readpacket.c
Author: cmaier@cmassoc.net

    /*====================================================================*
     *
     *   Copyright (c) 2013 Qualcomm Atheros, Inc.
     *
     *   All rights reserved.
     *
     *   Redistribution and use in source and binary forms, with or
     *   without modification, are permitted (subject to the limitations
     *   in the disclaimer below) provided that the following conditions
     *   are met:
     *
     *   * Redistributions of source code must retain the above copyright
     *     notice, this list of conditions and the following disclaimer.
     *
     *   * Redistributions in binary form must reproduce the above
     *     copyright notice, this list of conditions and the following
     *     disclaimer in the documentation and/or other materials
     *     provided with the distribution.
     *
     *   * Neither the name of Qualcomm Atheros nor the names of
     *     its contributors may be used to endorse or promote products
     *     derived from this software without specific prior written
     *     permission.
     *
     *   NO EXPRESS OR IMPLIED LICENSES TO ANY PARTY'S PATENT RIGHTS ARE
     *   GRANTED BY THIS LICENSE. THIS SOFTWARE IS PROVIDED BY THE
     *   COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
     *   IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
     *   WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     *   PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
     *   OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     *   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     *   NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
     *   LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     *   HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     *   CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
     *   OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
     *   SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     *
     *--------------------------------------------------------------------*/

    /*====================================================================*
     *
     *   ssize_t readpacket (struct channel const * channel, void * memory, ssize_t extent);
     *
     *   channel.h
     *
     *   read one packet from a raw packet channel;
     *
     *   return the packet size on success, 0 on timeout or -1 on error;
     *   dump packets on stdout when the channel VERBOSE flag is set;
     *
     *   constant __MAGIC__ enables code that reads frames from stdin,
     *   instead of the network; you may use it whenever a network or
     *   transmitting device is not available;
     *
     *
     *   Contributor(s):
     *	Charles Maier <cmaier@qca.qualcomm.com>
     *	Nathaniel Houghton <nhoughto@qca.qualcomm.com>
     *      Werner Henze <w.henze@avm.de>
     *
     *--------------------------------------------------------------------*/

    #ifndef READPACKET_SOURCE
    #define READPACKET_SOURCE

    #include <stdlib.h>
    #include <unistd.h>
    #include <memory.h>
    #include <errno.h>

    #include "../ether/channel.h"
    #include "../tools/memory.h"
    #include "../tools/error.h"
    #include "../tools/flags.h"

    #if defined (__MAGIC__)
    #include "../tools/hexload.c"
    #endif

    ssize_t readpacket (struct channel const * channel, void * memory, ssize_t extent)

    {

    #if defined (__MAGIC__)

    	memset (memory, 0, extent);
    	extent = hexload (memory, extent, stdin);
    	if (_anyset (channel->flags, CHANNEL_VERBOSE))
    	{
    		hexdump (memory, 0, extent, stdout);
    	}
    	return (extent);

    #elif defined (__linux__)

    #include <sys/poll.h>

    	struct pollfd pollfd =
    	{
    		channel->fd,
    		POLLIN,
    		0
    	};
    	signed status = poll (&pollfd, 1, channel->capture);
    	memset (memory, 0, extent);
    	if ((status < 0) && (errno != EINTR))
    	{
    		error (0, errno, "%s can't poll %s", __func__, channel->ifname);
    		return (-1);
    	}
    	if (status > 0)
    	{
    		status = recvfrom (channel->fd, memory, extent, 0, (struct sockaddr *) (0), (socklen_t *)(0));
    		if (status < 0)
    		{
    			error (0, errno, "%s can't read %s", __func__, channel->ifname);
    			return (-1);
    		}
    		if (status > 0)
    		{
    			extent = status;
    			if (_anyset (channel->flags, CHANNEL_VERBOSE))
    			{
    				hexdump (memory, 0, extent, stdout);
    			}
    			return (extent);
    		}
    	}

    #elif defined (__APPLE__) || defined (__OpenBSD__)

    	struct bpf_hdr * bpf_packet;
    	struct bpf * bpf = channel->bpf;;
    	memset (memory, 0, extent);
    	if (bpf->bpf_bufused <= 0)
    	{
    		bpf->bpf_bufused = read (channel->fd, bpf->bpf_buffer, bpf->bpf_length);
    		bpf->bpf_bp = bpf->bpf_buffer;
    	}
    	if (bpf->bpf_bufused < 0)
    	{
    		error (0, errno, "bpf");
    		return (-1);
    	}
    	if (bpf->bpf_bufused > 0)
    	{
    		bpf_packet = (struct bpf_hdr *)(bpf->bpf_bp);
    		if ((size_t) (extent) > bpf_packet->bh_caplen)
    		{
    			extent = bpf_packet->bh_caplen;
    		}
    		if ((size_t) (extent) < bpf_packet->bh_caplen)
    		{
    			if (_anyset (channel->flags, CHANNEL_VERBOSE))
    			{
    				error (0, 0, "Truncated incoming frame (%u -> %zd bytes)", bpf_packet->bh_caplen, extent);
    			}
    		}
    		memcpy (memory, bpf->bpf_bp + bpf_packet->bh_hdrlen, extent);
    		bpf->bpf_bufused -= BPF_WORDALIGN (bpf_packet->bh_hdrlen + bpf_packet->bh_caplen);
    		bpf->bpf_bp += BPF_WORDALIGN (bpf_packet->bh_hdrlen + bpf_packet->bh_caplen);
    		if (_anyset (channel->flags, CHANNEL_VERBOSE))
    		{
    			hexdump (memory, 0, extent, stdout);
    		}
    		return (extent);
    	}

    #elif defined (WINPCAP) || defined (LIBPCAP)

    	struct pcap_pkthdr * header;
    	const uint8_t *data;
    	signed status = pcap_next_ex (channel->socket, &header, &data);
    	memset (memory, 0, extent);
    	if (status < 0)
    	{
    		error (0, errno, "pcap_next_ex");
    		return (-1);
    	}
    	if (status > 0)
    	{
    		extent = header->caplen;
    		memcpy (memory, data, extent);
    		if (_anyset (channel->flags, CHANNEL_VERBOSE))
    		{
    			hexdump (memory, 0, extent, stdout);
    		}
    		return (extent);
    	}

    #else
    #error "Unknown Environment"
    #endif

    	return (0);
    }

    #endif

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