mirror of
https://github.com/SagerNet/sing-tun.git
synced 2025-04-03 03:47:39 +03:00
119 lines
2.9 KiB
Go
119 lines
2.9 KiB
Go
package tun
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import (
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"net/netip"
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"sync"
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"github.com/sagernet/sing-tun/internal/clashtcpip"
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)
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type NatMapping struct {
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access sync.RWMutex
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sessions map[RouteSession]RouteContext
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ipRewrite bool
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}
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func NewNatMapping(ipRewrite bool) *NatMapping {
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return &NatMapping{
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sessions: make(map[RouteSession]RouteContext),
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ipRewrite: ipRewrite,
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}
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}
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func (m *NatMapping) CreateSession(session RouteSession, context RouteContext) {
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if m.ipRewrite {
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session.Source = netip.AddrPort{}
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}
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m.access.Lock()
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m.sessions[session] = context
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m.access.Unlock()
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}
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func (m *NatMapping) DeleteSession(session RouteSession) {
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if m.ipRewrite {
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session.Source = netip.AddrPort{}
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}
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m.access.Lock()
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delete(m.sessions, session)
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m.access.Unlock()
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}
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func (m *NatMapping) WritePacket(packet []byte) (bool, error) {
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var routeSession RouteSession
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var ipHdr clashtcpip.IP
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switch ipVersion := packet[0] >> 4; ipVersion {
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case 4:
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routeSession.IPVersion = 4
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ipHdr = clashtcpip.IPv4Packet(packet)
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case 6:
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routeSession.IPVersion = 6
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ipHdr = clashtcpip.IPv6Packet(packet)
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default:
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return false, nil
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}
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routeSession.Network = ipHdr.Protocol()
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switch routeSession.Network {
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case clashtcpip.TCP:
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tcpHdr := clashtcpip.TCPPacket(ipHdr.Payload())
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routeSession.Destination = netip.AddrPortFrom(ipHdr.SourceIP(), tcpHdr.SourcePort())
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if !m.ipRewrite {
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routeSession.Source = netip.AddrPortFrom(ipHdr.DestinationIP(), tcpHdr.DestinationPort())
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}
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case clashtcpip.UDP:
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udpHdr := clashtcpip.UDPPacket(ipHdr.Payload())
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routeSession.Destination = netip.AddrPortFrom(ipHdr.SourceIP(), udpHdr.SourcePort())
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if !m.ipRewrite {
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routeSession.Source = netip.AddrPortFrom(ipHdr.DestinationIP(), udpHdr.DestinationPort())
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}
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default:
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routeSession.Destination = netip.AddrPortFrom(ipHdr.SourceIP(), 0)
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if !m.ipRewrite {
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routeSession.Source = netip.AddrPortFrom(ipHdr.DestinationIP(), 0)
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}
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}
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m.access.RLock()
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context, loaded := m.sessions[routeSession]
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m.access.RUnlock()
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if !loaded {
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return false, nil
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}
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return true, context.WritePacket(packet)
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}
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type NatWriter struct {
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inet4Address netip.Addr
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inet6Address netip.Addr
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}
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func NewNatWriter(inet4Address netip.Addr, inet6Address netip.Addr) *NatWriter {
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return &NatWriter{
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inet4Address: inet4Address,
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inet6Address: inet6Address,
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}
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}
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func (w *NatWriter) RewritePacket(packet []byte) {
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var ipHdr clashtcpip.IP
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var bindAddr netip.Addr
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switch ipVersion := packet[0] >> 4; ipVersion {
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case 4:
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ipHdr = clashtcpip.IPv4Packet(packet)
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bindAddr = w.inet4Address
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case 6:
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ipHdr = clashtcpip.IPv6Packet(packet)
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bindAddr = w.inet6Address
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default:
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return
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}
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ipHdr.SetSourceIP(bindAddr)
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switch ipHdr.Protocol() {
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case clashtcpip.TCP:
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tcpHdr := clashtcpip.TCPPacket(ipHdr.Payload())
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tcpHdr.ResetChecksum(ipHdr.PseudoSum())
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case clashtcpip.UDP:
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udpHdr := clashtcpip.UDPPacket(ipHdr.Payload())
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udpHdr.ResetChecksum(ipHdr.PseudoSum())
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default:
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}
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ipHdr.ResetChecksum()
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}
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