网络抓包与流量在线分析系统的设计与实现-基于libpcap在MacOS上实现记录这愉快（DT）的一周

要求：

基于LINUX系统设计并实现一个网络流量的分析系统。该系统具有以下功能：（1）实时抓取网络数据。（2）网络协议分析与显示。（3）将网络数据包聚合成数据流，以源IP、目的IP、源端口、目的端口及协议等五元组的形式存储。（4）计算并显示固定时间间隔内网络连接（双向流）的统计量（如上行与下行的数据包数目，上行与下行的数据量大小等）。在这些统计数据的基础上分析不同网络应用的流量特征。

关键词：linux,libpcap,流量分析，网络抓包，协议分析，哈希链表，文件操作，C语言

功能

（1）能够实时抓取网络中的数据包。并实时显示在程序界面上。用户可自定义过滤条件以抓取所需要的数据包。
（2）分析各个网络协议格式，能够显示各协议字段的实际意义。例如，能够通过该程序反映TCP三次握手的实现过程。
（3）采用Hash链表的形式将网络数据以连接（双向流）的形式存储。
（4）计算并显示固定时间间隔内网络连接（双向流）的统计量（如上行与下行的数据包数目，上行与下行的数据量大小等）。例如，抓取一段时间（如30分钟）的网络流量，将该段时间以固定时长（如1分钟）为单位分成若干个时间片，计算网络连接在每一个时间片内的相关统计量。并在上述统计数据的基础上分析不同应用如WEB、DNS、在线视频等服务的流量特征。注意，可根据实际的流量分析需要自己定义相关的统计量。

实验环境

硬件设备：
（1）MAC笔记本
软件设备：
（2）MACOS（UNIX内核）
（3）网络数据包捕获函数包，Linux平台下为libpcap
（4）编程语言选用C，IDE使用Xcode
实验环境的配置：
Lipcap 下载地址为：http://www.tcpdump.org/release/libpcap-1.7.3.tar.gz
libpcap（Packet Capture library）即数据包捕获函数库。该库提供的C函数接口可用于需要捕获经过网络接口（只要经过该接口，目标地址不一定为本机）数据包的系统开发上。由 Berkeley大学Lawrence Berkeley National Laboratory研究院的Van Jacobson、Craig Leres和Steven McCanne编写。该函数库支持Linux、Solaris和*BSD系统平台。libpcap主要由两部份组成：网络分接头(Network Tap)和数据过滤器(Packet Filter)。
lipcap的安装过程：
1）tar zxvf libpcap-1.7.3.tar.gz 解压文件，并将其放入自定义的安装目录。
2）打开网址：flex.sourceforge.net/ 下载 flex-2.5.35.tar.gz (1.40MB) 软件包，通过 tar zxvf flex-2.5.35.tar.gz 解压文件，并将其放入上述自定义的安装目录中。
注：如果没有编译安装此文件，在编译安装libpcap时，可能会出现 “configure: error: Your operating system’s lex is insufficient to compile libpcap.”的错误提示。
3）打开网址：ftp.gnu.org/gnu/bison/ 下载 bison-2.4.1.tar.gz (1.9MB) 软件包，通过 tar zxvf bison-2.4.1.tar.gz 解压文件，并将其放入上述自定义的安装目录中。
如果没有编译安装此文件，在编译安装libpcap时，可能会出现 “configure: WARNING: don’t have both flex and bison; reverting to lex/yacc checking for capable lex… insufficient” 的错误提示。
4）打开网址：ftp.gnu.org/gnu/m4/ 下载 m4-1.4.13.tar.gz (1.2MB)软件包，通过 tar zxvf m4-1.4.13.tar.gz 解压文件，并将其放入上述自定义的安装目录中。
注：如果没有编译安装此文件，在编译安装bison-2.4.1时，就会出现 “configure: error: GNU M4 1.4 is required”的错误提示。
5）依次进入目录m4-1.4.13，bison-2.4.1，flex-2.5.35，libpcap-1.0.0 并执行以下命令：
./configure
make
make instal
（备注：使用linux或unix系统的需要进入终端用shell指令安装，Xcode中使用libpcap将其当作第三方函数库使用时，需要手动点击蓝色的工程文件，在右边的BuildPhase中LinkBinaryWithLibraries中手动添加libpcap的函数库，并且c中支持的一些基于win平台的函数和头文件在MACOS中有所差异，如#include <malloc.h>需改成#include <mm_malloc.h>，还有一些细节需要自己发现）

源代码

（分为头文件与主c文件两部分）
/main.h 包括网络抓包与流量分析/
#include <stdio.h>
#include <mm_malloc.h>
#include <sys/malloc.h>
#include <time.h>
#include <string.h>
#include <pcap.h>
#include “protocol.h”
#include<netinet/in.h>
#include<arpa/inet.h>
#include<errno.h>
#include<unistd.h>

typedef struct _argument
{
pcap_t *handle;
int timeLen;
}argument;

void *thread_clock(void argv)
{
pcap_t handle = ((argument)argv)->handle;
int timeLen = ((argument)argv)->timeLen; // set time
sleep(timeLen);
pcap_breakloop(handle);
return 2;
}

void cb_getPacket(u_char *dumpfile, const struct pcap_pkthdr *pkthdr, const u_char *packet)
{
// ip_header seg_ip = (ip_header)(package + ETHER_LEN);
pcap_dump(dumpfile, pkthdr, packet);

static int id = 0;
printf(".  ");
if(++id % 30 == 0)
{printf("\n");
}

}

//timeval结构
typedef struct _shh_timeval{
int tv_sec; /* seconds 1900之后的秒数 /
int tv_usec; / and microseconds */
}shh_timeval;

// pcap_next()方法执行后，pcap_pkthdr类型的指针指向抓包的信息
typedef struct _shh_pkthdr {
shh_timeval ts; /* time stamp 时间 /
bpf_u_int32 caplen; / length of portion present 包的数据长度？？ /
bpf_u_int32 len; / length this packet (off wire) 包的实际长度 */
}shh_pkthdr;

typedef struct _net5set
{
u_int sip;
u_short sport;
u_int dip;
u_short dport;
u_char protocol;
}net5set;

typedef struct _net_link_node
{
net5set nln_5set;
int nln_upl_size;
int nln_downl_size;
int nln_upl_pkt;
int nln_downl_pkt;
u_char nln_status;
#define CLOSED 0x00
#define SYN_SENT 0x01 // client sent SYN
#define SYN_RECVD 0x02 // recieve SYN, and send SYN ACK
#define ESTABLISHED 0x03 // client get SYN & ACK, server get ACK

#define FIN_WAIT_1 0x04 // client send FIN
#define CLOSE_WAIT 0x05 // server recv FIN, and send ACK
#define FIN_WAIT_2 0x06 // client recv ACK
#define LAST_ACK 0x07 // server send FIN
#define TIME_WAIT 0x08 // client recv FIN
// CLOSED: client send ACK, server recv ACK
#define UNDEFINED 0xff
struct _net_link_node *next;
}net_link_node, *p_net_link;

typedef struct _net_link_header
{
int count_conn;
int count_upl_pkt;
int count_downl_pkt;
int count_upl;
int count_downl;
p_net_link link;
}net_link_header;

#define IPTOSBUFFERS 12
static char iptos(bpf_u_int32 in)
{
static char output[IPTOSBUFFERS][34+3+1];
static short which;
u_char *p;

p = (u_char *)&in;
which = (which + 1 == IPTOSBUFFERS ? 0 : which + 1);
sprintf(output[which], "%d.%d.%d.%d", p[0], p[1], p[2], p[3]);
return output[which];

}

char *long2time(long ltime)
{
time_t t;
struct tm *p;
static char s[100];

t = ltime;
p = gmtime(&t);strftime(s, sizeof(s), "%Y-%m-%d %H:%M:%S", p);
return s;

}

// 需要三个链表，一个哈希链表，保存处于连接状态的包
// 另两个链表分别保存tcp和udp的流量
net_link_header *FLowLink_TCP;
net_link_header *FLowLink_UDP;

/* ========== hash table ============= */
#define HASH_TABLE_SIZE 0xffff
p_net_link HashTable[HASH_TABLE_SIZE];

void init_flowLink(net_link_header *head)
{
head->count_conn = 0;
head->count_upl_pkt = 0;
head->count_downl_pkt = 0;
head->count_upl = 0;
head->count_downl = 0;
head->link = NULL;
}

void add_to_flowLink(net_link_header *head, const net_link_node *theNode)
{
net_link_node *newNode = (net_link_node *)malloc(sizeof(net_link_node));
memcpy(newNode, theNode, sizeof(net_link_node));

head->count_conn ++;
head->count_upl_pkt     += newNode->nln_upl_pkt;
head->count_downl_pkt   += newNode->nln_downl_pkt;
head->count_upl         += newNode->nln_upl_size;
head->count_downl       += newNode->nln_downl_size;newNode->next = head->link;
head->link = newNode;

}

void clear_flowLink(net_link_header *head)
{
if( head->link == NULL ){ return;}

net_link_node *pTemp1 = NULL;
net_link_node *pTemp2 = NULL;pTemp1 = head->link;
pTemp2 = pTemp1->next;
while( pTemp2 != NULL )
{free(pTemp1);pTemp1 = pTemp2;pTemp2 = pTemp1->next;
}
free(pTemp1);head->link = NULL;

}

void parse_flowLink_TCP(FILE *fOutput)
{
fprintf(fOutput, “TCP连接个数：\t%d\n”, FLowLink_TCP->count_conn);
fprintf(fOutput, “TCP数据包个数：\t%d\n”, FLowLink_TCP->count_upl_pkt + FLowLink_TCP->count_upl_pkt);
fprintf(fOutput, “TCP数据总流量：\t%d bytes\n”, FLowLink_TCP->count_upl + FLowLink_TCP->count_downl);
fprintf(fOutput, “TCP数据上传量：\t%d bytes\n”, FLowLink_TCP->count_upl);
fprintf(fOutput, “TCP数据下载量：\t%d bytes\n”, FLowLink_TCP->count_downl);
fprintf(fOutput, “-----------------------\n”);

net_link_node *pTemp = NULL;
pTemp = FLowLink_TCP->link;
while( pTemp != NULL )
{fprintf(fOutput, "%s\t%u\t", iptos(pTemp->nln_5set.sip), pTemp->nln_5set.sport);fprintf(fOutput, "==>\t%s\t%u\t", iptos(pTemp->nln_5set.dip), pTemp->nln_5set.dport);fprintf(fOutput, "上传包数量：%d\t", pTemp->nln_upl_pkt);fprintf(fOutput, "下载包数量：%d\t", pTemp->nln_downl_pkt);fprintf(fOutput, "upload：%d bytes\t", pTemp->nln_upl_size);fprintf(fOutput, "download：%d bytes\t", pTemp->nln_downl_size);fprintf(fOutput, "\n");pTemp = pTemp->next;
}clear_flowLink(FLowLink_TCP);

}

void parse_flowLink_UDP(FILE *fOutput)
{
fprintf(fOutput, “UDP数据包个数：\t%d\n”, FLowLink_UDP->count_upl_pkt + FLowLink_UDP->count_upl_pkt);
fprintf(fOutput, “UDP数据流量：\t%d bytes\n”, FLowLink_UDP->count_upl + FLowLink_UDP->count_downl);
clear_flowLink(FLowLink_UDP);
}

u_short get_ushort_net(u_short virtu)
{
return (u_short)(virtu >> 8 | virtu << 8);
}

u_short get_hash(const net5set *theSet)
{
u_int srcIP = theSet->sip;
u_int desIP = theSet->dip;
u_int port = (u_int)(theSet->sport * theSet->dport);
u_int res = (srcIP^desIP)port;
u_short hash= (u_short)((res & 0x00ff)^(res >> 16));
return hash;
}

void add_to_hashTable(u_short hash, const net_link_node *theNode, u_char flags)
{
net_link_node *HashNode = (net_link_node *)malloc(sizeof(net_link_node));
memcpy(HashNode, theNode, sizeof(net_link_node));

if(HashTable[hash] == NULL)
{HashTable[hash] = HashNode;return;
}
net_link_node *pTemp = HashTable[hash];
net_link_node *pBack = NULL;
int isSame_up = 0;
int isSame_down = 0;
while(pTemp != NULL)
{isSame_up = (pTemp->nln_5set.sip == HashNode->nln_5set.sip)&& (pTemp->nln_5set.dip == HashNode->nln_5set.dip)&& (pTemp->nln_5set.sport == HashNode->nln_5set.sport)&& (pTemp->nln_5set.dport == HashNode->nln_5set.dport);isSame_down = (pTemp->nln_5set.dip == HashNode->nln_5set.sip)&& (pTemp->nln_5set.sip == HashNode->nln_5set.dip)&& (pTemp->nln_5set.dport == HashNode->nln_5set.sport)&& (pTemp->nln_5set.sport == HashNode->nln_5set.dport);if( isSame_up ){pTemp->nln_upl_size += HashNode->nln_upl_size;pTemp->nln_upl_pkt ++;if(pTemp->nln_status == ESTABLISHED && (flags & TH_FIN) ){pTemp->nln_status = FIN_WAIT_1;}else if (pTemp->nln_status == TIME_WAIT && (flags & TH_ACK)){pTemp->nln_status = CLOSED;if(pBack == NULL){HashTable[hash] = NULL;}else{pBack->next = pTemp->next;}add_to_flowLink(FLowLink_TCP, pTemp);free(pTemp);}else if(pTemp->nln_status == CLOSE_WAIT && (flags & TH_FIN)){pTemp->nln_status = LAST_ACK;}free(HashNode);break;}else if( isSame_down ){pTemp->nln_downl_size += HashNode->nln_upl_size;pTemp->nln_downl_pkt ++;if(pTemp->nln_status == ESTABLISHED && (flags & TH_FIN)){pTemp->nln_status = CLOSE_WAIT;}else if(pTemp->nln_status == LAST_ACK && (flags & TH_ACK)){pTemp->nln_status = CLOSED;if(pBack == NULL){HashTable[hash] = NULL;}else{pBack->next = pTemp->next;}add_to_flowLink(FLowLink_TCP, pTemp);free(pTemp);}else if(pTemp->nln_status == FIN_WAIT_1 && (flags & TH_ACK)){pTemp->nln_status = FIN_WAIT_2;}else if(pTemp->nln_status == FIN_WAIT_2 && (flags & TH_FIN)){pTemp->nln_status = TIME_WAIT;}free(HashNode);break;}pBack = pTemp;pTemp = pTemp->next;
}
if(pTemp == NULL)
{pBack->next = HashNode;
}

}

void clear_hashTable()
{
int i = 0;
net_link_node *pTemp1 = NULL;
net_link_node *pTemp2 = NULL;
for(i = 0; i < HASH_TABLE_SIZE; i++)
{
if(HashTable[i] == NULL){ continue;}

    pTemp1 = HashTable[i];while(pTemp1 != NULL){pTemp2 = pTemp1->next;add_to_flowLink(FLowLink_TCP, pTemp1);free(pTemp1);pTemp1 = pTemp2;}HashTable[i] = NULL;
}

}

/*
在以太网中，规定最小的数据包为64个字节，如果数据包不足64字节，则会由网卡填充。
*/

int main(int argc, char const *argv[])
{
char *dev, errbuf[PCAP_ERRBUF_SIZE];
pcap_t *dev_handle;
bpf_u_int32 net, mask;
char packet_filter[] = “ip”;
struct bpf_program fcode;

dev = pcap_lookupdev(errbuf);
if(dev == NULL){printf("No Device:%s\n", errbuf);return 0;
} // */
/*char *wlan_dev = "wlan0";dev = wlan_dev; // */
printf("开始抓取数据，设备:%s\n", dev);dev_handle = pcap_open_live(dev, BUFSIZ, 1, 0, errbuf);
if(dev_handle == NULL){printf("pcap_open_live:%s\n", errbuf);return 0;
}
//args->handle = dev_handle;pcap_lookupnet(dev, &net, &mask, errbuf);//compile the filter
if (pcap_compile(dev_handle, &fcode, packet_filter, 1, mask) <0 )
{printf("\nUnable to compile the packet filter. Check the syntax.\n");return 0;
}
//set the filter
if (pcap_setfilter(dev_handle, &fcode) < 0)
{printf("\nError setting the filter.\n");return 0;
}// open file to save pcap
pcap_dumper_t *dumpfile;
dumpfile = pcap_dump_open(dev_handle, "traffic.data");
if(dumpfile == NULL){printf("\nError opening output file\n");return 0;
}// build a new thread
pthread_t ptClock;
argument args;
args.handle = dev_handle;
int argv_time = 30;
args.timeLen = (argv_time > 0) ? argv_time : 60;
printf("抓取时长：%d s\n", argv_time);
if(pthread_create(&ptClock, NULL, thread_clock, &args))
{printf("pthread_create(): Error!\n");return -1;
}
pcap_loop(dev_handle, -1, cb_getPacket, (u_char*)dumpfile);// close all handle
pcap_dump_close(dumpfile);
pcap_close(dev_handle);
printf("\nDone!\n");
//以上为抓包char *file_output = "/Users/ganyu/Desktop/result.data";
FILE *fOutput = fopen(file_output, "w");
fclose(fOutput);        // clear file
fOutput = fopen(file_output, "a+");char *filename = "traffic.data";
fprintf(fOutput, "数据文件：%s\n", filename);printf("载入文件...\n");
FILE *fp = fopen(filename, "r");shh_pkthdr      *pkthdr     = (shh_pkthdr *)malloc(sizeof(shh_pkthdr));
ether_header    *segEther   = (ether_header*)malloc(sizeof(ether_header));
ip_header       *segIP      = (ip_header*)malloc(sizeof(ip_header));
tcp_header      *segTCP     = (tcp_header*)malloc(sizeof(tcp_header));
udp_header      *segUDP     = (udp_header*)malloc(sizeof(udp_header));
net5set         *Cur5Set    = (net5set *)malloc(sizeof(net5set));
net_link_node   *LinkNode   = (net_link_node *)malloc(sizeof(net_link_node));FLowLink_TCP = (net_link_header *)malloc(sizeof(net_link_header));
init_flowLink(FLowLink_TCP);
FLowLink_UDP = (net_link_header *)malloc(sizeof(net_link_header));
init_flowLink(FLowLink_UDP);long    fileLen     = 0;
int     pktLen      = 0;    // pktLen = Ether + IP
int     trailerLen  = 0;
u_short ipLen_real  = 0;
u_short ipLen_total = 0;
u_short tcpLen_real = 0;
u_short dataLen     = 0;// get length of file
fseek(fp, 0, SEEK_END);
fileLen = ftell(fp);
fseek(fp, PCAP_HEADER_LEN, SEEK_SET);
// 移动文件位置指针。
// If successful, the function returns zero.
// Otherwise, it returns non-zero value.
// SEEK_SET:文件开头;SEEK_CUR:当前位置;SEEK_END:文件结尾fread(pkthdr, PACKET_HEADER_LEN, 1, fp);
fseek(fp, - PACKET_HEADER_LEN, SEEK_CUR);
int tstamp_start    = pkthdr->ts.tv_sec;
int tstamp_offset   = tstamp_start;
int tstamp_now      = tstamp_start;
int cycle           = 5;
cycle = (cycle > 0) ? cycle : 10;
fprintf(fOutput, "分析周期：%d s\n", cycle);//  int i = 0;
while( ftell(fp) > 0 &&  ftell(fp) < fileLen )
{fread(pkthdr, PACKET_HEADER_LEN, 1, fp);pktLen = pkthdr->caplen;tstamp_now = pkthdr->ts.tv_sec;if(tstamp_now - tstamp_offset >= cycle){fprintf(fOutput, "\n\n>>>>> 时间段：%s", long2time(tstamp_offset));fprintf(fOutput, " --> %s\n", long2time(tstamp_offset + cycle));fprintf(fOutput, "----------------------\n");clear_hashTable();parse_flowLink_UDP(fOutput);init_flowLink(FLowLink_UDP);fprintf(fOutput, "----------------------\n");parse_flowLink_TCP(fOutput);init_flowLink(FLowLink_TCP);tstamp_offset = tstamp_now;}//printf("%d\t", pktLen);//printf("\n%d\t", ++i);fread(segEther, ETHER_LEN, 1, fp);if( get_ushort_net(segEther->type) != ETHER_TYPE_IP ){//printf("------\t");fseek(fp, pktLen - ETHER_LEN, SEEK_CUR);continue;}fread(segIP, IP_LEN_MIN, 1, fp);ipLen_real = (segIP->ver_ihl & 0x0f)*4;ipLen_total = get_ushort_net(segIP->tlen);trailerLen = pktLen - ETHER_LEN - ipLen_total;fseek(fp, ipLen_real - IP_LEN_MIN, SEEK_CUR);if( segIP->proto != IP_TCP && segIP->proto != IP_UDP ){//printf("------\t");fseek(fp, ipLen_total - ipLen_real + trailerLen, SEEK_CUR);continue;}Cur5Set->sip = segIP->saddr;Cur5Set->dip = segIP->daddr;Cur5Set->protocol = segIP->proto;//printf("src:%s\t", iptos(Cur5Set->sip));//printf("des:%s\t", iptos(Cur5Set->dip));if(segIP->proto == IP_TCP){//printf("TCP\t");fread(segTCP, TCP_LEN_MIN, 1, fp);tcpLen_real = (((segTCP->th_len)>>4) & 0x0f) * 4;dataLen = ipLen_total - ipLen_real - tcpLen_real;Cur5Set->sport = get_ushort_net(segTCP->th_sport);Cur5Set->dport = get_ushort_net(segTCP->th_dport);fseek(fp, (tcpLen_real - TCP_LEN_MIN) + dataLen + trailerLen, SEEK_CUR);}else if(segIP->proto == IP_UDP){//printf("UDP\t");fread(segUDP, UDP_LEN, 1, fp);dataLen = ipLen_total - ipLen_real - UDP_LEN;Cur5Set->sport = get_ushort_net(segUDP->uh_sport);Cur5Set->dport = get_ushort_net(segUDP->uh_dport);fseek(fp, dataLen + trailerLen, SEEK_CUR);}LinkNode->nln_5set      = *Cur5Set;LinkNode->nln_upl_size  = dataLen;LinkNode->nln_downl_size= 0;LinkNode->nln_upl_pkt   = 1;LinkNode->nln_downl_pkt = 0;LinkNode->nln_status    = ESTABLISHED;LinkNode->next          = NULL;if(segIP->proto == IP_TCP){add_to_hashTable(get_hash(Cur5Set), LinkNode, segTCP->th_flags);}else{add_to_flowLink(FLowLink_UDP, LinkNode);}
}
fprintf(fOutput, "\nover\n");free(pkthdr);
free(segEther);
free(segIP);
free(segTCP);
free(segUDP);
free(Cur5Set);
free(LinkNode);
free(FLowLink_TCP);
free(FLowLink_UDP);
fclose(fOutput);printf("Done!\n");
return 0;

}

/** protocol.h
structs of ethernet, ip, tcp, udp
*/

#define PCAP_HEADER_LEN 24
#define PACKET_HEADER_LEN 16

/* ============= Ethernet ============ */
#define ETHER_LEN 14
#define ETHER_ADDR_LEN 6
#define ETHER_TYPE_LEN 2

#define ETHER_DEST_OFFSET (0 * ETHER_ADDR_LEN)
#define ETHER_SRC_OFFSET (1 * ETHER_ADDR_LEN)
#define ETHER_TYPE_OFFSET (2 * ETHER_ADDR_LEN)

typedef struct _ether_header{
u_char host_dest[ETHER_ADDR_LEN];
u_char host_src[ETHER_ADDR_LEN];
u_short type;
#define ETHER_TYPE_MIN 0x0600
#define ETHER_TYPE_IP 0x0800
#define ETHER_TYPE_ARP 0x0806
#define ETHER_TYPE_8021Q 0x8100
#define ETHER_TYPE_BRCM 0x886c
#define ETHER_TYPE_802_1X 0x888e
#define ETHER_TYPE_802_1X_PREAUTH 0x88c7
}ether_header;

/============== IP ================/
#define IP_LEN_MIN 20

/* 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 ident; // Identification
u_short flags_fo; // Flags (3 bits) + Fragment offset (13 bits)
u_char ttl; // Time to live
u_char proto; // Protocol
#define IP_ICMP 1
#define IP_IGMP 2
#define IP_TCP 6
#define IP_UDP 17
#define IP_IGRP 88
#define IP_OSPF 89
u_short crc; // Header checksum
u_int saddr; // Source address
u_int daddr; // Destination address
}ip_header;

/=============== TCP ================/
#define TCP_LEN_MIN 20
typedef struct _tcp_header
{
u_short th_sport; // source port
u_short th_dport; // destination port
u_int th_seq; // sequence number field
u_int th_ack; // acknowledgement number field
u_char th_len:4; // header length
u_char th_x2:4; // unused
u_char th_flags;
#define TH_FIN 0x01
#define TH_SYN 0x02
#define TH_RST 0x04
#define TH_PSH 0x08
#define TH_ACK 0x10
#define TH_URG 0x20
u_short th_win; /* window /
u_short th_sum; / checksum /
u_short th_urp; / urgent pointer /
}tcp_header; ///

/================ UDP ==================/
#define UDP_LEN 8
typedef struct _udp_header{
u_short uh_sport; // Source port
u_short uh_dport; // Destination port
u_short uh_len; // Datagram length
u_short uh_sum; // Checksum
}udp_header;

结果截图

程序会先抓包，存在traffic.data文件中，也可以自定义，建议不要动，容易出错，然后对包的内容进行分析，输出结果到result.data中，这个建议自定义文件目录，方便查看。抓取时长和分析周期可以自定义。