settings.c

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/*
 * 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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

FILE_LICENCE ( GPL2_OR_LATER );

#include <stdint.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <strings.h>
#include <byteswap.h>
#include <errno.h>
#include <assert.h>
#include <gpxe/in.h>
#include <gpxe/vsprintf.h>
#include <gpxe/dhcp.h>
#include <gpxe/uuid.h>
#include <gpxe/uri.h>
#include <gpxe/settings.h>

/** @file
 *
 * Configuration settings
 *
 */

/******************************************************************************
 *
 * Generic settings blocks
 *
 ******************************************************************************
 */

/**
 * A generic setting
 *
 */
struct generic_setting {
        /** List of generic settings */
        struct list_head list;
        /** Setting */
        struct setting setting;
        /** Size of setting name */
        size_t name_len;
        /** Size of setting data */
        size_t data_len;
};

/**
 * Get generic setting name
 *
 * @v generic           Generic setting
 * @ret name            Generic setting name
 */
static inline void * generic_setting_name ( struct generic_setting *generic ) {
        return ( ( ( void * ) generic ) + sizeof ( *generic ) );
}

/**
 * Get generic setting data
 *
 * @v generic           Generic setting
 * @ret data            Generic setting data
 */
static inline void * generic_setting_data ( struct generic_setting *generic ) {
        return ( ( ( void * ) generic ) + sizeof ( *generic ) +
                 generic->name_len );
}

/**
 * Find generic setting
 *
 * @v generics          Generic settings block
 * @v setting           Setting to find
 * @ret generic         Generic setting, or NULL
 */
static struct generic_setting *
find_generic_setting ( struct generic_settings *generics,
                       struct setting *setting ) {
        struct generic_setting *generic;

        list_for_each_entry ( generic, &generics->list, list ) {
                if ( setting_cmp ( &generic->setting, setting ) == 0 )
                        return generic;
        }
        return NULL;
}

/**
 * Store value of generic 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
 */
int generic_settings_store ( struct settings *settings,
                             struct setting *setting,
                             const void *data, size_t len ) {
        struct generic_settings *generics =
                container_of ( settings, struct generic_settings, settings );
        struct generic_setting *old;
        struct generic_setting *new = NULL;
        size_t name_len;

        /* Identify existing generic setting, if any */
        old = find_generic_setting ( generics, setting );

        /* Create new generic setting, if required */
        if ( len ) {
                /* Allocate new generic setting */
                name_len = ( strlen ( setting->name ) + 1 );
                new = zalloc ( sizeof ( *new ) + name_len + len );
                if ( ! new )
                        return -ENOMEM;

                /* Populate new generic setting */
                new->name_len = name_len;
                new->data_len = len;
                memcpy ( &new->setting, setting, sizeof ( new->setting ) );
                new->setting.name = generic_setting_name ( new );
                memcpy ( generic_setting_name ( new ),
                         setting->name, name_len );
                memcpy ( generic_setting_data ( new ), data, len );
        }

        /* Delete existing generic setting, if any */
        if ( old ) {
                list_del ( &old->list );
                free ( old );
        }

        /* Add new setting to list, if any */
        if ( new )
                list_add ( &new->list, &generics->list );

        return 0;
}

/**
 * Fetch value of generic 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
 */
int generic_settings_fetch ( struct settings *settings,
                             struct setting *setting,
                             void *data, size_t len ) {
        struct generic_settings *generics =
                container_of ( settings, struct generic_settings, settings );
        struct generic_setting *generic;

        /* Find generic setting */
        generic = find_generic_setting ( generics, setting );
        if ( ! generic )
                return -ENOENT;

        /* Copy out generic setting data */
        if ( len > generic->data_len )
                len = generic->data_len;
        memcpy ( data, generic_setting_data ( generic ), len );
        return generic->data_len;
}

/**
 * Clear generic settings block
 *
 * @v settings          Settings block
 */
void generic_settings_clear ( struct settings *settings ) {
        struct generic_settings *generics =
                container_of ( settings, struct generic_settings, settings );
        struct generic_setting *generic;
        struct generic_setting *tmp;

        list_for_each_entry_safe ( generic, tmp, &generics->list, list ) {
                list_del ( &generic->list );
                free ( generic );
        }
        assert ( list_empty ( &generics->list ) );
}

/** Generic settings operations */
struct settings_operations generic_settings_operations = {
        .store = generic_settings_store,
        .fetch = generic_settings_fetch,
        .clear = generic_settings_clear,
};

/******************************************************************************
 *
 * Registered settings blocks
 *
 ******************************************************************************
 */

/** Root generic settings block */
struct generic_settings generic_settings_root = {
        .settings = {
                .refcnt = NULL,
                .name = "",
                .siblings =
                    LIST_HEAD_INIT ( generic_settings_root.settings.siblings ),
                .children =
                    LIST_HEAD_INIT ( generic_settings_root.settings.children ),
                .op = &generic_settings_operations,
        },
        .list = LIST_HEAD_INIT ( generic_settings_root.list ),
};

/** Root settings block */
#define settings_root generic_settings_root.settings

/**
 * Find child named settings block
 *
 * @v parent            Parent settings block
 * @v name              Name within this parent
 * @ret settings        Settings block, or NULL
 */
static struct settings * find_child_settings ( struct settings *parent,
                                               const char *name ) {
        struct settings *settings;

        /* Treat empty name as meaning "this block" */
        if ( ! *name )
                return parent;

        /* Look for child with matching name */
        list_for_each_entry ( settings, &parent->children, siblings ) {
                if ( strcmp ( settings->name, name ) == 0 )
                        return settings;
        }

        return NULL;
}

/**
 * Find or create child named settings block
 *
 * @v parent            Parent settings block
 * @v name              Name within this parent
 * @ret settings        Settings block, or NULL
 */
static struct settings * autovivify_child_settings ( struct settings *parent,
                                                     const char *name ) {
        struct {
                struct generic_settings generic;
                char name[ strlen ( name ) + 1 /* NUL */ ];
        } *new_child;
        struct settings *settings;

        /* Return existing settings, if existent */
        if ( ( settings = find_child_settings ( parent, name ) ) != NULL )
                return settings;

        /* Create new generic settings block */
        new_child = zalloc ( sizeof ( *new_child ) );
        if ( ! new_child ) {
                DBGC ( parent, "Settings %p could not create child %s\n",
                       parent, name );
                return NULL;
        }
        memcpy ( new_child->name, name, sizeof ( new_child->name ) );
        generic_settings_init ( &new_child->generic, NULL, new_child->name );
        settings = &new_child->generic.settings;
        register_settings ( settings, parent );
        return settings;
}

/**
 * Return settings block name (for debug only)
 *
 * @v settings          Settings block
 * @ret name            Settings block name
 */
static const char * settings_name ( struct settings *settings ) {
        static char buf[64];
        char tmp[ sizeof ( buf ) ];
        int count;

        for ( count = 0 ; settings ; settings = settings->parent ) {
                memcpy ( tmp, buf, sizeof ( tmp ) );
                snprintf ( buf, sizeof ( buf ), "%s%c%s", settings->name,
                           ( count++ ? '.' : '\0' ), tmp );
        }
        return ( buf + 1 );
}

/**
 * Parse settings block name
 *
 * @v name              Name
 * @v get_child         Function to find or create child settings block
 * @ret settings        Settings block, or NULL
 */
static struct settings *
parse_settings_name ( const char *name,
                      struct settings * ( * get_child ) ( struct settings *,
                                                          const char * ) ) {
        struct settings *settings = &settings_root;
        char name_copy[ strlen ( name ) + 1 ];
        char *subname;
        char *remainder;

        /* Create modifiable copy of name */
        memcpy ( name_copy, name, sizeof ( name_copy ) );
        remainder = name_copy;

        /* Parse each name component in turn */
        while ( remainder ) {
                struct net_device *netdev;

                subname = remainder;
                remainder = strchr ( subname, '.' );
                if ( remainder )
                        *(remainder++) = '\0';

                /* Special case "netX" root settings block */
                if ( ( subname == name_copy ) && ! strcmp ( subname, "netX" ) &&
                     ( ( netdev = last_opened_netdev() ) != NULL ) )
                        settings = get_child ( settings, netdev->name );
                else
                        settings = get_child ( settings, subname );

                if ( ! settings )
                        break;
        }

        return settings;
}

/**
 * Find named settings block
 *
 * @v name              Name
 * @ret settings        Settings block, or NULL
 */
struct settings * find_settings ( const char *name ) {

        return parse_settings_name ( name, find_child_settings );
}

/**
 * Apply all settings
 *
 * @ret rc              Return status code
 */
static int apply_settings ( void ) {
        struct settings_applicator *applicator;
        int rc;

        /* Call all settings applicators */
        for_each_table_entry ( applicator, SETTINGS_APPLICATORS ) {
                if ( ( rc = applicator->apply() ) != 0 ) {
                        DBG ( "Could not apply settings using applicator "
                              "%p: %s\n", applicator, strerror ( rc ) );
                        return rc;
                }
        }

        return 0;
}

/**
 * Reprioritise settings
 *
 * @v settings          Settings block
 *
 * Reorders the settings block amongst its siblings according to its
 * priority.
 */
static void reprioritise_settings ( struct settings *settings ) {
        struct settings *parent = settings->parent;
        long priority;
        struct settings *tmp;
        long tmp_priority;

        /* Stop when we reach the top of the tree */
        if ( ! parent )
                return;

        /* Read priority, if present */
        priority = fetch_intz_setting ( settings, &priority_setting );

        /* Remove from siblings list */
        list_del ( &settings->siblings );

        /* Reinsert after any existing blocks which have a higher priority */
        list_for_each_entry ( tmp, &parent->children, siblings ) {
                tmp_priority = fetch_intz_setting ( tmp, &priority_setting );
                if ( priority > tmp_priority )
                        break;
        }
        list_add_tail ( &settings->siblings, &tmp->siblings );

        /* Recurse up the tree */
        reprioritise_settings ( parent );
}

/**
 * Register settings block
 *
 * @v settings          Settings block
 * @v parent            Parent settings block, or NULL
 * @ret rc              Return status code
 */
int register_settings ( struct settings *settings, struct settings *parent ) {
        struct settings *old_settings;

        /* NULL parent => add to settings root */
        assert ( settings != NULL );
        if ( parent == NULL )
                parent = &settings_root;

        /* Remove any existing settings with the same name */
        if ( ( old_settings = find_child_settings ( parent, settings->name ) ))
                unregister_settings ( old_settings );

        /* Add to list of settings */
        ref_get ( settings->refcnt );
        ref_get ( parent->refcnt );
        settings->parent = parent;
        list_add_tail ( &settings->siblings, &parent->children );
        DBGC ( settings, "Settings %p (\"%s\") registered\n",
               settings, settings_name ( settings ) );

        /* Fix up settings priority */
        reprioritise_settings ( settings );

        /* Apply potentially-updated settings */
        apply_settings();

        return 0;
}

/**
 * Unregister settings block
 *
 * @v settings          Settings block
 */
void unregister_settings ( struct settings *settings ) {

        DBGC ( settings, "Settings %p (\"%s\") unregistered\n",
               settings, settings_name ( settings ) );

        /* Remove from list of settings */
        ref_put ( settings->refcnt );
        ref_put ( settings->parent->refcnt );
        settings->parent = NULL;
        list_del ( &settings->siblings );

        /* Apply potentially-updated settings */
        apply_settings();
}

/******************************************************************************
 *
 * Core settings routines
 *
 ******************************************************************************
 */

/**
 * Store value of setting
 *
 * @v settings          Settings block, or NULL
 * @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
 */
int store_setting ( struct settings *settings, struct setting *setting,
                    const void *data, size_t len ) {
        int rc;

        /* NULL settings implies storing into the global settings root */
        if ( ! settings )
                settings = &settings_root;

        /* Sanity check */
        if ( ! settings->op->store )
                return -ENOTSUP;

        /* Store setting */
        if ( ( rc = settings->op->store ( settings, setting,
                                          data, len ) ) != 0 )
                return rc;

        /* Reprioritise settings if necessary */
        if ( setting_cmp ( setting, &priority_setting ) == 0 )
                reprioritise_settings ( settings );

        /* If these settings are registered, apply potentially-updated
         * settings
         */
        for ( ; settings ; settings = settings->parent ) {
                if ( settings == &settings_root ) {
                        if ( ( rc = apply_settings() ) != 0 )
                                return rc;
                        break;
                }
        }

        return 0;
}

/**
 * Fetch value of setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @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.
 */
int fetch_setting ( struct settings *settings, struct setting *setting,
                    void *data, size_t len ) {
        struct settings *child;
        int ret;

        /* Avoid returning uninitialised data on error */
        memset ( data, 0, len );

        /* NULL settings implies starting at the global settings root */
        if ( ! settings )
                settings = &settings_root;

        /* Sanity check */
        if ( ! settings->op->fetch )
                return -ENOTSUP;

        /* Try this block first */
        if ( ( ret = settings->op->fetch ( settings, setting,
                                           data, len ) ) >= 0 )
                return ret;

        /* Recurse into each child block in turn */
        list_for_each_entry ( child, &settings->children, siblings ) {
                if ( ( ret = fetch_setting ( child, setting,
                                             data, len ) ) >= 0 )
                        return ret;
        }

        return -ENOENT;
}

/**
 * Fetch length of setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @ret len             Length of setting data, or negative error
 *
 * This function can also be used as an existence check for the
 * setting.
 */
int fetch_setting_len ( struct settings *settings, struct setting *setting ) {
        return fetch_setting ( settings, setting, NULL, 0 );
}

/**
 * Fetch value of string setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v data              Buffer to fill with setting string data
 * @v len               Length of buffer
 * @ret len             Length of string setting, or negative error
 *
 * The resulting string is guaranteed to be correctly NUL-terminated.
 * The returned length will be the length of the underlying setting
 * data.
 */
int fetch_string_setting ( struct settings *settings, struct setting *setting,
                           char *data, size_t len ) {
        memset ( data, 0, len );
        return fetch_setting ( settings, setting, data,
                               ( ( len > 0 ) ? ( len - 1 ) : 0 ) );
}

/**
 * Fetch value of string setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v data              Buffer to allocate and fill with setting string data
 * @ret len             Length of string setting, or negative error
 *
 * The resulting string is guaranteed to be correctly NUL-terminated.
 * The returned length will be the length of the underlying setting
 * data.  The caller is responsible for eventually freeing the
 * allocated buffer.
 */
int fetch_string_setting_copy ( struct settings *settings,
                                struct setting *setting,
                                char **data ) {
        int len;
        int check_len = 0;

        len = fetch_setting_len ( settings, setting );
        if ( len < 0 )
                return len;

        *data = malloc ( len + 1 );
        if ( ! *data )
                return -ENOMEM;

        check_len = fetch_string_setting ( settings, setting, *data,
                                           ( len + 1 ) );
        assert ( check_len == len );
        return len;
}

/**
 * Fetch value of IPv4 address setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v inp               IPv4 address to fill in
 * @ret len             Length of setting, or negative error
 */
int fetch_ipv4_setting ( struct settings *settings, struct setting *setting,
                         struct in_addr *inp ) {
        int len;

        len = fetch_setting ( settings, setting, inp, sizeof ( *inp ) );
        if ( len < 0 )
                return len;
        if ( len < ( int ) sizeof ( *inp ) )
                return -ERANGE;
        return len;
}

/**
 * Fetch value of signed integer setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v value             Integer value to fill in
 * @ret len             Length of setting, or negative error
 */
int fetch_int_setting ( struct settings *settings, struct setting *setting,
                        long *value ) {
        union {
                uint8_t u8[ sizeof ( long ) ];
                int8_t s8[ sizeof ( long ) ];
        } buf;
        int len;
        int i;

        /* Avoid returning uninitialised data on error */
        *value = 0;

        /* Fetch raw (network-ordered, variable-length) setting */
        len = fetch_setting ( settings, setting, &buf, sizeof ( buf ) );
        if ( len < 0 )
                return len;
        if ( len > ( int ) sizeof ( buf ) )
                return -ERANGE;

        /* Convert to host-ordered signed long */
        *value = ( ( buf.s8[0] >= 0 ) ? 0 : -1L );
        for ( i = 0 ; i < len ; i++ ) {
                *value = ( ( *value << 8 ) | buf.u8[i] );
        }

        return len;
}

/**
 * Fetch value of unsigned integer setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v value             Integer value to fill in
 * @ret len             Length of setting, or negative error
 */
int fetch_uint_setting ( struct settings *settings, struct setting *setting,
                         unsigned long *value ) {
        long svalue;
        int len;

        /* Avoid returning uninitialised data on error */
        *value = 0;

        /* Fetch as a signed long */
        len = fetch_int_setting ( settings, setting, &svalue );
        if ( len < 0 )
                return len;

        /* Mask off sign-extended bits */
        assert ( len <= ( int ) sizeof ( long ) );
        *value = ( svalue & ( -1UL >> ( 8 * ( sizeof ( long ) - len ) ) ) );

        return len;
}

/**
 * Fetch value of signed integer setting, or zero
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @ret value           Setting value, or zero
 */
long fetch_intz_setting ( struct settings *settings, struct setting *setting ){
        long value;

        fetch_int_setting ( settings, setting, &value );
        return value;
}

/**
 * Fetch value of unsigned integer setting, or zero
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @ret value           Setting value, or zero
 */
unsigned long fetch_uintz_setting ( struct settings *settings,
                                    struct setting *setting ) {
        unsigned long value;

        fetch_uint_setting ( settings, setting, &value );
        return value;
}

/**
 * Fetch value of UUID setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v uuid              UUID to fill in
 * @ret len             Length of setting, or negative error
 */
int fetch_uuid_setting ( struct settings *settings, struct setting *setting,
                         union uuid *uuid ) {
        int len;

        len = fetch_setting ( settings, setting, uuid, sizeof ( *uuid ) );
        if ( len < 0 )
                return len;
        if ( len != sizeof ( *uuid ) )
                return -ERANGE;
        return len;
}

/**
 * Clear settings block
 *
 * @v settings          Settings block
 */
void clear_settings ( struct settings *settings ) {
        if ( settings->op->clear )
                settings->op->clear ( settings );
}

/**
 * Compare two settings
 *
 * @v a                 Setting to compare
 * @v b                 Setting to compare
 * @ret 0               Settings are the same
 * @ret non-zero        Settings are not the same
 */
int setting_cmp ( struct setting *a, struct setting *b ) {

        /* If the settings have tags, compare them */
        if ( a->tag && ( a->tag == b->tag ) )
                return 0;

        /* Otherwise, if the settings have names, compare them */
        if ( a->name && b->name && a->name[0] )
                return strcmp ( a->name, b->name );

        /* Otherwise, return a non-match */
        return ( ! 0 );
}

/******************************************************************************
 *
 * Formatted setting routines
 *
 ******************************************************************************
 */

/**
 * Store value of typed setting
 *
 * @v settings          Settings block
 * @v setting           Setting to store
 * @v type              Settings type
 * @v value             Formatted setting data, or NULL
 * @ret rc              Return status code
 */
int storef_setting ( struct settings *settings, struct setting *setting,
                     const char *value ) {

        /* NULL value implies deletion.  Avoid imposing the burden of
         * checking for NULL values on each typed setting's storef()
         * method.
         */
        if ( ! value )
                return delete_setting ( settings, setting );
                
        return setting->type->storef ( settings, setting, value );
}

/**
 * Find named setting
 *
 * @v name              Name
 * @ret setting         Named setting, or NULL
 */
static struct setting * find_setting ( const char *name ) {
        struct setting *setting;

        for_each_table_entry ( setting, SETTINGS ) {
                if ( strcmp ( name, setting->name ) == 0 )
                        return setting;
        }
        return NULL;
}

/**
 * Parse setting name as tag number
 *
 * @v name              Name
 * @ret tag             Tag number, or 0 if not a valid number
 */
static unsigned int parse_setting_tag ( const char *name ) {
        char *tmp = ( ( char * ) name );
        unsigned int tag = 0;

        while ( 1 ) {
                tag = ( ( tag << 8 ) | strtoul ( tmp, &tmp, 0 ) );
                if ( *tmp == 0 )
                        return tag;
                if ( *tmp != '.' )
                        return 0;
                tmp++;
        }
}

/**
 * Find setting type
 *
 * @v name              Name
 * @ret type            Setting type, or NULL
 */
static struct setting_type * find_setting_type ( const char *name ) {
        struct setting_type *type;

        for_each_table_entry ( type, SETTING_TYPES ) {
                if ( strcmp ( name, type->name ) == 0 )
                        return type;
        }
        return NULL;
}

/**
 * Parse setting name
 *
 * @v name              Name of setting
 * @v get_child         Function to find or create child settings block
 * @v settings          Settings block to fill in
 * @v setting           Setting to fill in
 * @v tmp_name          Buffer for copy of setting name
 * @ret rc              Return status code
 *
 * Interprets a name of the form
 * "[settings_name/]tag_name[:type_name]" and fills in the appropriate
 * fields.
 *
 * The @c tmp_name buffer must be large enough to hold a copy of the
 * setting name.
 */
static int
parse_setting_name ( const char *name,
                     struct settings * ( * get_child ) ( struct settings *,
                                                         const char * ),
                     struct settings **settings, struct setting *setting,
                     char *tmp_name ) {
        char *settings_name;
        char *setting_name;
        char *type_name;
        struct setting *named_setting;

        /* Set defaults */
        *settings = &settings_root;
        memset ( setting, 0, sizeof ( *setting ) );
        setting->name = "";
        setting->type = &setting_type_string;

        /* Split name into "[settings_name/]setting_name[:type_name]" */
        strcpy ( tmp_name, name );
        if ( ( setting_name = strchr ( tmp_name, '/' ) ) != NULL ) {
                *(setting_name++) = 0;
                settings_name = tmp_name;
        } else {
                setting_name = tmp_name;
                settings_name = NULL;
        }
        if ( ( type_name = strchr ( setting_name, ':' ) ) != NULL )
                *(type_name++) = 0;

        /* Identify settings block, if specified */
        if ( settings_name ) {
                *settings = parse_settings_name ( settings_name, get_child );
                if ( *settings == NULL ) {
                        DBG ( "Unrecognised settings block \"%s\" in \"%s\"\n",
                              settings_name, name );
                        return -ENODEV;
                }
        }

        /* Identify setting */
        if ( ( named_setting = find_setting ( setting_name ) ) != NULL ) {
                /* Matches a defined named setting; use that setting */
                memcpy ( setting, named_setting, sizeof ( *setting ) );
        } else if ( ( setting->tag = parse_setting_tag ( setting_name ) ) !=0){
                /* Is a valid numeric tag; use the tag */
                setting->tag |= (*settings)->tag_magic;
        } else {
                /* Use the arbitrary name */
                setting->name = setting_name;
        }

        /* Identify setting type, if specified */
        if ( type_name ) {
                setting->type = find_setting_type ( type_name );
                if ( setting->type == NULL ) {
                        DBG ( "Invalid setting type \"%s\" in \"%s\"\n",
                              type_name, name );
                        return -ENOTSUP;
                }
        }

        return 0;
}

/**
 * Parse and store value of named setting
 *
 * @v name              Name of setting
 * @v value             Formatted setting data, or NULL
 * @ret rc              Return status code
 */
int storef_named_setting ( const char *name, const char *value ) {
        struct settings *settings;
        struct setting setting;
        char tmp_name[ strlen ( name ) + 1 ];
        int rc;

        if ( ( rc = parse_setting_name ( name, autovivify_child_settings,
                                         &settings, &setting, tmp_name )) != 0)
                return rc;
        return storef_setting ( settings, &setting, value );
}

/**
 * Fetch and format value of named setting
 *
 * @v name              Name of setting
 * @v buf               Buffer to contain formatted value
 * @v len               Length of buffer
 * @ret len             Length of formatted value, or negative error
 */
int fetchf_named_setting ( const char *name, char *buf, size_t len ) {
        struct settings *settings;
        struct setting setting;
        char tmp_name[ strlen ( name ) + 1 ];
        int rc;

        if ( ( rc = parse_setting_name ( name, find_child_settings,
                                         &settings, &setting, tmp_name )) != 0)
                return rc;
        return fetchf_setting ( settings, &setting, buf, len );
}

/******************************************************************************
 *
 * Setting types
 *
 ******************************************************************************
 */

/**
 * Parse and store value of string setting
 *
 * @v settings          Settings block
 * @v setting           Setting to store
 * @v value             Formatted setting data
 * @ret rc              Return status code
 */
static int storef_string ( struct settings *settings, struct setting *setting,
                           const char *value ) {
        return store_setting ( settings, setting, value, strlen ( value ) );
}

/**
 * Fetch and format value of string setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v buf               Buffer to contain formatted value
 * @v len               Length of buffer
 * @ret len             Length of formatted value, or negative error
 */
static int fetchf_string ( struct settings *settings, struct setting *setting,
                           char *buf, size_t len ) {
        return fetch_string_setting ( settings, setting, buf, len );
}

/** A string setting type */
struct setting_type setting_type_string __setting_type = {
        .name = "string",
        .storef = storef_string,
        .fetchf = fetchf_string,
};

/**
 * Parse and store value of URI-encoded string setting
 *
 * @v settings          Settings block
 * @v setting           Setting to store
 * @v value             Formatted setting data
 * @ret rc              Return status code
 */
static int storef_uristring ( struct settings *settings,
                              struct setting *setting,
                              const char *value ) {
        char buf[ strlen ( value ) + 1 ]; /* Decoding never expands string */
        size_t len;

        len = uri_decode ( value, buf, sizeof ( buf ) );
        return store_setting ( settings, setting, buf, len );
}

/**
 * Fetch and format value of URI-encoded string setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v buf               Buffer to contain formatted value
 * @v len               Length of buffer
 * @ret len             Length of formatted value, or negative error
 */
static int fetchf_uristring ( struct settings *settings,
                              struct setting *setting,
                              char *buf, size_t len ) {
        ssize_t raw_len;

        /* We need to always retrieve the full raw string to know the
         * length of the encoded string.
         */
        raw_len = fetch_setting ( settings, setting, NULL, 0 );
        if ( raw_len < 0 )
                return raw_len;

        {
                char raw_buf[ raw_len + 1 ];
       
                fetch_string_setting ( settings, setting, raw_buf,
                                       sizeof ( raw_buf ) );
                return uri_encode ( raw_buf, buf, len, URI_FRAGMENT );
        }
}

/** A URI-encoded string setting type */
struct setting_type setting_type_uristring __setting_type = {
        .name = "uristring",
        .storef = storef_uristring,
        .fetchf = fetchf_uristring,
};

/**
 * Parse and store value of IPv4 address setting
 *
 * @v settings          Settings block
 * @v setting           Setting to store
 * @v value             Formatted setting data
 * @ret rc              Return status code
 */
static int storef_ipv4 ( struct settings *settings, struct setting *setting,
                         const char *value ) {
        struct in_addr ipv4;

        if ( inet_aton ( value, &ipv4 ) == 0 )
                return -EINVAL;
        return store_setting ( settings, setting, &ipv4, sizeof ( ipv4 ) );
}

/**
 * Fetch and format value of IPv4 address setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v buf               Buffer to contain formatted value
 * @v len               Length of buffer
 * @ret len             Length of formatted value, or negative error
 */
static int fetchf_ipv4 ( struct settings *settings, struct setting *setting,
                         char *buf, size_t len ) {
        struct in_addr ipv4;
        int raw_len;

        if ( ( raw_len = fetch_ipv4_setting ( settings, setting, &ipv4 ) ) < 0)
                return raw_len;
        return snprintf ( buf, len, "%s", inet_ntoa ( ipv4 ) );
}

/** An IPv4 address setting type */
struct setting_type setting_type_ipv4 __setting_type = {
        .name = "ipv4",
        .storef = storef_ipv4,
        .fetchf = fetchf_ipv4,
};

/**
 * Parse and store value of integer setting
 *
 * @v settings          Settings block
 * @v setting           Setting to store
 * @v value             Formatted setting data
 * @v size              Integer size, in bytes
 * @ret rc              Return status code
 */
static int storef_int ( struct settings *settings, struct setting *setting,
                        const char *value, unsigned int size ) {
        union {
                uint32_t num;
                uint8_t bytes[4];
        } u;
        char *endp;

        u.num = htonl ( strtoul ( value, &endp, 0 ) );
        if ( *endp )
                return -EINVAL;
        return store_setting ( settings, setting, 
                               &u.bytes[ sizeof ( u ) - size ], size );
}

/**
 * Parse and store value of 8-bit integer setting
 *
 * @v settings          Settings block
 * @v setting           Setting to store
 * @v value             Formatted setting data
 * @v size              Integer size, in bytes
 * @ret rc              Return status code
 */
static int storef_int8 ( struct settings *settings, struct setting *setting,
                         const char *value ) {
        return storef_int ( settings, setting, value, 1 );
}

/**
 * Parse and store value of 16-bit integer setting
 *
 * @v settings          Settings block
 * @v setting           Setting to store
 * @v value             Formatted setting data
 * @v size              Integer size, in bytes
 * @ret rc              Return status code
 */
static int storef_int16 ( struct settings *settings, struct setting *setting,
                          const char *value ) {
        return storef_int ( settings, setting, value, 2 );
}

/**
 * Parse and store value of 32-bit integer setting
 *
 * @v settings          Settings block
 * @v setting           Setting to store
 * @v value             Formatted setting data
 * @v size              Integer size, in bytes
 * @ret rc              Return status code
 */
static int storef_int32 ( struct settings *settings, struct setting *setting,
                          const char *value ) {
        return storef_int ( settings, setting, value, 4 );
}

/**
 * Fetch and format value of signed integer setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v buf               Buffer to contain formatted value
 * @v len               Length of buffer
 * @ret len             Length of formatted value, or negative error
 */
static int fetchf_int ( struct settings *settings, struct setting *setting,
                        char *buf, size_t len ) {
        long value;
        int rc;

        if ( ( rc = fetch_int_setting ( settings, setting, &value ) ) < 0 )
                return rc;
        return snprintf ( buf, len, "%ld", value );
}

/**
 * Fetch and format value of unsigned integer setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v buf               Buffer to contain formatted value
 * @v len               Length of buffer
 * @ret len             Length of formatted value, or negative error
 */
static int fetchf_uint ( struct settings *settings, struct setting *setting,
                         char *buf, size_t len ) {
        unsigned long value;
        int rc;

        if ( ( rc = fetch_uint_setting ( settings, setting, &value ) ) < 0 )
                return rc;
        return snprintf ( buf, len, "%#lx", value );
}

/** A signed 8-bit integer setting type */
struct setting_type setting_type_int8 __setting_type = {
        .name = "int8",
        .storef = storef_int8,
        .fetchf = fetchf_int,
};

/** A signed 16-bit integer setting type */
struct setting_type setting_type_int16 __setting_type = {
        .name = "int16",
        .storef = storef_int16,
        .fetchf = fetchf_int,
};

/** A signed 32-bit integer setting type */
struct setting_type setting_type_int32 __setting_type = {
        .name = "int32",
        .storef = storef_int32,
        .fetchf = fetchf_int,
};

/** An unsigned 8-bit integer setting type */
struct setting_type setting_type_uint8 __setting_type = {
        .name = "uint8",
        .storef = storef_int8,
        .fetchf = fetchf_uint,
};

/** An unsigned 16-bit integer setting type */
struct setting_type setting_type_uint16 __setting_type = {
        .name = "uint16",
        .storef = storef_int16,
        .fetchf = fetchf_uint,
};

/** An unsigned 32-bit integer setting type */
struct setting_type setting_type_uint32 __setting_type = {
        .name = "uint32",
        .storef = storef_int32,
        .fetchf = fetchf_uint,
};

/**
 * Parse and store value of hex string setting
 *
 * @v settings          Settings block
 * @v setting           Setting to store
 * @v value             Formatted setting data
 * @ret rc              Return status code
 */
static int storef_hex ( struct settings *settings, struct setting *setting,
                        const char *value ) {
        char *ptr = ( char * ) value;
        uint8_t bytes[ strlen ( value ) ]; /* cannot exceed strlen(value) */
        unsigned int len = 0;

        while ( 1 ) {
                bytes[len++] = strtoul ( ptr, &ptr, 16 );
                switch ( *ptr ) {
                case '\0' :
                        return store_setting ( settings, setting, bytes, len );
                case ':' :
                        ptr++;
                        break;
                default :
                        return -EINVAL;
                }
        }
}

/**
 * Fetch and format value of hex string setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v buf               Buffer to contain formatted value
 * @v len               Length of buffer
 * @ret len             Length of formatted value, or negative error
 */
static int fetchf_hex ( struct settings *settings, struct setting *setting,
                        char *buf, size_t len ) {
        int raw_len;
        int check_len;
        int used = 0;
        int i;

        raw_len = fetch_setting_len ( settings, setting );
        if ( raw_len < 0 )
                return raw_len;

        {
                uint8_t raw[raw_len];

                check_len = fetch_setting ( settings, setting, raw,
                                            sizeof ( raw ) );
                if ( check_len < 0 )
                        return check_len;
                assert ( check_len == raw_len );
                
                if ( len )
                        buf[0] = 0; /* Ensure that a terminating NUL exists */
                for ( i = 0 ; i < raw_len ; i++ ) {
                        used += ssnprintf ( ( buf + used ), ( len - used ),
                                            "%s%02x", ( used ? ":" : "" ),
                                            raw[i] );
                }
                return used;
        }
}

/** A hex-string setting */
struct setting_type setting_type_hex __setting_type = {
        .name = "hex",
        .storef = storef_hex,
        .fetchf = fetchf_hex,
};

/**
 * Parse and store value of UUID setting
 *
 * @v settings          Settings block
 * @v setting           Setting to store
 * @v value             Formatted setting data
 * @ret rc              Return status code
 */
static int storef_uuid ( struct settings *settings __unused,
                         struct setting *setting __unused,
                         const char *value __unused ) {
        return -ENOTSUP;
}

/**
 * Fetch and format value of UUID setting
 *
 * @v settings          Settings block, or NULL to search all blocks
 * @v setting           Setting to fetch
 * @v buf               Buffer to contain formatted value
 * @v len               Length of buffer
 * @ret len             Length of formatted value, or negative error
 */
static int fetchf_uuid ( struct settings *settings, struct setting *setting,
                         char *buf, size_t len ) {
        union uuid uuid;
        int raw_len;

        if ( ( raw_len = fetch_uuid_setting ( settings, setting, &uuid ) ) < 0)
                return raw_len;
        return snprintf ( buf, len, "%s", uuid_ntoa ( &uuid ) );
}

/** UUID setting type */
struct setting_type setting_type_uuid __setting_type = {
        .name = "uuid",
        .storef = storef_uuid,
        .fetchf = fetchf_uuid,
};

/******************************************************************************
 *
 * Settings
 *
 ******************************************************************************
 */

/** Hostname setting */
struct setting hostname_setting __setting = {
        .name = "hostname",
        .description = "Host name",
        .tag = DHCP_HOST_NAME,
        .type = &setting_type_string,
};

/** Filename setting */
struct setting filename_setting __setting = {
        .name = "filename",
        .description = "Boot filename",
        .tag = DHCP_BOOTFILE_NAME,
        .type = &setting_type_string,
};

/** Root path setting */
struct setting root_path_setting __setting = {
        .name = "root-path",
        .description = "iSCSI root path",
        .tag = DHCP_ROOT_PATH,
        .type = &setting_type_string,
};

/** Username setting */
struct setting username_setting __setting = {
        .name = "username",
        .description = "User name",
        .tag = DHCP_EB_USERNAME,
        .type = &setting_type_string,
};

/** Password setting */
struct setting password_setting __setting = {
        .name = "password",
        .description = "Password",
        .tag = DHCP_EB_PASSWORD,
        .type = &setting_type_string,
};

/** Priority setting */
struct setting priority_setting __setting = {
        .name = "priority",
        .description = "Priority of these settings",
        .tag = DHCP_EB_PRIORITY,
        .type = &setting_type_int8,
};