Fix SetSendTimeout/SetReceiveTimeout

They were implemented using SO_SNDTIMEO/SO_RCVTIMEO on the
socket descriptor - but that doesn't work now the socket is
non-blocking. Instead, set deadlines on the file read/write.

Signed-off-by: Rob Murray <[email protected]>

Author: robmry

handle_test.go

@@ -12,11 +12,9 @@ import (
 	"sync/atomic"
 	"testing"
 	"time"
-	"unsafe"
 
 	"github.com/vishvananda/netlink/nl"
 	"github.com/vishvananda/netns"
-	"golang.org/x/sys/unix"
 )
 
 func TestHandleCreateClose(t *testing.T) {
@@ -122,13 +120,22 @@ func TestHandleTimeout(t *testing.T) {
 	defer h.Close()
 
 	for _, sh := range h.sockets {
-		verifySockTimeVal(t, sh.Socket.GetFd(), unix.Timeval{Sec: 0, Usec: 0})
+		verifySockTimeVal(t, sh.Socket, time.Duration(0))
 	}
 
-	h.SetSocketTimeout(2*time.Second + 8*time.Millisecond)
+	const timeout = 2*time.Second + 8*time.Millisecond
+	h.SetSocketTimeout(timeout)
 
 	for _, sh := range h.sockets {
-		verifySockTimeVal(t, sh.Socket.GetFd(), unix.Timeval{Sec: 2, Usec: 8000})
+		verifySockTimeVal(t, sh.Socket, timeout)
+	}
+}
+
+func verifySockTimeVal(t *testing.T, socket *nl.NetlinkSocket, expTimeout time.Duration) {
+	t.Helper()
+	send, receive := socket.GetTimeouts()
+	if send != expTimeout || receive != expTimeout {
+		t.Fatalf("Expected timeout: %v, got Send: %v, Receive: %v", expTimeout, send, receive)
 	}
 }
 
@@ -157,30 +164,6 @@ func TestHandleReceiveBuffer(t *testing.T) {
 	}
 }
 
-func verifySockTimeVal(t *testing.T, fd int, tv unix.Timeval) {
-	var (
-		tr unix.Timeval
-		v  = uint32(0x10)
-	)
-	_, _, errno := unix.Syscall6(unix.SYS_GETSOCKOPT, uintptr(fd), unix.SOL_SOCKET, unix.SO_SNDTIMEO, uintptr(unsafe.Pointer(&tr)), uintptr(unsafe.Pointer(&v)), 0)
-	if errno != 0 {
-		t.Fatal(errno)
-	}
-
-	if tr.Sec != tv.Sec || tr.Usec != tv.Usec {
-		t.Fatalf("Unexpected timeout value read: %v. Expected: %v", tr, tv)
-	}
-
-	_, _, errno = unix.Syscall6(unix.SYS_GETSOCKOPT, uintptr(fd), unix.SOL_SOCKET, unix.SO_RCVTIMEO, uintptr(unsafe.Pointer(&tr)), uintptr(unsafe.Pointer(&v)), 0)
-	if errno != 0 {
-		t.Fatal(errno)
-	}
-
-	if tr.Sec != tv.Sec || tr.Usec != tv.Usec {
-		t.Fatalf("Unexpected timeout value read: %v. Expected: %v", tr, tv)
-	}
-}
-
 var (
 	iter      = 10
 	numThread = uint32(4)

nl/nl_linux.go

@@ -4,13 +4,15 @@ package nl
 import (
 	"bytes"
 	"encoding/binary"
+	"errors"
 	"fmt"
 	"net"
 	"os"
 	"runtime"
 	"sync"
 	"sync/atomic"
 	"syscall"
+	"time"
 	"unsafe"
 
 	"github.com/vishvananda/netns"
@@ -656,9 +658,11 @@ func NewNetlinkRequest(proto, flags int) *NetlinkRequest {
 }
 
 type NetlinkSocket struct {
-	fd   int32
-	file *os.File
-	lsa  unix.SockaddrNetlink
+	fd             int32
+	file           *os.File
+	lsa            unix.SockaddrNetlink
+	sendTimeout    int64 // Access using atomic.Load/StoreInt64
+	receiveTimeout int64 // Access using atomic.Load/StoreInt64
 	sync.Mutex
 }
 
@@ -802,8 +806,44 @@ func (s *NetlinkSocket) GetFd() int {
 	return int(s.fd)
 }
 
+func (s *NetlinkSocket) GetTimeouts() (send, receive time.Duration) {
+	return time.Duration(atomic.LoadInt64(&s.sendTimeout)),
+		time.Duration(atomic.LoadInt64(&s.receiveTimeout))
+}
+
 func (s *NetlinkSocket) Send(request *NetlinkRequest) error {
-	return unix.Sendto(int(s.fd), request.Serialize(), 0, &s.lsa)
+	rawConn, err := s.file.SyscallConn()
+	if err != nil {
+		return err
+	}
+	var (
+		deadline time.Time
+		innerErr error
+	)
+	sendTimeout := atomic.LoadInt64(&s.sendTimeout)
+	if sendTimeout != 0 {
+		deadline = time.Now().Add(time.Duration(sendTimeout))
+	}
+	if err := s.file.SetWriteDeadline(deadline); err != nil {
+		return err
+	}
+	serializedReq := request.Serialize()
+	err = rawConn.Write(func(fd uintptr) (done bool) {
+		innerErr = unix.Sendto(int(s.fd), serializedReq, 0, &s.lsa)
+		return innerErr != unix.EWOULDBLOCK
+	})
+	if innerErr != nil {
+		return innerErr
+	}
+	if err != nil {
+		// The timeout was previously implemented using SO_SNDTIMEO on a blocking
+		// socket. So, continue to return EAGAIN when the timeout is reached.
+		if errors.Is(err, os.ErrDeadlineExceeded) {
+			return unix.EAGAIN
+		}
+		return err
+	}
+	return nil
 }
 
 func (s *NetlinkSocket) Receive() ([]syscall.NetlinkMessage, *unix.SockaddrNetlink, error) {
@@ -812,20 +852,33 @@ func (s *NetlinkSocket) Receive() ([]syscall.NetlinkMessage, *unix.SockaddrNetli
 		return nil, nil, err
 	}
 	var (
+		deadline time.Time
 		fromAddr *unix.SockaddrNetlink
 		rb       [RECEIVE_BUFFER_SIZE]byte
 		nr       int
 		from     unix.Sockaddr
 		innerErr error
 	)
+	receiveTimeout := atomic.LoadInt64(&s.receiveTimeout)
+	if receiveTimeout != 0 {
+		deadline = time.Now().Add(time.Duration(receiveTimeout))
+	}
+	if err := s.file.SetReadDeadline(deadline); err != nil {
+		return nil, nil, err
+	}
 	err = rawConn.Read(func(fd uintptr) (done bool) {
 		nr, from, innerErr = unix.Recvfrom(int(fd), rb[:], 0)
 		return innerErr != unix.EWOULDBLOCK
 	})
 	if innerErr != nil {
-		err = innerErr
+		return nil, nil, innerErr
 	}
 	if err != nil {
+		// The timeout was previously implemented using SO_RCVTIMEO on a blocking
+		// socket. So, continue to return EAGAIN when the timeout is reached.
+		if errors.Is(err, os.ErrDeadlineExceeded) {
+			return nil, nil, unix.EAGAIN
+		}
 		return nil, nil, err
 	}
 	fromAddr, ok := from.(*unix.SockaddrNetlink)
@@ -847,16 +900,14 @@ func (s *NetlinkSocket) Receive() ([]syscall.NetlinkMessage, *unix.SockaddrNetli
 
 // SetSendTimeout allows to set a send timeout on the socket
 func (s *NetlinkSocket) SetSendTimeout(timeout *unix.Timeval) error {
-	// Set a send timeout of SOCKET_SEND_TIMEOUT, this will allow the Send to periodically unblock and avoid that a routine
-	// remains stuck on a send on a closed fd
-	return unix.SetsockoptTimeval(int(s.fd), unix.SOL_SOCKET, unix.SO_SNDTIMEO, timeout)
+	atomic.StoreInt64(&s.sendTimeout, timeout.Nano())
+	return nil
 }
 
 // SetReceiveTimeout allows to set a receive timeout on the socket
 func (s *NetlinkSocket) SetReceiveTimeout(timeout *unix.Timeval) error {
-	// Set a read timeout of SOCKET_READ_TIMEOUT, this will allow the Read to periodically unblock and avoid that a routine
-	// remains stuck on a recvmsg on a closed fd
-	return unix.SetsockoptTimeval(int(s.fd), unix.SOL_SOCKET, unix.SO_RCVTIMEO, timeout)
+	atomic.StoreInt64(&s.receiveTimeout, timeout.Nano())
+	return nil
 }
 
 // SetReceiveBufferSize allows to set a receive buffer size on the socket

nl/nl_linux_test.go

@@ -97,6 +97,69 @@ func TestIfSocketCloses(t *testing.T) {
 	}
 }
 
+func TestReceiveTimeout(t *testing.T) {
+	nlSock, err := getNetlinkSocket(unix.NETLINK_ROUTE)
+	if err != nil {
+		t.Fatalf("Error creating the socket: %v", err)
+	}
+	// Even if the test fails because the timeout doesn't work, closing the
+	// socket at the end of the test should result in an EAGAIN (as long as
+	// TestIfSocketCloses completed, otherwise this test will leak the
+	// goroutines running the Receive).
+	defer nlSock.Close()
+	const failAfter = time.Second
+
+	tests := []struct {
+		name    string
+		timeout time.Duration
+	}{
+		{
+			name:    "1us timeout", // The smallest value accepted by Handle.SetSocketTimeout
+			timeout: time.Microsecond,
+		},
+		{
+			name:    "100ms timeout",
+			timeout: 100 * time.Millisecond,
+		},
+		{
+			name:    "500ms timeout",
+			timeout: 500 * time.Millisecond,
+		},
+	}
+	for _, tc := range tests {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			timeout := unix.NsecToTimeval(int64(tc.timeout))
+			nlSock.SetReceiveTimeout(&timeout)
+
+			doneC := make(chan time.Duration)
+			errC := make(chan error)
+			go func() {
+				start := time.Now()
+				_, _, err := nlSock.Receive()
+				dur := time.Since(start)
+				if err != unix.EAGAIN {
+					errC <- err
+					return
+				}
+				doneC <- dur
+			}()
+
+			failTimerC := time.After(failAfter)
+			select {
+			case dur := <-doneC:
+				if dur < tc.timeout || dur > (tc.timeout+(100*time.Millisecond)) {
+					t.Fatalf("Expected timeout %v got %v", tc.timeout, dur)
+				}
+			case err := <-errC:
+				t.Fatalf("Expected EAGAIN, but got: %v", err)
+			case <-failTimerC:
+				t.Fatalf("No timeout received")
+			}
+		})
+	}
+}
+
 func (msg *CnMsgOp) write(b []byte) {
 	native := NativeEndian()
 	native.PutUint32(b[0:4], msg.ID.Idx)