C/C++实现HTTP协议解析的示例代码

...
void got_packet(u_char *args, const struct pcap_pkthdr *header, const u_char *packet)
{

    ...

	/* print source and destination IP addresses */
	printf("       From: %s\n", inet_ntoa(ip->ip_src));
	printf("         To: %s\n", inet_ntoa(ip->ip_dst));
	
	/* determine protocol */	
	switch(ip->ip_p) 
	{
		case IPPROTO_TCP:
			printf("   Protocol: TCP\n");
			break;
		case IPPROTO_UDP:
			printf("   Protocol: UDP\n");
			break;
		case IPPROTO_ICMP:
			printf("   Protocol: ICMP\n");
			return;
		case IPPROTO_IP:
			printf("   Protocol: IP\n");
			return;
		default:
			printf("   Protocol: unknown\n");
			return;
	}
	
	/*
	 *  OK, this packet is TCP.
	 */
	
	/* define/compute tcp header offset */
	if(ip->ip_p == IPPROTO_TCP)
	{
        ...
	
		printf("   Src port: %d\n", ntohs(tcp->th_sport));
		printf("   Dst port: %d\n", ntohs(tcp->th_dport));
		int sport = ntohs(tcp->th_sport);
		int dport = ntohs(tcp->th_dport);

        ...
		if (size_payload > 0) 
		{
			printf("   Payload (%d bytes):\n", size_payload);
			//print_payload(payload, size_payload);
		
            if ((sport == 80) || (dport == 80))
			{
				printf("   HTTP prase:\n");
				prase_http(payload, size_payload);
			}
			else if(sport == 443 || dport == 443)
			{
				printf("   SSL/TLS prase:\n");
				prase_ssl_tls(payload, size_payload);
			}
		}
	}
	...

}

int main(int argc, char *argv[])
{
    	
	char errbuf[100];
	pcap_t *desc = 0;
    char *filename = argv[1];
    if (argc != 2)
    {
        printf("usage: ./dissect_http [pcap file]\n");
        return -1;
    }

    printf("ProcessFile: process file: %s\n", filename);
    if ((desc = pcap_open_offline(filename, errbuf)) == NULL)
    {   
        printf("pcap_open_offline: %s error!\n", filename);
        return -1; 
    }   	
	
	
    pcap_loop(desc, -1, got_packet, NULL);

    pcap_close(desc);
    return 0;
}