icmp.c

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/*
 * Copyright (C) 2009 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

FILE_LICENCE ( GPL2_OR_LATER );

#include <string.h>
#include <errno.h>
#include <gpxe/iobuf.h>
#include <gpxe/in.h>
#include <gpxe/tcpip.h>
#include <gpxe/icmp.h>

/** @file
 *
 * ICMP protocol
 *
 */

struct tcpip_protocol icmp_protocol __tcpip_protocol;

/**
 * Process a received packet
 *
 * @v iobuf             I/O buffer
 * @v st_src            Partially-filled source address
 * @v st_dest           Partially-filled destination address
 * @v pshdr_csum        Pseudo-header checksum
 * @ret rc              Return status code
 */
static int icmp_rx ( struct io_buffer *iobuf, struct sockaddr_tcpip *st_src,
                     struct sockaddr_tcpip *st_dest,
                     uint16_t pshdr_csum __unused ) {
        struct icmp_header *icmp = iobuf->data;
        size_t len = iob_len ( iobuf );
        unsigned int csum;
        int rc;

        /* Sanity check */
        if ( len < sizeof ( *icmp ) ) {
                DBG ( "ICMP packet too short at %zd bytes (min %zd bytes)\n",
                      len, sizeof ( *icmp ) );
                rc = -EINVAL;
                goto done;
        }

        /* Verify checksum */
        csum = tcpip_chksum ( icmp, len );
        if ( csum != 0 ) {
                DBG ( "ICMP checksum incorrect (is %04x, should be 0000)\n",
                      csum );
                DBG_HD ( icmp, len );
                rc = -EINVAL;
                goto done;
        }

        /* We respond only to pings */
        if ( icmp->type != ICMP_ECHO_REQUEST ) {
                DBG ( "ICMP ignoring type %d\n", icmp->type );
                rc = 0;
                goto done;
        }

        DBG ( "ICMP responding to ping\n" );

        /* Change type to response and recalculate checksum */
        icmp->type = ICMP_ECHO_RESPONSE;
        icmp->chksum = 0;
        icmp->chksum = tcpip_chksum ( icmp, len );

        /* Transmit the response */
        if ( ( rc = tcpip_tx ( iob_disown ( iobuf ), &icmp_protocol, st_dest,
                               st_src, NULL, NULL ) ) != 0 ) {
                DBG ( "ICMP could not transmit ping response: %s\n",
                      strerror ( rc ) );
                goto done;
        }

 done:
        free_iob ( iobuf );
        return rc;
}

/** ICMP TCP/IP protocol */
struct tcpip_protocol icmp_protocol __tcpip_protocol = {
        .name = "ICMP",
        .rx = icmp_rx,
        .tcpip_proto = IP_ICMP,
};