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16<title>mtcp_ppeek</title>
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21<h1 align="center">mtcp_ppeek</h1>
22<!--
23<a href="#NAME">NAME</a><br>
24<a href="#SYNOPSIS">SYNOPSIS</a><br>
25<a href="#DESCRIPTION">DESCRIPTION</a><br>
26<a href="#RETURN VALUE">RETURN VALUE</a><br>
27<a href="#ERRORS">ERRORS</a><br>
28<a href="#AUTHORS">AUTHORS</a><br>
29<a href="#SEE ALSO">SEE ALSO</a><br>
30<a href="#COLOPHON">COLOPHON</a><br>
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33
34<h2>NAME
35<a name="NAME"></a>
36</h2>
37
38
39<p style="margin-left:11%; margin-top: 1em">mtcp_ppeek
40&minus; Peek into the bytestream from a monitoring socket
41from a given offset</p>
42
43<h2>SYNOPSIS
44<a name="SYNOPSIS"></a>
45</h2>
46
47
48<p style="margin-left:11%; margin-top: 1em"><b>#include
49&lt;mos_api.h&gt;</b></p>
50
51<p style="margin-left:11%; margin-top: 1em"><b>ssize_t
52mtcp_ppeek(mctx_t</b> <i>mctx</i><b>, int</b>
53<i>sockid</i><b>, int</b> <i>side</i><b>, char
54*</b><i>buf</i><b>, size_t</b> <i>len</i><b>, uint64_t</b>
55<i>off</i><b>);</b></p>
56
57<h2>DESCRIPTION
58<a name="DESCRIPTION"></a>
59</h2>
60
61
62
63<p style="margin-left:11%; margin-top: 1em"><b>mtcp_ppeek</b>()
64can be used to peek up to <i>len</i> number of bytes from a
65monitoring socket via socket descriptor <i>sockid</i> into
66the buffer starting at <i>buf. from off ;</i> value which is
67the offset distance (in bytes) from the TCP initial sequence
68number. It is the responsibility of the user to allocate
69memory for <i>buf</i> array.</p>
70
71<p style="margin-left:11%; margin-top: 1em">For cases when
72the total number of buffered unread bytes in the socket are
73less than <i>len,</i> <b>mtcp_ppeek()</b> copies entire data
74to <i>buf</i> and returns the actual number of bytes that
75can be used by the application.</p>
76
77<p style="margin-left:11%; margin-top: 1em">Note that the
78<i>off</i> can also point to the data in the fragmented
79buffer list of the TCP ring buffer (see
80<b>mtcp_getsockopt()).</b> If there is no received byte at
81<i>off</i> in the TCP ring buffer, it returns error. If
82there are received bytes starting from <i>off ,</i> len is
83set to be the number of bytes read from the buffer. After
84<b>mtcp_ppeek(),</b> the data in the TCP ring buffer will
85not be flushed, and the monitor offset used by
86<b>mtcp_peek()</b> is not changed.</p>
87
88<p style="margin-left:11%; margin-top: 1em">An
89<b>mtcp_ppeek</b>() call takes two additional argument named
90<i>mctx ,</i> that represents the per-core mTCP context in
91an application (see <b>mtcp_create_context()</b> for
92details); and <i>side</i> that informs the stack whether it
93needs to peek the client (MOS_SIDE_CLI) or server
94(MOS_SIDE_SVR) side.</p>
95
96<h2>RETURN VALUE
97<a name="RETURN VALUE"></a>
98</h2>
99
100
101<p style="margin-left:11%; margin-top: 1em">On success, the
102number of bytes read is returned. It is not an error if this
103number is smaller than the number of bytes requested; this
104may happen when the socket has fewer number of bytes
105buffered at that moment. On all errors, -1 is returned and
106<i>errno</i> is set appropriately.</p>
107
108<h2>ERRORS
109<a name="ERRORS"></a>
110</h2>
111
112
113<table width="100%" border="0" rules="none" frame="void"
114       cellspacing="0" cellpadding="0">
115<tr valign="top" align="left">
116<td width="11%"></td>
117<td width="23%">
118
119
120<p style="margin-top: 1em"><b>EACCES</b></p></td>
121<td width="4%"></td>
122<td width="62%">
123
124
125<p style="margin-top: 1em">The <i>mctx</i> argument is
126invalid.</p> </td></tr>
127<tr valign="top" align="left">
128<td width="11%"></td>
129<td width="23%">
130
131
132<p><b>EBADF</b></p></td>
133<td width="4%"></td>
134<td width="62%">
135
136
137<p>The socket descriptor <i>sockid</i> is invalid.</p></td></tr>
138<tr valign="top" align="left">
139<td width="11%"></td>
140<td width="23%">
141
142
143<p><b>EINVAL</b></p></td>
144<td width="4%"></td>
145<td width="62%">
146
147
148<p>The buffer management of the monitoring socket with
149<i>sockid</i> was already disabled.</p></td></tr>
150<tr valign="top" align="left">
151<td width="11%"></td>
152<td width="23%">
153
154
155<p><b>ESOCKTNOSUPPORT</b></p></td>
156<td width="4%"></td>
157<td width="62%">
158
159
160<p>The socket referred to by <i>sockid</i> has invalid
161<i>type</i></p> </td></tr>
162<tr valign="top" align="left">
163<td width="11%"></td>
164<td width="23%">
165
166
167<p><b>ENOTCONN</b></p></td>
168<td width="4%"></td>
169<td width="62%">
170
171
172<p>Th socket referred to by <i>sockid</i> is in a TCP state
173that disallows read operations.</p></td></tr>
174<tr valign="top" align="left">
175<td width="11%"></td>
176<td width="23%">
177
178
179<p><b>ENODATA</b></p></td>
180<td width="4%"></td>
181<td width="62%">
182
183
184<p>The socket referred to by <i>sockid</i> does not have
185any available bytes in its buffer for reading.</p></td></tr>
186<tr valign="top" align="left">
187<td width="11%"></td>
188<td width="23%">
189
190
191<p><b>EPERM</b></p></td>
192<td width="4%"></td>
193<td width="62%">
194
195
196<p>The caller is not permitted to access this function.</p></td></tr>
197</table>
198
199<h2>AUTHORS
200<a name="AUTHORS"></a>
201</h2>
202
203
204<p style="margin-left:11%; margin-top: 1em">mOS development
205team &lt;[email protected]&gt;</p>
206
207
208<!----------------------------------------------------------->
209<h2>EXAMPLES
210  <a name="EXAMPLES"></a>
211</h2>
212
213<p style="margin-left:11%; margin-top: 1em">
214  <a href="http://mos.kaist.edu/guide/programmer/05_api_example.html#monitoring-reassembled-tcp-payload">
215	http://mos.kaist.edu/guide/programmer/05_api_example.html#monitoring-reassembled-tcp-payload
216  </a>
217</p>
218<!----------------------------------------------------------->
219
220
221<h2>SEE ALSO
222<a name="SEE ALSO"></a>
223</h2>
224
225
226
227<p style="margin-left:11%; margin-top: 1em"><b>mtcp_peek</b>(),
228<b>mtcp_socket</b>(),</p>
229
230<h2>COLOPHON
231<a name="COLOPHON"></a>
232</h2>
233
234
235<p style="margin-left:11%; margin-top: 1em">This page is
236part of mOS release 0.3 <i>docs</i> section. A description
237of the project, and information about reporting bugs, can be
238found at http://mos.kaist.edu/.</p>
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