keep listener after erroring with invalid upstream

protocol.go

@@ -2,18 +2,26 @@ package proxyproto
 
 import (
 	"bufio"
+	"errors"
+	"fmt"
 	"io"
 	"net"
 	"sync"
 	"sync/atomic"
 	"time"
 )
 
-// DefaultReadHeaderTimeout is how long header processing waits for header to
-// be read from the wire, if Listener.ReaderHeaderTimeout is not set.
-// It's kept as a global variable so to make it easier to find and override,
-// e.g. go build -ldflags -X "github.com/pires/go-proxyproto.DefaultReadHeaderTimeout=1s"
-var DefaultReadHeaderTimeout = 10 * time.Second
+var (
+	// DefaultReadHeaderTimeout is how long header processing waits for header to
+	// be read from the wire, if Listener.ReaderHeaderTimeout is not set.
+	// It's kept as a global variable so to make it easier to find and override,
+	// e.g. go build -ldflags -X "github.com/pires/go-proxyproto.DefaultReadHeaderTimeout=1s"
+	DefaultReadHeaderTimeout = 10 * time.Second
+
+	// ErrInvalidUpstream should be returned when an upstream connection address
+	// is not trusted, and therefore is invalid.
+	ErrInvalidUpstream = fmt.Errorf("proxyproto: upstream connection address not trusted for PROXY information")
+)
 
 // Listener is used to wrap an underlying listener,
 // whose connections may be using the HAProxy Proxy Protocol.
@@ -72,53 +80,61 @@ func SetReadHeaderTimeout(t time.Duration) func(*Conn) {
 	}
 }
 
-// Accept waits for and returns the next connection to the listener.
+// Accept waits for and returns the next valid connection to the listener.
 func (p *Listener) Accept() (net.Conn, error) {
-	// Get the underlying connection
-	conn, err := p.Listener.Accept()
-	if err != nil {
-		return nil, err
-	}
-
-	proxyHeaderPolicy := USE
-	if p.Policy != nil && p.ConnPolicy != nil {
-		panic("only one of policy or connpolicy must be provided.")
-	}
-	if p.Policy != nil || p.ConnPolicy != nil {
-		if p.Policy != nil {
-			proxyHeaderPolicy, err = p.Policy(conn.RemoteAddr())
-		} else {
-			proxyHeaderPolicy, err = p.ConnPolicy(ConnPolicyOptions{
-				Upstream:   conn.RemoteAddr(),
-				Downstream: conn.LocalAddr(),
-			})
-		}
+	for {
+		// Get the underlying connection
+		conn, err := p.Listener.Accept()
 		if err != nil {
-			// can't decide the policy, we can't accept the connection
-			conn.Close()
 			return nil, err
 		}
-		// Handle a connection as a regular one
-		if proxyHeaderPolicy == SKIP {
-			return conn, nil
+
+		proxyHeaderPolicy := USE
+		if p.Policy != nil && p.ConnPolicy != nil {
+			panic("only one of policy or connpolicy must be provided.")
 		}
-	}
+		if p.Policy != nil || p.ConnPolicy != nil {
+			if p.Policy != nil {
+				proxyHeaderPolicy, err = p.Policy(conn.RemoteAddr())
+			} else {
+				proxyHeaderPolicy, err = p.ConnPolicy(ConnPolicyOptions{
+					Upstream:   conn.RemoteAddr(),
+					Downstream: conn.LocalAddr(),
+				})
+			}
+			if err != nil {
+				// can't decide the policy, we can't accept the connection
+				conn.Close()
 
-	newConn := NewConn(
-		conn,
-		WithPolicy(proxyHeaderPolicy),
-		ValidateHeader(p.ValidateHeader),
-	)
+				if errors.Is(err, ErrInvalidUpstream) {
+					// keep listening for other connections
+					continue
+				}
 
-	// If the ReadHeaderTimeout for the listener is unset, use the default timeout.
-	if p.ReadHeaderTimeout == 0 {
-		p.ReadHeaderTimeout = DefaultReadHeaderTimeout
-	}
+				return nil, err
+			}
+			// Handle a connection as a regular one
+			if proxyHeaderPolicy == SKIP {
+				return conn, nil
+			}
+		}
 
-	// Set the readHeaderTimeout of the new conn to the value of the listener
-	newConn.readHeaderTimeout = p.ReadHeaderTimeout
+		newConn := NewConn(
+			conn,
+			WithPolicy(proxyHeaderPolicy),
+			ValidateHeader(p.ValidateHeader),
+		)
 
-	return newConn, nil
+		// If the ReadHeaderTimeout for the listener is unset, use the default timeout.
+		if p.ReadHeaderTimeout == 0 {
+			p.ReadHeaderTimeout = DefaultReadHeaderTimeout
+		}
+
+		// Set the readHeaderTimeout of the new conn to the value of the listener
+		newConn.readHeaderTimeout = p.ReadHeaderTimeout
+
+		return newConn, nil
+	}
 }
 
 // Close closes the underlying listener.

protocol_test.go

@@ -13,6 +13,8 @@ import (
 	"io"
 	"io/ioutil"
 	"net"
+	"net/http"
+	"sync/atomic"
 	"testing"
 	"time"
 )
@@ -83,7 +85,6 @@ func TestRequiredWithReadHeaderTimeout(t *testing.T) {
 			start := time.Now()
 
 			l, err := net.Listen("tcp", "127.0.0.1:0")
-
 			if err != nil {
 				t.Fatalf("err: %v", err)
 			}
@@ -138,7 +139,6 @@ func TestUseWithReadHeaderTimeout(t *testing.T) {
 			start := time.Now()
 
 			l, err := net.Listen("tcp", "127.0.0.1:0")
-
 			if err != nil {
 				t.Fatalf("err: %v", err)
 			}
@@ -848,6 +848,7 @@ func TestReadingIsRefusedWhenProxyHeaderPresentButNotAllowed(t *testing.T) {
 		t.Fatalf("client error: %v", err)
 	}
 }
+
 func TestIgnorePolicyIgnoresIpFromProxyHeader(t *testing.T) {
 	l, err := net.Listen("tcp", "127.0.0.1:0")
 	if err != nil {
@@ -1275,6 +1276,67 @@ func Test_ConnectionErrorsWhenHeaderValidationFails(t *testing.T) {
 	}
 }
 
+func Test_ConnectionHandlesInvalidUpstreamError(t *testing.T) {
+	l, err := net.Listen("tcp", "localhost:8080")
+	if err != nil {
+		t.Fatalf("error creating listener: %v", err)
+	}
+
+	var connectionCounter atomic.Int32
+
+	newLn := &Listener{
+		Listener: l,
+		ConnPolicy: func(_ ConnPolicyOptions) (Policy, error) {
+			// Return the invalid upstream error on the first call, the listener
+			// should remain open and accepting.
+			times := connectionCounter.Load()
+			if times == 0 {
+				connectionCounter.Store(times + 1)
+				return REJECT, ErrInvalidUpstream
+			}
+
+			return REJECT, ErrNoProxyProtocol
+		},
+	}
+
+	// Kick off the listener and return any error via the chanel.
+	errCh := make(chan error)
+	defer close(errCh)
+	go func(t *testing.T) {
+		_, err := newLn.Accept()
+		errCh <- err
+	}(t)
+
+	// Make two calls to trigger the listener's accept, the first should experience
+	// the ErrInvalidUpstream and keep the listener open, the second should experience
+	// a different error which will cause the listener to close.
+	_, _ = http.Get("http://localhost:8080")
+	// Wait a few seconds to ensure we didn't get anything back on our channel.
+	select {
+	case err := <-errCh:
+		if err != nil {
+			t.Fatalf("invalid upstream shouldn't return an error: %v", err)
+		}
+	case <-time.After(2 * time.Second):
+		// No error returned (as expected, we're still listening though)
+	}
+
+	_, _ = http.Get("http://localhost:8080")
+	// Wait a few seconds before we fail the test as we should have received an
+	// error that was not invalid upstream.
+	select {
+	case err := <-errCh:
+		if err == nil {
+			t.Fatalf("errors other than invalid upstream should error")
+		}
+		if !errors.Is(ErrNoProxyProtocol, err) {
+			t.Fatalf("unexpected error type: %v", err)
+		}
+	case <-time.After(2 * time.Second):
+		t.Fatalf("timed out waiting for listener")
+	}
+}
+
 type TestTLSServer struct {
 	Listener net.Listener
 
@@ -1483,9 +1545,11 @@ func (c *testConn) ReadFrom(r io.Reader) (int64, error) {
 	b, err := ioutil.ReadAll(r)
 	return int64(len(b)), err
 }
+
 func (c *testConn) Write(p []byte) (int, error) {
 	return len(p), nil
 }
+
 func (c *testConn) Read(p []byte) (int, error) {
 	if c.reads == 0 {
 		return 0, io.EOF
@@ -1534,7 +1598,7 @@ func TestCopyFromWrappedConnectionToWrappedConnection(t *testing.T) {
 }
 
 func benchmarkTCPProxy(size int, b *testing.B) {
-	//create and start the echo backend
+	// create and start the echo backend
 	backend, err := net.Listen("tcp", "127.0.0.1:0")
 	if err != nil {
 		b.Fatalf("err: %v", err)
@@ -1555,7 +1619,7 @@ func benchmarkTCPProxy(size int, b *testing.B) {
 		}
 	}()
 
-	//start the proxyprotocol enabled tcp proxy
+	// start the proxyprotocol enabled tcp proxy
 	l, err := net.Listen("tcp", "127.0.0.1:0")
 	if err != nil {
 		b.Fatalf("err: %v", err)
@@ -1604,7 +1668,7 @@ func benchmarkTCPProxy(size int, b *testing.B) {
 		},
 	}
 
-	//now for the actual benchmark
+	// now for the actual benchmark
 	b.ResetTimer()
 	for n := 0; n < b.N; n++ {
 		conn, err := net.Dial("tcp", pl.Addr().String())
@@ -1615,16 +1679,15 @@ func benchmarkTCPProxy(size int, b *testing.B) {
 		if _, err := header.WriteTo(conn); err != nil {
 			b.Fatalf("err: %v", err)
 		}
-		//send data
+		// send data
 		go func() {
 			_, err = conn.Write(data)
 			_ = conn.(*net.TCPConn).CloseWrite()
 			if err != nil {
 				panic(fmt.Sprintf("Failed to write data: %v", err))
 			}
-
 		}()
-		//receive data
+		// receive data
 		n, err := io.Copy(ioutil.Discard, conn)
 		if n != int64(len(data)) {
 			b.Fatalf("Expected to receive %d bytes, got %d", len(data), n)
@@ -1639,24 +1702,31 @@ func benchmarkTCPProxy(size int, b *testing.B) {
 func BenchmarkTCPProxy16KB(b *testing.B) {
 	benchmarkTCPProxy(16*1024, b)
 }
+
 func BenchmarkTCPProxy32KB(b *testing.B) {
 	benchmarkTCPProxy(32*1024, b)
 }
+
 func BenchmarkTCPProxy64KB(b *testing.B) {
 	benchmarkTCPProxy(64*1024, b)
 }
+
 func BenchmarkTCPProxy128KB(b *testing.B) {
 	benchmarkTCPProxy(128*1024, b)
 }
+
 func BenchmarkTCPProxy256KB(b *testing.B) {
 	benchmarkTCPProxy(256*1024, b)
 }
+
 func BenchmarkTCPProxy512KB(b *testing.B) {
 	benchmarkTCPProxy(512*1024, b)
 }
+
 func BenchmarkTCPProxy1024KB(b *testing.B) {
 	benchmarkTCPProxy(1024*1024, b)
 }
+
 func BenchmarkTCPProxy2048KB(b *testing.B) {
 	benchmarkTCPProxy(2048*1024, b)
 }