reverseproxy: Implement read & write timeouts for HTTP transport (#4905)

modules/caddyhttp/reverseproxy/caddyfile.go

@@ -875,6 +875,26 @@ func (h *HTTPTransport) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
 				}
 				h.WriteBufferSize = int(size)
 
+			case "read_timeout":
+				if !d.NextArg() {
+					return d.ArgErr()
+				}
+				timeout, err := caddy.ParseDuration(d.Val())
+				if err != nil {
+					return d.Errf("invalid read timeout duration '%s': %v", d.Val(), err)
+				}
+				h.ReadTimeout = caddy.Duration(timeout)
+
+			case "write_timeout":
+				if !d.NextArg() {
+					return d.ArgErr()
+				}
+				timeout, err := caddy.ParseDuration(d.Val())
+				if err != nil {
+					return d.Errf("invalid write timeout duration '%s': %v", d.Val(), err)
+				}
+				h.WriteTimeout = caddy.Duration(timeout)
+
 			case "max_response_header":
 				if !d.NextArg() {
 					return d.ArgErr()

modules/caddyhttp/reverseproxy/httptransport.go

@@ -30,6 +30,7 @@ import (
 
 	"github.com/caddyserver/caddy/v2"
 	"github.com/caddyserver/caddy/v2/modules/caddytls"
+	"go.uber.org/zap"
 	"golang.org/x/net/http2"
 )
 
@@ -88,6 +89,12 @@ type HTTPTransport struct {
 	// The size of the read buffer in bytes. Default: `4KiB`.
 	ReadBufferSize int `json:"read_buffer_size,omitempty"`
 
+	// The maximum time to wait for next read from backend. Default: no timeout.
+	ReadTimeout caddy.Duration `json:"read_timeout,omitempty"`
+
+	// The maximum time to wait for next write to backend. Default: no timeout.
+	WriteTimeout caddy.Duration `json:"write_timeout,omitempty"`
+
 	// The versions of HTTP to support. As a special case, "h2c"
 	// can be specified to use H2C (HTTP/2 over Cleartext) to the
 	// upstream (this feature is experimental and subject to
@@ -147,7 +154,7 @@ func (h *HTTPTransport) Provision(ctx caddy.Context) error {
 }
 
 // NewTransport builds a standard-lib-compatible http.Transport value from h.
-func (h *HTTPTransport) NewTransport(ctx caddy.Context) (*http.Transport, error) {
+func (h *HTTPTransport) NewTransport(caddyCtx caddy.Context) (*http.Transport, error) {
 	// Set keep-alive defaults if it wasn't otherwise configured
 	if h.KeepAlive == nil {
 		h.KeepAlive = &KeepAlive{
@@ -194,6 +201,7 @@ func (h *HTTPTransport) NewTransport(ctx caddy.Context) (*http.Transport, error)
 				network = dialInfo.Network
 				address = dialInfo.Address
 			}
+
 			conn, err := dialer.DialContext(ctx, network, address)
 			if err != nil {
 				// identify this error as one that occurred during
@@ -201,6 +209,18 @@ func (h *HTTPTransport) NewTransport(ctx caddy.Context) (*http.Transport, error)
 				// decide whether to retry a request
 				return nil, DialError{err}
 			}
+
+			// if read/write timeouts are configured and this is a TCP connection, enforce the timeouts
+			// by wrapping the connection with our own type
+			if tcpConn, ok := conn.(*net.TCPConn); ok && (h.ReadTimeout > 0 || h.WriteTimeout > 0) {
+				conn = &tcpRWTimeoutConn{
+					TCPConn:      tcpConn,
+					readTimeout:  time.Duration(h.ReadTimeout),
+					writeTimeout: time.Duration(h.WriteTimeout),
+					logger:       caddyCtx.Logger(h),
+				}
+			}
+
 			return conn, nil
 		},
 		MaxConnsPerHost:        h.MaxConnsPerHost,
@@ -214,7 +234,7 @@ func (h *HTTPTransport) NewTransport(ctx caddy.Context) (*http.Transport, error)
 	if h.TLS != nil {
 		rt.TLSHandshakeTimeout = time.Duration(h.TLS.HandshakeTimeout)
 		var err error
-		rt.TLSClientConfig, err = h.TLS.MakeTLSClientConfig(ctx)
+		rt.TLSClientConfig, err = h.TLS.MakeTLSClientConfig(caddyCtx)
 		if err != nil {
 			return nil, fmt.Errorf("making TLS client config: %v", err)
 		}
@@ -510,6 +530,36 @@ type KeepAlive struct {
 	IdleConnTimeout caddy.Duration `json:"idle_timeout,omitempty"`
 }
 
+// tcpRWTimeoutConn enforces read/write timeouts for a TCP connection.
+// If it fails to set deadlines, the error is logged but does not abort
+// the read/write attempt (ignoring the error is consistent with what
+// the standard library does: https://github.com/golang/go/blob/c5da4fb7ac5cb7434b41fc9a1df3bee66c7f1a4d/src/net/http/server.go#L981-L986)
+type tcpRWTimeoutConn struct {
+	*net.TCPConn
+	readTimeout, writeTimeout time.Duration
+	logger                    *zap.Logger
+}
+
+func (c *tcpRWTimeoutConn) Read(b []byte) (int, error) {
+	if c.readTimeout > 0 {
+		err := c.TCPConn.SetReadDeadline(time.Now().Add(c.readTimeout))
+		if err != nil {
+			c.logger.Error("failed to set read deadline", zap.Error(err))
+		}
+	}
+	return c.TCPConn.Read(b)
+}
+
+func (c *tcpRWTimeoutConn) Write(b []byte) (int, error) {
+	if c.writeTimeout > 0 {
+		err := c.TCPConn.SetWriteDeadline(time.Now().Add(c.writeTimeout))
+		if err != nil {
+			c.logger.Error("failed to set write deadline", zap.Error(err))
+		}
+	}
+	return c.TCPConn.Write(b)
+}
+
 // decodeBase64DERCert base64-decodes, then DER-decodes, certStr.
 func decodeBase64DERCert(certStr string) (*x509.Certificate, error) {
 	// decode base64