package tcp import ( "errors" "fmt" "io" "net" "syscall" "time" "github.com/pires/go-proxyproto" "github.com/traefik/traefik/v2/pkg/config/dynamic" "github.com/traefik/traefik/v2/pkg/log" ) // Proxy forwards a TCP request to a TCP service. type Proxy struct { address string tcpAddr *net.TCPAddr terminationDelay time.Duration proxyProtocol *dynamic.ProxyProtocol } // NewProxy creates a new Proxy. func NewProxy(address string, terminationDelay time.Duration, proxyProtocol *dynamic.ProxyProtocol) (*Proxy, error) { if proxyProtocol != nil && (proxyProtocol.Version < 1 || proxyProtocol.Version > 2) { return nil, fmt.Errorf("unknown proxyProtocol version: %d", proxyProtocol.Version) } // Creates the tcpAddr only for IP based addresses, // because there is no need to resolve the name on every new connection, // and building it should happen once. var tcpAddr *net.TCPAddr if host, _, err := net.SplitHostPort(address); err == nil && net.ParseIP(host) != nil { tcpAddr, err = net.ResolveTCPAddr("tcp", address) if err != nil { return nil, err } } return &Proxy{ address: address, tcpAddr: tcpAddr, terminationDelay: terminationDelay, proxyProtocol: proxyProtocol, }, nil } // ServeTCP forwards the connection to a service. func (p *Proxy) ServeTCP(conn WriteCloser) { log.WithoutContext().Debugf("Handling connection from %s to %s", conn.RemoteAddr(), p.address) // needed because of e.g. server.trackedConnection defer conn.Close() connBackend, err := p.dialBackend() if err != nil { log.WithoutContext().Errorf("Error while connecting to backend: %v", err) return } // maybe not needed, but just in case defer connBackend.Close() errChan := make(chan error) if p.proxyProtocol != nil && p.proxyProtocol.Version > 0 && p.proxyProtocol.Version < 3 { header := proxyproto.HeaderProxyFromAddrs(byte(p.proxyProtocol.Version), conn.RemoteAddr(), conn.LocalAddr()) if _, err := header.WriteTo(connBackend); err != nil { log.WithoutContext().Errorf("Error while writing proxy protocol headers to backend connection: %v", err) return } } go p.connCopy(conn, connBackend, errChan) go p.connCopy(connBackend, conn, errChan) err = <-errChan if err != nil { // Treat connection reset error during a read operation with a lower log level. // This allows to not report an RST packet sent by the peer as an error, // as it is an abrupt but possible end for the TCP session if isReadConnResetError(err) { log.WithoutContext().Debugf("Error during connection: %v", err) } else { log.WithoutContext().Errorf("Error during connection: %v", err) } } <-errChan } func (p Proxy) dialBackend() (*net.TCPConn, error) { // Dial using directly the TCPAddr for IP based addresses. if p.tcpAddr != nil { return net.DialTCP("tcp", nil, p.tcpAddr) } log.WithoutContext().Debugf("Dial with lookup to address %s", p.address) // Dial with DNS lookup for host based addresses. conn, err := net.Dial("tcp", p.address) if err != nil { return nil, err } return conn.(*net.TCPConn), nil } func (p Proxy) connCopy(dst, src WriteCloser, errCh chan error) { _, err := io.Copy(dst, src) errCh <- err // Ends the connection with the dst connection peer. // It corresponds to sending a FIN packet to gracefully end the TCP session. errClose := dst.CloseWrite() if errClose != nil { // Calling CloseWrite() on a connection which have a socket which is "not connected" is expected to fail. // It happens notably when the dst connection has ended receiving an RST packet from the peer (within the other connCopy call). // In that case, logging the error is superfluous, // as in the first place we should not have needed to call CloseWrite. if !isSocketNotConnectedError(errClose) { log.WithoutContext().Debugf("Error while terminating connection: %v", errClose) } return } if p.terminationDelay >= 0 { err := dst.SetReadDeadline(time.Now().Add(p.terminationDelay)) if err != nil { log.WithoutContext().Debugf("Error while setting deadline: %v", err) } } } // isSocketNotConnectedError reports whether err is a socket not connected error. func isSocketNotConnectedError(err error) bool { var oerr *net.OpError return errors.As(err, &oerr) && errors.Is(err, syscall.ENOTCONN) }