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packet.7: Improve sockopt documentation for packet sockets 

Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Carsten Andrich <carsten.andrich@tu-ilmenau.de>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Carsten Andrich 2014-04-29 13:57:47 +02:00 committed by Michael Kerrisk
parent 49f7fca5ba
commit 43f5be18ff
1 changed files with 42 additions and 14 deletions
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56
man7/packet.7
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@ -9,7 +9,7 @@
.\"
.\" $Id: packet.7,v 1.13 2000/08/14 08:03:45 ak Exp $
.\"
.TH PACKET 7 2014-04-24 "Linux" "Linux Programmer's Manual"
.TH PACKET 7 2014-04-28 "Linux" "Linux Programmer's Manual"
.SH NAME
packet \- packet interface on device level
.SH SYNOPSIS
@ -319,14 +319,25 @@ original fanout algorithm selects a backlogged socket, the packet
rolls over to the next available one.
.TP
.BR PACKET_LOSS " (with " PACKET_TX_RING )
When a malformed packet is encountered on a transmit ring, the default is to
set its status to
When a malformed packet is encountered on a transmit ring, the default is
to reset its
.I tp_status
to
.BR TP_STATUS_WRONG_FORMAT
and abort the transmission immediately (it and following packets are left
lingering on the ring).
and abort the transmission immediately.
The malformed packet blocks itself and subsequent enqueued packets from
being sent.
The format error must be fixed, the associated
.I tp_status
reset to
.BR TP_STATUS_SEND_REQUEST
and the transmission process restarted via
.BR send (2) .
However, if
.BR PACKET_LOSS
is set, any malformed packet will be skipped, its status reset to
is set, any malformed packet will be skipped, its
.I tp_status
reset to
.BR TP_STATUS_AVAILABLE ,
and the transmission process continued.
.TP
@ -360,15 +371,21 @@ Packet socket and application communicate the head and tail of the ring
through the
.I tp_status
field.
The packet socket owns all slots with status
The packet socket owns all slots with
.I tp_status
equal to
.BR TP_STATUS_KERNEL .
After filling a slot, it changes the status of the slot to transfer
ownership to the application.
During normal operation, the new status has the
During normal operation, the new
.I tp_status
value has at least the
.BR TP_STATUS_USER
bit set to signal that a received packet has been stored.
When the application has finished processing a packet, it transfers
ownership of the slot back to the socket by setting the status to
ownership of the slot back to the socket by setting
.I tp_status
equal to
.BR TP_STATUS_KERNEL .
Packet sockets implement multiple variants of the packet ring.
The implementation details are described in
@ -407,9 +424,13 @@ Create a memory-mapped ring buffer for packet transmission.
This option is similar to
.BR PACKET_RX_RING
and takes the same arguments.
The application writes packets into slots with status
The application writes packets into slots with
.I tp_status
equal to
.BR TP_STATUS_AVAILABLE
and schedules them for transmission by changing the status to
and schedules them for transmission by changing
.I tp_status
to
.BR TP_STATUS_SEND_REQUEST .
When packets are ready to be transmitted, the application calls
.BR send (2)
@ -424,7 +445,9 @@ If an address is passed using
or
.BR sendmsg (2),
then that overrides the socket default.
On successful transmission, the socket resets the slot to
On successful transmission, the socket resets
.I tp_status
to
.BR TP_STATUS_AVAILABLE .
It immediately aborts the transmission on error unless
.BR PACKET_LOSS
@ -633,6 +656,11 @@ The
.I <linux/if_ether.h>
include file for physical layer protocols.
The example source file
The Linux kernel source tree.
.IR /Documentation/networking/filter.txt
describes how to apply Berkeley Packet Filters to packet sockets.
.IR /tools/testing/selftests/net/psock_tpacket.c
in the Linux kernel source tree.
contains example source code for all available versions of
.BR PACKET_RX_RING
and
.BR PACKET_TX_RING .