'\" t
.\"     Title: skb_cow
.\"    Author: [FIXME: author] [see http://docbook.sf.net/el/author]
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: July 2017
.\"    Manual: Linux Networking
.\"    Source: Kernel Hackers Manual 4.12.2
.\"  Language: English
.\"
.TH "SKB_COW" "9" "July 2017" "Kernel Hackers Manual 4\&.12\&" "Linux Networking"
.\" -----------------------------------------------------------------
.\" * Define some portability stuff
.\" -----------------------------------------------------------------
.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.\" http://bugs.debian.org/507673
.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.ie \n(.g .ds Aq \(aq
.el       .ds Aq '
.\" -----------------------------------------------------------------
.\" * set default formatting
.\" -----------------------------------------------------------------
.\" disable hyphenation
.nh
.\" disable justification (adjust text to left margin only)
.ad l
.\" -----------------------------------------------------------------
.\" * MAIN CONTENT STARTS HERE *
.\" -----------------------------------------------------------------
.SH "NAME"
skb_cow \- copy header of skb when it is required
.SH "SYNOPSIS"
.HP \w'int\ skb_cow('u
.BI "int skb_cow(struct\ sk_buff\ *\ " "skb" ", unsigned\ int\ " "headroom" ");"
.SH "ARGUMENTS"
.PP
\fIstruct sk_buff * skb\fR
.RS 4
buffer to cow
.RE
.PP
\fIunsigned int headroom\fR
.RS 4
needed headroom
.RE
.SH "DESCRIPTION"
.PP
If the skb passed lacks sufficient headroom or its data part is shared, data is reallocated\&. If reallocation fails, an error is returned and original skb is not changed\&.
.PP
The result is skb with writable area skb\->head\&.\&.\&.skb\->tail and at least
\fIheadroom\fR
of space at head\&.
.SH "COPYRIGHT"
.br