ipv4.c

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/*
 * Copyright (C) 2006 Michael Brown <mbrown@fensystems.co.uk>.
 * Copyright (C) 2006 Nikhil Chandru Rao
 *
 * 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 (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

#include <string.h>
#include <stdint.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <byteswap.h>
#include <ipxe/list.h>
#include <ipxe/in.h>
#include <ipxe/arp.h>
#include <ipxe/if_ether.h>
#include <ipxe/iobuf.h>
#include <ipxe/netdevice.h>
#include <ipxe/ip.h>
#include <ipxe/tcpip.h>
#include <ipxe/dhcp.h>
#include <ipxe/settings.h>
#include <ipxe/fragment.h>
#include <ipxe/ipstat.h>
#include <ipxe/profile.h>

/** @file
 *
 * IPv4 protocol
 *
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

/* Unique IP datagram identification number (high byte) */
static uint8_t next_ident_high = 0;

/** List of IPv4 miniroutes */
struct list_head ipv4_miniroutes = LIST_HEAD_INIT ( ipv4_miniroutes );

/** IPv4 statistics */
static struct ip_statistics ipv4_stats;

/** IPv4 statistics family */
struct ip_statistics_family
ipv4_stats_family __ip_statistics_family ( IP_STATISTICS_IPV4 ) = {
        .version = 4,
        .stats = &ipv4_stats,
};

/** Transmit profiler */
static struct profiler ipv4_tx_profiler __profiler = { .name = "ipv4.tx" };

/** Receive profiler */
static struct profiler ipv4_rx_profiler __profiler = { .name = "ipv4.rx" };

/**
 * Add IPv4 minirouting table entry
 *
 * @v netdev            Network device
 * @v address           IPv4 address
 * @v network           Subnet address
 * @v netmask           Subnet mask
 * @v gateway           Gateway address (if any)
 * @ret rc              Return status code
 */
static int ipv4_add_miniroute ( struct net_device *netdev,
                                struct in_addr address,
                                struct in_addr network,
                                struct in_addr netmask,
                                struct in_addr gateway ) {
        struct ipv4_miniroute *miniroute;
        struct ipv4_miniroute *before;
        struct in_addr hostmask;
        struct in_addr broadcast;

        /* Calculate host mask */
        if ( gateway.s_addr || IN_IS_SMALL ( netmask.s_addr ) ) {
                hostmask.s_addr = INADDR_NONE;
        } else {
                hostmask.s_addr = ~netmask.s_addr;
        }
        broadcast.s_addr = ( network.s_addr | hostmask.s_addr );

        /* Print debugging information */
        DBGC ( netdev, "IPv4 add %s", inet_ntoa ( address ) );
        DBGC ( netdev, " for %s", inet_ntoa ( network ) );
        DBGC ( netdev, "/%s ", inet_ntoa ( netmask ) );
        DBGC ( netdev, "bc %s ", inet_ntoa ( broadcast ) );
        if ( gateway.s_addr )
                DBGC ( netdev, "gw %s ", inet_ntoa ( gateway ) );
        DBGC ( netdev, "via %s\n", netdev->name );

        /* Allocate and populate miniroute structure */
        miniroute = malloc ( sizeof ( *miniroute ) );
        if ( ! miniroute ) {
                DBGC ( netdev, "IPv4 could not add miniroute\n" );
                return -ENOMEM;
        }

        /* Record routing information */
        miniroute->netdev = netdev_get ( netdev );
        miniroute->address = address;
        miniroute->network = network;
        miniroute->netmask = netmask;
        miniroute->hostmask = hostmask;
        miniroute->gateway = gateway;

        /* Add to routing table ahead of any less specific routes */
        list_for_each_entry ( before, &ipv4_miniroutes, list ) {
                if ( netmask.s_addr & ~before->netmask.s_addr )
                        break;
        }
        list_add_tail ( &miniroute->list, &before->list );

        return 0;
}

/**
 * Add static route minirouting table entries
 *
 * @v netdev            Network device
 * @v address           IPv4 address
 * @v routes            Static routes
 * @v len               Length of static routes
 * @ret rc              Return status code
 */
static int ipv4_add_static ( struct net_device *netdev, struct in_addr address,
                             const void *routes, size_t len ) {
        const struct {
                struct in_addr address;
        } __attribute__ (( packed )) *encoded;
        struct in_addr netmask;
        struct in_addr network;
        struct in_addr gateway;
        unsigned int width;
        unsigned int masklen;
        size_t remaining;
        const void *data;
        int rc;

        /* Parse and add static routes */
        for ( data = routes, remaining = len ; remaining ; ) {

                /* Extract subnet mask width */
                width = *( ( uint8_t * ) data );
                data++;
                remaining--;
                masklen = ( ( width + 7 ) / 8 );

                /* Check remaining length */
                if ( ( masklen + sizeof ( gateway ) ) > remaining ) {
                        DBGC ( netdev, "IPv4 invalid static route:\n" );
                        DBGC_HDA ( netdev, 0, routes, len );
                        return -EINVAL;
                }

                /* Calculate subnet mask */
                if ( width ) {
                        netmask.s_addr = htonl ( -1UL << ( 32 - width ) );
                } else {
                        netmask.s_addr = 0;
                }

                /* Extract network address */
                encoded = data;
                network.s_addr = ( encoded->address.s_addr & netmask.s_addr );
                data += masklen;
                remaining -= masklen;

                /* Extract gateway address */
                encoded = data;
                gateway.s_addr = encoded->address.s_addr;
                data += sizeof ( gateway );
                remaining -= sizeof ( gateway );

                /* Add route */
                if ( ( rc = ipv4_add_miniroute ( netdev, address, network,
                                                 netmask, gateway ) ) != 0 )
                        return rc;
        }

        return 0;
}

/**
 * Add IPv4 minirouting table entries
 *
 * @v netdev            Network device
 * @v address           IPv4 address
 * @ret rc              Return status code
 */
static int ipv4_add_miniroutes ( struct net_device *netdev,
                                 struct in_addr address ) {
        struct settings *settings = netdev_settings ( netdev );
        struct in_addr none = { 0 };
        struct in_addr netmask;
        struct in_addr gateway;
        struct in_addr network;
        void *routes;
        int len;
        int rc;

        /* Get subnet mask */
        fetch_ipv4_setting ( settings, &netmask_setting, &netmask );

        /* Calculate default netmask, if necessary */
        if ( ! netmask.s_addr ) {
                if ( IN_IS_CLASSA ( address.s_addr ) ) {
                        netmask.s_addr = INADDR_NET_CLASSA;
                } else if ( IN_IS_CLASSB ( address.s_addr ) ) {
                        netmask.s_addr = INADDR_NET_CLASSB;
                } else if ( IN_IS_CLASSC ( address.s_addr ) ) {
                        netmask.s_addr = INADDR_NET_CLASSC;
                }
        }

        /* Get default gateway, if present */
        fetch_ipv4_setting ( settings, &gateway_setting, &gateway );

        /* Get static routes, if present */
        len = fetch_raw_setting_copy ( settings, &static_route_setting,
                                       &routes );

        /* Add local address */
        network.s_addr = ( address.s_addr & netmask.s_addr );
        if ( ( rc = ipv4_add_miniroute ( netdev, address, network, netmask,
                                         none ) ) != 0 )
                goto done;

        /* Add static routes or default gateway, as applicable */
        if ( len >= 0 ) {
                if ( ( rc = ipv4_add_static ( netdev, address, routes,
                                              len ) ) != 0 )
                        goto done;
        } else if ( gateway.s_addr ) {
                if ( ( rc = ipv4_add_miniroute ( netdev, address, none, none,
                                                 gateway ) ) != 0 )
                        goto done;
        }

 done:
        free ( routes );
        return rc;
}

/**
 * Delete IPv4 minirouting table entry
 *
 * @v miniroute         Routing table entry
 */
static void ipv4_del_miniroute ( struct ipv4_miniroute *miniroute ) {
        struct net_device *netdev = miniroute->netdev;

        DBGC ( netdev, "IPv4 del %s", inet_ntoa ( miniroute->address ) );
        DBGC ( netdev, " for %s", inet_ntoa ( miniroute->network ) );
        DBGC ( netdev, "/%s ", inet_ntoa ( miniroute->netmask ) );
        if ( miniroute->gateway.s_addr )
                DBGC ( netdev, "gw %s ", inet_ntoa ( miniroute->gateway ) );
        DBGC ( netdev, "via %s\n", miniroute->netdev->name );

        netdev_put ( miniroute->netdev );
        list_del ( &miniroute->list );
        free ( miniroute );
}

/**
 * Delete IPv4 minirouting table entries
 *
 */
static void ipv4_del_miniroutes ( void ) {
        struct ipv4_miniroute *miniroute;
        struct ipv4_miniroute *tmp;

        /* Delete all existing routes */
        list_for_each_entry_safe ( miniroute, tmp, &ipv4_miniroutes, list )
                ipv4_del_miniroute ( miniroute );
}

/**
 * Perform IPv4 routing
 *
 * @v scope_id          Destination address scope ID
 * @v dest              Final destination address
 * @ret dest            Next hop destination address
 * @ret miniroute       Routing table entry to use, or NULL if no route
 *
 * If the route requires use of a gateway, the next hop destination
 * address will be overwritten with the gateway address.
 */
struct ipv4_miniroute * ipv4_route ( unsigned int scope_id,
                                     struct in_addr *dest ) {
        struct ipv4_miniroute *miniroute;

        /* Find first usable route in routing table */
        list_for_each_entry ( miniroute, &ipv4_miniroutes, list ) {

                /* Skip closed network devices */
                if ( ! netdev_is_open ( miniroute->netdev ) )
                        continue;

                if ( IN_IS_MULTICAST ( dest->s_addr ) ) {

                        /* If destination is non-global, and the scope
                         * ID matches this network device, then use
                         * the first matching route.
                         */
                        if ( miniroute->netdev->scope_id == scope_id )
                                return miniroute;

                } else {

                        /* If destination is global, then use the
                         * first matching route (via its gateway if
                         * specified).
                         */
                        if ( ( ( dest->s_addr ^ miniroute->network.s_addr )
                               & miniroute->netmask.s_addr ) == 0 ) {
                                if ( miniroute->gateway.s_addr )
                                        *dest = miniroute->gateway;
                                return miniroute;
                        }
                }
        }

        return NULL;
}

/**
 * Determine transmitting network device
 *
 * @v st_dest           Destination network-layer address
 * @ret netdev          Transmitting network device, or NULL
 */
static struct net_device * ipv4_netdev ( struct sockaddr_tcpip *st_dest ) {
        struct sockaddr_in *sin_dest = ( ( struct sockaddr_in * ) st_dest );
        struct in_addr dest = sin_dest->sin_addr;
        struct ipv4_miniroute *miniroute;

        /* Find routing table entry */
        miniroute = ipv4_route ( sin_dest->sin_scope_id, &dest );
        if ( ! miniroute )
                return NULL;

        return miniroute->netdev;
}

/**
 * Check if IPv4 fragment matches fragment reassembly buffer
 *
 * @v fragment          Fragment reassembly buffer
 * @v iobuf             I/O buffer
 * @v hdrlen            Length of non-fragmentable potion of I/O buffer
 * @ret is_fragment     Fragment matches this reassembly buffer
 */
static int ipv4_is_fragment ( struct fragment *fragment,
                              struct io_buffer *iobuf,
                              size_t hdrlen __unused ) {
        struct iphdr *frag_iphdr = fragment->iobuf->data;
        struct iphdr *iphdr = iobuf->data;

        return ( ( iphdr->src.s_addr == frag_iphdr->src.s_addr ) &&
                 ( iphdr->ident == frag_iphdr->ident ) );
}

/**
 * Get IPv4 fragment offset
 *
 * @v iobuf             I/O buffer
 * @v hdrlen            Length of non-fragmentable potion of I/O buffer
 * @ret offset          Offset
 */
static size_t ipv4_fragment_offset ( struct io_buffer *iobuf,
                                     size_t hdrlen __unused ) {
        struct iphdr *iphdr = iobuf->data;

        return ( ( ntohs ( iphdr->frags ) & IP_MASK_OFFSET ) << 3 );
}

/**
 * Check if more fragments exist
 *
 * @v iobuf             I/O buffer
 * @v hdrlen            Length of non-fragmentable potion of I/O buffer
 * @ret more_frags      More fragments exist
 */
static int ipv4_more_fragments ( struct io_buffer *iobuf,
                                 size_t hdrlen __unused ) {
        struct iphdr *iphdr = iobuf->data;

        return ( iphdr->frags & htons ( IP_MASK_MOREFRAGS ) );
}

/** IPv4 fragment reassembler */
static struct fragment_reassembler ipv4_reassembler = {
        .list = LIST_HEAD_INIT ( ipv4_reassembler.list ),
        .is_fragment = ipv4_is_fragment,
        .fragment_offset = ipv4_fragment_offset,
        .more_fragments = ipv4_more_fragments,
        .stats = &ipv4_stats,
};

/**
 * Add IPv4 pseudo-header checksum to existing checksum
 *
 * @v iobuf             I/O buffer
 * @v csum              Existing checksum
 * @ret csum            Updated checksum
 */
static uint16_t ipv4_pshdr_chksum ( struct io_buffer *iobuf, uint16_t csum ) {
        struct ipv4_pseudo_header pshdr;
        struct iphdr *iphdr = iobuf->data;
        size_t hdrlen = ( ( iphdr->verhdrlen & IP_MASK_HLEN ) * 4 );

        /* Build pseudo-header */
        pshdr.src = iphdr->src;
        pshdr.dest = iphdr->dest;
        pshdr.zero_padding = 0x00;
        pshdr.protocol = iphdr->protocol;
        pshdr.len = htons ( iob_len ( iobuf ) - hdrlen );

        /* Update the checksum value */
        return tcpip_continue_chksum ( csum, &pshdr, sizeof ( pshdr ) );
}

/**
 * Transmit IP packet
 *
 * @v iobuf             I/O buffer
 * @v tcpip             Transport-layer protocol
 * @v st_src            Source network-layer address
 * @v st_dest           Destination network-layer address
 * @v netdev            Network device to use if no route found, or NULL
 * @v trans_csum        Transport-layer checksum to complete, or NULL
 * @ret rc              Status
 *
 * This function expects a transport-layer segment and prepends the IP header
 */
static int ipv4_tx ( struct io_buffer *iobuf,
                     struct tcpip_protocol *tcpip_protocol,
                     struct sockaddr_tcpip *st_src,
                     struct sockaddr_tcpip *st_dest,
                     struct net_device *netdev,
                     uint16_t *trans_csum ) {
        struct iphdr *iphdr = iob_push ( iobuf, sizeof ( *iphdr ) );
        struct sockaddr_in *sin_src = ( ( struct sockaddr_in * ) st_src );
        struct sockaddr_in *sin_dest = ( ( struct sockaddr_in * ) st_dest );
        struct ipv4_miniroute *miniroute;
        struct in_addr next_hop;
        struct in_addr hostmask = { .s_addr = INADDR_NONE };
        uint8_t ll_dest_buf[MAX_LL_ADDR_LEN];
        const void *ll_dest;
        int rc;

        /* Start profiling */
        profile_start ( &ipv4_tx_profiler );

        /* Update statistics */
        ipv4_stats.out_requests++;

        /* Fill up the IP header, except source address */
        memset ( iphdr, 0, sizeof ( *iphdr ) );
        iphdr->verhdrlen = ( IP_VER | ( sizeof ( *iphdr ) / 4 ) );
        iphdr->service = IP_TOS;
        iphdr->len = htons ( iob_len ( iobuf ) );       
        iphdr->ttl = IP_TTL;
        iphdr->protocol = tcpip_protocol->tcpip_proto;
        iphdr->dest = sin_dest->sin_addr;

        /* Use routing table to identify next hop and transmitting netdev */
        next_hop = iphdr->dest;
        if ( sin_src )
                iphdr->src = sin_src->sin_addr;
        if ( ( next_hop.s_addr != INADDR_BROADCAST ) &&
             ( ( miniroute = ipv4_route ( sin_dest->sin_scope_id,
                                          &next_hop ) ) != NULL ) ) {
                iphdr->src = miniroute->address;
                hostmask = miniroute->hostmask;
                netdev = miniroute->netdev;
        }
        if ( ! netdev ) {
                DBGC ( sin_dest->sin_addr, "IPv4 has no route to %s\n",
                       inet_ntoa ( iphdr->dest ) );
                ipv4_stats.out_no_routes++;
                rc = -ENETUNREACH;
                goto err;
        }

        /* (Ab)use the "ident" field to convey metadata about the
         * network device statistics into packet traces.  Useful for
         * extracting debug information from non-debug builds.
         */
        iphdr->ident = htons ( ( (++next_ident_high) << 8 ) |
                               ( ( netdev->rx_stats.bad & 0xf ) << 4 ) |
                               ( ( netdev->rx_stats.good & 0xf ) << 0 ) );

        /* Fix up checksums */
        if ( trans_csum ) {
                *trans_csum = ipv4_pshdr_chksum ( iobuf, *trans_csum );
                if ( ! *trans_csum )
                        *trans_csum = tcpip_protocol->zero_csum;
        }
        iphdr->chksum = tcpip_chksum ( iphdr, sizeof ( *iphdr ) );

        /* Print IP4 header for debugging */
        DBGC2 ( sin_dest->sin_addr, "IPv4 TX %s->", inet_ntoa ( iphdr->src ) );
        DBGC2 ( sin_dest->sin_addr, "%s len %d proto %d id %04x csum %04x\n",
                inet_ntoa ( iphdr->dest ), ntohs ( iphdr->len ),
                iphdr->protocol, ntohs ( iphdr->ident ),
                ntohs ( iphdr->chksum ) );

        /* Calculate link-layer destination address, if possible */
        if ( ( ( ~next_hop.s_addr ) & hostmask.s_addr ) == 0 ) {
                /* Broadcast address */
                ipv4_stats.out_bcast_pkts++;
                ll_dest = netdev->ll_broadcast;
        } else if ( IN_IS_MULTICAST ( next_hop.s_addr ) ) {
                /* Multicast address */
                ipv4_stats.out_mcast_pkts++;
                if ( ( rc = netdev->ll_protocol->mc_hash ( AF_INET, &next_hop,
                                                           ll_dest_buf ) ) !=0){
                        DBGC ( sin_dest->sin_addr, "IPv4 could not hash "
                               "multicast %s: %s\n",
                               inet_ntoa ( next_hop ), strerror ( rc ) );
                        goto err;
                }
                ll_dest = ll_dest_buf;
        } else {
                /* Unicast address */
                ll_dest = NULL;
        }

        /* Update statistics */
        ipv4_stats.out_transmits++;
        ipv4_stats.out_octets += iob_len ( iobuf );

        /* Hand off to link layer (via ARP if applicable) */
        if ( ll_dest ) {
                if ( ( rc = net_tx ( iobuf, netdev, &ipv4_protocol, ll_dest,
                                     netdev->ll_addr ) ) != 0 ) {
                        DBGC ( sin_dest->sin_addr, "IPv4 could not transmit "
                               "packet via %s: %s\n",
                               netdev->name, strerror ( rc ) );
                        return rc;
                }
        } else {
                if ( ( rc = arp_tx ( iobuf, netdev, &ipv4_protocol, &next_hop,
                                     &iphdr->src, netdev->ll_addr ) ) != 0 ) {
                        DBGC ( sin_dest->sin_addr, "IPv4 could not transmit "
                               "packet via %s: %s\n",
                               netdev->name, strerror ( rc ) );
                        return rc;
                }
        }

        profile_stop ( &ipv4_tx_profiler );
        return 0;

 err:
        free_iob ( iobuf );
        return rc;
}

/**
 * Check if network device has any IPv4 address
 *
 * @v netdev            Network device
 * @ret has_any_addr    Network device has any IPv4 address
 */
int ipv4_has_any_addr ( struct net_device *netdev ) {
        struct ipv4_miniroute *miniroute;

        list_for_each_entry ( miniroute, &ipv4_miniroutes, list ) {
                if ( miniroute->netdev == netdev )
                        return 1;
        }
        return 0;
}

/**
 * Check if network device has a specific IPv4 address
 *
 * @v netdev            Network device
 * @v addr              IPv4 address
 * @ret has_addr        Network device has this IPv4 address
 */
static int ipv4_has_addr ( struct net_device *netdev, struct in_addr addr ) {
        struct ipv4_miniroute *miniroute;

        list_for_each_entry ( miniroute, &ipv4_miniroutes, list ) {
                if ( ( miniroute->netdev == netdev ) &&
                     ( miniroute->address.s_addr == addr.s_addr ) ) {
                        /* Found matching address */
                        return 1;
                }
        }
        return 0;
}

/**
 * Process incoming packets
 *
 * @v iobuf             I/O buffer
 * @v netdev            Network device
 * @v ll_dest           Link-layer destination address
 * @v ll_source         Link-layer destination source
 * @v flags             Packet flags
 * @ret rc              Return status code
 *
 * This function expects an IP4 network datagram. It processes the headers 
 * and sends it to the transport layer.
 */
static int ipv4_rx ( struct io_buffer *iobuf,
                     struct net_device *netdev,
                     const void *ll_dest __unused,
                     const void *ll_source __unused,
                     unsigned int flags ) {
        struct iphdr *iphdr = iobuf->data;
        size_t hdrlen;
        size_t len;
        union {
                struct sockaddr_in sin;
                struct sockaddr_tcpip st;
        } src, dest;
        uint16_t csum;
        uint16_t pshdr_csum;
        int rc;

        /* Start profiling */
        profile_start ( &ipv4_rx_profiler );

        /* Update statistics */
        ipv4_stats.in_receives++;
        ipv4_stats.in_octets += iob_len ( iobuf );
        if ( flags & LL_BROADCAST ) {
                ipv4_stats.in_bcast_pkts++;
        } else if ( flags & LL_MULTICAST ) {
                ipv4_stats.in_mcast_pkts++;
        }

        /* Sanity check the IPv4 header */
        if ( iob_len ( iobuf ) < sizeof ( *iphdr ) ) {
                DBGC ( iphdr->src, "IPv4 packet too short at %zd bytes (min "
                       "%zd bytes)\n", iob_len ( iobuf ), sizeof ( *iphdr ) );
                goto err_header;
        }
        if ( ( iphdr->verhdrlen & IP_MASK_VER ) != IP_VER ) {
                DBGC ( iphdr->src, "IPv4 version %#02x not supported\n",
                       iphdr->verhdrlen );
                goto err_header;
        }
        hdrlen = ( ( iphdr->verhdrlen & IP_MASK_HLEN ) * 4 );
        if ( hdrlen < sizeof ( *iphdr ) ) {
                DBGC ( iphdr->src, "IPv4 header too short at %zd bytes (min "
                       "%zd bytes)\n", hdrlen, sizeof ( *iphdr ) );
                goto err_header;
        }
        if ( hdrlen > iob_len ( iobuf ) ) {
                DBGC ( iphdr->src, "IPv4 header too long at %zd bytes "
                       "(packet is %zd bytes)\n", hdrlen, iob_len ( iobuf ) );
                goto err_header;
        }
        if ( ( csum = tcpip_chksum ( iphdr, hdrlen ) ) != 0 ) {
                DBGC ( iphdr->src, "IPv4 checksum incorrect (is %04x "
                       "including checksum field, should be 0000)\n", csum );
                goto err_header;
        }
        len = ntohs ( iphdr->len );
        if ( len < hdrlen ) {
                DBGC ( iphdr->src, "IPv4 length too short at %zd bytes "
                       "(header is %zd bytes)\n", len, hdrlen );
                goto err_header;
        }
        if ( len > iob_len ( iobuf ) ) {
                DBGC ( iphdr->src, "IPv4 length too long at %zd bytes "
                       "(packet is %zd bytes)\n", len, iob_len ( iobuf ) );
                ipv4_stats.in_truncated_pkts++;
                goto err_other;
        }

        /* Truncate packet to correct length */
        iob_unput ( iobuf, ( iob_len ( iobuf ) - len ) );

        /* Print IPv4 header for debugging */
        DBGC2 ( iphdr->src, "IPv4 RX %s<-", inet_ntoa ( iphdr->dest ) );
        DBGC2 ( iphdr->src, "%s len %d proto %d id %04x csum %04x\n",
                inet_ntoa ( iphdr->src ), ntohs ( iphdr->len ), iphdr->protocol,
                ntohs ( iphdr->ident ), ntohs ( iphdr->chksum ) );

        /* Discard unicast packets not destined for us */
        if ( ( ! ( flags & LL_MULTICAST ) ) &&
             ( iphdr->dest.s_addr != INADDR_BROADCAST ) &&
             ipv4_has_any_addr ( netdev ) &&
             ( ! ipv4_has_addr ( netdev, iphdr->dest ) ) ) {
                DBGC ( iphdr->src, "IPv4 discarding non-local unicast packet "
                       "for %s\n", inet_ntoa ( iphdr->dest ) );
                ipv4_stats.in_addr_errors++;
                goto err_other;
        }

        /* Perform fragment reassembly if applicable */
        if ( iphdr->frags & htons ( IP_MASK_OFFSET | IP_MASK_MOREFRAGS ) ) {
                /* Pass the fragment to fragment_reassemble() which returns
                 * either a fully reassembled I/O buffer or NULL.
                 */
                iobuf = fragment_reassemble ( &ipv4_reassembler, iobuf,
                                              &hdrlen );
                if ( ! iobuf )
                        return 0;
                iphdr = iobuf->data;
        }

        /* Construct socket addresses, calculate pseudo-header
         * checksum, and hand off to transport layer
         */
        memset ( &src, 0, sizeof ( src ) );
        src.sin.sin_family = AF_INET;
        src.sin.sin_addr = iphdr->src;
        memset ( &dest, 0, sizeof ( dest ) );
        dest.sin.sin_family = AF_INET;
        dest.sin.sin_addr = iphdr->dest;
        pshdr_csum = ipv4_pshdr_chksum ( iobuf, TCPIP_EMPTY_CSUM );
        iob_pull ( iobuf, hdrlen );
        if ( ( rc = tcpip_rx ( iobuf, netdev, iphdr->protocol, &src.st,
                               &dest.st, pshdr_csum, &ipv4_stats ) ) != 0 ) {
                DBGC ( src.sin.sin_addr, "IPv4 received packet rejected by "
                       "stack: %s\n", strerror ( rc ) );
                return rc;
        }

        profile_stop ( &ipv4_rx_profiler );
        return 0;

 err_header:
        ipv4_stats.in_hdr_errors++;
 err_other:
        free_iob ( iobuf );
        return -EINVAL;
}

/** 
 * Check existence of IPv4 address for ARP
 *
 * @v netdev            Network device
 * @v net_addr          Network-layer address
 * @ret rc              Return status code
 */
static int ipv4_arp_check ( struct net_device *netdev, const void *net_addr ) {
        const struct in_addr *address = net_addr;

        if ( ipv4_has_addr ( netdev, *address ) )
                return 0;

        return -ENOENT;
}

/**
 * Parse IPv4 address
 *
 * @v string            IPv4 address string
 * @ret in              IPv4 address to fill in
 * @ret ok              IPv4 address is valid
 *
 * Note that this function returns nonzero iff the address is valid,
 * to match the standard BSD API function of the same name.  Unlike
 * most other iPXE functions, a zero therefore indicates failure.
 */
int inet_aton ( const char *string, struct in_addr *in ) {
        const char *separator = "...";
        uint8_t *byte = ( ( uint8_t * ) in );
        char *endp;
        unsigned long value;

        while ( 1 ) {
                value = strtoul ( string, &endp, 0 );
                if ( string == endp )
                        return 0;
                if ( value > 0xff )
                        return 0;
                *(byte++) = value;
                if ( *endp != *separator )
                        return 0;
                if ( ! *(separator++) )
                        return 1;
                string = ( endp + 1 );
        }
}

/**
 * Convert IPv4 address to dotted-quad notation
 *
 * @v in                IPv4 address
 * @ret string          IPv4 address in dotted-quad notation
 */
char * inet_ntoa ( struct in_addr in ) {
        static char buf[16]; /* "xxx.xxx.xxx.xxx" */
        uint8_t *bytes = ( uint8_t * ) &in;
        
        sprintf ( buf, "%d.%d.%d.%d", bytes[0], bytes[1], bytes[2], bytes[3] );
        return buf;
}

/**
 * Transcribe IPv4 address
 *
 * @v net_addr          IPv4 address
 * @ret string          IPv4 address in dotted-quad notation
 *
 */
static const char * ipv4_ntoa ( const void *net_addr ) {
        return inet_ntoa ( * ( ( struct in_addr * ) net_addr ) );
}

/**
 * Transcribe IPv4 socket address
 *
 * @v sa                Socket address
 * @ret string          Socket address in standard notation
 */
static const char * ipv4_sock_ntoa ( struct sockaddr *sa ) {
        struct sockaddr_in *sin = ( ( struct sockaddr_in * ) sa );

        return inet_ntoa ( sin->sin_addr );
}

/**
 * Parse IPv4 socket address
 *
 * @v string            Socket address string
 * @v sa                Socket address to fill in
 * @ret rc              Return status code
 */
static int ipv4_sock_aton ( const char *string, struct sockaddr *sa ) {
        struct sockaddr_in *sin = ( ( struct sockaddr_in * ) sa );
        struct in_addr in;

        if ( inet_aton ( string, &in ) ) {
                sin->sin_addr = in;
                return 0;
        }
        return -EINVAL;
}

/** IPv4 protocol */
struct net_protocol ipv4_protocol __net_protocol = {
        .name = "IP",
        .net_proto = htons ( ETH_P_IP ),
        .net_addr_len = sizeof ( struct in_addr ),
        .rx = ipv4_rx,
        .ntoa = ipv4_ntoa,
};

/** IPv4 TCPIP net protocol */
struct tcpip_net_protocol ipv4_tcpip_protocol __tcpip_net_protocol = {
        .name = "IPv4",
        .sa_family = AF_INET,
        .header_len = sizeof ( struct iphdr ),
        .net_protocol = &ipv4_protocol,
        .tx = ipv4_tx,
        .netdev = ipv4_netdev,
};

/** IPv4 ARP protocol */
struct arp_net_protocol ipv4_arp_protocol __arp_net_protocol = {
        .net_protocol = &ipv4_protocol,
        .check = ipv4_arp_check,
};

/** IPv4 socket address converter */
struct sockaddr_converter ipv4_sockaddr_converter __sockaddr_converter = {
        .family = AF_INET,
        .ntoa = ipv4_sock_ntoa,
        .aton = ipv4_sock_aton,
};

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

/**
 * Parse IPv4 address setting value
 *
 * @v type              Setting type
 * @v value             Formatted setting value
 * @v buf               Buffer to contain raw value
 * @v len               Length of buffer
 * @ret len             Length of raw value, or negative error
 */
int parse_ipv4_setting ( const struct setting_type *type __unused,
                         const char *value, void *buf, size_t len ) {
        struct in_addr ipv4;

        /* Parse IPv4 address */
        if ( inet_aton ( value, &ipv4 ) == 0 )
                return -EINVAL;

        /* Copy to buffer */
        if ( len > sizeof ( ipv4 ) )
                len = sizeof ( ipv4 );
        memcpy ( buf, &ipv4, len );

        return ( sizeof ( ipv4 ) );
}

/**
 * Format IPv4 address setting value
 *
 * @v type              Setting type
 * @v raw               Raw setting value
 * @v raw_len           Length of raw setting value
 * @v buf               Buffer to contain formatted value
 * @v len               Length of buffer
 * @ret len             Length of formatted value, or negative error
 */
int format_ipv4_setting ( const struct setting_type *type __unused,
                          const void *raw, size_t raw_len, char *buf,
                          size_t len ) {
        const struct in_addr *ipv4 = raw;

        if ( raw_len < sizeof ( *ipv4 ) )
                return -EINVAL;
        return snprintf ( buf, len, "%s", inet_ntoa ( *ipv4 ) );
}

/** IPv4 address setting */
const struct setting ip_setting __setting ( SETTING_IP4, ip ) = {
        .name = "ip",
        .description = "IP address",
        .tag = DHCP_EB_YIADDR,
        .type = &setting_type_ipv4,
};

/** IPv4 subnet mask setting */
const struct setting netmask_setting __setting ( SETTING_IP4, netmask ) = {
        .name = "netmask",
        .description = "Subnet mask",
        .tag = DHCP_SUBNET_MASK,
        .type = &setting_type_ipv4,
};

/** Default gateway setting */
const struct setting gateway_setting __setting ( SETTING_IP4, gateway ) = {
        .name = "gateway",
        .description = "Default gateway",
        .tag = DHCP_ROUTERS,
        .type = &setting_type_ipv4,
};

/** Classless static routes setting */
const struct setting static_route_setting __setting ( SETTING_IP4,
                                                      static_routes ) = {
        .name = "static-routes",
        .description = "Static routes",
        .tag = DHCP_STATIC_ROUTES,
        .type = &setting_type_hex,
};

/**
 * Send gratuitous ARP, if applicable
 *
 * @v netdev            Network device
 * @v address           IPv4 address
 * @ret rc              Return status code
 */
static int ipv4_gratuitous_arp ( struct net_device *netdev,
                                 struct in_addr address ) {
        int rc;

        /* Do nothing if network device already has this IPv4 address */
        if ( ipv4_has_addr ( netdev, address ) )
                return 0;

        /* Transmit gratuitous ARP */
        DBGC ( netdev, "IPv4 sending gratuitous ARP for %s via %s\n",
               inet_ntoa ( address ), netdev->name );
        if ( ( rc = arp_tx_request ( netdev, &ipv4_protocol, &address,
                                     &address ) ) != 0 ) {
                DBGC ( netdev, "IPv4 could not transmit gratuitous ARP: %s\n",
                       strerror ( rc ) );
                /* Treat failures as non-fatal */
        }

        return 0;
}

/**
 * Process IPv4 network device settings
 *
 * @v apply             Application method
 * @ret rc              Return status code
 */
static int ipv4_settings ( int ( * apply ) ( struct net_device *netdev,
                                             struct in_addr address ) ) {
        struct net_device *netdev;
        struct settings *settings;
        struct in_addr address;
        int rc;

        /* Process settings for each network device */
        for_each_netdev ( netdev ) {

                /* Get network device settings */
                settings = netdev_settings ( netdev );

                /* Get IPv4 address */
                fetch_ipv4_setting ( settings, &ip_setting, &address );
                if ( ! address.s_addr )
                        continue;

                /* Apply settings */
                if ( ( rc = apply ( netdev, address ) ) != 0 )
                        return rc;
        }

        return 0;
}

/**
 * Create IPv4 routing table based on configured settings
 *
 * @ret rc              Return status code
 */
static int ipv4_apply_routes ( void ) {
        int rc;

        /* Send gratuitous ARPs for any new IPv4 addresses */
        ipv4_settings ( ipv4_gratuitous_arp );

        /* Delete all existing routes */
        ipv4_del_miniroutes();

        /* Create routes for each configured network device */
        if ( ( rc = ipv4_settings ( ipv4_add_miniroutes ) ) != 0 )
                return rc;

        return 0;
}

/** IPv4 settings applicator */
struct settings_applicator ipv4_settings_applicator __settings_applicator = {
        .apply = ipv4_apply_routes,
};

/* Drag in objects via ipv4_protocol */
REQUIRING_SYMBOL ( ipv4_protocol );

/* Drag in ICMPv4 */
REQUIRE_OBJECT ( icmpv4 );