[tftp] Explicitly abort connection whenever parent interface is closed

Fetching the TFTP file size is currently implemented via a custom
"tftpsize://" protocol hack.  Generalise this approach to instead
close the TFTP connection whenever the parent data-transfer interface
is closed.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/arch/i386/interface/pxe/pxe_tftp.c

  * @ret rc		Return status code
  */
 static int pxe_tftp_open ( uint32_t ipaddress, unsigned int port,
-			   const unsigned char *filename, size_t blksize,
-			   int sizeonly ) {
+			   const unsigned char *filename, size_t blksize ) {
 	char uri_string[PXE_TFTP_URI_LEN];
 	struct in_addr address;
 	int rc;
 	address.s_addr = ipaddress;
 	if ( ! port )
 		port = htons ( TFTP_PORT );
-	snprintf ( uri_string, sizeof ( uri_string ), "tftp%s://%s:%d%s%s",
-		   sizeonly ? "size" : "", inet_ntoa ( address ),
-		   ntohs ( port ), ( ( filename[0] == '/' ) ? "" : "/" ),
-		   filename );
+	snprintf ( uri_string, sizeof ( uri_string ), "tftp://%s:%d%s%s",
+		   inet_ntoa ( address ), ntohs ( port ),
+		   ( ( filename[0] == '/' ) ? "" : "/" ), filename );
 	DBG ( " %s", uri_string );
 
 	/* Open PXE TFTP connection */
 	if ( ( rc = pxe_tftp_open ( tftp_open->ServerIPAddress,
 				    tftp_open->TFTPPort,
 				    tftp_open->FileName,
-				    tftp_open->PacketSize,
-				    0) ) != 0 ) {
+				    tftp_open->PacketSize ) ) != 0 ) {
 		tftp_open->Status = PXENV_STATUS ( rc );
 		return PXENV_EXIT_FAILURE;
 	}
 
 	/* Open TFTP file */
 	if ( ( rc = pxe_tftp_open ( tftp_read_file->ServerIPAddress, 0,
-				    tftp_read_file->FileName, 0, 0 ) ) != 0 ) {
+				    tftp_read_file->FileName, 0 ) ) != 0 ) {
 		tftp_read_file->Status = PXENV_STATUS ( rc );
 		return PXENV_EXIT_FAILURE;
 	}
 
 	/* Open TFTP file */
 	if ( ( rc = pxe_tftp_open ( tftp_get_fsize->ServerIPAddress, 0,
-				    tftp_get_fsize->FileName, 0, 1 ) ) != 0 ) {
+				    tftp_get_fsize->FileName, 0 ) ) != 0 ) {
 		tftp_get_fsize->Status = PXENV_STATUS ( rc );
 		return PXENV_EXIT_FAILURE;
 	}

src/net/udp/tftp.c

 	TFTP_FL_RRQ_MULTICAST = 0x0004,
 	/** Perform MTFTP recovery on timeout */
 	TFTP_FL_MTFTP_RECOVERY = 0x0008,
-	/** Only get filesize and then abort the transfer */
-	TFTP_FL_SIZEONLY = 0x0010,
 };
 
 /** Maximum number of MTFTP open requests before falling back to TFTP */
 			goto done;
 	}
 
-	/* Abort request if only trying to determine file size */
-	if ( tftp->flags & TFTP_FL_SIZEONLY ) {
-		rc = 0;
-		tftp_send_error ( tftp, 0, "TFTP Aborted" );
-		tftp_done ( tftp, rc );
-		return rc;
-	}
-
 	/* Request next data block */
 	tftp_send_packet ( tftp );
 
 	size_t data_len;
 	int rc;
 
-	if ( tftp->flags & TFTP_FL_SIZEONLY ) {
-		/* If we get here then server doesn't support SIZE option */
-		rc = -ENOTSUP;
-		tftp_send_error ( tftp, 0, "TFTP Aborted" );
-		goto done;
-	}
-
 	/* Sanity check */
 	if ( iob_len ( iobuf ) < sizeof ( *data ) ) {
 		DBGC ( tftp, "TFTP %p received underlength DATA packet "
 	return tftp->blksize;
 }
 
+/**
+ * Terminate download
+ *
+ * @v tftp		TFTP connection
+ * @v rc		Reason for close
+ */
+static void tftp_close ( struct tftp_request *tftp, int rc ) {
+
+	/* Abort download */
+	tftp_send_error ( tftp, 0, "TFTP Aborted" );
+
+	/* Close TFTP request */
+	tftp_done ( tftp, rc );
+}
+
 /** TFTP data transfer interface operations */
 static struct interface_operation tftp_xfer_operations[] = {
 	INTF_OP ( xfer_window, struct tftp_request *, tftp_xfer_window ),
-	INTF_OP ( intf_close, struct tftp_request *, tftp_done ),
+	INTF_OP ( intf_close, struct tftp_request *, tftp_close ),
 };
 
 /** TFTP data transfer interface descriptor */
 	.open	= tftp_open,
 };
 
-/**
- * Initiate TFTP-size request
- *
- * @v xfer		Data transfer interface
- * @v uri		Uniform Resource Identifier
- * @ret rc		Return status code
- */
-static int tftpsize_open ( struct interface *xfer, struct uri *uri ) {
-	return tftp_core_open ( xfer, uri, TFTP_PORT, NULL,
-				( TFTP_FL_RRQ_SIZES |
-				  TFTP_FL_SIZEONLY ) );
-
-}
-
-/** TFTP URI opener */
-struct uri_opener tftpsize_uri_opener __uri_opener = {
-	.scheme	= "tftpsize",
-	.open	= tftpsize_open,
-};
-
 /**
  * Initiate TFTM download
  *