--- /dev/null
+/*
+ * Copyright (C) 2008 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., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+#include <ipxe/dhcp.h>
+#include <ipxe/dhcpopts.h>
+
+/** @file
+ *
+ * DHCP options
+ *
+ */
+
+/**
+ * Obtain printable version of a DHCP option tag
+ *
+ * @v tag DHCP option tag
+ * @ret name String representation of the tag
+ *
+ */
+static inline char * dhcp_tag_name ( unsigned int tag ) {
+ static char name[8];
+
+ if ( DHCP_IS_ENCAP_OPT ( tag ) ) {
+ snprintf ( name, sizeof ( name ), "%d.%d",
+ DHCP_ENCAPSULATOR ( tag ),
+ DHCP_ENCAPSULATED ( tag ) );
+ } else {
+ snprintf ( name, sizeof ( name ), "%d", tag );
+ }
+ return name;
+}
+
+/**
+ * Get pointer to DHCP option
+ *
+ * @v options DHCP options block
+ * @v offset Offset within options block
+ * @ret option DHCP option
+ */
+static inline __attribute__ (( always_inline )) struct dhcp_option *
+dhcp_option ( struct dhcp_options *options, unsigned int offset ) {
+ return ( ( struct dhcp_option * ) ( options->data + offset ) );
+}
+
+/**
+ * Get offset of a DHCP option
+ *
+ * @v options DHCP options block
+ * @v option DHCP option
+ * @ret offset Offset within options block
+ */
+static inline __attribute__ (( always_inline )) int
+dhcp_option_offset ( struct dhcp_options *options,
+ struct dhcp_option *option ) {
+ return ( ( ( void * ) option ) - options->data );
+}
+
+/**
+ * Calculate length of any DHCP option
+ *
+ * @v option DHCP option
+ * @ret len Length (including tag and length field)
+ */
+static unsigned int dhcp_option_len ( struct dhcp_option *option ) {
+ if ( ( option->tag == DHCP_END ) || ( option->tag == DHCP_PAD ) ) {
+ return 1;
+ } else {
+ return ( option->len + DHCP_OPTION_HEADER_LEN );
+ }
+}
+
+/**
+ * Find DHCP option within DHCP options block, and its encapsulator (if any)
+ *
+ * @v options DHCP options block
+ * @v tag DHCP option tag to search for
+ * @ret encap_offset Offset of encapsulating DHCP option
+ * @ret offset Offset of DHCP option, or negative error
+ *
+ * Searches for the DHCP option matching the specified tag within the
+ * DHCP option block. Encapsulated options may be searched for by
+ * using DHCP_ENCAP_OPT() to construct the tag value.
+ *
+ * If the option is encapsulated, and @c encap_offset is non-NULL, it
+ * will be filled in with the offset of the encapsulating option.
+ *
+ * This routine is designed to be paranoid. It does not assume that
+ * the option data is well-formatted, and so must guard against flaws
+ * such as options missing a @c DHCP_END terminator, or options whose
+ * length would take them beyond the end of the data block.
+ */
+static int find_dhcp_option_with_encap ( struct dhcp_options *options,
+ unsigned int tag,
+ int *encap_offset ) {
+ unsigned int original_tag __attribute__ (( unused )) = tag;
+ struct dhcp_option *option;
+ int offset = 0;
+ ssize_t remaining = options->used_len;
+ unsigned int option_len;
+
+ /* Sanity check */
+ if ( tag == DHCP_PAD )
+ return -ENOENT;
+
+ /* Search for option */
+ while ( remaining ) {
+ /* Calculate length of this option. Abort processing
+ * if the length is malformed (i.e. takes us beyond
+ * the end of the data block).
+ */
+ option = dhcp_option ( options, offset );
+ option_len = dhcp_option_len ( option );
+ remaining -= option_len;
+ if ( remaining < 0 )
+ break;
+ /* Check for explicit end marker */
+ if ( option->tag == DHCP_END ) {
+ if ( tag == DHCP_END )
+ /* Special case where the caller is interested
+ * in whether we have this marker or not.
+ */
+ return offset;
+ else
+ break;
+ }
+ /* Check for matching tag */
+ if ( option->tag == tag ) {
+ DBGC ( options, "DHCPOPT %p found %s (length %d)\n",
+ options, dhcp_tag_name ( original_tag ),
+ option_len );
+ return offset;
+ }
+ /* Check for start of matching encapsulation block */
+ if ( DHCP_IS_ENCAP_OPT ( tag ) &&
+ ( option->tag == DHCP_ENCAPSULATOR ( tag ) ) ) {
+ if ( encap_offset )
+ *encap_offset = offset;
+ /* Continue search within encapsulated option block */
+ tag = DHCP_ENCAPSULATED ( tag );
+ remaining = option_len;
+ offset += DHCP_OPTION_HEADER_LEN;
+ continue;
+ }
+ offset += option_len;
+ }
+
+ return -ENOENT;
+}
+
+/**
+ * Refuse to reallocate DHCP option block
+ *
+ * @v options DHCP option block
+ * @v len New length
+ * @ret rc Return status code
+ */
+int dhcpopt_no_realloc ( struct dhcp_options *options, size_t len ) {
+ return ( ( len <= options->alloc_len ) ? 0 : -ENOSPC );
+}
+
+/**
+ * Resize a DHCP option
+ *
+ * @v options DHCP option block
+ * @v offset Offset of option to resize
+ * @v encap_offset Offset of encapsulating offset (or -ve for none)
+ * @v old_len Old length (including header)
+ * @v new_len New length (including header)
+ * @ret rc Return status code
+ */
+static int resize_dhcp_option ( struct dhcp_options *options,
+ int offset, int encap_offset,
+ size_t old_len, size_t new_len ) {
+ struct dhcp_option *encapsulator;
+ struct dhcp_option *option;
+ ssize_t delta = ( new_len - old_len );
+ size_t old_alloc_len;
+ size_t new_used_len;
+ size_t new_encapsulator_len;
+ void *source;
+ void *dest;
+ int rc;
+
+ /* Check for sufficient space */
+ if ( new_len > DHCP_MAX_LEN ) {
+ DBGC ( options, "DHCPOPT %p overlength option\n", options );
+ return -ENOSPC;
+ }
+ new_used_len = ( options->used_len + delta );
+
+ /* Expand options block, if necessary */
+ if ( new_used_len > options->alloc_len ) {
+ /* Reallocate options block */
+ old_alloc_len = options->alloc_len;
+ if ( ( rc = options->realloc ( options, new_used_len ) ) != 0 ){
+ DBGC ( options, "DHCPOPT %p could not reallocate to "
+ "%zd bytes\n", options, new_used_len );
+ return rc;
+ }
+ /* Clear newly allocated space */
+ memset ( ( options->data + old_alloc_len ), 0,
+ ( options->alloc_len - old_alloc_len ) );
+ }
+
+ /* Update encapsulator, if applicable */
+ if ( encap_offset >= 0 ) {
+ encapsulator = dhcp_option ( options, encap_offset );
+ new_encapsulator_len = ( encapsulator->len + delta );
+ if ( new_encapsulator_len > DHCP_MAX_LEN ) {
+ DBGC ( options, "DHCPOPT %p overlength encapsulator\n",
+ options );
+ return -ENOSPC;
+ }
+ encapsulator->len = new_encapsulator_len;
+ }
+
+ /* Update used length */
+ options->used_len = new_used_len;
+
+ /* Move remainder of option data */
+ option = dhcp_option ( options, offset );
+ source = ( ( ( void * ) option ) + old_len );
+ dest = ( ( ( void * ) option ) + new_len );
+ memmove ( dest, source, ( new_used_len - offset - new_len ) );
+
+ /* Shrink options block, if applicable */
+ if ( new_used_len < options->alloc_len ) {
+ if ( ( rc = options->realloc ( options, new_used_len ) ) != 0 ){
+ DBGC ( options, "DHCPOPT %p could not reallocate to "
+ "%zd bytes\n", options, new_used_len );
+ return rc;
+ }
+ }
+
+ return 0;
+}
+
+/**
+ * Set value of DHCP option
+ *
+ * @v options DHCP option block
+ * @v tag DHCP option tag
+ * @v data New value for DHCP option
+ * @v len Length of value, in bytes
+ * @ret offset Offset of DHCP option, or negative error
+ *
+ * Sets the value of a DHCP option within the options block. The
+ * option may or may not already exist. Encapsulators will be created
+ * (and deleted) as necessary.
+ *
+ * This call may fail due to insufficient space in the options block.
+ * If it does fail, and the option existed previously, the option will
+ * be left with its original value.
+ */
+static int set_dhcp_option ( struct dhcp_options *options, unsigned int tag,
+ const void *data, size_t len ) {
+ static const uint8_t empty_encap[] = { DHCP_END };
+ int offset;
+ int encap_offset = -1;
+ int creation_offset;
+ struct dhcp_option *option;
+ unsigned int encap_tag = DHCP_ENCAPSULATOR ( tag );
+ size_t old_len = 0;
+ size_t new_len = ( len ? ( len + DHCP_OPTION_HEADER_LEN ) : 0 );
+ int rc;
+
+ /* Sanity check */
+ if ( tag == DHCP_PAD )
+ return -ENOTTY;
+
+ creation_offset = find_dhcp_option_with_encap ( options, DHCP_END,
+ NULL );
+ if ( creation_offset < 0 )
+ creation_offset = options->used_len;
+ /* Find old instance of this option, if any */
+ offset = find_dhcp_option_with_encap ( options, tag, &encap_offset );
+ if ( offset >= 0 ) {
+ old_len = dhcp_option_len ( dhcp_option ( options, offset ) );
+ DBGC ( options, "DHCPOPT %p resizing %s from %zd to %zd\n",
+ options, dhcp_tag_name ( tag ), old_len, new_len );
+ } else {
+ DBGC ( options, "DHCPOPT %p creating %s (length %zd)\n",
+ options, dhcp_tag_name ( tag ), new_len );
+ }
+
+ /* Ensure that encapsulator exists, if required */
+ if ( encap_tag ) {
+ if ( encap_offset < 0 ) {
+ encap_offset =
+ set_dhcp_option ( options, encap_tag,
+ empty_encap,
+ sizeof ( empty_encap ) );
+ }
+ if ( encap_offset < 0 )
+ return encap_offset;
+ creation_offset = ( encap_offset + DHCP_OPTION_HEADER_LEN );
+ }
+
+ /* Create new option if necessary */
+ if ( offset < 0 )
+ offset = creation_offset;
+
+ /* Resize option to fit new data */
+ if ( ( rc = resize_dhcp_option ( options, offset, encap_offset,
+ old_len, new_len ) ) != 0 )
+ return rc;
+
+ /* Copy new data into option, if applicable */
+ if ( len ) {
+ option = dhcp_option ( options, offset );
+ option->tag = tag;
+ option->len = len;
+ memcpy ( &option->data, data, len );
+ }
+
+ /* Delete encapsulator if there's nothing else left in it */
+ if ( encap_offset >= 0 ) {
+ option = dhcp_option ( options, encap_offset );
+ if ( option->len <= 1 )
+ set_dhcp_option ( options, encap_tag, NULL, 0 );
+ }
+
+ return offset;
+}
+
+/**
+ * Check applicability of DHCP option setting
+ *
+ * @v tag Setting tag number
+ * @ret applies Setting applies to this option block
+ */
+int dhcpopt_applies ( unsigned int tag ) {
+
+ return ( tag && ( tag <= DHCP_ENCAP_OPT ( DHCP_MAX_OPTION,
+ DHCP_MAX_OPTION ) ) );
+}
+
+/**
+ * Store value of DHCP option setting
+ *
+ * @v options DHCP option block
+ * @v tag Setting tag number
+ * @v data Setting data, or NULL to clear setting
+ * @v len Length of setting data
+ * @ret rc Return status code
+ */
+int dhcpopt_store ( struct dhcp_options *options, unsigned int tag,
+ const void *data, size_t len ) {
+ int offset;
+
+ offset = set_dhcp_option ( options, tag, data, len );
+ if ( offset < 0 )
+ return offset;
+ return 0;
+}
+
+/**
+ * Fetch value of DHCP option setting
+ *
+ * @v options DHCP option block
+ * @v tag Setting tag number
+ * @v data Buffer to fill with setting data
+ * @v len Length of buffer
+ * @ret len Length of setting data, or negative error
+ */
+int dhcpopt_fetch ( struct dhcp_options *options, unsigned int tag,
+ void *data, size_t len ) {
+ int offset;
+ struct dhcp_option *option;
+ size_t option_len;
+
+ offset = find_dhcp_option_with_encap ( options, tag, NULL );
+ if ( offset < 0 )
+ return offset;
+
+ option = dhcp_option ( options, offset );
+ option_len = option->len;
+ if ( len > option_len )
+ len = option_len;
+ memcpy ( data, option->data, len );
+
+ return option_len;
+}
+
+/**
+ * Recalculate length of DHCP options block
+ *
+ * @v options Uninitialised DHCP option block
+ *
+ * The "used length" field will be updated based on scanning through
+ * the block to find the end of the options.
+ */
+void dhcpopt_update_used_len ( struct dhcp_options *options ) {
+ struct dhcp_option *option;
+ int offset = 0;
+ ssize_t remaining = options->alloc_len;
+ unsigned int option_len;
+
+ /* Find last non-pad option */
+ options->used_len = 0;
+ while ( remaining ) {
+ option = dhcp_option ( options, offset );
+ option_len = dhcp_option_len ( option );
+ remaining -= option_len;
+ if ( remaining < 0 )
+ break;
+ offset += option_len;
+ if ( option->tag != DHCP_PAD )
+ options->used_len = offset;
+ }
+}
+
+/**
+ * Initialise prepopulated block of DHCP options
+ *
+ * @v options Uninitialised DHCP option block
+ * @v data Memory for DHCP option data
+ * @v alloc_len Length of memory for DHCP option data
+ * @v realloc DHCP option block reallocator
+ *
+ * The memory content must already be filled with valid DHCP options.
+ * A zeroed block counts as a block of valid DHCP options.
+ */
+void dhcpopt_init ( struct dhcp_options *options, void *data, size_t alloc_len,
+ int ( * realloc ) ( struct dhcp_options *options,
+ size_t len ) ) {
+
+ /* Fill in fields */
+ options->data = data;
+ options->alloc_len = alloc_len;
+ options->realloc = realloc;
+
+ /* Update length */
+ dhcpopt_update_used_len ( options );
+
+ DBGC ( options, "DHCPOPT %p created (data %p lengths %#zx,%#zx)\n",
+ options, options->data, options->used_len, options->alloc_len );
+}
Code Review / kvmfornfv.git / blobdiff