145 lines
2.9 KiB
Go
145 lines
2.9 KiB
Go
package tun
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import (
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"context"
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"net/netip"
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"sync"
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"time"
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)
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type TCPNat struct {
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timeout time.Duration
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portIndex uint16
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portAccess sync.RWMutex
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addrAccess sync.RWMutex
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addrMap map[tcpNatKey]uint16
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portMap map[uint16]*TCPSession
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}
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type tcpNatKey struct {
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Source netip.AddrPort
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Destination netip.AddrPort
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}
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type TCPSession struct {
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sync.Mutex
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Source netip.AddrPort
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Destination netip.AddrPort
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LastActive time.Time
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}
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func NewNat(ctx context.Context, timeout time.Duration) *TCPNat {
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natMap := &TCPNat{
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timeout: timeout,
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portIndex: 10000,
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addrMap: make(map[tcpNatKey]uint16),
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portMap: make(map[uint16]*TCPSession),
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}
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go natMap.loopCheckTimeout(ctx)
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return natMap
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}
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func (n *TCPNat) loopCheckTimeout(ctx context.Context) {
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ticker := time.NewTicker(n.timeout)
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defer ticker.Stop()
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for {
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select {
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case <-ticker.C:
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n.checkTimeout()
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case <-ctx.Done():
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return
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}
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}
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}
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func (n *TCPNat) checkTimeout() {
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now := time.Now()
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type expiredSession struct {
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port uint16
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session *TCPSession
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}
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var expired []expiredSession
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n.portAccess.RLock()
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for natPort, session := range n.portMap {
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session.Lock()
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timedOut := now.Sub(session.LastActive) > n.timeout
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session.Unlock()
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if timedOut {
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expired = append(expired, expiredSession{port: natPort, session: session})
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}
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}
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n.portAccess.RUnlock()
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if len(expired) == 0 {
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return
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}
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n.addrAccess.Lock()
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n.portAccess.Lock()
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for _, e := range expired {
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e.session.Lock()
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if now.Sub(e.session.LastActive) > n.timeout {
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delete(n.addrMap, tcpNatKey{Source: e.session.Source, Destination: e.session.Destination})
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delete(n.portMap, e.port)
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}
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e.session.Unlock()
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}
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n.portAccess.Unlock()
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n.addrAccess.Unlock()
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}
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func (n *TCPNat) LookupBack(port uint16) *TCPSession {
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n.portAccess.RLock()
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session := n.portMap[port]
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n.portAccess.RUnlock()
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if session != nil {
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session.Lock()
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if time.Since(session.LastActive) > time.Second {
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session.LastActive = time.Now()
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}
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session.Unlock()
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}
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return session
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}
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func (n *TCPNat) Lookup(source netip.AddrPort, destination netip.AddrPort) uint16 {
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key := tcpNatKey{Source: source, Destination: destination}
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n.addrAccess.RLock()
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port, loaded := n.addrMap[key]
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n.addrAccess.RUnlock()
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if loaded {
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return port
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}
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n.addrAccess.Lock()
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defer n.addrAccess.Unlock()
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if port, loaded = n.addrMap[key]; loaded {
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return port
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}
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n.portAccess.Lock()
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defer n.portAccess.Unlock()
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nextPort, ok := n.allocatePortLocked()
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if !ok {
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return 0
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}
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n.portMap[nextPort] = &TCPSession{
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Source: source,
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Destination: destination,
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LastActive: time.Now(),
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}
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n.addrMap[key] = nextPort
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return nextPort
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}
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func (n *TCPNat) allocatePortLocked() (uint16, bool) {
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for range 65535 - 10000 + 1 {
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nextPort := n.portIndex
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if nextPort == 0 {
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nextPort = 10000
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n.portIndex = 10001
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} else {
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n.portIndex++
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}
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if _, occupied := n.portMap[nextPort]; !occupied {
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return nextPort, true
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}
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}
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return 0, false
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}
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