一、过滤数据包.DOC

一、过滤数据包 #include “pcap.h”#include “remote-ext.h”#pragma comment(lib, “wpcap.lib”)#pragma comment(lib,”ws2_32.lib”) /* 4字节的IP地址 */typedef struct ip_address{u_char byte1;u_char byte2;u_char byte3;u_char byte4;}ip_address; /* IPv4 首部 */typedef struct ip_header{u_char ver_ihl; // 版本 (4 bits) + 首部长度 (4 bits)u_char tos; // 服务类型(Type of service)u_short tlen; // 总长(Total length)u_short identification; // 标识(Identification)u_short flags_fo; // 标志位(Flags) (3 bits) + 段偏移量(Fragment offset) (13 bits)u_char ttl; // 存活时间(Time to live)u_char proto; // 协议(Protocol)u_short crc; // 首部校验和(Header checksum)ip_address saddr; // 源地址(Source address)ip_address daddr; // 目的地址(Destination address)u_int op_pad; // 选项与填充(Option + Padding)}ip_header; /* UDP 首部*/typedef struct udp_header{u_short sport; // 源端口(Source port)u_short dport; // 目的端口(Destination port)u_short len; // UDP数据包长度(Datagram length)u_short crc; // 校验和(Checksum)}udp_header; /* 回调函数原型 */void packet_handler(u_char *param, const struct pcap_pkthdr *header, const u_char *pkt_data);main(){pcap_if_t *alldevs;pcap_if_t *d;int inum;int i=0;pcap_t *adhandle;char errbuf[PCAP_ERRBUF_SIZE];u_int netmask;char packet_filter[] = “ip and udp”;struct bpf_program fcode; /* 获得设备列表 */if (pcap_findalldevs_ex(PCAP_SRC_IF_STRING, NULL, alldevs, errbuf) == -1){fprintf(stderr,”Error in pcap_findalldevs: %s\n”, errbuf);exit(1);} /* 打印列表 */for(d=alldevs; d; d=d-next){printf(“%d. %s”, ++i, d-name);if (d-description)printf(” (%s)\n”, d-description);elseprintf(” (No description available)\n”);} if(i==0){printf(“\nNo interfaces found! Make sure WinPcap is installed.\n”);return -1;} printf(“Enter the interface number (1-%d):”,i);scanf(“%d”, inum); if(inum 1 || inum i){printf(“\nInterface number out of range.\n”);/* 释放设备列表 */pcap_freealldevs(alldevs);return -1;} /* 跳转到已选设备 */for(d=alldevs, i=0; i inum-1 ;d=d-next, i++); /* 打开适配器 */if ( (adhandle= pcap_open(d-name, // 设备名65536, // 要捕捉的数据包的部分//