#include<stdio.h>
#include<stdlib.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<errno.h>
#include<net/if.h>
#include<net/ethernet.h>
#include<netinet/ip.h>
#include<netinet/tcp.h>

int sock;

//プロトタイプ宣言
void PacketAnalysis(u_char* buf);
void printEtherHeader(u_char* buf);
void printIPHeader(u_char* buf);
void printTCPHeader(u_char* buf);

int main(int argc,char* argv[]){
	u_char buf[65535];
	sock = socket(PF_PACKET,SOCK_RAW,htons(ETH_P_ALL));
	if(sock<0){
		perror("socket");
		printf("%d\n",errno);
		return 1;
	}
	//ループ内でデータを受信し、解析用の関数に渡す
	while(1){
		read(sock,buf,sizeof(buf));
		PacketAnalysis(buf);
	}

	return 0;
}
//パケット解析用関数
void PacketAnalysis(u_char* buf){
	u_char* pack;
	struct ether_header *eth;
	struct iphdr *ip;
	pack=buf;
	eth=(struct ether_header *)buf;
	pack+=sizeof(struct ether_header);
	printf("type:");
	switch(ntohs(eth->ether_type)){
		case ETH_P_IP:
			printf("ETH_P_IP\n");
			printIPHeader(pack);
			ip=(struct iphdr *)pack;
			if(ip->protocol==6){//ipv6の時
				pack+=((struct iphdr *)pack)->ihl*4;
				printTCPHeader(pack);
			}
			break;
		case ETH_P_IPV6:
			printf("IPv6\n");
			break;
		case ETH_P_ARP:
			printf("ETH_P_ARP\n");
			break;
		default:
			printf("unknown\n");
			break;
	}
}

//ipヘッダーを表示する関数
void printIPHeader(u_char* buf){
	struct iphdr *ip;
	ip=(struct iphdr *)buf;
	printf("-----IP header-----\n");
	printf("version:%u\n",ip->version);
	printf("Interner header length:%x\n",ip->ihl);
	printf("type of service:%x\n",ip->tos);
	printf("total length:%u\n",ntohs(ip->tot_len));
	printf("id:%u\n",ntohs(ip->id));
	printf("time to live:%u\n",ip->ttl);
	printf("protocol:%u\n\n",ip->protocol);
}

//tcpヘッダーを表示する関数
void printTCPHeader(u_char* buf){
	struct tcphdr *tcp;
	tcp = (struct tcphdr *)buf;
	printf("-----TCP Header----\n");
	printf("source port:%u\n",ntohs(tcp->source));
	printf("dest port:%u\n\n",ntohs(tcp->dest));
}