读取pcap文件，过滤非tcp包，获取IP及tcp端口信息

// 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);
}