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108 lines
2.9 KiB
Go
108 lines
2.9 KiB
Go
package tcp
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import (
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"errors"
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"io"
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"net"
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"syscall"
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"time"
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"github.com/rs/zerolog/log"
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)
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// Proxy forwards a TCP request to a TCP service.
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type Proxy struct {
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address string
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dialer Dialer
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}
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// NewProxy creates a new Proxy.
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func NewProxy(address string, dialer Dialer) (*Proxy, error) {
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return &Proxy{
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address: address,
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dialer: dialer,
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}, nil
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}
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// ServeTCP forwards the connection to a service.
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func (p *Proxy) ServeTCP(conn WriteCloser) {
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log.Debug().
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Str("address", p.address).
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Str("remoteAddr", conn.RemoteAddr().String()).
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Msg("Handling TCP connection")
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// needed because of e.g. server.trackedConnection
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defer conn.Close()
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connBackend, err := p.dialBackend(conn)
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if err != nil {
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log.Error().Err(err).Msg("Error while dialing backend")
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return
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}
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// maybe not needed, but just in case
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defer connBackend.Close()
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errChan := make(chan error)
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go p.connCopy(conn, connBackend, errChan)
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go p.connCopy(connBackend, conn, errChan)
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err = <-errChan
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if err != nil {
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// Treat connection reset error during a read operation with a lower log level.
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// This allows to not report an RST packet sent by the peer as an error,
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// as it is an abrupt but possible end for the TCP session
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if isReadConnResetError(err) {
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log.Debug().Err(err).Msg("Error while handling TCP connection")
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} else {
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log.Error().Err(err).Msg("Error while handling TCP connection")
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}
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}
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<-errChan
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}
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func (p *Proxy) dialBackend(clientConn net.Conn) (WriteCloser, error) {
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// The clientConn is passed to the dialer so that it can use information from it if needed,
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// to build a PROXY protocol header.
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conn, err := p.dialer.Dial("tcp", p.address, clientConn)
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if err != nil {
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return nil, err
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}
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return conn.(WriteCloser), nil
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}
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func (p *Proxy) connCopy(dst, src WriteCloser, errCh chan error) {
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_, err := io.Copy(dst, src)
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errCh <- err
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// Ends the connection with the dst connection peer.
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// It corresponds to sending a FIN packet to gracefully end the TCP session.
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errClose := dst.CloseWrite()
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if errClose != nil {
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// Calling CloseWrite() on a connection which have a socket which is "not connected" is expected to fail.
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// It happens notably when the dst connection has ended receiving an RST packet from the peer (within the other connCopy call).
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// In that case, logging the error is superfluous,
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// as in the first place we should not have needed to call CloseWrite.
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if !isSocketNotConnectedError(errClose) {
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log.Debug().Err(errClose).Msg("Error while terminating TCP connection")
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}
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return
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}
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if p.dialer.TerminationDelay() >= 0 {
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err := dst.SetReadDeadline(time.Now().Add(p.dialer.TerminationDelay()))
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if err != nil {
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log.Debug().Err(err).Msg("Error while setting TCP connection deadline")
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}
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}
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}
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// isSocketNotConnectedError reports whether err is a socket not connected error.
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func isSocketNotConnectedError(err error) bool {
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var oerr *net.OpError
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return errors.As(err, &oerr) && errors.Is(err, syscall.ENOTCONN)
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}
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