source: bootcd/isolinux/syslinux-6.03/gpxe/src/net/ipv4.c @ e16e8f2

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

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

FILE_LICENCE ( GPL2_OR_LATER );

/* Unique IP datagram identification number */
static uint16_t next_ident = 0;

struct net_protocol ipv4_protocol;

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

/** List of fragment reassembly buffers */
static LIST_HEAD ( frag_buffers );

/**
 * Add IPv4 minirouting table entry
 *
 * @v netdev            Network device
 * @v address           IPv4 address
 * @v netmask           Subnet mask
 * @v gateway           Gateway address (if any)
 * @ret miniroute       Routing table entry, or NULL
 */
static struct ipv4_miniroute * __malloc
add_ipv4_miniroute ( struct net_device *netdev, struct in_addr address,
                     struct in_addr netmask, struct in_addr gateway ) {
        struct ipv4_miniroute *miniroute;

        DBG ( "IPv4 add %s", inet_ntoa ( address ) );
        DBG ( "/%s ", inet_ntoa ( netmask ) );
        if ( gateway.s_addr )
                DBG ( "gw %s ", inet_ntoa ( gateway ) );
        DBG ( "via %s\n", netdev->name );

        /* Allocate and populate miniroute structure */
        miniroute = malloc ( sizeof ( *miniroute ) );
        if ( ! miniroute ) {
                DBG ( "IPv4 could not add miniroute\n" );
                return NULL;
        }

        /* Record routing information */
        miniroute->netdev = netdev_get ( netdev );
        miniroute->address = address;
        miniroute->netmask = netmask;
        miniroute->gateway = gateway;
                
        /* Add to end of list if we have a gateway, otherwise
         * to start of list.
         */
        if ( gateway.s_addr ) {
                list_add_tail ( &miniroute->list, &ipv4_miniroutes );
        } else {
                list_add ( &miniroute->list, &ipv4_miniroutes );
        }

        return miniroute;
}

/**
 * Delete IPv4 minirouting table entry
 *
 * @v miniroute         Routing table entry
 */
static void del_ipv4_miniroute ( struct ipv4_miniroute *miniroute ) {

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

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

/**
 * Perform IPv4 routing
 *
 * @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.
 */
static struct ipv4_miniroute * ipv4_route ( struct in_addr *dest ) {
        struct ipv4_miniroute *miniroute;
        int local;
        int has_gw;

        /* Never attempt to route the broadcast address */
        if ( dest->s_addr == INADDR_BROADCAST )
                return NULL;

        /* Find first usable route in routing table */
        list_for_each_entry ( miniroute, &ipv4_miniroutes, list ) {
                if ( ! ( miniroute->netdev->state & NETDEV_OPEN ) )
                        continue;
                local = ( ( ( dest->s_addr ^ miniroute->address.s_addr )
                            & miniroute->netmask.s_addr ) == 0 );
                has_gw = ( miniroute->gateway.s_addr );
                if ( local || has_gw ) {
                        if ( ! local )
                                *dest = miniroute->gateway;
                        return miniroute;
                }
        }

        return NULL;
}

/**
 * Fragment reassembly counter timeout
 *
 * @v timer     Retry timer
 * @v over      If asserted, the timer is greater than @c MAX_TIMEOUT 
 */
static void ipv4_frag_expired ( struct retry_timer *timer __unused,
                                int over ) {
        if ( over ) {
                DBG ( "Fragment reassembly timeout" );
                /* Free the fragment buffer */
        }
}

/**
 * Free fragment buffer
 *
 * @v fragbug   Fragment buffer
 */
static void free_fragbuf ( struct frag_buffer *fragbuf ) {
        free ( fragbuf );
}

/**
 * Fragment reassembler
 *
 * @v iobuf             I/O buffer, fragment of the datagram
 * @ret frag_iob        Reassembled packet, or NULL
 */
static struct io_buffer * ipv4_reassemble ( struct io_buffer * iobuf ) {
        struct iphdr *iphdr = iobuf->data;
        struct frag_buffer *fragbuf;
        
        /**
         * Check if the fragment belongs to any fragment series
         */
        list_for_each_entry ( fragbuf, &frag_buffers, list ) {
                if ( fragbuf->ident == iphdr->ident &&
                     fragbuf->src.s_addr == iphdr->src.s_addr ) {
                        /**
                         * Check if the packet is the expected fragment
                         * 
                         * The offset of the new packet must be equal to the
                         * length of the data accumulated so far (the length of
                         * the reassembled I/O buffer
                         */
                        if ( iob_len ( fragbuf->frag_iob ) == 
                              ( iphdr->frags & IP_MASK_OFFSET ) ) {
                                /**
                                 * Append the contents of the fragment to the
                                 * reassembled I/O buffer
                                 */
                                iob_pull ( iobuf, sizeof ( *iphdr ) );
                                memcpy ( iob_put ( fragbuf->frag_iob,
                                                        iob_len ( iobuf ) ),
                                         iobuf->data, iob_len ( iobuf ) );
                                free_iob ( iobuf );

                                /** Check if the fragment series is over */
                                if ( ! ( iphdr->frags & IP_MASK_MOREFRAGS ) ) {
                                        iobuf = fragbuf->frag_iob;
                                        free_fragbuf ( fragbuf );
                                        return iobuf;
                                }

                        } else {
                                /* Discard the fragment series */
                                free_fragbuf ( fragbuf );
                                free_iob ( iobuf );
                        }
                        return NULL;
                }
        }
        
        /** Check if the fragment is the first in the fragment series */
        if ( iphdr->frags & IP_MASK_MOREFRAGS &&
                        ( ( iphdr->frags & IP_MASK_OFFSET ) == 0 ) ) {
        
                /** Create a new fragment buffer */
                fragbuf = ( struct frag_buffer* ) malloc ( sizeof( *fragbuf ) );
                fragbuf->ident = iphdr->ident;
                fragbuf->src = iphdr->src;

                /* Set up the reassembly I/O buffer */
                fragbuf->frag_iob = alloc_iob ( IP_FRAG_IOB_SIZE );
                iob_pull ( iobuf, sizeof ( *iphdr ) );
                memcpy ( iob_put ( fragbuf->frag_iob, iob_len ( iobuf ) ),
                         iobuf->data, iob_len ( iobuf ) );
                free_iob ( iobuf );

                /* Set the reassembly timer */
                fragbuf->frag_timer.timeout = IP_FRAG_TIMEOUT;
                fragbuf->frag_timer.expired = ipv4_frag_expired;
                start_timer ( &fragbuf->frag_timer );

                /* Add the fragment buffer to the list of fragment buffers */
                list_add ( &fragbuf->list, &frag_buffers );
        }
        
        return NULL;
}

/**
 * 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 ) );
}

/**
 * Determine link-layer address
 *
 * @v dest              IPv4 destination address
 * @v src               IPv4 source address
 * @v netdev            Network device
 * @v ll_dest           Link-layer destination address buffer
 * @ret rc              Return status code
 */
static int ipv4_ll_addr ( struct in_addr dest, struct in_addr src,
                          struct net_device *netdev, uint8_t *ll_dest ) {
        struct ll_protocol *ll_protocol = netdev->ll_protocol;

        if ( dest.s_addr == INADDR_BROADCAST ) {
                /* Broadcast address */
                memcpy ( ll_dest, netdev->ll_broadcast,
                         ll_protocol->ll_addr_len );
                return 0;
        } else if ( IN_MULTICAST ( ntohl ( dest.s_addr ) ) ) {
                return ll_protocol->mc_hash ( AF_INET, &dest, ll_dest );
        } else {
                /* Unicast address: resolve via ARP */
                return arp_resolve ( netdev, &ipv4_protocol, &dest,
                                     &src, ll_dest );
        }
}

/**
 * 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;
        uint8_t ll_dest[MAX_LL_ADDR_LEN];
        int rc;

        /* 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->ident = htons ( ++next_ident );
        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 ) &&
             ( ! IN_MULTICAST ( ntohl ( next_hop.s_addr ) ) ) &&
             ( ( miniroute = ipv4_route ( &next_hop ) ) != NULL ) ) {
                iphdr->src = miniroute->address;
                netdev = miniroute->netdev;
        }
        if ( ! netdev ) {
                DBG ( "IPv4 has no route to %s\n", inet_ntoa ( iphdr->dest ) );
                rc = -ENETUNREACH;
                goto err;
        }

        /* Determine link-layer destination address */
        if ( ( rc = ipv4_ll_addr ( next_hop, iphdr->src, netdev,
                                   ll_dest ) ) != 0 ) {
                DBG ( "IPv4 has no link-layer address for %s: %s\n",
                      inet_ntoa ( next_hop ), strerror ( rc ) );
                goto err;
        }

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

        /* Print IP4 header for debugging */
        DBG ( "IPv4 TX %s->", inet_ntoa ( iphdr->src ) );
        DBG ( "%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 ) );

        /* Hand off to link layer */
        if ( ( rc = net_tx ( iobuf, netdev, &ipv4_protocol, ll_dest ) ) != 0 ) {
                DBG ( "IPv4 could not transmit packet via %s: %s\n",
                      netdev->name, strerror ( rc ) );
                return rc;
        }

        return 0;

 err:
        free_iob ( iobuf );
        return rc;
}

/**
 * Process incoming packets
 *
 * @v iobuf     I/O buffer
 * @v netdev    Network device
 * @v ll_source Link-layer destination source
 *
 * 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 __unused,
                     const void *ll_source __unused ) {
        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;

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

        /* Print IPv4 header for debugging */
        DBG ( "IPv4 RX %s<-", inet_ntoa ( iphdr->dest ) );
        DBG ( "%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 ) );

        /* Truncate packet to correct length, calculate pseudo-header
         * checksum and then strip off the IPv4 header.
         */
        iob_unput ( iobuf, ( iob_len ( iobuf ) - len ) );
        pshdr_csum = ipv4_pshdr_chksum ( iobuf, TCPIP_EMPTY_CSUM );
        iob_pull ( iobuf, hdrlen );

        /* Fragment reassembly */
        if ( ( iphdr->frags & htons ( IP_MASK_MOREFRAGS ) ) || 
             ( ( iphdr->frags & htons ( IP_MASK_OFFSET ) ) != 0 ) ) {
                /* Pass the fragment to ipv4_reassemble() which either
                 * returns a fully reassembled I/O buffer or NULL.
                 */
                iobuf = ipv4_reassemble ( iobuf );
                if ( ! iobuf )
                        return 0;
        }

        /* Construct socket addresses 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;
        if ( ( rc = tcpip_rx ( iobuf, iphdr->protocol, &src.st,
                               &dest.st, pshdr_csum ) ) != 0 ) {
                DBG ( "IPv4 received packet rejected by stack: %s\n",
                      strerror ( rc ) );
                return rc;
        }

        return 0;

 err:
        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;
        struct ipv4_miniroute *miniroute;

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

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

/** 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,
        .tx = ipv4_tx,
};

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

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

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

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

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

/**
 * Create IPv4 routing table based on configured settings
 *
 * @ret rc              Return status code
 */
static int ipv4_create_routes ( void ) {
        struct ipv4_miniroute *miniroute;
        struct ipv4_miniroute *tmp;
        struct net_device *netdev;
        struct settings *settings;
        struct in_addr address = { 0 };
        struct in_addr netmask = { 0 };
        struct in_addr gateway = { 0 };

        /* Delete all existing routes */
        list_for_each_entry_safe ( miniroute, tmp, &ipv4_miniroutes, list )
                del_ipv4_miniroute ( miniroute );

        /* Create a route for each configured network device */
        for_each_netdev ( netdev ) {
                settings = netdev_settings ( netdev );
                /* Get IPv4 address */
                address.s_addr = 0;
                fetch_ipv4_setting ( settings, &ip_setting, &address );
                if ( ! address.s_addr )
                        continue;
                /* Get subnet mask */
                fetch_ipv4_setting ( settings, &netmask_setting, &netmask );
                /* Calculate default netmask, if necessary */
                if ( ! netmask.s_addr ) {
                        if ( IN_CLASSA ( ntohl ( address.s_addr ) ) ) {
                                netmask.s_addr = htonl ( IN_CLASSA_NET );
                        } else if ( IN_CLASSB ( ntohl ( address.s_addr ) ) ) {
                                netmask.s_addr = htonl ( IN_CLASSB_NET );
                        } else if ( IN_CLASSC ( ntohl ( address.s_addr ) ) ) {
                                netmask.s_addr = htonl ( IN_CLASSC_NET );
                        }
                }
                /* Get default gateway, if present */
                fetch_ipv4_setting ( settings, &gateway_setting, &gateway );
                /* Configure route */
                miniroute = add_ipv4_miniroute ( netdev, address,
                                                 netmask, gateway );
                if ( ! miniroute )
                        return -ENOMEM;
        }

        return 0;
}

/** IPv4 settings applicator */
struct settings_applicator ipv4_settings_applicator __settings_applicator = {
        .apply = ipv4_create_routes,
};

/* Drag in ICMP */
REQUIRE_OBJECT ( icmp );