Hi all,I am programming in c++ with 'winpcap' . I read a .pcap file and after I want to get the source and destination of packets in that file,but i coulden't get the right answer!!here is a piece of my code:
Code:
////I define the sructures here
#pragma pack(1)
struct sniff_ethernet {
u_char ether_dhost[ETHER_ADDR_LEN]; /* Destination host address */
u_char ether_shost[ETHER_ADDR_LEN]; /* Source host address */
u_short ether_type; /* IP? ARP? RARP? etc */
};
/* IP header */
#pragma pack(1)
struct sniff_ip {
u_char ip_vhl; /* version << 4 | header length >> 2 */
u_char ip_tos; /* type of service */
u_short ip_len; /* total length */
u_short ip_id; /* identification */
u_short ip_off; /* fragment offset field */
#define IP_RF 0x8000 /* reserved fragment flag */
#define IP_DF 0x4000 /* dont fragment flag */
#define IP_MF 0x2000 /* more fragments flag */
#define IP_OFFMASK 0x1fff /* mask for fragmenting bits */
u_char ip_ttl; /* time to live */
u_char ip_p; /* protocol */
u_short ip_sum; /* checksum */
struct in_addr ip_src;
struct in_addr ip_dst; /* source and dest address */
};
#pragma pack(1)
struct sniff_tcp {
u_short th_sport; /* source port */
u_short th_dport; /* destination port */
u_int32_t th_seq; /* sequence number */
u_int32_t th_ack; /* acknowledgement number */
u_char th_offx2; /* data offset, rsvd */
#define TH_OFF(th) (((th)->th_offx2 & 0xf0) >> 4)
u_char th_flags;
#define TH_FIN 0x01
#define TH_SYN 0x02
#define TH_RST 0x04
#define TH_PUSH 0x08
#define TH_ACK 0x10
#define TH_URG 0x20
#define TH_ECE 0x40
#define TH_CWR 0x80
#define TH_FLAGS (TH_FIN|TH_SYN|TH_RST|TH_ACK|TH_URG|TH_ECE|TH_CWR)
u_short th_win; /* window */
u_short th_sum; /* checksum */
u_short th_urp; /* urgent pointer */
};
and in the main() I'v write this code for reading the source and destination port:
Code:
while (pcap_next_ex(handler, &header, &packet) >= 0)
{
ethernet = (struct sniff_ethernet*)(packet);
ip = (struct sniff_ip*)(packet + SIZE_ETHERNET);
tcp = (struct sniff_tcp*)(packet + SIZE_ETHERNET + size_ip);
printf("src port: %d dest port: %d \n", tcp->th_sport, tcp->th_dport);
fprintf(fp,"src port: %d dest port: %d \n", tcp->th_sport, tcp->th_dport);
}
but the result is incorrect? where is the problem?plz help me