libpcap 파일 포맷

libpcap file format

1. Global Header - 24bytes

typedef struct pcap_hdr_s {

        guint32 magic_number;   /* magic number */

        guint16 version_major;  /* major version number */

        guint16 version_minor;  /* minor version number */

        gint32  thiszone;       /* GMT to local correction */

        guint32 sigfigs;        /* accuracy of timestamps */

        guint32 snaplen;        /* max length of captured packets, in octets */

        guint32 network;        /* data link type */

} pcap_hdr_t;

2. Packet Header - 16bytes

typedef struct pcaprec_hdr_s {

        guint32 ts_sec;         /* timestamp seconds */

        guint32 ts_usec;        /* timestamp microseconds */

        guint32 incl_len;       /* number of octets of packet saved in file */

        guint32 orig_len;       /* actual length of packet */

} pcaprec_hdr_t;

- incl_len : pcap file안에 저장되어 있는 패킷 데이터의 길이. orig_len이나 snaplen보다 클 수 없다.

- orig_len : 실제 네트워크 상에서 캡처된 패킷 데이터의 길이.