Add Sequence number to OpError type

conn_linux_error_test.go

@@ -37,15 +37,16 @@ func TestConnReceiveErrorLinux(t *testing.T) {
 				Header: netlink.Header{
 					Length:   20,
 					Type:     netlink.Error,
-					Sequence: 1,
+					Sequence: 1234,
 					PID:      1,
 				},
 				// -2, little endian (ENOENT)
 				Data: []byte{0xfe, 0xff, 0xff, 0xff},
 			}},
 			want: &netlink.OpError{
-				Op:  "receive",
-				Err: unix.ENOENT,
+				Op:       "receive",
+				Err:      unix.ENOENT,
+				Sequence: 1234,
 			},
 		},
 		{

errors.go

@@ -63,6 +63,11 @@ type OpError struct {
 	// library.
 	Err error
 
+	// Sequence contains the sequence number of the netlink message which caused
+	// this error. This will only be valid if Op is "receive", otherwise this
+	// field will be set to zero.
+	Sequence uint32
+
 	// Message and Offset contain additional error information provided by the
 	// kernel when the ExtendedAcknowledge option is set on a Conn and the
 	// kernel indicates the AcknowledgeTLVs flag in a response. If this option

message.go

@@ -276,24 +276,27 @@ func checkMessage(m Message) error {
 		return nil
 	}
 
+	oerr := &OpError{
+		Op: "receive",
+		Sequence: m.Header.Sequence,
+	}
+
 	// Errno occupies 4 bytes.
 	const endErrno = 4
 	if len(m.Data) < endErrno {
-		return newOpError("receive", errShortErrorMessage)
+		oerr.Err = errShortErrorMessage
+		return oerr
 	}
 
 	c := nlenc.Int32(m.Data[:endErrno])
 	if c == 0 {
 		// 0 indicates no error.
 		return nil
-	}
-
-	oerr := &OpError{
-		Op: "receive",
+	} else {
 		// Error code is a negative integer, convert it into an OS-specific raw
 		// system call error, but do not wrap with os.NewSyscallError to signify
 		// that this error was produced by a netlink message; not a system call.
-		Err: newError(-1 * int(c)),
+		oerr.Err = newError(-1 * int(c))
 	}
 
 	// TODO(mdlayher): investigate the Capped flag.
@@ -309,7 +312,8 @@ func checkMessage(m Message) error {
 	if hasHeader {
 		// There is an nlmsghdr preceding the TLVs.
 		if len(m.Data) < endErrno+nlmsgHeaderLen {
-			return newOpError("receive", errShortErrorMessage)
+			oerr.Err = errShortErrorMessage
+			return oerr
 		}
 
 		// The TLVs should be at the offset indicated by the nlmsghdr.length,
@@ -319,7 +323,8 @@ func checkMessage(m Message) error {
 		off = endErrno + int(h.Length)
 
 		if len(m.Data) < off {
-			return newOpError("receive", errShortErrorMessage)
+			oerr.Err = errShortErrorMessage
+			return oerr
 		}
 	} else {
 		// There is no nlmsghdr preceding the TLVs, parse them directly.