'\" t
.\"     Title: __skb_try_recv_datagram
.\"    Author: [FIXME: author] [see http://docbook.sf.net/el/author]
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: January 2017
.\"    Manual: Linux Networking
.\"    Source: Kernel Hackers Manual 4.8.15
.\"  Language: English
.\"
.TH "__SKB_TRY_RECV_DATAG" "9" "January 2017" "Kernel Hackers Manual 4\&.8\&." "Linux Networking"
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.SH "NAME"
__skb_try_recv_datagram \- Receive a datagram skbuff
.SH "SYNOPSIS"
.HP \w'struct\ sk_buff\ *\ __skb_try_recv_datagram('u
.BI "struct sk_buff * __skb_try_recv_datagram(struct\ sock\ *\ " "sk" ", unsigned\ int\ " "flags" ", int\ *\ " "peeked" ", int\ *\ " "off" ", int\ *\ " "err" ", struct\ sk_buff\ **\ " "last" ");"
.SH "ARGUMENTS"
.PP
\fIsk\fR
.RS 4
socket
.RE
.PP
\fIflags\fR
.RS 4
MSG_ flags
.RE
.PP
\fIpeeked\fR
.RS 4
returns non\-zero if this packet has been seen before
.RE
.PP
\fIoff\fR
.RS 4
an offset in bytes to peek skb from\&. Returns an offset within an skb where data actually starts
.RE
.PP
\fIerr\fR
.RS 4
error code returned
.RE
.PP
\fIlast\fR
.RS 4
set to last peeked message to inform the wait function what to look for when peeking
.RE
.SH "DESCRIPTION"
.PP
Get a datagram skbuff, understands the peeking, nonblocking wakeups and possible races\&. This replaces identical code in packet, raw and udp, as well as the IPX AX\&.25 and Appletalk\&. It also finally fixes the long standing peek and read race for datagram sockets\&. If you alter this routine remember it must be re\-entrant\&.
.PP
This function will lock the socket if a skb is returned, so the caller needs to unlock the socket in that case (usually by calling skb_free_datagram)\&. Returns NULL with *err set to \-EAGAIN if no data was available or to some other value if an error was detected\&.
.PP
* It does not lock socket since today\&. This function is * free of race conditions\&. This measure should/can improve * significantly datagram socket latencies at high loads, * when data copying to user space takes lots of time\&. * (BTW I\*(Aqve just killed the last
\fBcli\fR
in IP/IPv6/core/netlink/packet * 8) Great win\&.) * \-\-ANK (980729)
.PP
The order of the tests when we find no data waiting are specified quite explicitly by POSIX 1003\&.1g, don\*(Aqt change them without having the standard around please\&.
.SH "COPYRIGHT"
.br