1<html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>skb_cow_data</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"><link rel="home" href="index.html" title="Linux Networking and Network Devices APIs"><link rel="up" href="ch01s02.html" title="Socket Buffer Functions"><link rel="prev" href="API-skb-segment.html" title="skb_segment"><link rel="next" href="API-skb-clone-sk.html" title="skb_clone_sk"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><span class="phrase">skb_cow_data</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="API-skb-segment.html">Prev</a>&#160;</td><th width="60%" align="center">Socket Buffer Functions</th><td width="20%" align="right">&#160;<a accesskey="n" href="API-skb-clone-sk.html">Next</a></td></tr></table><hr></div><div class="refentry"><a name="API-skb-cow-data"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>skb_cow_data &#8212; 
2     Check that a socket buffer's data buffers are writable
3 </p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">skb_cow_data </b>(</code></td><td>struct sk_buff * <var class="pdparam">skb</var>, </td></tr><tr><td>&#160;</td><td>int <var class="pdparam">tailbits</var>, </td></tr><tr><td>&#160;</td><td>struct sk_buff ** <var class="pdparam">trailer</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer">&#160;</div></div></div><div class="refsect1"><a name="idp1096387604"></a><h2>Arguments</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="parameter"><code>skb</code></em></span></dt><dd><p>
4     The socket buffer to check.
5    </p></dd><dt><span class="term"><em class="parameter"><code>tailbits</code></em></span></dt><dd><p>
6     Amount of trailing space to be added
7    </p></dd><dt><span class="term"><em class="parameter"><code>trailer</code></em></span></dt><dd><p>
8     Returned pointer to the skb where the <em class="parameter"><code>tailbits</code></em> space begins
9    </p></dd></dl></div></div><div class="refsect1"><a name="idp1096391660"></a><h2>Description</h2><p>
10   Make sure that the data buffers attached to a socket buffer are
11   writable. If they are not, private copies are made of the data buffers
12   and the socket buffer is set to use these instead.
13   </p><p>
14
15   If <em class="parameter"><code>tailbits</code></em> is given, make sure that there is space to write <em class="parameter"><code>tailbits</code></em>
16   bytes of data beyond current end of socket buffer.  <em class="parameter"><code>trailer</code></em> will be
17   set to point to the skb in which this space begins.
18   </p><p>
19
20   The number of scatterlist elements required to completely map the
21   COW'd and extended socket buffer will be returned.
22</p></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="API-skb-segment.html">Prev</a>&#160;</td><td width="20%" align="center"><a accesskey="u" href="ch01s02.html">Up</a></td><td width="40%" align="right">&#160;<a accesskey="n" href="API-skb-clone-sk.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><span class="phrase">skb_segment</span>&#160;</td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top">&#160;<span class="phrase">skb_clone_sk</span></td></tr></table></div></body></html>
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