWriter(inet4Address netip.Addr, inet6Address netip.Addr) *NatWriter { |
| 71 | + return &NatWriter{ |
| 72 | + inet4Address: inet4Address, |
| 73 | + inet6Address: inet6Address, |
| 74 | + } |
| 75 | +} |
| 76 | + |
| 77 | +func (w *NatWriter) RewritePacket(packet []byte) { |
| 78 | + var ipHdr header.Network |
| 79 | + var bindAddr netip.Addr |
| 80 | + switch header.IPVersion(packet) { |
| 81 | + case header.IPv4Version: |
| 82 | + ipHdr = header.IPv4(packet) |
| 83 | + bindAddr = w.inet4Address |
| 84 | + case header.IPv6Version: |
| 85 | + ipHdr = header.IPv6(packet) |
| 86 | + bindAddr = w.inet6Address |
| 87 | + default: |
| 88 | + return |
| 89 | + } |
| 90 | + ipHdr.SetSourceAddr(bindAddr) |
| 91 | + switch ipHdr.TransportProtocol() { |
| 92 | + case header.ICMPv4ProtocolNumber: |
| 93 | + icmpHdr := header.ICMPv4(packet) |
| 94 | + icmpHdr.SetChecksum(0) |
| 95 | + icmpHdr.SetChecksum(header.ICMPv4Checksum(icmpHdr[:header.ICMPv4MinimumSize], checksum.Checksum(icmpHdr.Payload(), 0))) |
| 96 | + case header.ICMPv6ProtocolNumber: |
| 97 | + icmpHdr := header.ICMPv6(packet) |
| 98 | + icmpHdr.SetChecksum(0) |
| 99 | + icmpHdr.SetChecksum(header.ICMPv6Checksum(header.ICMPv6ChecksumParams{ |
| 100 | + Header: icmpHdr, |
| 101 | + Src: ipHdr.SourceAddress(), |
| 102 | + Dst: ipHdr.DestinationAddress(), |
| 103 | + })) |
| 104 | + } |
| 105 | + if ipHdr4, isIPv4 := ipHdr.(header.IPv4); isIPv4 { |
| 106 | + ipHdr4.SetChecksum(0) |
| 107 | + ipHdr4.SetChecksum(^ipHdr4.CalculateChecksum()) |
| 108 | + } |
| 109 | +} |
0 commit comments