QNX RTOS v4 Knowledge Base
QNX RTOS v4 Knowledge Base
| Title |
Structure of QNX4 Arcnet packet header |
| Ref. No. |
QNX.000009479 |
| Category(ies) |
Network |
| Issue |
We have a software utility which allows us to view the structure of a packet on the network. We are trying to figure out what is the structure of the QNX header. What information will we find in this header?
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| Solution |
Here is the structure we use for the header of a QNX4 Arcnet packet.
struct _phys_hdr /* 20 byte header on every QNX4 ARCNET pkt */
{
unsigned char system_code; /* ARCNET std - QNX is 0xDC */
unsigned char sub_code; /* QNX POSIX ver 4.00 is 1 */
unsigned char zero1; /* per-vid seq_num, WAS zero1 */
unsigned char seq; /* sequence number, per node */
unsigned char class; /* CTRL or DATA pkt */
unsigned char type; /* type of CTRL or DATA pkt */
unsigned char old_class; /* must not be 2|3 for qnx2 */
unsigned char flags; /* BEGIN, END flags */
short unsigned int rcv_vid; /* VID on recvng end */
short unsigned int vid_seq; /* per-vid seq_num, WAS ext_rcv */
short unsigned int rcv_off; /* offset into rcvng data seg */
short unsigned int src_vid; /* was ext_rcv_off == 0 */
short unsigned int rcv_seg; /* segment of rcvng data */
short unsigned int len; /* length of data[] after hdr */
unsigned char data[]; /* pointer to data xferred */
};
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