写程序实现wireshark的抓包功能

选修了一门信息安全专业的课，做了个实验，是实现网络抓包的功能：

代码如下：

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#include<stdio.h> #include<stdlib.h> #include<string.h> #include<netinet/ip_icmp.h> #include<netinet/tcp.h> #include<netinet/udp.h> #include<arpa/inet.h> #include<sys/socket.h> #include<sys/types.h>   #define BUFFSIZE 1024   int main(int argc,char **argv ){     if(argc!=2){     printf("Usage:Proto_Name\n");     return 0;   }     int rawsock;     unsigned char buff[BUFFSIZE];     int n;     int count = 0;   char *ipr_name=argv[1];   char *ipr_tcp="TCP";   char *ipr_udp="UDP";   char *ipr_icmp="ICMP";   if(strcmp(ipr_name,ipr_tcp)==0)        rawsock = socket(AF_INET,SOCK_RAW,IPPROTO_TCP);     else if(strcmp(ipr_name,ipr_udp)==0)        rawsock = socket(AF_INET,SOCK_RAW,IPPROTO_UDP);     else if(strcmp(ipr_name,ipr_icmp)==0)        rawsock = socket(AF_INET,SOCK_RAW,IPPROTO_ICMP);     if(rawsock < 0){         printf("raw socket error!\n");         exit(1);     }     while(1) {       n = recvfrom(rawsock,buff,BUFFSIZE,0,NULL,NULL);     if(n<0){         printf("receive error!\n");         exit(1);     }               count++;     struct ip *ip = (struct ip*)buff;     printf("%4d %15s",count,inet_ntoa(ip->ip_src));     printf("%15s    %5d %5d\n",inet_ntoa(ip->ip_dst),ip->ip_p,ntohs(ip->ip_len));        int i=0,j=0;     for(i=0;i<n;i++)     {         if(i!=0 && i%16==0)                 {             printf("    ");             for(j=i-16;j<i;j++)             {                 if(buff[j]>=32&&buff[j]<=128)                 printf("%c",buff[j]);                 else printf(".");             }         printf("\n");         }     if(i%16 == 0) printf("%04x  ",i);               printf("%02x",buff[i]);           if(i==n-1)     {         for(j=0;j<15-i%16;j++) printf("  ");         printf("    ");         for(j=i-i%16;j<=i;j++)        {             if(buff[j]>=32&&buff[j]<127)                                 printf("%c",buff[j]);                                 else printf(".");              }       }    }               printf("\n");       printf("internet protocol\n");       printf("version:%u\n",ip->ip_v);       printf("Header Length:%u bytes\n",(ip->ip_hl)*4);       printf("totle length:%d\n",ntohs(ip->ip_len));       printf("Identification:%u\n",ip->ip_id);       if((IP_RF&0x8000)!=0)         printf("reserved bits:set\n");       else         printf("reserved bits:not set\n");       if((IP_DF&0x4000)!=0)         printf("dont fragment: not set\n");       else         printf("dont fragment: set\n");       if((IP_MF&0x2000)!=0)         printf("more fragment: set\n");       else         printf("more fragment: not set\n");       printf("Time to live:%u\n",ip->ip_ttl);       if(ip->ip_p==6)         printf("protocol TCP(6)\n");       else if(ip->ip_p==1)         printf("protocol ICMP(1)\n");       else if(ip->ip_p==17)         printf("protocol UDP(17)\n");       printf("source ip:%s\n",inet_ntoa(ip->ip_src));       printf("destination ip:%s\n",inet_ntoa(ip->ip_dst));                 //TCP       if(ip->ip_p==6)       {       printf("transmission control protocol\n");       struct tcphdr *tcp=(struct tcphdr *)(buff+(ip->ip_hl)*4);        printf("source port:%u\n",ntohs(tcp->source));       printf("destation port:%u\n",ntohs(tcp->dest));       printf("sequence number:%u\n",ntohl(tcp->seq));       printf("acknowledgement number:%u\n",ntohl(tcp->ack_seq));       printf("head length:%d\n",ntohs((tcp->doff)*4));       if(tcp->urg==1)         printf("urgent:set\n");       else         printf("urgent:not set\n");       if(tcp->ack==1)         printf("acknowledgment:set\n");       else         printf("acknowledgment:not set\n");       if(tcp->psh==1)         printf("push:set\n");       else         printf("push:not set\n");       if(tcp->rst==1)         printf("reset:set\n");       else         printf("reset:not set\n");       if(tcp->syn==1)         printf("syn:set\n");       else         printf("syn:not set\n");                 if(tcp->fin==1)         printf("fin:set\n");       else         printf("fin:not set\n");       printf("window size:%u\n",ntohs(tcp->window));     }           //UDP    if(ip->ip_p==17)     {         struct udphdr *udp=(struct udphdr*)(buff+(ip->ip_hl)*4);         printf("user datagram protocol\n");         printf("source port:%u\n",udp->source);         printf("destination port:%u\n",udp->dest);         printf("length:%u\n",ntohs(udp->len));     }     //ICMP    if(ip->ip_p==1)     {         struct icmphdr *icmp = (struct icmphdr *)(buff+(ip->ip_hl)*4);         printf("Internet Control Message Protocol\n");         printf("type:%u",icmp->type);         if(icmp->type==0)             printf("(Echo Reply)\n");         else if(icmp->type==8)             printf("(Echo)\n");         else if(icmp->type==5)             printf("(Redirect)\n");         else if(icmp->type==3)             printf("(Dest Unreach)\n");         else if(icmp->type==4)             printf("(Source quench)\n");         else if(icmp->type==13)             printf("(Time Stamp)\n");         else if(icmp->type==14)             printf("(Time Stamp Reply)\n");         printf("Code:%u\n",icmp->code);         if(icmp->type==0||icmp->type==8)             {                 printf("idetifier:0x%x\n",ntohs(icmp->un.echo.id));                 printf("Sequence:%u\n",ntohs(icmp->un.echo.sequence));             }         if(icmp->type==3||icmp->type==4)             {                 printf("Unused:%u\n",ntohs(icmp->un.frag.__unused));                 printf("Mtu:%u\n",ntohs(icmp->un.frag.mtu));             }           if(icmp->type==5)             printf("Gateway:%u\n",ntohs(icmp->un.gateway));     }         printf("\n\n"); }   }