nvo.c

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/*
 * Copyright (C) 2006 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.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
FILE_SECBOOT ( PERMITTED );

#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <ipxe/dhcp.h>
#include <ipxe/nvs.h>
#include <ipxe/nvo.h>

/** @file
 *
 * Non-volatile stored options
 *
 */

/**
 * Calculate checksum over non-volatile stored options
 *
 * @v nvo               Non-volatile options block
 * @ret sum             Checksum
 */
static unsigned int nvo_checksum ( struct nvo_block *nvo ) {
        uint8_t *data = nvo->data;
        uint8_t sum = 0;
        unsigned int i;

        for ( i = 0 ; i < nvo->len ; i++ ) {
                sum += *(data++);
        }
        return sum;
}

/**
 * Reallocate non-volatile stored options block
 *
 * @v nvo               Non-volatile options block
 * @v len               New length
 * @ret rc              Return status code
 */
static int nvo_realloc ( struct nvo_block *nvo, size_t len ) {
        void *new_data;

        /* Reallocate data */
        new_data = realloc ( nvo->data, len );
        if ( ! new_data ) {
                DBGC ( nvo, "NVO %p could not allocate %zd bytes\n",
                       nvo, len );
                return -ENOMEM;
        }
        nvo->data = new_data;
        nvo->len = len;

        /* Update DHCP option block */
        if ( len ) {
                nvo->dhcpopts.data = ( nvo->data + 1 /* checksum */ );
                nvo->dhcpopts.alloc_len = ( len - 1 /* checksum */ );
        } else {
                nvo->dhcpopts.data = NULL;
                nvo->dhcpopts.used_len = 0;
                nvo->dhcpopts.alloc_len = 0;
        }

        return 0;
}

/**
 * Reallocate non-volatile stored options DHCP option block
 *
 * @v options           DHCP option block
 * @v len               New length
 * @ret rc              Return status code
 */
static int nvo_realloc_dhcpopt ( struct dhcp_options *options, size_t len ) {
        struct nvo_block *nvo =
                container_of ( options, struct nvo_block, dhcpopts );
        int rc;

        /* Refuse to reallocate if we have no way to resize the block */
        if ( ! nvo->resize )
                return dhcpopt_no_realloc ( options, len );

        /* Allow one byte for the checksum (if any data is present) */
        if ( len )
                len += 1;

        /* Resize underlying non-volatile options block */
        if ( ( rc = nvo->resize ( nvo, len ) ) != 0 ) {
                DBGC ( nvo, "NVO %p could not resize to %zd bytes: %s\n",
                       nvo, len, strerror ( rc ) );
                return rc;
        }

        /* Reallocate in-memory options block */
        if ( ( rc = nvo_realloc ( nvo, len ) ) != 0 )
                return rc;

        return 0;
}

/**
 * Load non-volatile stored options from non-volatile storage device
 *
 * @v nvo               Non-volatile options block
 * @ret rc              Return status code
 */
static int nvo_load ( struct nvo_block *nvo ) {
        uint8_t *options_data = nvo->dhcpopts.data;
        int rc;

        /* Skip reading zero-length NVO fields */
        if ( nvo->len == 0 ) {
                DBGC ( nvo, "NVO %p is empty; skipping load\n", nvo );
                return 0;
        }

        /* Read data */
        if ( ( rc = nvs_read ( nvo->nvs, nvo->address, nvo->data,
                               nvo->len ) ) != 0 ) {
                DBGC ( nvo, "NVO %p could not read %zd bytes at %#04x: %s\n",
                       nvo, nvo->len, nvo->address, strerror ( rc ) );
                return rc;
        }

        /* If checksum fails, or options data starts with a zero,
         * assume the whole block is invalid.  This should capture the
         * case of random initial contents.
         */
        if ( ( nvo_checksum ( nvo ) != 0 ) || ( options_data[0] == 0 ) ) {
                DBGC ( nvo, "NVO %p has checksum %02x and initial byte %02x; "
                       "assuming empty\n", nvo, nvo_checksum ( nvo ),
                       options_data[0] );
                memset ( nvo->data, 0, nvo->len );
        }

        /* Rescan DHCP option block */
        dhcpopt_update_used_len ( &nvo->dhcpopts );

        DBGC ( nvo, "NVO %p loaded from non-volatile storage\n", nvo );
        return 0;
}

/**
 * Save non-volatile stored options back to non-volatile storage device
 *
 * @v nvo               Non-volatile options block
 * @ret rc              Return status code
 */
static int nvo_save ( struct nvo_block *nvo ) {
        uint8_t *checksum = nvo->data;
        int rc;

        /* Recalculate checksum, if applicable */
        if ( nvo->len > 0 )
                *checksum -= nvo_checksum ( nvo );

        /* Write data */
        if ( ( rc = nvs_write ( nvo->nvs, nvo->address, nvo->data,
                                nvo->len ) ) != 0 ) {
                DBGC ( nvo, "NVO %p could not write %zd bytes at %#04x: %s\n",
                       nvo, nvo->len, nvo->address, strerror ( rc ) );
                return rc;
        }

        DBGC ( nvo, "NVO %p saved to non-volatile storage\n", nvo );
        return 0;
}

/**
 * Check applicability of NVO setting
 *
 * @v settings          Settings block
 * @v setting           Setting
 * @ret applies         Setting applies within this settings block
 */
int nvo_applies ( struct settings *settings __unused,
                  const struct setting *setting ) {

        return ( ( setting->scope == NULL ) &&
                 dhcpopt_applies ( setting->tag ) );
}

/**
 * Store value of NVO setting
 *
 * @v settings          Settings block
 * @v setting           Setting to store
 * @v data              Setting data, or NULL to clear setting
 * @v len               Length of setting data
 * @ret rc              Return status code
 */
static int nvo_store ( struct settings *settings, const struct setting *setting,
                       const void *data, size_t len ) {
        struct nvo_block *nvo =
                container_of ( settings, struct nvo_block, settings );
        int rc;

        /* Update stored options */
        if ( ( rc = dhcpopt_store ( &nvo->dhcpopts, setting->tag,
                                    data, len ) ) != 0 ) {
                DBGC ( nvo, "NVO %p could not store %zd bytes: %s\n",
                       nvo, len, strerror ( rc ) );
                return rc;
        }

        /* Save updated options to NVS */
        if ( ( rc = nvo_save ( nvo ) ) != 0 )
                return rc;

        return 0;
}

/**
 * Fetch value of NVO setting
 *
 * @v settings          Settings block
 * @v setting           Setting to fetch
 * @v data              Buffer to fill with setting data
 * @v len               Length of buffer
 * @ret len             Length of setting data, or negative error
 *
 * The actual length of the setting will be returned even if
 * the buffer was too small.
 */
static int nvo_fetch ( struct settings *settings, struct setting *setting,
                       void *data, size_t len ) {
        struct nvo_block *nvo =
                container_of ( settings, struct nvo_block, settings );

        return dhcpopt_fetch ( &nvo->dhcpopts, setting->tag, data, len );
}

/** NVO settings operations */
static struct settings_operations nvo_settings_operations = {
        .applies = nvo_applies,
        .store = nvo_store,
        .fetch = nvo_fetch,
};

/**
 * Initialise non-volatile stored options
 *
 * @v nvo               Non-volatile options block
 * @v nvs               Underlying non-volatile storage device
 * @v address           Address within NVS device
 * @v len               Length of non-volatile options data
 * @v resize            Resize method
 * @v refcnt            Containing object reference counter, or NULL
 */
void nvo_init ( struct nvo_block *nvo, struct nvs_device *nvs,
                size_t address, size_t len,
                int ( * resize ) ( struct nvo_block *nvo, size_t len ),
                struct refcnt *refcnt ) {
        nvo->nvs = nvs;
        nvo->address = address;
        nvo->len = len;
        nvo->resize = resize;
        dhcpopt_init ( &nvo->dhcpopts, NULL, 0, nvo_realloc_dhcpopt );
        settings_init ( &nvo->settings, &nvo_settings_operations,
                        refcnt, NULL );
}

/**
 * Register non-volatile stored options
 *
 * @v nvo               Non-volatile options block
 * @v parent            Parent settings block, or NULL
 * @ret rc              Return status code
 */
int register_nvo ( struct nvo_block *nvo, struct settings *parent ) {
        int rc;

        /* Allocate memory for options */
        if ( ( rc = nvo_realloc ( nvo, nvo->len ) ) != 0 )
                goto err_realloc;

        /* Read data from NVS */
        if ( ( rc = nvo_load ( nvo ) ) != 0 )
                goto err_load;

        /* Register settings */
        if ( ( rc = register_settings ( &nvo->settings, parent,
                                        NVO_SETTINGS_NAME ) ) != 0 )
                goto err_register;

        DBGC ( nvo, "NVO %p registered\n", nvo );
        return 0;
        
 err_register:
 err_load:
        nvo_realloc ( nvo, 0 );
 err_realloc:
        return rc;
}

/**
 * Unregister non-volatile stored options
 *
 * @v nvo               Non-volatile options block
 */
void unregister_nvo ( struct nvo_block *nvo ) {
        unregister_settings ( &nvo->settings );
        nvo_realloc ( nvo, 0 );
        DBGC ( nvo, "NVO %p unregistered\n", nvo );
}