读取pcap文件，过滤非tcp包，获取IP及tcp端口信息

来自http://www.cnblogs.com/ErinCodeMM/archive/2011/07/10/2102517.html

// OpenAndFilterAndPres.cpp : Defines the entry point for the console application.
  //
  
 #include "stdafx.h" 
 #include "pcap.h"
 #include "remote-ext.h"
 #include"stdlib.h"
 
  /* 4 bytes IP address */
 typedef struct ip_address{
     u_char byte1;
     u_char byte2;
     u_char byte3;
     u_char byte4;
 }ip_address;
 
 /* IPv4 header */
 typedef struct ip_header{
     u_char  ver_ihl;        // Version (4 bits) + Internet header length (4 bits)
     u_char  tos;            // Type of service 
     u_short tlen;           // Total length 
     u_short identification; // Identification
     u_short flags_fo;       // Flags (3 bits) + Fragment offset (13 bits)
     u_char  ttl;            // Time to live
     u_char  proto;          // Protocol
     u_short crc;            // Header checksum
     ip_address  saddr;      // Source address
     ip_address  daddr;      // Destination address
     u_int   op_pad;         // Option + Padding
 }ip_header;
 
 /* UDP header*/
 typedef struct udp_header{
     u_short sport;          // Source port
     u_short dport;          // Destination port
     u_short len;            // Datagram length
     u_short crc;            // Checksum
 }udp_header;
 
 // TCP首部
 typedef struct tcp_header{
     WORD  source_port;       // (16 bits)                         Winsock 内置函数 ntohs（），主要作用将大端转换为小端！
     WORD  destination_port;  // (16 bits)                         Winsock 内置函数 ntohs（），主要作用将大端转换为小端！
     DWORD seq_number;        // Sequence Number (32 bits)         大小端原因，高低位4个8bit的存放顺序是反的，intel使用小端模式
     DWORD ack_number;        // Acknowledgment Number (32 bits)     大小端原因，高低位4个8bit的存放顺序是反的，intel使用小端模式
     WORD  info_ctrl;         // Data Offset (4 bits), Reserved (6 bits), Control bits (6 bits)                intel使用小端模式
     WORD  window;            // (16 bits)
     WORD  checksum;          // (16 bits)
     WORD  urgent_pointer;    // (16 bits)
 } tcp_header;
 
 /* prototype of the packet handler */
 void dispatcher_handler(u_char *temp1, 
                         const struct pcap_pkthdr *header, const u_char *pkt_data);
 
 
 int main(int argc, char* argv[])
 {
     pcap_t *fp;
     char errbuf[PCAP_ERRBUF_SIZE];
     char source[PCAP_BUF_SIZE];
     //char packet_filter[] = "tcp";
     //有tcp必有ip
     char packet_filter[] = "ip and tcp";
     struct bpf_program fcode;
     u_int netmask;
 
     if(argc != 2){
         printf("usage: %s filename", argv[0]);
         return -1;
     }
 
     /* Create the source string according to the new WinPcap syntax */
     if ( pcap_createsrcstr( source,         // variable that will keep the source string
                             PCAP_SRC_FILE,  // we want to open a file
                             NULL,           // remote host
                             NULL,           // port on the remote host
                             argv[1],        // name of the file we want to open
                             errbuf          // error buffer
                             ) != 0)
     {
         fprintf(stderr,"\nError creating a source string\n");
         return -1;
     }
     
     /* Open the capture file */
     if ( (fp= pcap_open(source,         // name of the device
                         65536,          // portion of the packet to capture
                                         // 65536 guarantees that the whole packet will be captured on all the link layers
                          PCAP_OPENFLAG_PROMISCUOUS,     // promiscuous mode
                          1000,              // read timeout
                          NULL,              // authentication on the remote machine
                          errbuf         // error buffer
                          ) ) == NULL)
     {
         fprintf(stderr,"\nUnable to open the file %s.\n", source);
         return -1;
     }
 
     netmask=0xffffff; 
 
     //compile the filter
     if (pcap_compile(fp, &fcode, packet_filter, 1, netmask) <0 )
     {
         fprintf(stderr,"\nUnable to compile the packet filter. Check the syntax.\n");
         return -1;
     }
     
     //set the filter
     if (pcap_setfilter(fp, &fcode)<0)
     {
         fprintf(stderr,"\nError setting the filter.\n");
         return -1;
     }
 
     // read and dispatch packets until EOF is reached
     pcap_loop(fp, 0, dispatcher_handler, NULL);
 
     return 0;
 }
 
 void dispatcher_handler(u_char *temp1, 
                         const struct pcap_pkthdr *header, const u_char *pkt_data)
 {
     struct tm *ltime;
     char timestr[16];
     ip_header *ih;
     tcp_header *th;
     u_int ip_len;
     u_short sport,dport;
     time_t local_tv_sec;
 
     /* convert the timestamp to readable format */
     local_tv_sec = header->ts.tv_sec;
     ltime=localtime(&local_tv_sec);
     strftime( timestr, sizeof timestr, "%H:%M:%S", ltime);
 
     /* print timestamp and length of the packet */
     printf("%s.%.6d len:%d ", timestr, header->ts.tv_usec, header->len);
 
     /* retireve the position of the ip header */
     ih = (ip_header *) (pkt_data +
         14); //length of ethernet header
 
     /* retireve the position of the tcp header */
     //从IPV4首部中取出"首部长度(4 bits)"
     ip_len = (ih->ver_ihl & 0xf) * 4;
     //强制类型转换，便于用自己的命名处理
     th = (tcp_header *) ((u_char*)ih + ip_len);
 
     /* convert from network byte order to host byte order */
     sport = ntohs( th->source_port );
     dport = ntohs( th->destination_port );
 
     /* print ip addresses and udp ports */
     printf("%d.%d.%d.%d.%d -> %d.%d.%d.%d.%d\n",
         ih->saddr.byte1,
         ih->saddr.byte2,
         ih->saddr.byte3,
         ih->saddr.byte4,
         sport,
         ih->daddr.byte1,
         ih->daddr.byte2,
         ih->daddr.byte3,
         ih->daddr.byte4,
         dport);    
 }