gdbudp.c

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/*
 * Copyright (C) 2008 Stefan Hajnoczi <stefanha@gmail.com>.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

#include <stdio.h>
#include <string.h>
#include <byteswap.h>
#include <ipxe/iobuf.h>
#include <ipxe/in.h>
#include <ipxe/if_arp.h>
#include <ipxe/if_ether.h>
#include <ipxe/ip.h>
#include <ipxe/udp.h>
#include <ipxe/netdevice.h>
#include <ipxe/nap.h>
#include <ipxe/gdbstub.h>
#include <ipxe/gdbudp.h>

/** @file
 *
 * GDB over UDP transport
 *
 */

enum {
        DEFAULT_PORT = 43770, /* UDP listen port */
};

struct gdb_transport udp_gdb_transport __gdb_transport;

static struct net_device *netdev;
static uint8_t dest_eth[ETH_ALEN];
static struct sockaddr_in dest_addr;
static struct sockaddr_in source_addr;

static void gdbudp_ensure_netdev_open ( struct net_device *netdev ) {
        /* The device may have been closed between breakpoints */
        assert ( netdev );
        netdev_open ( netdev );

        /* Strictly speaking, we may need to close the device when leaving the interrupt handler */
}

static size_t gdbudp_recv ( char *buf, size_t len ) {
        struct io_buffer *iob;
        struct ethhdr *ethhdr;
        struct arphdr *arphdr;
        struct iphdr *iphdr;
        struct udp_header *udphdr;
        size_t payload_len;

        gdbudp_ensure_netdev_open ( netdev );

        for ( ; ; ) {
                netdev_poll ( netdev );
                while ( ( iob = netdev_rx_dequeue ( netdev ) ) != NULL ) {
                        /* Ethernet header */
                        if ( iob_len ( iob ) < sizeof ( *ethhdr ) ) {
                                goto bad_packet;
                        }
                        ethhdr = iob->data;
                        iob_pull ( iob, sizeof ( *ethhdr ) );

                        /* Handle ARP requests so the client can find our MAC */
                        if ( ethhdr->h_protocol == htons ( ETH_P_ARP ) ) {
                                arphdr = iob->data;
                                if ( iob_len ( iob ) < sizeof ( *arphdr ) + 2 * ( ETH_ALEN + sizeof ( struct in_addr ) ) ||
                                                arphdr->ar_hrd != htons ( ARPHRD_ETHER ) ||
                                                arphdr->ar_pro != htons ( ETH_P_IP ) ||
                                                arphdr->ar_hln != ETH_ALEN ||
                                                arphdr->ar_pln != sizeof ( struct in_addr ) ||
                                                arphdr->ar_op != htons ( ARPOP_REQUEST ) ||
                                                * ( uint32_t * ) arp_target_pa ( arphdr ) != source_addr.sin_addr.s_addr ) {
                                        goto bad_packet;
                                }

                                /* Generate an ARP reply */
                                arphdr->ar_op = htons ( ARPOP_REPLY );
                                memswap ( arp_sender_pa ( arphdr ), arp_target_pa ( arphdr ), sizeof ( struct in_addr ) );
                                memcpy ( arp_target_ha ( arphdr ), arp_sender_ha ( arphdr ), ETH_ALEN );
                                memcpy ( arp_sender_ha ( arphdr ), netdev->ll_addr, ETH_ALEN );

                                /* Fix up ethernet header */
                                ethhdr = iob_push ( iob, sizeof ( *ethhdr ) );
                                memcpy ( ethhdr->h_dest, ethhdr->h_source, ETH_ALEN );
                                memcpy ( ethhdr->h_source, netdev->ll_addr, ETH_ALEN );

                                netdev_tx ( netdev, iob );
                                continue; /* no need to free iob */
                        }

                        if ( ethhdr->h_protocol != htons ( ETH_P_IP ) ) {
                                goto bad_packet;
                        }

                        /* IP header */
                        if ( iob_len ( iob ) < sizeof ( *iphdr ) ) {
                                goto bad_packet;
                        }
                        iphdr = iob->data;
                        iob_pull ( iob, sizeof ( *iphdr ) );
                        if ( iphdr->protocol != IP_UDP || iphdr->dest.s_addr != source_addr.sin_addr.s_addr ) {
                                goto bad_packet;
                        }

                        /* UDP header */
                        if ( iob_len ( iob ) < sizeof ( *udphdr ) ) {
                                goto bad_packet;
                        }
                        udphdr = iob->data;
                        if ( udphdr->dest != source_addr.sin_port ) {
                                goto bad_packet;
                        }

                        /* Learn the remote connection details */
                        memcpy ( dest_eth, ethhdr->h_source, ETH_ALEN );
                        dest_addr.sin_addr.s_addr = iphdr->src.s_addr;
                        dest_addr.sin_port = udphdr->src;

                        /* Payload */
                        payload_len = ntohs ( udphdr->len );
                        if ( payload_len < sizeof ( *udphdr ) || payload_len > iob_len ( iob ) ) {
                                goto bad_packet;
                        }
                        payload_len -= sizeof ( *udphdr );
                        iob_pull ( iob, sizeof ( *udphdr ) );
                        if ( payload_len > len ) {
                                goto bad_packet;
                        }
                        memcpy ( buf, iob->data, payload_len );

                        free_iob ( iob );
                        return payload_len;

bad_packet:
                        free_iob ( iob );
                }
                cpu_nap();
        }
}

static void gdbudp_send ( const char *buf, size_t len ) {
        struct io_buffer *iob;
        struct ethhdr *ethhdr;
        struct iphdr *iphdr;
        struct udp_header *udphdr;

        /* Check that we are connected */
        if ( dest_addr.sin_port == 0 ) {
                return;
        }

        gdbudp_ensure_netdev_open ( netdev );

        iob = alloc_iob ( sizeof ( *ethhdr ) + sizeof ( *iphdr ) + sizeof ( *udphdr ) + len );
        if ( !iob ) {
                return;
        }

        /* Payload */
        iob_reserve ( iob, sizeof ( *ethhdr ) + sizeof ( *iphdr ) + sizeof ( *udphdr ) );
        memcpy ( iob_put ( iob, len ), buf, len );

        /* UDP header */
        udphdr = iob_push ( iob, sizeof ( *udphdr ) );
        udphdr->src = source_addr.sin_port;
        udphdr->dest = dest_addr.sin_port;
        udphdr->len = htons ( iob_len ( iob ) );
        udphdr->chksum = 0; /* optional and we are not using it */

        /* IP header */
        iphdr = iob_push ( iob, sizeof ( *iphdr ) );
        memset ( iphdr, 0, sizeof ( *iphdr ) );
        iphdr->verhdrlen = ( IP_VER | ( sizeof ( *iphdr ) / 4 ) );
        iphdr->service = IP_TOS;
        iphdr->len = htons ( iob_len ( iob ) ); 
        iphdr->ttl = IP_TTL;
        iphdr->protocol = IP_UDP;
        iphdr->dest.s_addr = dest_addr.sin_addr.s_addr;
        iphdr->src.s_addr = source_addr.sin_addr.s_addr;
        iphdr->chksum = tcpip_chksum ( iphdr, sizeof ( *iphdr ) );

        /* Ethernet header */
        ethhdr = iob_push ( iob, sizeof ( *ethhdr ) );
        memcpy ( ethhdr->h_dest, dest_eth, ETH_ALEN );
        memcpy ( ethhdr->h_source, netdev->ll_addr, ETH_ALEN );
        ethhdr->h_protocol = htons ( ETH_P_IP );

        netdev_tx ( netdev, iob );
}

struct gdb_transport *gdbudp_configure ( const char *name, struct sockaddr_in *addr ) {
        struct settings *settings;

        /* Release old network device */
        netdev_put ( netdev );

        netdev = find_netdev ( name );
        if ( !netdev ) {
                return NULL;
        }

        /* Hold network device */
        netdev_get ( netdev );

        /* Source UDP port */
        source_addr.sin_port = ( addr && addr->sin_port ) ? addr->sin_port : htons ( DEFAULT_PORT );

        /* Source IP address */
        if ( addr && addr->sin_addr.s_addr ) {
                source_addr.sin_addr.s_addr = addr->sin_addr.s_addr;
        } else {
                settings = netdev_settings ( netdev );
                fetch_ipv4_setting ( settings, &ip_setting, &source_addr.sin_addr );
                if ( source_addr.sin_addr.s_addr == 0 ) {
                        netdev_put ( netdev );
                        netdev = NULL;
                        return NULL;
                }
        }

        return &udp_gdb_transport;
}

static int gdbudp_init ( int argc, char **argv ) {
        if ( argc != 1 ) {
                printf ( "udp: missing <interface> argument\n" );
                return 1;
        }

        if ( !gdbudp_configure ( argv[0], NULL ) ) {
                printf ( "%s: device does not exist or has no IP address\n", argv[0] );
                return 1;
        }
        return 0;
}

struct gdb_transport udp_gdb_transport __gdb_transport = {
        .name = "udp",
        .init = gdbudp_init,
        .send = gdbudp_send,
        .recv = gdbudp_recv,
};