66 lines
2 KiB
C
66 lines
2 KiB
C
#include <pcap.h>
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/* Ethernet addresses are 6 bytes */
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#define ETHER_ADDR_LEN 6
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/* Ethernet header */
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struct sniff_ethernet {
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u_char ether_dhost[ETHER_ADDR_LEN]; /* Destination host address */
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u_char ether_shost[ETHER_ADDR_LEN]; /* Source host address */
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u_short ether_type; /* IP? ARP? RARP? etc */
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};
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/* IP header */
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struct sniff_ip {
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u_char ip_vhl; /* version << 4 | header length >> 2 */
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u_char ip_tos; /* type of service */
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u_short ip_len; /* total length */
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u_short ip_id; /* identification */
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u_short ip_off; /* fragment offset field */
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#define IP_RF 0x8000 /* reserved fragment flag */
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#define IP_DF 0x4000 /* dont fragment flag */
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#define IP_MF 0x2000 /* more fragments flag */
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#define IP_OFFMASK 0x1fff /* mask for fragmenting bits */
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u_char ip_ttl; /* time to live */
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u_char ip_p; /* protocol */
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u_short ip_sum; /* checksum */
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struct in_addr {}ip_src,ip_dst; /* source and dest address */
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};
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#define IP_HL(ip) (((ip)->ip_vhl) & 0x0f)
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#define IP_V(ip) (((ip)->ip_vhl) >> 4)
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/* TCP header */
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typedef u_int tcp_seq;
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struct sniff_tcp {
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u_short th_sport; /* source port */
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u_short th_dport; /* destination port */
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tcp_seq th_seq; /* sequence number */
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tcp_seq th_ack; /* acknowledgement number */
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u_char th_offx2; /* data offset, rsvd */
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#define TH_OFF(th) (((th)->th_offx2 & 0xf0) >> 4)
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u_char th_flags;
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#define TH_FIN 0x01
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#define TH_SYN 0x02
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#define TH_RST 0x04
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#define TH_PUSH 0x08
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#define TH_ACK 0x10
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#define TH_URG 0x20
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#define TH_ECE 0x40
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#define TH_CWR 0x80
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#define TH_FLAGS (TH_FIN|TH_SYN|TH_RST|TH_ACK|TH_URG|TH_ECE|TH_CWR)
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u_short th_win; /* window */
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u_short th_sum; /* checksum */
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u_short th_urp; /* urgent pointer */
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};
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/* ethernet headers are always exactly 14 bytes */
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#define SIZE_ETHERNET 14
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const struct sniff_ethernet *ethernet; /* The ethernet header */
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const struct sniff_ip *ip; /* The IP header */
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const struct sniff_tcp *tcp; /* The TCP header */
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const char *payload; /* Packet payload */
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u_int size_ip;
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u_int size_tcp;
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