pckt.7 (2010 09)

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pckt(7) pckt(7)

NAME

pckt - Packet Mode module for STREAMS pty (pseudo-terminal)

SYNOPSIS

#include <sys/stropts.h>

int ioctl(fd_slave, I_PUSH, "pckt");

DESCRIPTION

The Packet Mode feature for STREAMS pty devices allows the user process on the master side of the

pty device to be informed of state changes in the pty. To enable

Packet Mode in the STREAMS pty

device, the user process must push the

pckt module onto the master side of the pty with a call to the

STREAMS

I_PUSH ioctl (2) system call. When the

pckt module is pushed onto a STREAMS pty mas-

ter, certain STREAMS messages going upstream on the master side will get packetized so they can be

subsequently retrieved by the master side with a

getmsg function.

When the user process writes data, the

pckt

module passes the message unchanged downstream on to

the next module or driver. When the user process reads data or when the pckt module receives certain

STREAMS message types, it constructs a packet out of the message for forwarding upstream. To con-

struct a message packet, the module creates an

M_PROTO message. This M_PROTO message contains

the original message type in the ﬁrst data block and the original message in as many data blocks as

needed. The user process can then retrieve the

M_PROTO message with a call to the getmsg() func-

tion.

The

pckt module packetizes the following STREAMS message types:

M_DATA, M_IOCTL, M_PROTO, M_PCPROTO, M_FLUSH, M_START, M_STOP, M_STARTI,

M_STOPI,

M_READ.

All other messages are passed unchanged upstream.

If the message is an

M_FLUSH message, the pckt module looks at the ﬂag and takes the following

actions:

• If the ﬂag is

FLUSHW, the module changes it to FLUSHR before creating the

M_PROTO message

and passing the message upstream. This prevents the stream head’s read queue from being

ﬂushed by the original

M_FLUSHmessage.

• If the ﬂag is

FLUSHR, the module changes it to FLUSHW before creating the

M_PROTO message

and passing it upstream. To ﬂush the write queues properly, the module also sends an

M_FLUSH message with the FLUSHW ﬂag set.

• If the ﬂag is

FLUSHRW, the module changes it to FLUSHW before creating the

M_PROTO mes-

sage and passing it upstream. To ﬂush the write queues properly, the module also sends an

M_FLUSH message with the FLUSHW ﬂag set.

AUTHOR

pckt(7) was developed by HP and OSF.

Summary of content (2 pages)

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pckt(7) pckt(7) NAME pckt - Packet Mode module for STREAMS pty (pseudo-terminal) SYNOPSIS #include int ioctl(fd_slave, I_PUSH, "pckt"); DESCRIPTION The Packet Mode feature for STREAMS pty devices allows the user process on the master side of the pty device to be informed of state changes in the pty. To enable Packet Mode in the STREAMS pty device, the user process must push the pckt module onto the master side of the pty with a call to the STREAMS I_PUSH ioctl (2) system call.
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(Notes) A (Notes) pA 2 Hewlett-Packard Company −1− HP-UX 11i Version 3: September 2010