Add gPXE into the source tree; build unified imagesyslinux-3.70-pre7

1 files changed, 584 insertions, 0 deletions

diff --git a/gpxe/src/interface/pxe/pxe_tftp.c b/gpxe/src/interface/pxe/pxe_tftp.c
new file mode 100644
index 00000000..976298a8
--- /dev/null
+++ b/gpxe/src/interface/pxe/pxe_tftp.c
@@ -0,0 +1,584 @@
+/** @file
+ *
+ * PXE TFTP API
+ *
+ */
+
+/*
+ * Copyright (C) 2004 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <errno.h>
+#include <byteswap.h>
+#include <gpxe/uaccess.h>
+#include <gpxe/in.h>
+#include <gpxe/tftp.h>
+#include <gpxe/xfer.h>
+#include <gpxe/open.h>
+#include <gpxe/process.h>
+#include <pxe.h>
+
+/** A PXE TFTP connection */
+struct pxe_tftp_connection {
+	/** Data transfer interface */
+	struct xfer_interface xfer;
+	/** Data buffer */
+	userptr_t buffer;
+	/** Size of data buffer */
+	size_t size;
+	/** Starting offset of data buffer */
+	size_t start;
+	/** File position */
+	size_t offset;
+	/** Maximum file position */
+	size_t max_offset;
+	/** Block size */
+	size_t blksize;
+	/** Block index */
+	unsigned int blkidx;
+	/** Overall return status code */
+	int rc;
+};
+
+/** The PXE TFTP connection */
+static struct pxe_tftp_connection pxe_tftp = {
+	.xfer = XFER_INIT ( &null_xfer_ops ),
+};
+
+/**
+ * Close PXE TFTP connection
+ *
+ * @v rc		Final status code
+ */
+static void pxe_tftp_close ( int rc ) {
+	xfer_nullify ( &pxe_tftp.xfer );
+	xfer_close ( &pxe_tftp.xfer, rc );
+	pxe_tftp.rc = rc;
+}
+
+/**
+ * Receive new data
+ *
+ * @v xfer		Data transfer interface
+ * @v iobuf		I/O buffer
+ * @v meta		Transfer metadata
+ * @ret rc		Return status code
+ */
+static int pxe_tftp_xfer_deliver_iob ( struct xfer_interface *xfer __unused,
+				       struct io_buffer *iobuf,
+				       struct xfer_metadata *meta ) {
+	size_t len = iob_len ( iobuf );
+	int rc = 0;
+
+	/* Calculate new buffer position */
+	if ( meta->whence != SEEK_CUR )
+		pxe_tftp.offset = 0;
+	pxe_tftp.offset += meta->offset;
+
+	/* Copy data block to buffer */
+	if ( len == 0 ) {
+		/* No data (pure seek); treat as success */
+	} else if ( pxe_tftp.offset < pxe_tftp.start ) {
+		DBG ( " buffer underrun at %zx (min %zx)",
+		      pxe_tftp.offset, pxe_tftp.start );
+		rc = -ENOBUFS;
+	} else if ( ( pxe_tftp.offset + len ) >
+		    ( pxe_tftp.start + pxe_tftp.size ) ) {
+		DBG ( " buffer overrun at %zx (max %zx)",
+		      ( pxe_tftp.offset + len ),
+		      ( pxe_tftp.start + pxe_tftp.size ) );
+		rc = -ENOBUFS;
+	} else {
+		copy_to_user ( pxe_tftp.buffer,
+			       ( pxe_tftp.offset - pxe_tftp.start ),
+			       iobuf->data, len );
+	}
+
+	/* Calculate new buffer position */
+	pxe_tftp.offset += len;
+
+	/* Mildly ugly hack; assume that the first non-zero seek
+	 * indicates the block size.
+	 */
+	if ( pxe_tftp.blksize == 0 )
+		pxe_tftp.blksize = pxe_tftp.offset;
+
+	/* Record maximum offset as the file size */
+	if ( pxe_tftp.max_offset < pxe_tftp.offset )
+		pxe_tftp.max_offset = pxe_tftp.offset;
+
+	/* Terminate transfer on error */
+	if ( rc != 0 )
+		pxe_tftp_close ( rc );
+
+	free_iob ( iobuf );
+	return rc;
+}
+
+/**
+ * Handle close() event
+ *
+ * @v xfer		Data transfer interface
+ * @v rc		Reason for close
+ */
+static void pxe_tftp_xfer_close ( struct xfer_interface *xfer __unused,
+				  int rc ) {
+	pxe_tftp_close ( rc );
+}
+
+static struct xfer_interface_operations pxe_tftp_xfer_ops = {
+	.close		= pxe_tftp_xfer_close,
+	.vredirect	= xfer_vopen,
+	.window		= unlimited_xfer_window,
+	.alloc_iob	= default_xfer_alloc_iob,
+	.deliver_iob	= pxe_tftp_xfer_deliver_iob,
+	.deliver_raw	= xfer_deliver_as_iob,
+};
+
+/**
+ * Maximum length of a PXE TFTP URI
+ *
+ * The PXE TFTP API provides 128 characters for the filename; the
+ * extra 128 bytes allow for the remainder of the URI.
+ */
+#define PXE_TFTP_URI_LEN 256
+
+/**
+ * Open PXE TFTP connection
+ *
+ * @v ipaddress		IP address
+ * @v port		TFTP server port
+ * @v filename		File name
+ * @v blksize		Requested block size
+ * @ret rc		Return status code
+ */
+static int pxe_tftp_open ( uint32_t ipaddress, unsigned int port,
+			   const unsigned char *filename, size_t blksize ) {
+	char uri_string[PXE_TFTP_URI_LEN];
+	struct in_addr address;
+	int rc;
+
+	/* Intel bug-for-bug hack */
+	pxe_set_cached_filename ( filename );
+
+	/* Reset PXE TFTP connection structure */
+	memset ( &pxe_tftp, 0, sizeof ( pxe_tftp ) );
+	xfer_init ( &pxe_tftp.xfer, &pxe_tftp_xfer_ops, NULL );
+	pxe_tftp.rc = -EINPROGRESS;
+
+	/* Construct URI string */
+	address.s_addr = ipaddress;
+	if ( ! port )
+		port = htons ( TFTP_PORT );
+	if ( blksize < TFTP_DEFAULT_BLKSIZE )
+		blksize = TFTP_DEFAULT_BLKSIZE;
+	snprintf ( uri_string, sizeof ( uri_string ),
+		   "tftp://%s:%d%s%s?blksize=%d",
+		   inet_ntoa ( address ), ntohs ( port ),
+		   ( ( filename[0] == '/' ) ? "" : "/" ), filename, blksize );
+	DBG ( " %s", uri_string );
+
+	/* Open PXE TFTP connection */
+	if ( ( rc = xfer_open_uri_string ( &pxe_tftp.xfer,
+					   uri_string ) ) != 0 ) {
+		DBG ( " could not open (%s)\n", strerror ( rc ) );
+		return rc;
+	}
+
+	return 0;
+}
+
+/**
+ * TFTP OPEN
+ *
+ * @v tftp_open				Pointer to a struct s_PXENV_TFTP_OPEN
+ * @v s_PXENV_TFTP_OPEN::ServerIPAddress TFTP server IP address
+ * @v s_PXENV_TFTP_OPEN::GatewayIPAddress Relay agent IP address, or 0.0.0.0
+ * @v s_PXENV_TFTP_OPEN::FileName	Name of file to open
+ * @v s_PXENV_TFTP_OPEN::TFTPPort	TFTP server UDP port
+ * @v s_PXENV_TFTP_OPEN::PacketSize	TFTP blksize option to request
+ * @ret #PXENV_EXIT_SUCCESS		File was opened
+ * @ret #PXENV_EXIT_FAILURE		File was not opened
+ * @ret s_PXENV_TFTP_OPEN::Status	PXE status code
+ * @ret s_PXENV_TFTP_OPEN::PacketSize	Negotiated blksize
+ * @err #PXENV_STATUS_TFTP_INVALID_PACKET_SIZE Requested blksize too small
+ *
+ * Opens a TFTP connection for downloading a file a block at a time
+ * using pxenv_tftp_read().
+ *
+ * If s_PXENV_TFTP_OPEN::GatewayIPAddress is 0.0.0.0, normal IP
+ * routing will take place.  See the relevant
+ * @ref pxe_routing "implementation note" for more details.
+ *
+ * On x86, you must set the s_PXE::StatusCallout field to a nonzero
+ * value before calling this function in protected mode.  You cannot
+ * call this function with a 32-bit stack segment.  (See the relevant
+ * @ref pxe_x86_pmode16 "implementation note" for more details.)
+ * 
+ * @note According to the PXE specification version 2.1, this call
+ * "opens a file for reading/writing", though how writing is to be
+ * achieved without the existence of an API call %pxenv_tftp_write()
+ * is not made clear.
+ *
+ * @note Despite the existence of the numerous statements within the
+ * PXE specification of the form "...if a TFTP/MTFTP or UDP connection
+ * is active...", you cannot use pxenv_tftp_open() and
+ * pxenv_tftp_read() to read a file via MTFTP; only via plain old
+ * TFTP.  If you want to use MTFTP, use pxenv_tftp_read_file()
+ * instead.  Astute readers will note that, since
+ * pxenv_tftp_read_file() is an atomic operation from the point of
+ * view of the PXE API, it is conceptually impossible to issue any
+ * other PXE API call "if an MTFTP connection is active".
+ */
+PXENV_EXIT_t pxenv_tftp_open ( struct s_PXENV_TFTP_OPEN *tftp_open ) {
+	int rc;
+
+	DBG ( "PXENV_TFTP_OPEN" );
+
+	/* Guard against callers that fail to close before re-opening */
+	pxe_tftp_close ( 0 );
+
+	/* Open connection */
+	if ( ( rc = pxe_tftp_open ( tftp_open->ServerIPAddress,
+				    tftp_open->TFTPPort,
+				    tftp_open->FileName,
+				    tftp_open->PacketSize ) ) != 0 ) {
+		tftp_open->Status = PXENV_STATUS ( rc );
+		return PXENV_EXIT_FAILURE;
+	}
+
+	/* Wait for OACK to arrive so that we have the block size */
+	while ( ( ( rc = pxe_tftp.rc ) == -EINPROGRESS ) &&
+		( pxe_tftp.blksize == 0 ) ) {
+		step();
+	}
+	tftp_open->PacketSize = pxe_tftp.blksize;
+
+	/* EINPROGRESS is normal; we don't wait for the whole transfer */
+	if ( rc == -EINPROGRESS )
+		rc = 0;
+
+	tftp_open->Status = PXENV_STATUS ( rc );
+	return ( rc ? PXENV_EXIT_FAILURE : PXENV_EXIT_SUCCESS );
+}
+
+/**
+ * TFTP CLOSE
+ *
+ * @v tftp_close			Pointer to a struct s_PXENV_TFTP_CLOSE
+ * @ret #PXENV_EXIT_SUCCESS		File was closed successfully
+ * @ret #PXENV_EXIT_FAILURE		File was not closed
+ * @ret s_PXENV_TFTP_CLOSE::Status	PXE status code
+ * @err None				-
+ *
+ * Close a connection previously opened with pxenv_tftp_open().  You
+ * must have previously opened a connection with pxenv_tftp_open().
+ *
+ * On x86, you must set the s_PXE::StatusCallout field to a nonzero
+ * value before calling this function in protected mode.  You cannot
+ * call this function with a 32-bit stack segment.  (See the relevant
+ * @ref pxe_x86_pmode16 "implementation note" for more details.)
+ */
+PXENV_EXIT_t pxenv_tftp_close ( struct s_PXENV_TFTP_CLOSE *tftp_close ) {
+	DBG ( "PXENV_TFTP_CLOSE" );
+
+	pxe_tftp_close ( 0 );
+	tftp_close->Status = PXENV_STATUS_SUCCESS;
+	return PXENV_EXIT_SUCCESS;
+}
+
+/**
+ * TFTP READ
+ *
+ * @v tftp_read				Pointer to a struct s_PXENV_TFTP_READ
+ * @v s_PXENV_TFTP_READ::Buffer		Address of data buffer
+ * @ret #PXENV_EXIT_SUCCESS		Data was read successfully
+ * @ret #PXENV_EXIT_FAILURE		Data was not read
+ * @ret s_PXENV_TFTP_READ::Status	PXE status code
+ * @ret s_PXENV_TFTP_READ::PacketNumber	TFTP packet number
+ * @ret s_PXENV_TFTP_READ::BufferSize	Length of data written into buffer
+ *
+ * Reads a single packet from a connection previously opened with
+ * pxenv_tftp_open() into the data buffer pointed to by
+ * s_PXENV_TFTP_READ::Buffer.  You must have previously opened a
+ * connection with pxenv_tftp_open().  The data written into
+ * s_PXENV_TFTP_READ::Buffer is just the file data; the various
+ * network headers have already been removed.
+ *
+ * The buffer must be large enough to contain a packet of the size
+ * negotiated via the s_PXENV_TFTP_OPEN::PacketSize field in the
+ * pxenv_tftp_open() call.  It is worth noting that the PXE
+ * specification does @b not require the caller to fill in
+ * s_PXENV_TFTP_READ::BufferSize before calling pxenv_tftp_read(), so
+ * the PXE stack is free to ignore whatever value the caller might
+ * place there and just assume that the buffer is large enough.  That
+ * said, it may be worth the caller always filling in
+ * s_PXENV_TFTP_READ::BufferSize to guard against PXE stacks that
+ * mistake it for an input parameter.
+ *
+ * The length of the TFTP data packet will be returned via
+ * s_PXENV_TFTP_READ::BufferSize.  If this length is less than the
+ * blksize negotiated via s_PXENV_TFTP_OPEN::PacketSize in the call to
+ * pxenv_tftp_open(), this indicates that the block is the last block
+ * in the file.  Note that zero is a valid length for
+ * s_PXENV_TFTP_READ::BufferSize, and will occur when the length of
+ * the file is a multiple of the blksize.
+ *
+ * The PXE specification doesn't actually state that calls to
+ * pxenv_tftp_read() will return the data packets in strict sequential
+ * order, though most PXE stacks will probably do so.  The sequence
+ * number of the packet will be returned in
+ * s_PXENV_TFTP_READ::PacketNumber.  The first packet in the file has
+ * a sequence number of one, not zero.
+ *
+ * To guard against flawed PXE stacks, the caller should probably set
+ * s_PXENV_TFTP_READ::PacketNumber to one less than the expected
+ * returned value (i.e. set it to zero for the first call to
+ * pxenv_tftp_read() and then re-use the returned s_PXENV_TFTP_READ
+ * parameter block for subsequent calls without modifying
+ * s_PXENV_TFTP_READ::PacketNumber between calls).  The caller should
+ * also guard against potential problems caused by flawed
+ * implementations returning the occasional duplicate packet, by
+ * checking that the value returned in s_PXENV_TFTP_READ::PacketNumber
+ * is as expected (i.e. one greater than that returned from the
+ * previous call to pxenv_tftp_read()).
+ *
+ * On x86, you must set the s_PXE::StatusCallout field to a nonzero
+ * value before calling this function in protected mode.  You cannot
+ * call this function with a 32-bit stack segment.  (See the relevant
+ * @ref pxe_x86_pmode16 "implementation note" for more details.)
+ */
+PXENV_EXIT_t pxenv_tftp_read ( struct s_PXENV_TFTP_READ *tftp_read ) {
+	int rc;
+
+	DBG ( "PXENV_TFTP_READ to %04x:%04x",
+	      tftp_read->Buffer.segment, tftp_read->Buffer.offset );
+
+	/* Read single block into buffer */
+	pxe_tftp.buffer = real_to_user ( tftp_read->Buffer.segment,
+					 tftp_read->Buffer.offset );
+	pxe_tftp.size = pxe_tftp.blksize;
+	pxe_tftp.start = pxe_tftp.offset;
+	while ( ( ( rc = pxe_tftp.rc ) == -EINPROGRESS ) &&
+		( pxe_tftp.offset == pxe_tftp.start ) )
+		step();
+	pxe_tftp.buffer = UNULL;
+	tftp_read->BufferSize = ( pxe_tftp.offset - pxe_tftp.start );
+	tftp_read->PacketNumber = ++pxe_tftp.blkidx;
+
+	/* EINPROGRESS is normal if we haven't reached EOF yet */
+	if ( rc == -EINPROGRESS )
+		rc = 0;
+
+	tftp_read->Status = PXENV_STATUS ( rc );
+	return ( rc ? PXENV_EXIT_FAILURE : PXENV_EXIT_SUCCESS );
+}
+
+/**
+ * TFTP/MTFTP read file
+ *
+ * @v tftp_read_file		     Pointer to a struct s_PXENV_TFTP_READ_FILE
+ * @v s_PXENV_TFTP_READ_FILE::FileName		File name
+ * @v s_PXENV_TFTP_READ_FILE::BufferSize 	Size of the receive buffer
+ * @v s_PXENV_TFTP_READ_FILE::Buffer		Address of the receive buffer
+ * @v s_PXENV_TFTP_READ_FILE::ServerIPAddress	TFTP server IP address
+ * @v s_PXENV_TFTP_READ_FILE::GatewayIPAddress	Relay agent IP address
+ * @v s_PXENV_TFTP_READ_FILE::McastIPAddress	File's multicast IP address
+ * @v s_PXENV_TFTP_READ_FILE::TFTPClntPort	Client multicast UDP port
+ * @v s_PXENV_TFTP_READ_FILE::TFTPSrvPort	Server multicast UDP port
+ * @v s_PXENV_TFTP_READ_FILE::TFTPOpenTimeOut	Time to wait for first packet
+ * @v s_PXENV_TFTP_READ_FILE::TFTPReopenDelay	MTFTP inactivity timeout
+ * @ret #PXENV_EXIT_SUCCESS			File downloaded successfully
+ * @ret #PXENV_EXIT_FAILURE			File not downloaded
+ * @ret s_PXENV_TFTP_READ_FILE::Status		PXE status code
+ * @ret s_PXENV_TFTP_READ_FILE::BufferSize	Length of downloaded file
+ *
+ * Downloads an entire file via either TFTP or MTFTP into the buffer
+ * pointed to by s_PXENV_TFTP_READ_FILE::Buffer.
+ *
+ * The PXE specification does not make it clear how the caller
+ * requests that MTFTP be used rather than TFTP (or vice versa).  One
+ * reasonable guess is that setting
+ * s_PXENV_TFTP_READ_FILE::McastIPAddress to 0.0.0.0 would cause TFTP
+ * to be used instead of MTFTP, though it is conceivable that some PXE
+ * stacks would interpret that as "use the DHCP-provided multicast IP
+ * address" instead.  Some PXE stacks will not implement MTFTP at all,
+ * and will always use TFTP.
+ *
+ * It is not specified whether or not
+ * s_PXENV_TFTP_READ_FILE::TFTPSrvPort will be used as the TFTP server
+ * port for TFTP (rather than MTFTP) downloads.  Callers should assume
+ * that the only way to access a TFTP server on a non-standard port is
+ * to use pxenv_tftp_open() and pxenv_tftp_read().
+ *
+ * If s_PXENV_TFTP_READ_FILE::GatewayIPAddress is 0.0.0.0, normal IP
+ * routing will take place.  See the relevant
+ * @ref pxe_routing "implementation note" for more details.
+ *
+ * It is interesting to note that s_PXENV_TFTP_READ_FILE::Buffer is an
+ * #ADDR32_t type, i.e. nominally a flat physical address.  Some PXE
+ * NBPs (e.g. NTLDR) are known to call pxenv_tftp_read_file() in real
+ * mode with s_PXENV_TFTP_READ_FILE::Buffer set to an address above
+ * 1MB.  This means that PXE stacks must be prepared to write to areas
+ * outside base memory.  Exactly how this is to be achieved is not
+ * specified, though using INT 15,87 is as close to a standard method
+ * as any, and should probably be used.  Switching to protected-mode
+ * in order to access high memory will fail if pxenv_tftp_read_file()
+ * is called in V86 mode; it is reasonably to expect that a V86
+ * monitor would intercept the relatively well-defined INT 15,87 if it
+ * wants the PXE stack to be able to write to high memory.
+ *
+ * Things get even more interesting if pxenv_tftp_read_file() is
+ * called in protected mode, because there is then absolutely no way
+ * for the PXE stack to write to an absolute physical address.  You
+ * can't even get around the problem by creating a special "access
+ * everything" segment in the s_PXE data structure, because the
+ * #SEGDESC_t descriptors are limited to 64kB in size.
+ *
+ * Previous versions of the PXE specification (e.g. WfM 1.1a) provide
+ * a separate API call, %pxenv_tftp_read_file_pmode(), specifically to
+ * work around this problem.  The s_PXENV_TFTP_READ_FILE_PMODE
+ * parameter block splits s_PXENV_TFTP_READ_FILE::Buffer into
+ * s_PXENV_TFTP_READ_FILE_PMODE::BufferSelector and
+ * s_PXENV_TFTP_READ_FILE_PMODE::BufferOffset, i.e. it provides a
+ * protected-mode segment:offset address for the data buffer.  This
+ * API call is no longer present in version 2.1 of the PXE
+ * specification.
+ *
+ * Etherboot makes the assumption that s_PXENV_TFTP_READ_FILE::Buffer
+ * is an offset relative to the caller's data segment, when
+ * pxenv_tftp_read_file() is called in protected mode.
+ *
+ * On x86, you must set the s_PXE::StatusCallout field to a nonzero
+ * value before calling this function in protected mode.  You cannot
+ * call this function with a 32-bit stack segment.  (See the relevant
+ * @ref pxe_x86_pmode16 "implementation note" for more details.)
+ *
+ * @note Microsoft's NTLDR assumes that the filename passed in via
+ * s_PXENV_TFTP_READ_FILE::FileName will be stored in the "file" field
+ * of the stored DHCPACK packet, whence it will be returned via any
+ * subsequent calls to pxenv_get_cached_info().  Though this is
+ * essentially a bug in the Intel PXE implementation (not, for once,
+ * in the specification!), it is a bug that Microsoft relies upon, and
+ * so we implement this bug-for-bug compatibility by overwriting the
+ * filename stored DHCPACK packet with the filename passed in
+ * s_PXENV_TFTP_READ_FILE::FileName.
+ *
+ */
+PXENV_EXIT_t pxenv_tftp_read_file ( struct s_PXENV_TFTP_READ_FILE
+				    *tftp_read_file ) {
+	int rc;
+
+	DBG ( "PXENV_TFTP_READ_FILE to %08lx+%lx", tftp_read_file->Buffer,
+	      tftp_read_file->BufferSize );
+
+	/* Open TFTP file */
+	if ( ( rc = pxe_tftp_open ( tftp_read_file->ServerIPAddress, 0,
+				    tftp_read_file->FileName, 0 ) ) != 0 ) {
+		tftp_read_file->Status = PXENV_STATUS ( rc );
+		return PXENV_EXIT_FAILURE;
+	}
+
+	/* Read entire file */
+	pxe_tftp.buffer = phys_to_user ( tftp_read_file->Buffer );
+	pxe_tftp.size = tftp_read_file->BufferSize;
+	while ( ( rc = pxe_tftp.rc ) == -EINPROGRESS )
+		step();
+	pxe_tftp.buffer = UNULL;
+	tftp_read_file->BufferSize = pxe_tftp.max_offset;
+
+	/* Close TFTP file */
+	pxe_tftp_close ( rc );
+
+	tftp_read_file->Status = PXENV_STATUS ( rc );
+	return ( rc ? PXENV_EXIT_FAILURE : PXENV_EXIT_SUCCESS );
+}
+
+/**
+ * TFTP GET FILE SIZE
+ *
+ * @v tftp_get_fsize		     Pointer to a struct s_PXENV_TFTP_GET_FSIZE
+ * @v s_PXENV_TFTP_GET_FSIZE::ServerIPAddress	TFTP server IP address
+ * @v s_PXENV_TFTP_GET_FSIZE::GatewayIPAddress	Relay agent IP address
+ * @v s_PXENV_TFTP_GET_FSIZE::FileName	File name
+ * @ret #PXENV_EXIT_SUCCESS		File size was determined successfully
+ * @ret #PXENV_EXIT_FAILURE		File size was not determined
+ * @ret s_PXENV_TFTP_GET_FSIZE::Status	PXE status code
+ * @ret s_PXENV_TFTP_GET_FSIZE::FileSize	File size
+ *
+ * Determine the size of a file on a TFTP server.  This uses the
+ * "tsize" TFTP option, and so will not work with a TFTP server that
+ * does not support TFTP options, or that does not support the "tsize"
+ * option.
+ *
+ * The PXE specification states that this API call will @b not open a
+ * TFTP connection for subsequent use with pxenv_tftp_read().  (This
+ * is somewhat daft, since the only way to obtain the file size via
+ * the "tsize" option involves issuing a TFTP open request, but that's
+ * life.)
+ *
+ * You cannot call pxenv_tftp_get_fsize() while a TFTP or UDP
+ * connection is open.
+ *
+ * If s_PXENV_TFTP_GET_FSIZE::GatewayIPAddress is 0.0.0.0, normal IP
+ * routing will take place.  See the relevant
+ * @ref pxe_routing "implementation note" for more details.
+ *
+ * On x86, you must set the s_PXE::StatusCallout field to a nonzero
+ * value before calling this function in protected mode.  You cannot
+ * call this function with a 32-bit stack segment.  (See the relevant
+ * @ref pxe_x86_pmode16 "implementation note" for more details.)
+ * 
+ * @note There is no way to specify the TFTP server port with this API
+ * call.  Though you can open a file using a non-standard TFTP server
+ * port (via s_PXENV_TFTP_OPEN::TFTPPort or, potentially,
+ * s_PXENV_TFTP_READ_FILE::TFTPSrvPort), you can only get the size of
+ * a file from a TFTP server listening on the standard TFTP port.
+ * "Consistency" is not a word in Intel's vocabulary.
+ */
+PXENV_EXIT_t pxenv_tftp_get_fsize ( struct s_PXENV_TFTP_GET_FSIZE
+				    *tftp_get_fsize ) {
+	int rc;
+
+	DBG ( "PXENV_TFTP_GET_FSIZE" );
+
+	/* Open TFTP file */
+	if ( ( rc = pxe_tftp_open ( tftp_get_fsize->ServerIPAddress, 0,
+				    tftp_get_fsize->FileName, 0 ) ) != 0 ) {
+		tftp_get_fsize->Status = PXENV_STATUS ( rc );
+		return PXENV_EXIT_FAILURE;
+	}
+
+	/* Wait for initial seek to arrive, and record size */
+	while ( ( ( rc = pxe_tftp.rc ) == -EINPROGRESS ) &&
+		( pxe_tftp.max_offset == 0 ) ) {
+		step();
+	}
+	tftp_get_fsize->FileSize = pxe_tftp.max_offset;
+
+	/* EINPROGRESS is normal; we don't wait for the whole transfer */
+	if ( rc == -EINPROGRESS )
+		rc = 0;
+
+	/* Close TFTP file */
+	pxe_tftp_close ( rc );
+
+	tftp_get_fsize->Status = PXENV_STATUS ( rc );
+	return ( rc ? PXENV_EXIT_FAILURE : PXENV_EXIT_SUCCESS );
+}