ndp.c

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/*
 * Copyright (C) 2013 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 );
FILE_SECBOOT ( PERMITTED );

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <byteswap.h>
#include <ipxe/in.h>
#include <ipxe/iobuf.h>
#include <ipxe/tcpip.h>
#include <ipxe/ipv6.h>
#include <ipxe/icmpv6.h>
#include <ipxe/neighbour.h>
#include <ipxe/dhcpv6.h>
#include <ipxe/timer.h>
#include <ipxe/ndp.h>

/** @file
 *
 * IPv6 neighbour discovery protocol
 *
 */

/** Router discovery minimum timeout */
#define IPV6CONF_MIN_TIMEOUT ( TICKS_PER_SEC / 8 )

/** Router discovery maximum timeout */
#define IPV6CONF_MAX_TIMEOUT ( TICKS_PER_SEC * 3 )

/** Router discovery blocked link retry timeout */
#define IPV6CONF_BLOCK_TIMEOUT ( TICKS_PER_SEC )

/** Router discovery maximum number of deferrals */
#define IPV6CONF_MAX_DEFERRALS 180

static struct ipv6conf * ipv6conf_demux ( struct net_device *netdev );
static int
ipv6conf_rx_router_advertisement ( struct net_device *netdev,
                                   struct in6_addr *router,
                                   struct ndp_router_advertisement_header *radv,
                                   size_t len );

/**
 * Transmit NDP packet with link-layer address option
 *
 * @v netdev            Network device
 * @v sin6_src          Source socket address
 * @v sin6_dest         Destination socket address
 * @v data              NDP header
 * @v len               Size of NDP header
 * @v option_type       NDP option type
 * @ret rc              Return status code
 */
static int ndp_tx_ll_addr ( struct net_device *netdev,
                            struct sockaddr_in6 *sin6_src,
                            struct sockaddr_in6 *sin6_dest,
                            const void *data, size_t len,
                            unsigned int option_type ) {
        struct sockaddr_tcpip *st_src =
                ( ( struct sockaddr_tcpip * ) sin6_src );
        struct sockaddr_tcpip *st_dest =
                ( ( struct sockaddr_tcpip * ) sin6_dest );
        struct ll_protocol *ll_protocol = netdev->ll_protocol;
        struct io_buffer *iobuf;
        struct ndp_ll_addr_option *ll_addr_opt;
        union ndp_header *ndp;
        size_t option_len;
        int rc;

        /* Allocate and populate buffer */
        option_len = ( ( sizeof ( *ll_addr_opt ) +
                         ll_protocol->ll_addr_len + NDP_OPTION_BLKSZ - 1 ) &
                       ~( NDP_OPTION_BLKSZ - 1 ) );
        iobuf = alloc_iob ( MAX_LL_NET_HEADER_LEN + len + option_len );
        if ( ! iobuf )
                return -ENOMEM;
        iob_reserve ( iobuf, MAX_LL_NET_HEADER_LEN );
        memcpy ( iob_put ( iobuf, len ), data, len );
        ll_addr_opt = iob_put ( iobuf, option_len );
        ll_addr_opt->header.type = option_type;
        ll_addr_opt->header.blocks = ( option_len / NDP_OPTION_BLKSZ );
        memcpy ( ll_addr_opt->ll_addr, netdev->ll_addr,
                 ll_protocol->ll_addr_len );
        ndp = iobuf->data;
        ndp->icmp.chksum = tcpip_chksum ( ndp, ( len + option_len ) );

        /* Transmit packet */
        if ( ( rc = tcpip_tx ( iobuf, &icmpv6_protocol, st_src, st_dest,
                               netdev, &ndp->icmp.chksum ) ) != 0 ) {
                DBGC ( netdev, "NDP %s could not transmit packet: %s\n",
                       netdev->name, strerror ( rc ) );
                return rc;
        }

        return 0;
}

/**
 * Transmit NDP neighbour discovery request
 *
 * @v netdev            Network device
 * @v net_protocol      Network-layer protocol
 * @v net_dest          Destination network-layer address
 * @v net_source        Source network-layer address
 * @ret rc              Return status code
 */
static int ndp_tx_request ( struct net_device *netdev,
                            struct net_protocol *net_protocol __unused,
                            const void *net_dest, const void *net_source ) {
        struct sockaddr_in6 sin6_src;
        struct sockaddr_in6 sin6_dest;
        struct ndp_neighbour_header neigh;
        int rc;

        /* Construct source address */
        memset ( &sin6_src, 0, sizeof ( sin6_src ) );
        sin6_src.sin6_family = AF_INET6;
        memcpy ( &sin6_src.sin6_addr, net_source,
                 sizeof ( sin6_src.sin6_addr ) );

        /* Construct multicast destination address */
        memset ( &sin6_dest, 0, sizeof ( sin6_dest ) );
        sin6_dest.sin6_family = AF_INET6;
        sin6_dest.sin6_scope_id = netdev->scope_id;
        ipv6_solicited_node ( &sin6_dest.sin6_addr, net_dest );

        /* Construct neighbour header */
        memset ( &neigh, 0, sizeof ( neigh ) );
        neigh.icmp.type = ICMPV6_NEIGHBOUR_SOLICITATION;
        memcpy ( &neigh.target, net_dest, sizeof ( neigh.target ) );

        /* Transmit neighbour discovery packet */
        if ( ( rc = ndp_tx_ll_addr ( netdev, &sin6_src, &sin6_dest, &neigh,
                                     sizeof ( neigh ),
                                     NDP_OPT_LL_SOURCE ) ) != 0 )
                return rc;

        return 0;
}

/** NDP neighbour discovery protocol */
struct neighbour_discovery ndp_discovery = {
        .name = "NDP",
        .tx_request = ndp_tx_request,
};

/**
 * Transmit NDP router solicitation
 *
 * @v netdev            Network device
 * @ret rc              Return status code
 */
static int ndp_tx_router_solicitation ( struct net_device *netdev ) {
        struct ndp_router_solicitation_header rsol;
        struct sockaddr_in6 sin6_dest;
        int rc;

        /* Construct multicast destination address */
        memset ( &sin6_dest, 0, sizeof ( sin6_dest ) );
        sin6_dest.sin6_family = AF_INET6;
        sin6_dest.sin6_scope_id = netdev->scope_id;
        ipv6_all_routers ( &sin6_dest.sin6_addr );

        /* Construct router solicitation */
        memset ( &rsol, 0, sizeof ( rsol ) );
        rsol.icmp.type = ICMPV6_ROUTER_SOLICITATION;

        /* Transmit packet */
        if ( ( rc = ndp_tx_ll_addr ( netdev, NULL, &sin6_dest, &rsol,
                                     sizeof ( rsol ), NDP_OPT_LL_SOURCE ) ) !=0)
                return rc;

        return 0;
}

/**
 * Process NDP neighbour solicitation source link-layer address option
 *
 * @v netdev            Network device
 * @v sin6_src          Source socket address
 * @v ndp               NDP packet
 * @v option            NDP option
 * @v len               NDP option length
 * @ret rc              Return status code
 */
static int
ndp_rx_neighbour_solicitation_ll_source ( struct net_device *netdev,
                                          struct sockaddr_in6 *sin6_src,
                                          union ndp_header *ndp,
                                          union ndp_option *option,
                                          size_t len ) {
        struct ndp_neighbour_header *neigh = &ndp->neigh;
        struct ndp_ll_addr_option *ll_addr_opt = &option->ll_addr;
        struct ll_protocol *ll_protocol = netdev->ll_protocol;
        int rc;

        /* Silently ignore neighbour solicitations for addresses we do
         * not own.
         */
        if ( ! ipv6_has_addr ( netdev, &neigh->target ) )
                return 0;

        /* Sanity check */
        if ( offsetof ( typeof ( *ll_addr_opt ),
                        ll_addr[ll_protocol->ll_addr_len] ) > len ) {
                DBGC ( netdev, "NDP %s neighbour solicitation link-layer "
                       "address option too short at %zd bytes\n",
                       netdev->name, len );
                return -EINVAL;
        }

        /* Create or update neighbour cache entry */
        if ( ( rc = neighbour_define ( netdev, &ipv6_protocol,
                                       &sin6_src->sin6_addr,
                                       ll_addr_opt->ll_addr ) ) != 0 ) {
                DBGC ( netdev, "NDP %s could not define %s => %s: %s\n",
                       netdev->name, inet6_ntoa ( &sin6_src->sin6_addr ),
                       ll_protocol->ntoa ( ll_addr_opt->ll_addr ),
                       strerror ( rc ) );
                return rc;
        }

        /* Convert neighbour header to advertisement */
        memset ( neigh, 0, offsetof ( typeof ( *neigh ), target ) );
        neigh->icmp.type = ICMPV6_NEIGHBOUR_ADVERTISEMENT;
        neigh->flags = ( NDP_NEIGHBOUR_SOLICITED | NDP_NEIGHBOUR_OVERRIDE );

        /* Send neighbour advertisement */
        if ( ( rc = ndp_tx_ll_addr ( netdev, NULL, sin6_src, neigh,
                                     sizeof ( *neigh ),
                                     NDP_OPT_LL_TARGET ) ) != 0 )
                return rc;

        return 0;
}

/**
 * Process NDP neighbour advertisement target link-layer address option
 *
 * @v netdev            Network device
 * @v sin6_src          Source socket address
 * @v ndp               NDP packet
 * @v option            NDP option
 * @v len               NDP option length
 * @ret rc              Return status code
 */
static int
ndp_rx_neighbour_advertisement_ll_target ( struct net_device *netdev,
                                           struct sockaddr_in6 *sin6_src
                                                   __unused,
                                           union ndp_header *ndp,
                                           union ndp_option *option,
                                           size_t len ) {
        struct ndp_neighbour_header *neigh = &ndp->neigh;
        struct ndp_ll_addr_option *ll_addr_opt = &option->ll_addr;
        struct ll_protocol *ll_protocol = netdev->ll_protocol;
        int rc;

        /* Sanity check */
        if ( offsetof ( typeof ( *ll_addr_opt ),
                        ll_addr[ll_protocol->ll_addr_len] ) > len ) {
                DBGC ( netdev, "NDP %s neighbour advertisement link-layer "
                       "address option too short at %zd bytes\n",
                       netdev->name, len );
                return -EINVAL;
        }

        /* Update neighbour cache entry, if any */
        if ( ( rc = neighbour_update ( netdev, &ipv6_protocol, &neigh->target,
                                       ll_addr_opt->ll_addr ) ) != 0 ) {
                DBGC ( netdev, "NDP %s could not update %s => %s: %s\n",
                       netdev->name, inet6_ntoa ( &neigh->target ),
                       ll_protocol->ntoa ( ll_addr_opt->ll_addr ),
                       strerror ( rc ) );
                return rc;
        }

        return 0;
}

/**
 * Process NDP router advertisement source link-layer address option
 *
 * @v netdev            Network device
 * @v sin6_src          Source socket address
 * @v ndp               NDP packet
 * @v option            NDP option
 * @v len               NDP option length
 * @ret rc              Return status code
 */
static int
ndp_rx_router_advertisement_ll_source ( struct net_device *netdev,
                                        struct sockaddr_in6 *sin6_src,
                                        union ndp_header *ndp __unused,
                                        union ndp_option *option, size_t len ) {
        struct ndp_ll_addr_option *ll_addr_opt = &option->ll_addr;
        struct ll_protocol *ll_protocol = netdev->ll_protocol;
        int rc;

        /* Sanity check */
        if ( offsetof ( typeof ( *ll_addr_opt ),
                        ll_addr[ll_protocol->ll_addr_len] ) > len ) {
                DBGC ( netdev, "NDP %s router advertisement link-layer address "
                       "option too short at %zd bytes\n", netdev->name, len );
                return -EINVAL;
        }

        /* Define neighbour cache entry */
        if ( ( rc = neighbour_define ( netdev, &ipv6_protocol,
                                       &sin6_src->sin6_addr,
                                       ll_addr_opt->ll_addr ) ) != 0 ) {
                DBGC ( netdev, "NDP %s could not define %s => %s: %s\n",
                       netdev->name, inet6_ntoa ( &sin6_src->sin6_addr ),
                       ll_protocol->ntoa ( ll_addr_opt->ll_addr ),
                       strerror ( rc ) );
                return rc;
        }

        return 0;
}

/**
 * Process NDP router advertisement prefix information option
 *
 * @v netdev            Network device
 * @v sin6_src          Source socket address
 * @v ndp               NDP packet
 * @v option            NDP option
 * @v len               NDP option length
 * @ret rc              Return status code
 */
static int
ndp_rx_router_advertisement_prefix ( struct net_device *netdev,
                                     struct sockaddr_in6 *sin6_src,
                                     union ndp_header *ndp,
                                     union ndp_option *option, size_t len ) {
        struct ndp_router_advertisement_header *radv = &ndp->radv;
        struct ndp_prefix_information_option *prefix_opt = &option->prefix;

        /* Sanity check */
        if ( sizeof ( *prefix_opt ) > len ) {
                DBGC ( netdev, "NDP %s router advertisement prefix option too "
                       "short at %zd bytes\n", netdev->name, len );
                return -EINVAL;
        }

        DBGC ( netdev, "NDP %s found %sdefault router %s ",
               netdev->name, ( radv->lifetime ? "" : "non-" ),
               inet6_ntoa ( &sin6_src->sin6_addr ) );
        DBGC ( netdev, "for %s-link %sautonomous prefix %s/%d\n",
               ( ( prefix_opt->flags & NDP_PREFIX_ON_LINK ) ? "on" : "off" ),
               ( ( prefix_opt->flags & NDP_PREFIX_AUTONOMOUS ) ? "" : "non-" ),
               inet6_ntoa ( &prefix_opt->prefix ), prefix_opt->prefix_len );

        return 0;
}

/** An NDP option handler */
struct ndp_option_handler {
        /** ICMPv6 type */
        uint8_t icmp_type;
        /** Option type */
        uint8_t option_type;
        /**
         * Handle received option
         *
         * @v netdev            Network device
         * @v sin6_src          Source socket address
         * @v ndp               NDP packet
         * @v option            NDP option
         * @ret rc              Return status code
         */
        int ( * rx ) ( struct net_device *netdev, struct sockaddr_in6 *sin6_src,
                       union ndp_header *ndp, union ndp_option *option,
                       size_t len );
};

/** NDP option handlers */
static struct ndp_option_handler ndp_option_handlers[] = {
        {
                .icmp_type = ICMPV6_NEIGHBOUR_SOLICITATION,
                .option_type = NDP_OPT_LL_SOURCE,
                .rx = ndp_rx_neighbour_solicitation_ll_source,
        },
        {
                .icmp_type = ICMPV6_NEIGHBOUR_ADVERTISEMENT,
                .option_type = NDP_OPT_LL_TARGET,
                .rx = ndp_rx_neighbour_advertisement_ll_target,
        },
        {
                .icmp_type = ICMPV6_ROUTER_ADVERTISEMENT,
                .option_type = NDP_OPT_LL_SOURCE,
                .rx = ndp_rx_router_advertisement_ll_source,
        },
        {
                .icmp_type = ICMPV6_ROUTER_ADVERTISEMENT,
                .option_type = NDP_OPT_PREFIX,
                .rx = ndp_rx_router_advertisement_prefix,
        },
};

/**
 * Process received NDP option
 *
 * @v netdev            Network device
 * @v sin6_src          Source socket address
 * @v ndp               NDP packet
 * @v option            NDP option
 * @v len               Option length
 * @ret rc              Return status code
 */
static int ndp_rx_option ( struct net_device *netdev,
                           struct sockaddr_in6 *sin6_src, union ndp_header *ndp,
                           union ndp_option *option, size_t len ) {
        struct ndp_option_handler *handler;
        unsigned int i;

        /* Locate a suitable option handler, if any */
        for ( i = 0 ; i < ( sizeof ( ndp_option_handlers ) /
                            sizeof ( ndp_option_handlers[0] ) ) ; i++ ) {
                handler = &ndp_option_handlers[i];
                if ( ( handler->icmp_type == ndp->icmp.type ) &&
                     ( handler->option_type == option->header.type ) ) {
                        return handler->rx ( netdev, sin6_src, ndp,
                                             option, len );
                }
        }

        /* Silently ignore unknown options as per RFC 4861 */
        return 0;
}

/**
 * Process received NDP packet options
 *
 * @v netdev            Network device
 * @v sin6_src          Source socket address
 * @v ndp               NDP header
 * @v offset            Offset to NDP options
 * @v len               Length of NDP packet
 * @ret rc              Return status code
 */
static int ndp_rx_options ( struct net_device *netdev,
                            struct sockaddr_in6 *sin6_src,
                            union ndp_header *ndp, size_t offset, size_t len ) {
        union ndp_option *option;
        size_t remaining;
        size_t option_len;
        int rc;

        /* Sanity check */
        if ( len < offset ) {
                DBGC ( netdev, "NDP %s packet too short at %zd bytes (min %zd "
                       "bytes)\n", netdev->name, len, offset );
                return -EINVAL;
        }

        /* Search for option */
        option = ( ( ( void * ) ndp ) + offset );
        remaining = ( len - offset );
        while ( remaining ) {

                /* Sanity check */
                if ( ( remaining < sizeof ( option->header ) ) ||
                     ( option->header.blocks == 0 ) ||
                     ( remaining < ( option->header.blocks *
                                     NDP_OPTION_BLKSZ ) ) ) {
                        DBGC ( netdev, "NDP %s bad option length:\n",
                               netdev->name );
                        DBGC_HDA ( netdev, 0, option, remaining );
                        return -EINVAL;
                }
                option_len = ( option->header.blocks * NDP_OPTION_BLKSZ );

                /* Handle option */
                if ( ( rc = ndp_rx_option ( netdev, sin6_src, ndp, option,
                                            option_len ) ) != 0 )
                        return rc;

                /* Move to next option */
                option = ( ( ( void * ) option ) + option_len );
                remaining -= option_len;
        }

        return 0;
}

/**
 * Process received NDP neighbour solicitation or advertisement
 *
 * @v iobuf             I/O buffer
 * @v netdev            Network device
 * @v sin6_src          Source socket address
 * @v sin6_dest         Destination socket address
 * @ret rc              Return status code
 */
static int ndp_rx_neighbour ( struct io_buffer *iobuf,
                              struct net_device *netdev,
                              struct sockaddr_in6 *sin6_src,
                              struct sockaddr_in6 *sin6_dest __unused ) {
        union ndp_header *ndp = iobuf->data;
        struct ndp_neighbour_header *neigh = &ndp->neigh;
        size_t len = iob_len ( iobuf );
        int rc;

        /* Process options */
        if ( ( rc = ndp_rx_options ( netdev, sin6_src, ndp,
                                     offsetof ( typeof ( *neigh ), option ),
                                     len ) ) != 0 )
                goto err_options;

 err_options:
        free_iob ( iobuf );
        return rc;
}

/**
 * Process received NDP router advertisement
 *
 * @v iobuf             I/O buffer
 * @v netdev            Network device
 * @v sin6_src          Source socket address
 * @v sin6_dest         Destination socket address
 * @ret rc              Return status code
 */
static int
ndp_rx_router_advertisement ( struct io_buffer *iobuf,
                              struct net_device *netdev,
                              struct sockaddr_in6 *sin6_src,
                              struct sockaddr_in6 *sin6_dest __unused ) {
        union ndp_header *ndp = iobuf->data;
        struct ndp_router_advertisement_header *radv = &ndp->radv;
        struct in6_addr *router = &sin6_src->sin6_addr;
        size_t len = iob_len ( iobuf );
        int rc;

        /* Process options */
        if ( ( rc = ndp_rx_options ( netdev, sin6_src, ndp,
                                     offsetof ( typeof ( *radv ), option ),
                                     len ) ) != 0 )
                goto err_options;

        /* Pass to IPv6 autoconfiguration */
        if ( ( rc = ipv6conf_rx_router_advertisement ( netdev, router,
                                                       radv, len ) ) != 0 )
                goto err_ipv6conf;

 err_ipv6conf:
 err_options:
        free_iob ( iobuf );
        return rc;
}

/** NDP ICMPv6 handlers */
struct icmpv6_handler ndp_handlers[] __icmpv6_handler = {
        {
                .type = ICMPV6_NEIGHBOUR_SOLICITATION,
                .rx = ndp_rx_neighbour,
        },
        {
                .type = ICMPV6_NEIGHBOUR_ADVERTISEMENT,
                .rx = ndp_rx_neighbour,
        },
        {
                .type = ICMPV6_ROUTER_ADVERTISEMENT,
                .rx = ndp_rx_router_advertisement,
        },
};

/****************************************************************************
 *
 * NDP settings
 *
 */

/** An NDP prefix settings block */
struct ndp_prefix_settings {
        /** Settings interface */
        struct settings settings;
        /** Name */
        char name[4];
        /** Prefix information option */
        struct ndp_prefix_information_option *prefix;
};

/** An NDP settings block */
struct ndp_settings {
        /** Reference counter */
        struct refcnt refcnt;
        /** Settings interface */
        struct settings settings;
        /** Router address */
        struct in6_addr router;
        /** Router lifetime */
        unsigned int lifetime;
        /** Length of NDP options */
        size_t len;
        /** NDP options */
        union ndp_option options[0];
};

/** NDP settings scope */
static const struct settings_scope ndp_settings_scope;

/**
 * Construct NDP tag
 *
 * @v type              NDP option type
 * @v offset            Starting offset of data
 * @v len               Length of data (or 0 to use all remaining data)
 * @ret tag             NDP tag
 */
#define NDP_TAG( type, offset, len ) \
        ( ( (len) << 16 ) | ( (offset) << 8 ) | (type) )

/**
 * Extract NDP tag type
 *
 * @v tag               NDP tag
 * @ret type            NDP option type
 */
#define NDP_TAG_TYPE( tag ) ( ( (tag) >> 0 ) & 0xff )

/**
 * Extract NDP tag offset
 *
 * @v tag               NDP tag
 * @ret offset          Starting offset of data
 */
#define NDP_TAG_OFFSET( tag ) ( ( (tag) >> 8 ) & 0xff )

/**
 * Extract NDP tag length
 *
 * @v tag               NDP tag
 * @ret len             Length of data (or 0 to use all remaining data)
 */
#define NDP_TAG_LEN( tag ) ( ( (tag) >> 16 ) & 0xff )

/**
 * Extract NDP tag instance
 *
 * @v tag               NDP tag
 * @ret instance        Instance
 */
#define NDP_TAG_INSTANCE( tag ) ( ( (tag) >> 24 ) & 0xff )

/**
 * Check applicability of NDP setting
 *
 * @v settings          Settings block
 * @v setting           Setting to fetch
 * @ret applies         Setting applies within this settings block
 */
static int ndp_applies ( struct settings *settings __unused,
                         const struct setting *setting ) {

        return ( setting->scope == &ndp_settings_scope );
}

/**
 * Fetch value of NDP 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
 */
static int ndp_fetch ( struct settings *settings,
                       struct setting *setting,
                       void *data, size_t len ) {
        struct ndp_settings *ndpset =
                container_of ( settings, struct ndp_settings, settings );
        struct net_device *netdev =
                container_of ( settings->parent, struct net_device,
                               settings.settings );
        union ndp_option *option;
        unsigned int tag_type;
        unsigned int tag_offset;
        unsigned int tag_len;
        unsigned int tag_instance;
        size_t offset;
        size_t option_len;
        void *option_data;

        /* Parse setting tag */
        tag_type = NDP_TAG_TYPE ( setting->tag );
        tag_offset = NDP_TAG_OFFSET ( setting->tag );
        tag_len = NDP_TAG_LEN ( setting->tag );
        tag_instance = NDP_TAG_INSTANCE ( setting->tag );

        /* Scan through NDP options for requested type.  We can assume
         * that the options are well-formed, otherwise they would have
         * been rejected prior to being stored.
         */
        for ( offset = 0 ; offset < ndpset->len ; offset += option_len ) {

                /* Calculate option length */
                option = ( ( ( void * ) ndpset->options ) + offset );
                option_len = ( option->header.blocks * NDP_OPTION_BLKSZ );

                /* Skip options that do not match this tag */
                if ( option->header.type != tag_type )
                        continue;

                /* Skip previous instances of this option */
                if ( tag_instance-- != 0 )
                        continue;

                /* Sanity check */
                if ( ( tag_offset + tag_len ) > option_len ) {
                        DBGC ( netdev, "NDP %s option %d too short\n",
                               netdev->name, tag_type );
                        return -EINVAL;
                }
                if ( ! tag_len )
                        tag_len = ( option_len - tag_offset );
                option_data = ( ( ( void * ) option ) + tag_offset );

                /* Copy data to output buffer */
                if ( len > tag_len )
                        len = tag_len;
                memcpy ( data, option_data, len );

                /* Default to hex if no type is specified */
                if ( ! setting->type )
                        setting->type = &setting_type_hex;

                return tag_len;
        }

        return -ENOENT;
}

/** NDP settings operations */
static struct settings_operations ndp_settings_operations = {
        .applies = ndp_applies,
        .fetch = ndp_fetch,
};

/**
 * Check applicability of NDP per-prefix setting
 *
 * @v settings          Settings block
 * @v setting           Setting to fetch
 * @ret applies         Setting applies within this settings block
 */
static int ndp_prefix_applies ( struct settings *settings __unused,
                                const struct setting *setting ) {

        return ( setting->scope == &ipv6_settings_scope );
}

/**
 * Fetch value of NDP IPv6 address setting
 *
 * @v settings          Settings block
 * @v data              Buffer to fill with setting data
 * @v len               Length of buffer
 * @ret len             Length of setting data, or negative error
 */
static int ndp_prefix_fetch_ip6 ( struct settings *settings, void *data,
                                  size_t len ) {
        struct ndp_prefix_settings *prefset =
                container_of ( settings, struct ndp_prefix_settings, settings );
        struct ndp_settings *ndpset =
                container_of ( settings->parent, struct ndp_settings, settings);
        struct net_device *netdev =
                container_of ( ndpset->settings.parent, struct net_device,
                               settings.settings );
        struct ndp_prefix_information_option *prefix = prefset->prefix;
        struct in6_addr *ip6 = &prefix->prefix;
        struct in6_addr slaac;
        int prefix_len;
        int rc;

        /* Skip dead prefixes */
        if ( ! prefix->valid )
                return -ENOENT;

        /* Construct IPv6 address via SLAAC, if applicable */
        if ( prefix->flags & NDP_PREFIX_AUTONOMOUS ) {
                memcpy ( &slaac, ip6, sizeof ( slaac ) );
                prefix_len = ipv6_eui64 ( &slaac, netdev );
                if ( prefix_len == prefix->prefix_len ) {
                        /* Correctly configured prefix: use SLAAC address */
                        ip6 = &slaac;
                } else if ( prefix_len < 0 ) {
                        /* Link layer does not support SLAAC */
                        rc = prefix_len;
                        DBGC ( netdev, "NDP %s does not support SLAAC: %s\n",
                               netdev->name, strerror ( rc ) );
                } else {
                        /* Prefix length incorrect: assume a badly
                         * configured router and ignore SLAAC address.
                         */
                        DBGC ( netdev, "NDP %s ignoring misconfigured SLAAC "
                               "on prefix %s/%d\n", netdev->name,
                               inet6_ntoa ( ip6 ), prefix->prefix_len );
                }
        }

        /* Fill in IPv6 address */
        if ( len > sizeof ( *ip6 ) )
                len = sizeof ( *ip6 );
        memcpy ( data, ip6, len );

        return sizeof ( *ip6 );
}

/**
 * Fetch value of NDP prefix length setting
 *
 * @v settings          Settings block
 * @v data              Buffer to fill with setting data
 * @v len               Length of buffer
 * @ret len             Length of setting data, or negative error
 */
static int ndp_prefix_fetch_len6 ( struct settings *settings, void *data,
                                   size_t len ) {
        struct ndp_prefix_settings *prefset =
                container_of ( settings, struct ndp_prefix_settings, settings );
        struct ndp_prefix_information_option *prefix = prefset->prefix;
        uint8_t *len6;

        /* Fill in prefix length */
        if ( len >= sizeof ( *len6 ) ) {
                /* We treat an off-link prefix as having a prefix
                 * length covering the entire IPv6 address.
                 */
                len6 = data;
                *len6 = ( ( prefix->flags & NDP_PREFIX_ON_LINK ) ?
                          prefix->prefix_len : -1UL );
        }

        return sizeof ( *len6 );
}

/**
 * Fetch value of NDP router address setting
 *
 * @v settings          Settings block
 * @v data              Buffer to fill with setting data
 * @v len               Length of buffer
 * @ret len             Length of setting data, or negative error
 */
static int ndp_prefix_fetch_gateway6 ( struct settings *settings,
                                       void *data, size_t len ) {
        struct ndp_settings *ndpset =
                container_of ( settings->parent, struct ndp_settings, settings);

        /* Treat non-routing router as non-existent */
        if ( ! ndpset->lifetime )
                return -ENOENT;

        /* Fill in router address */
        if ( len > sizeof ( ndpset->router ) )
                len = sizeof ( ndpset->router );
        memcpy ( data, &ndpset->router, len );

        return sizeof ( ndpset->router );
}

/** An NDP per-prefix setting operation */
struct ndp_prefix_operation {
        /** Generic setting */
        const struct setting *setting;
        /**
         * Fetch value of setting
         *
         * @v settings          Settings block
         * @v data              Buffer to fill with setting data
         * @v len               Length of buffer
         * @ret len             Length of setting data, or negative error
         */
        int ( * fetch ) ( struct settings *settings, void *data, size_t len );
};

/** NDP per-prefix settings operations */
static struct ndp_prefix_operation ndp_prefix_operations[] = {
        { &ip6_setting, ndp_prefix_fetch_ip6 },
        { &len6_setting, ndp_prefix_fetch_len6 },
        { &gateway6_setting, ndp_prefix_fetch_gateway6 },
};

/**
 * Fetch value of NDP pre-prefix 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
 */
static int ndp_prefix_fetch ( struct settings *settings,
                              struct setting *setting,
                              void *data, size_t len ) {
        struct ndp_prefix_operation *op;
        unsigned int i;

        /* Handle per-prefix settings */
        for ( i = 0 ; i < ( sizeof ( ndp_prefix_operations ) /
                            sizeof ( ndp_prefix_operations[0] ) ) ; i++ ) {
                op = &ndp_prefix_operations[i];
                if ( setting_cmp ( setting, op->setting ) == 0 )
                        return op->fetch ( settings, data, len );
        }

        return -ENOENT;
}

/** NDP per-prefix settings operations */
static struct settings_operations ndp_prefix_settings_operations = {
        .applies = ndp_prefix_applies,
        .fetch = ndp_prefix_fetch,
};

/**
 * Register NDP settings
 *
 * @v netdev            Network device
 * @v router            Router address
 * @v lifetime          Router lifetime
 * @v options           NDP options
 * @v len               Length of options
 * @ret rc              Return status code
 */
static int ndp_register_settings ( struct net_device *netdev,
                                   struct in6_addr *router,
                                   unsigned int lifetime,
                                   union ndp_option *options, size_t len ) {
        struct settings *parent = netdev_settings ( netdev );
        union ndp_option *option;
        struct ndp_settings *ndpset;
        struct ndp_prefix_settings *prefset;
        size_t offset;
        size_t option_len;
        unsigned int prefixes;
        unsigned int instance;
        int order;
        int rc;

        /* Count number of prefix options.  We can assume that the
         * options are well-formed, otherwise they would have been
         * rejected prior to being stored.
         */
        order = IPV6_ORDER_PREFIX_ONLY;
        for ( prefixes = 0, offset = 0 ; offset < len ; offset += option_len ) {

                /* Skip non-prefix options */
                option = ( ( ( void * ) options ) + offset );
                option_len = ( option->header.blocks * NDP_OPTION_BLKSZ );
                if ( option->header.type != NDP_OPT_PREFIX )
                        continue;

                /* Count number of prefixes */
                prefixes++;

                /* Increase overall order if we have SLAAC addresses */
                if ( option->prefix.flags & NDP_PREFIX_AUTONOMOUS )
                        order = IPV6_ORDER_SLAAC;
        }

        /* Allocate and initialise structure */
        ndpset = zalloc ( sizeof ( *ndpset ) + len +
                          ( prefixes * sizeof ( *prefset ) ) );
        if ( ! ndpset ) {
                rc = -ENOMEM;
                goto err_alloc;
        }
        ref_init ( &ndpset->refcnt, NULL );
        settings_init ( &ndpset->settings, &ndp_settings_operations,
                        &ndpset->refcnt, &ndp_settings_scope );
        ndpset->settings.order = order;
        memcpy ( &ndpset->router, router, sizeof ( ndpset->router ) );
        ndpset->lifetime = lifetime;
        ndpset->len = len;
        memcpy ( ndpset->options, options, len );
        prefset = ( ( ( void * ) ndpset->options ) + len );

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

        /* Construct and register per-prefix settings */
        for ( instance = 0, offset = 0 ; offset < len ; offset += option_len ) {

                /* Skip non-prefix options */
                option = ( ( ( void * ) ndpset->options ) + offset );
                option_len = ( option->header.blocks * NDP_OPTION_BLKSZ );
                if ( option->header.type != NDP_OPT_PREFIX )
                        continue;

                /* Initialise structure */
                settings_init ( &prefset->settings,
                                &ndp_prefix_settings_operations,
                                &ndpset->refcnt, &ndp_settings_scope );
                prefset->settings.order =
                        ( ( option->prefix.flags & NDP_PREFIX_AUTONOMOUS ) ?
                          IPV6_ORDER_SLAAC : IPV6_ORDER_PREFIX_ONLY );
                prefset->prefix = &option->prefix;
                snprintf ( prefset->name, sizeof ( prefset->name ), "%d",
                           instance++ );

                /* Register settings */
                if ( ( rc = register_settings ( &prefset->settings,
                                                &ndpset->settings,
                                                prefset->name ) ) != 0 )
                        goto err_register_prefix;

                /* Move to next per-prefix settings */
                prefset++;
        }
        assert ( instance == prefixes );

        ref_put ( &ndpset->refcnt );
        return 0;

 err_register_prefix:
        unregister_settings ( &ndpset->settings );
 err_register:
        ref_put ( &ndpset->refcnt );
 err_alloc:
        return rc;
}

/** DNS server setting */
const struct setting ndp_dns6_setting __setting ( SETTING_IP6_EXTRA, dns6 ) = {
        .name = "dns6",
        .description = "DNS server",
        .tag = NDP_TAG ( NDP_OPT_RDNSS,
                         offsetof ( struct ndp_rdnss_option, addresses ), 0 ),
        .type = &setting_type_ipv6,
        .scope = &ndp_settings_scope,
};

/** DNS search list setting */
const struct setting ndp_dnssl_setting __setting ( SETTING_IP_EXTRA, dnssl ) = {
        .name = "dnssl",
        .description = "DNS search list",
        .tag = NDP_TAG ( NDP_OPT_DNSSL,
                         offsetof ( struct ndp_dnssl_option, names ), 0 ),
        .type = &setting_type_dnssl,
        .scope = &ndp_settings_scope,
};

/****************************************************************************
 *
 * IPv6 autoconfiguration
 *
 */

/** An IPv6 configurator */
struct ipv6conf {
        /** Reference count */
        struct refcnt refcnt;
        /** List of configurators */
        struct list_head list;

        /** Job control interface */
        struct interface job;
        /** DHCPv6 interface */
        struct interface dhcp;

        /** Network device being configured */
        struct net_device *netdev;

        /** Retransmission timer */
        struct retry_timer timer;

        /** Deferred discovery counter */
        unsigned int deferred;
};

/** List of IPv6 configurators */
static LIST_HEAD ( ipv6confs );

/**
 * Free IPv6 configurator
 *
 * @v refcnt            Reference count
 */
static void ipv6conf_free ( struct refcnt *refcnt ) {
        struct ipv6conf *ipv6conf =
                container_of ( refcnt, struct ipv6conf, refcnt );

        netdev_put ( ipv6conf->netdev );
        free ( ipv6conf );
}

/**
 * Identify IPv6 configurator by network device
 *
 * @v netdev            Network device
 * @ret ipv6            IPv6 configurator, or NULL
 */
static struct ipv6conf * ipv6conf_demux ( struct net_device *netdev ) {
        struct ipv6conf *ipv6conf;

        list_for_each_entry ( ipv6conf, &ipv6confs, list ) {
                if ( ipv6conf->netdev == netdev )
                        return ipv6conf;
        }
        return NULL;
}

/**
 * Finish IPv6 autoconfiguration
 *
 * @v ipv6              IPv6 configurator
 * @v rc                Reason for finishing
 */
static void ipv6conf_done ( struct ipv6conf *ipv6conf, int rc ) {

        /* Shut down interfaces */
        intf_shutdown ( &ipv6conf->job, rc );
        intf_shutdown ( &ipv6conf->dhcp, rc );

        /* Stop timer */
        stop_timer ( &ipv6conf->timer );

        /* Remove from list and drop list's reference */
        list_del ( &ipv6conf->list );
        ref_put ( &ipv6conf->refcnt );
}

/**
 * Handle IPv6 configurator timer expiry
 *
 * @v timer             Retry timer
 * @v fail              Failure indicator
 */
static void ipv6conf_expired ( struct retry_timer *timer, int fail ) {
        struct ipv6conf *ipv6conf =
                container_of ( timer, struct ipv6conf, timer );
        struct net_device *netdev = ipv6conf->netdev;

        /* If we have failed, terminate autoconfiguration */
        if ( fail ) {
                ipv6conf_done ( ipv6conf, -ETIMEDOUT );
                return;
        }

        /* Otherwise, transmit router solicitation and restart timer */
        start_timer ( &ipv6conf->timer );
        ndp_tx_router_solicitation ( netdev );

        /* If link is blocked, defer router discovery timeout */
        if ( netdev_link_blocked ( netdev ) &&
             ( ipv6conf->deferred++ <= IPV6CONF_MAX_DEFERRALS ) ) {
                DBGC ( netdev, "NDP %s deferring discovery timeout\n",
                       netdev->name );
                start_timer_fixed ( &ipv6conf->timer, IPV6CONF_BLOCK_TIMEOUT );
        }
}

/**
 * Handle router advertisement during IPv6 autoconfiguration
 *
 * @v netdev            Network device
 * @v router            Router address
 * @v radv              Router advertisement
 * @v len               Length of router advertisement
 * @ret rc              Return status code
 *
 * This function assumes that the router advertisement is well-formed,
 * since it must have already passed through option processing.
 */
static int
ipv6conf_rx_router_advertisement ( struct net_device *netdev,
                                   struct in6_addr *router,
                                   struct ndp_router_advertisement_header *radv,
                                   size_t len ) {
        struct ipv6conf *ipv6conf;
        size_t option_len;
        int stateful;
        int rc;

        /* Identify IPv6 configurator, if any */
        ipv6conf = ipv6conf_demux ( netdev );

        /* Do nothing unless IPv6 autoconfiguration is in progress */
        if ( ! ipv6conf )
                return 0;

        /* If this is not the first solicited router advertisement, ignore it */
        if ( ! timer_running ( &ipv6conf->timer ) )
                return 0;

        /* Stop router solicitation timer */
        stop_timer ( &ipv6conf->timer );

        /* Register NDP settings */
        option_len = ( len - offsetof ( typeof ( *radv ), option ) );
        if ( ( rc = ndp_register_settings ( netdev, router,
                                            ntohl ( radv->lifetime ),
                                            radv->option, option_len ) ) != 0 )
                return rc;

        /* Start DHCPv6 if required */
        if ( radv->flags & ( NDP_ROUTER_MANAGED | NDP_ROUTER_OTHER ) ) {
                stateful = ( radv->flags & NDP_ROUTER_MANAGED );
                if ( ( rc = start_dhcpv6 ( &ipv6conf->dhcp, netdev, router,
                                           stateful ) ) != 0 ) {
                        DBGC ( netdev, "NDP %s could not start state%s DHCPv6: "
                               "%s\n", netdev->name,
                               ( stateful ? "ful" : "less" ), strerror ( rc ) );
                        ipv6conf_done ( ipv6conf, rc );
                        return rc;
                }
                return 0;
        }

        /* Otherwise, terminate autoconfiguration */
        ipv6conf_done ( ipv6conf, 0 );

        return 0;
}

/** IPv6 configurator job interface operations */
static struct interface_operation ipv6conf_job_op[] = {
        INTF_OP ( intf_close, struct ipv6conf *, ipv6conf_done ),
};

/** IPv6 configurator job interface descriptor */
static struct interface_descriptor ipv6conf_job_desc =
        INTF_DESC ( struct ipv6conf, job, ipv6conf_job_op );

/** IPv6 configurator DHCPv6 interface operations */
static struct interface_operation ipv6conf_dhcp_op[] = {
        INTF_OP ( intf_close, struct ipv6conf *, ipv6conf_done ),
};

/** IPv6 configurator DHCPv6 interface descriptor */
static struct interface_descriptor ipv6conf_dhcp_desc =
        INTF_DESC ( struct ipv6conf, dhcp, ipv6conf_dhcp_op );

/**
 * Start IPv6 autoconfiguration
 *
 * @v job               Job control interface
 * @v netdev            Network device
 * @ret rc              Return status code
 */
int start_ipv6conf ( struct interface *job, struct net_device *netdev ) {
        struct ipv6conf *ipv6conf;

        /* Allocate and initialise structure */
        ipv6conf = zalloc ( sizeof ( *ipv6conf ) );
        if ( ! ipv6conf )
                return -ENOMEM;
        ref_init ( &ipv6conf->refcnt, ipv6conf_free );
        intf_init ( &ipv6conf->job, &ipv6conf_job_desc, &ipv6conf->refcnt );
        intf_init ( &ipv6conf->dhcp, &ipv6conf_dhcp_desc, &ipv6conf->refcnt );
        timer_init ( &ipv6conf->timer, ipv6conf_expired, &ipv6conf->refcnt );
        set_timer_limits ( &ipv6conf->timer, IPV6CONF_MIN_TIMEOUT,
                           IPV6CONF_MAX_TIMEOUT );
        ipv6conf->netdev = netdev_get ( netdev );

        /* Start timer to initiate router solicitation */
        start_timer_nodelay ( &ipv6conf->timer );

        /* Attach parent interface, transfer reference to list, and return */
        intf_plug_plug ( &ipv6conf->job, job );
        list_add ( &ipv6conf->list, &ipv6confs );
        return 0;
}

/** IPv6 network device configurator */
struct net_device_configurator ipv6_configurator __net_device_configurator = {
        .name = "ipv6",
        .start = start_ipv6conf,
};