467 lines
13 KiB
C
467 lines
13 KiB
C
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/*
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* Copyright (c) 2005 - 2006
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* CACE Technologies, Davis, CA
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of CACE Technologies nor the names of its
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* contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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*/
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/*
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* This simple program implements a user-level bridge.
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* It opens two adapters specified by the user and starts two threads.
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* The first thread receives packets from adapter 1 and sends them down to
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* adapter 2. The second thread does the same, but in the opposite
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* direction.
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*/
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#include <signal.h>
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#include "pcap.h"
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/* Storage data structure used to pass parameters to the threads */
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typedef struct _in_out_adapters
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{
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unsigned int state; /* Some simple state information */
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pcap_t *input_adapter;
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pcap_t *output_adapter;
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}in_out_adapters;
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/* Prototypes */
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DWORD WINAPI CaptureAndForwardThread(LPVOID lpParameter);
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void ctrlc_handler(int sig);
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/* This prevents the two threads to mess-up when they do printfs */
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CRITICAL_SECTION print_cs;
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/* Thread handlers. Global because we wait on the threads from the CTRL+C handler */
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HANDLE threads[2];
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/* This global variable tells the forwarder threads they must terminate */
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volatile int kill_forwaders = 0;
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/*******************************************************************/
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int main()
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{
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pcap_if_t *alldevs;
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pcap_if_t *d;
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int inum1, inum2;
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int i=0;
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pcap_t *adhandle1, *adhandle2;
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char errbuf[PCAP_ERRBUF_SIZE];
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u_int netmask1, netmask2;
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char packet_filter[256];
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struct bpf_program fcode;
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in_out_adapters couple0, couple1;
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/*
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* Retrieve the device list
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*/
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if (pcap_findalldevs_ex(PCAP_SRC_IF_STRING, NULL, &alldevs, errbuf) == -1)
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{
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fprintf(stderr,"Error in pcap_findalldevs: %s\n", errbuf);
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exit(1);
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}
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/* Print the list */
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for(d=alldevs; d; d=d->next)
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{
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printf("%d. ", ++i);
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if (d->description)
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printf("%s\n", d->description);
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else
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printf("<unknown adapter>\n");
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}
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if(i==0)
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{
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printf("\nNo interfaces found! Make sure WinPcap is installed.\n");
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return -1;
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}
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/*
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* Get input from the user
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*/
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/* Get the filter*/
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printf("\nSpecify filter (hit return for no filter):");
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fgets(packet_filter, sizeof(packet_filter), stdin);
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/* Get the first interface number*/
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printf("\nEnter the number of the first interface to use (1-%d):",i);
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scanf_s("%d", &inum1);
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if(inum1 < 1 || inum1 > i)
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{
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printf("\nInterface number out of range.\n");
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/* Free the device list */
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pcap_freealldevs(alldevs);
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return -1;
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}
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/* Get the second interface number*/
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printf("Enter the number of the first interface to use (1-%d):",i);
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scanf_s("%d", &inum2);
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if(inum2 < 1 || inum2 > i)
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{
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printf("\nInterface number out of range.\n");
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/* Free the device list */
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pcap_freealldevs(alldevs);
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return -1;
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}
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if(inum1 == inum2 )
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{
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printf("\nCannot bridge packets on the same interface.\n");
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/* Free the device list */
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pcap_freealldevs(alldevs);
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return -1;
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}
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/*
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* Open the specified couple of adapters
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*/
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/* Jump to the first selected adapter */
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for(d = alldevs, i = 0; i< inum1 - 1 ;d = d->next, i++);
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/*
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* Open the first adapter.
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* *NOTICE* the flags we are using, they are important for the behavior of the prgram:
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* - PCAP_OPENFLAG_PROMISCUOUS: tells the adapter to go in promiscuous mode.
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* This means that we are capturing all the traffic, not only the one to or from
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* this machine.
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* - PCAP_OPENFLAG_NOCAPTURE_LOCAL: prevents the adapter from capturing again the packets
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* transmitted by itself. This avoids annoying loops.
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* - PCAP_OPENFLAG_MAX_RESPONSIVENESS: configures the adapter to provide minimum latency,
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* at the cost of higher CPU usage.
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*/
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if((adhandle1 = pcap_open(d->name, // name of the device
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65536, // portion of the packet to capture.
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// 65536 grants that the whole packet will be captured on every link layer.
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PCAP_OPENFLAG_PROMISCUOUS | // flags. We specify that we don't want to capture loopback packets, and that the driver should deliver us the packets as fast as possible
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PCAP_OPENFLAG_NOCAPTURE_LOCAL |
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PCAP_OPENFLAG_MAX_RESPONSIVENESS,
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500, // read timeout
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NULL, // remote authentication
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errbuf // error buffer
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)) == NULL)
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{
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fprintf(stderr,"\nUnable to open the adapter. %s is not supported by WinPcap\n", d->description);
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/* Free the device list */
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pcap_freealldevs(alldevs);
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return -1;
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}
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if(d->addresses != NULL)
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{
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/* Retrieve the mask of the first address of the interface */
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netmask1 = ((struct sockaddr_in *)(d->addresses->netmask))->sin_addr.S_un.S_addr;
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}
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else
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{
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/* If the interface is without addresses we suppose to be in a C class network */
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netmask1 = 0xffffff;
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}
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/* Jump to the second selected adapter */
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for(d = alldevs, i = 0; i< inum2 - 1 ;d = d->next, i++);
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/* Open the second adapter */
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if((adhandle2 = pcap_open(d->name, // name of the device
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65536, // portion of the packet to capture.
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// 65536 grants that the whole packet will be captured on every link layer.
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PCAP_OPENFLAG_PROMISCUOUS | // flags. We specify that we don't want to capture loopback packets, and that the driver should deliver us the packets as fast as possible
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PCAP_OPENFLAG_NOCAPTURE_LOCAL |
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PCAP_OPENFLAG_MAX_RESPONSIVENESS,
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500, // read timeout
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NULL, // remote authentication
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errbuf // error buffer
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)) == NULL)
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{
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fprintf(stderr,"\nUnable to open the adapter. %s is not supported by WinPcap\n", d->description);
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/* Free the device list */
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pcap_freealldevs(alldevs);
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return -1;
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}
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if(d->addresses != NULL)
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{
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/* Retrieve the mask of the first address of the interface */
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netmask2 = ((struct sockaddr_in *)(d->addresses->netmask))->sin_addr.S_un.S_addr;
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}
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else
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{
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/* If the interface is without addresses we suppose to be in a C class network */
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netmask2 = 0xffffff;
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}
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/*
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* Compile and set the filters
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*/
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/* compile the filter for the first adapter */
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if (pcap_compile(adhandle1, &fcode, packet_filter, 1, netmask1) <0 )
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{
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fprintf(stderr,"\nUnable to compile the packet filter. Check the syntax.\n");
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/* Close the adapters */
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pcap_close(adhandle1);
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pcap_close(adhandle2);
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/* Free the device list */
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pcap_freealldevs(alldevs);
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return -1;
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}
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/* set the filter for the first adapter*/
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if (pcap_setfilter(adhandle1, &fcode)<0)
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{
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fprintf(stderr,"\nError setting the filter.\n");
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/* Close the adapters */
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pcap_close(adhandle1);
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pcap_close(adhandle2);
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/* Free the device list */
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pcap_freealldevs(alldevs);
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return -1;
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}
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/* compile the filter for the second adapter */
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if (pcap_compile(adhandle2, &fcode, packet_filter, 1, netmask2) <0 )
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{
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fprintf(stderr,"\nUnable to compile the packet filter. Check the syntax.\n");
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/* Close the adapters */
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pcap_close(adhandle1);
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pcap_close(adhandle2);
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/* Free the device list */
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pcap_freealldevs(alldevs);
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return -1;
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}
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/* set the filter for the second adapter*/
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if (pcap_setfilter(adhandle2, &fcode)<0)
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{
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fprintf(stderr,"\nError setting the filter.\n");
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/* Close the adapters */
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pcap_close(adhandle1);
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pcap_close(adhandle2);
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/* Free the device list */
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pcap_freealldevs(alldevs);
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return -1;
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}
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/* At this point, we don't need the device list any more. Free it */
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pcap_freealldevs(alldevs);
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/*
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* Start the threads that will forward the packets
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*/
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/* Initialize the critical section that will be used by the threads for console output */
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InitializeCriticalSection(&print_cs);
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/* Init input parameters of the threads */
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couple0.state = 0;
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couple0.input_adapter = adhandle1;
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couple0.output_adapter = adhandle2;
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couple1.state = 1;
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couple1.input_adapter = adhandle2;
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couple1.output_adapter = adhandle1;
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/* Start first thread */
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if((threads[0] = CreateThread(
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NULL,
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0,
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CaptureAndForwardThread,
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&couple0,
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0,
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NULL)) == NULL)
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{
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fprintf(stderr, "error creating the first forward thread");
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/* Close the adapters */
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pcap_close(adhandle1);
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pcap_close(adhandle2);
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/* Free the device list */
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pcap_freealldevs(alldevs);
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return -1;
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}
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/* Start second thread */
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if((threads[1] = CreateThread(
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NULL,
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0,
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CaptureAndForwardThread,
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&couple1,
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0,
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NULL)) == NULL)
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{
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fprintf(stderr, "error creating the second forward thread");
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/* Kill the first thread. Not very gentle at all...*/
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TerminateThread(threads[0], 0);
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/* Close the adapters */
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pcap_close(adhandle1);
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pcap_close(adhandle2);
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/* Free the device list */
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pcap_freealldevs(alldevs);
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return -1;
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}
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/*
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* Install a CTRL+C handler that will do the cleanups on exit
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*/
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signal(SIGINT, ctrlc_handler);
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/*
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* Done!
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* Wait for the Greek calends...
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*/
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printf("\nStart bridging the two adapters...\n", d->description);
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Sleep(INFINITE);
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return 0;
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}
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/*******************************************************************
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* Forwarding thread.
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* Gets the packets from the input adapter and sends them to the output one.
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*******************************************************************/
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DWORD WINAPI CaptureAndForwardThread(LPVOID lpParameter)
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{
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struct pcap_pkthdr *header;
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const u_char *pkt_data;
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int res = 0;
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in_out_adapters* ad_couple = lpParameter;
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unsigned int n_fwd = 0;
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/*
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* Loop receiving packets from the first input adapter
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*/
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while((!kill_forwaders) && (res = pcap_next_ex(ad_couple->input_adapter, &header, &pkt_data)) >= 0)
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{
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if(res != 0) /* Note: res=0 means "read timeout elapsed"*/
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{
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/*
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* Print something, just to show when we have activity.
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* BEWARE: acquiring a critical section and printing strings with printf
|
||
|
|
* is something inefficient that you seriously want to avoid in your packet loop!
|
||
|
|
* However, since this is a *sample program*, we privilege visual output to efficiency.
|
||
|
|
*/
|
||
|
|
EnterCriticalSection(&print_cs);
|
||
|
|
|
||
|
|
if(ad_couple->state == 0)
|
||
|
|
printf(">> Len: %u\n", header->caplen);
|
||
|
|
else
|
||
|
|
printf("<< Len: %u\n", header->caplen);
|
||
|
|
|
||
|
|
LeaveCriticalSection(&print_cs);
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Send the just received packet to the output adaper
|
||
|
|
*/
|
||
|
|
if(pcap_sendpacket(ad_couple->output_adapter, pkt_data, header->caplen) != 0)
|
||
|
|
{
|
||
|
|
EnterCriticalSection(&print_cs);
|
||
|
|
|
||
|
|
printf("Error sending a %u bytes packets on interface %u: %s\n",
|
||
|
|
header->caplen,
|
||
|
|
ad_couple->state,
|
||
|
|
pcap_geterr(ad_couple->output_adapter));
|
||
|
|
|
||
|
|
LeaveCriticalSection(&print_cs);
|
||
|
|
}
|
||
|
|
else
|
||
|
|
{
|
||
|
|
n_fwd++;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
/*
|
||
|
|
* We're out of the main loop. Check the reason.
|
||
|
|
*/
|
||
|
|
if(res < 0)
|
||
|
|
{
|
||
|
|
EnterCriticalSection(&print_cs);
|
||
|
|
|
||
|
|
printf("Error capturing the packets: %s\n", pcap_geterr(ad_couple->input_adapter));
|
||
|
|
fflush(stdout);
|
||
|
|
|
||
|
|
LeaveCriticalSection(&print_cs);
|
||
|
|
}
|
||
|
|
else
|
||
|
|
{
|
||
|
|
EnterCriticalSection(&print_cs);
|
||
|
|
|
||
|
|
printf("End of bridging on interface %u. Forwarded packets:%u\n",
|
||
|
|
ad_couple->state,
|
||
|
|
n_fwd);
|
||
|
|
fflush(stdout);
|
||
|
|
|
||
|
|
LeaveCriticalSection(&print_cs);
|
||
|
|
}
|
||
|
|
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
/*******************************************************************
|
||
|
|
* CTRL+C hanlder.
|
||
|
|
* We order the threads to die and then we patiently wait for their
|
||
|
|
* suicide.
|
||
|
|
*******************************************************************/
|
||
|
|
void ctrlc_handler(int sig)
|
||
|
|
{
|
||
|
|
/*
|
||
|
|
* unused variable
|
||
|
|
*/
|
||
|
|
(VOID)(sig);
|
||
|
|
|
||
|
|
kill_forwaders = 1;
|
||
|
|
|
||
|
|
WaitForMultipleObjects(2,
|
||
|
|
threads,
|
||
|
|
TRUE, /* Wait for all the handles */
|
||
|
|
5000); /* Timeout */
|
||
|
|
|
||
|
|
exit(0);
|
||
|
|
}
|