142 lines
3.7 KiB
Go
142 lines
3.7 KiB
Go
package ping
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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"
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"github.com/sagernet/sing-tun/internal/gtcpip/header"
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)
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type Rewriter struct {
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access sync.RWMutex
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sessions map[tun.DirectRouteSession]tun.DirectRouteContext
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source4Address map[uint16]netip.Addr
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source6Address map[uint16]netip.Addr
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inet4Address netip.Addr
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inet6Address netip.Addr
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}
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func NewRewriter(inet4Address netip.Addr, inet6Address netip.Addr) *Rewriter {
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return &Rewriter{
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sessions: make(map[tun.DirectRouteSession]tun.DirectRouteContext),
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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 (m *Rewriter) CreateSession(session tun.DirectRouteSession, context tun.DirectRouteContext) {
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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 *Rewriter) DeleteSession(session tun.DirectRouteSession) {
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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 *Rewriter) RewritePacket(packet []byte) {
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var ipHdr header.Network
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var bindAddr netip.Addr
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switch header.IPVersion(packet) {
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case header.IPv4Version:
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ipHdr = header.IPv4(packet)
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bindAddr = m.inet4Address
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case header.IPv6Version:
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ipHdr = header.IPv6(packet)
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bindAddr = m.inet6Address
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default:
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return
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}
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sourceAddr := ipHdr.SourceAddr()
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ipHdr.SetSourceAddr(bindAddr)
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if ipHdr4, isIPv4 := ipHdr.(header.IPv4); isIPv4 {
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ipHdr4.SetChecksum(0)
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ipHdr4.SetChecksum(^ipHdr4.CalculateChecksum())
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}
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switch ipHdr.TransportProtocol() {
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case header.ICMPv4ProtocolNumber:
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icmpHdr := header.ICMPv4(ipHdr.Payload())
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m.access.Lock()
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m.source4Address[icmpHdr.Ident()] = sourceAddr
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m.access.Lock()
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case header.ICMPv6ProtocolNumber:
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icmpHdr := header.ICMPv6(ipHdr.Payload())
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icmpHdr.SetChecksum(0)
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icmpHdr.SetChecksum(header.ICMPv6Checksum(header.ICMPv6ChecksumParams{
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Header: icmpHdr,
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Src: ipHdr.SourceAddressSlice(),
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Dst: ipHdr.DestinationAddressSlice(),
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}))
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m.access.Lock()
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m.source6Address[icmpHdr.Ident()] = sourceAddr
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m.access.Lock()
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}
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}
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func (m *Rewriter) WriteBack(packet []byte) (bool, error) {
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var ipHdr header.Network
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var routeSession tun.DirectRouteSession
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switch header.IPVersion(packet) {
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case header.IPv4Version:
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ipHdr = header.IPv4(packet)
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routeSession.Destination = ipHdr.SourceAddr()
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case header.IPv6Version:
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ipHdr = header.IPv6(packet)
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routeSession.Destination = ipHdr.SourceAddr()
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default:
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return false, nil
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}
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switch ipHdr.TransportProtocol() {
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case header.ICMPv4ProtocolNumber:
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icmpHdr := header.ICMPv4(ipHdr.Payload())
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m.access.Lock()
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ident := icmpHdr.Ident()
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source, loaded := m.source4Address[ident]
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if !loaded {
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m.access.Unlock()
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return false, nil
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}
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delete(m.source4Address, icmpHdr.Ident())
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m.access.Lock()
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routeSession.Source = source
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case header.ICMPv6ProtocolNumber:
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icmpHdr := header.ICMPv6(ipHdr.Payload())
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m.access.Lock()
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ident := icmpHdr.Ident()
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source, loaded := m.source6Address[ident]
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if !loaded {
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m.access.Unlock()
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return false, nil
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}
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delete(m.source6Address, icmpHdr.Ident())
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m.access.Lock()
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routeSession.Source = source
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default:
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return false, nil
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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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ipHdr.SetDestinationAddr(routeSession.Source)
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if ipHdr4, isIPv4 := ipHdr.(header.IPv4); isIPv4 {
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ipHdr4.SetChecksum(0)
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ipHdr4.SetChecksum(^ipHdr4.CalculateChecksum())
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}
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switch ipHdr.TransportProtocol() {
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case header.ICMPv6ProtocolNumber:
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icmpHdr := header.ICMPv6(ipHdr.Payload())
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icmpHdr.SetChecksum(0)
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icmpHdr.SetChecksum(header.ICMPv6Checksum(header.ICMPv6ChecksumParams{
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Header: icmpHdr,
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Src: ipHdr.SourceAddressSlice(),
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Dst: ipHdr.DestinationAddressSlice(),
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}))
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}
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return true, context.WritePacket(packet)
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}
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