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16*91df013fSAsim Jamshed<title>mtcp_peek</title>
17*91df013fSAsim Jamshed
18*91df013fSAsim Jamshed</head>
19*91df013fSAsim Jamshed<body>
20*91df013fSAsim Jamshed
21*91df013fSAsim Jamshed<h1 align="center">mtcp_peek</h1>
22*91df013fSAsim Jamshed
23*91df013fSAsim Jamshed<a href="#NAME">NAME</a><br>
24*91df013fSAsim Jamshed<a href="#SYNOPSIS">SYNOPSIS</a><br>
25*91df013fSAsim Jamshed<a href="#DESCRIPTION">DESCRIPTION</a><br>
26*91df013fSAsim Jamshed<a href="#RETURN VALUE">RETURN VALUE</a><br>
27*91df013fSAsim Jamshed<a href="#ERRORS">ERRORS</a><br>
28*91df013fSAsim Jamshed<a href="#NOTES">NOTES</a><br>
29*91df013fSAsim Jamshed<a href="#AUTHORS">AUTHORS</a><br>
30*91df013fSAsim Jamshed<a href="#SEE ALSO">SEE ALSO</a><br>
31*91df013fSAsim Jamshed<a href="#COLOPHON">COLOPHON</a><br>
32*91df013fSAsim Jamshed
33*91df013fSAsim Jamshed<hr>
34*91df013fSAsim Jamshed
35*91df013fSAsim Jamshed
36*91df013fSAsim Jamshed<h2>NAME
37*91df013fSAsim Jamshed<a name="NAME"></a>
38*91df013fSAsim Jamshed</h2>
39*91df013fSAsim Jamshed
40*91df013fSAsim Jamshed
41*91df013fSAsim Jamshed<p style="margin-left:11%; margin-top: 1em">mtcp_peek
42*91df013fSAsim Jamshed&minus; Peek into the bytestream from a monitoring
43*91df013fSAsim Jamshedsocket</p>
44*91df013fSAsim Jamshed
45*91df013fSAsim Jamshed<h2>SYNOPSIS
46*91df013fSAsim Jamshed<a name="SYNOPSIS"></a>
47*91df013fSAsim Jamshed</h2>
48*91df013fSAsim Jamshed
49*91df013fSAsim Jamshed
50*91df013fSAsim Jamshed<p style="margin-left:11%; margin-top: 1em"><b>#include
51*91df013fSAsim Jamshed&lt;mos_api.h&gt;</b></p>
52*91df013fSAsim Jamshed
53*91df013fSAsim Jamshed<p style="margin-left:11%; margin-top: 1em"><b>ssize_t
54*91df013fSAsim Jamshedmtcp_peek(mctx_t</b> <i>mctx</i><b>, int</b>
55*91df013fSAsim Jamshed<i>sockid</i><b>, int</b> <i>side</i><b>, char
56*91df013fSAsim Jamshed*</b><i>buf</i><b>, size_t</b> <i>len</i><b>);</b></p>
57*91df013fSAsim Jamshed
58*91df013fSAsim Jamshed<h2>DESCRIPTION
59*91df013fSAsim Jamshed<a name="DESCRIPTION"></a>
60*91df013fSAsim Jamshed</h2>
61*91df013fSAsim Jamshed
62*91df013fSAsim Jamshed
63*91df013fSAsim Jamshed
64*91df013fSAsim Jamshed<p style="margin-left:11%; margin-top: 1em"><b>mtcp_peek</b>()
65*91df013fSAsim Jamshedcan be used to peek up to <i>len</i> number of bytes from a
66*91df013fSAsim Jamshedmonitoring socket via socket descriptor <i>sockid</i> into
67*91df013fSAsim Jamshedthe buffer (unfragmented) starting at <i>buf.</i> It is the
68*91df013fSAsim Jamshedresponsibility of the user to allocate memory for <i>buf</i>
69*91df013fSAsim Jamshedarray.</p>
70*91df013fSAsim Jamshed
71*91df013fSAsim Jamshed<p style="margin-left:11%; margin-top: 1em">For cases when
72*91df013fSAsim Jamshedthe total number of buffered unread bytes in the socket are
73*91df013fSAsim Jamshedless than <i>len,</i> <b>mtcp_peek()</b> copies entire data
74*91df013fSAsim Jamshedto <i>buf</i> and returns the actual number of bytes that
75*91df013fSAsim Jamshedcan be used by the application.</p>
76*91df013fSAsim Jamshed
77*91df013fSAsim Jamshed<p style="margin-left:11%; margin-top: 1em">An
78*91df013fSAsim Jamshed<b>mtcp_peek</b>() call takes two additional argument named
79*91df013fSAsim Jamshed<i>mctx ,</i> that represents the per-core mTCP context in
80*91df013fSAsim Jamshedan application (see <b>mtcp_create_context()</b> for
81*91df013fSAsim Jamsheddetails); and <i>side</i> that informs the stack whether it
82*91df013fSAsim Jamshedneeds to peek the client (MOS_SIDE_CLI) or server
83*91df013fSAsim Jamshed(MOS_SIDE_SVR) side.</p>
84*91df013fSAsim Jamshed
85*91df013fSAsim Jamshed<h2>RETURN VALUE
86*91df013fSAsim Jamshed<a name="RETURN VALUE"></a>
87*91df013fSAsim Jamshed</h2>
88*91df013fSAsim Jamshed
89*91df013fSAsim Jamshed
90*91df013fSAsim Jamshed<p style="margin-left:11%; margin-top: 1em">On success, the
91*91df013fSAsim Jamshednumber of bytes read is returned. It is not an error if this
92*91df013fSAsim Jamshednumber is smaller than the number of bytes requested; this
93*91df013fSAsim Jamshedmay happen when the socket has fewer number of bytes
94*91df013fSAsim Jamshedbuffered at that moment. On all errors, -1 is returned and
95*91df013fSAsim Jamshed<i>errno</i> is set appropriately.</p>
96*91df013fSAsim Jamshed
97*91df013fSAsim Jamshed<h2>ERRORS
98*91df013fSAsim Jamshed<a name="ERRORS"></a>
99*91df013fSAsim Jamshed</h2>
100*91df013fSAsim Jamshed
101*91df013fSAsim Jamshed
102*91df013fSAsim Jamshed<table width="100%" border="0" rules="none" frame="void"
103*91df013fSAsim Jamshed       cellspacing="0" cellpadding="0">
104*91df013fSAsim Jamshed<tr valign="top" align="left">
105*91df013fSAsim Jamshed<td width="11%"></td>
106*91df013fSAsim Jamshed<td width="12%">
107*91df013fSAsim Jamshed
108*91df013fSAsim Jamshed
109*91df013fSAsim Jamshed<p style="margin-top: 1em"><b>EACCES</b></p></td>
110*91df013fSAsim Jamshed<td width="3%"></td>
111*91df013fSAsim Jamshed<td width="74%">
112*91df013fSAsim Jamshed
113*91df013fSAsim Jamshed
114*91df013fSAsim Jamshed<p style="margin-top: 1em">The <i>mctx</i> argument is
115*91df013fSAsim Jamshedinvalid.</p> </td></tr>
116*91df013fSAsim Jamshed<tr valign="top" align="left">
117*91df013fSAsim Jamshed<td width="11%"></td>
118*91df013fSAsim Jamshed<td width="12%">
119*91df013fSAsim Jamshed
120*91df013fSAsim Jamshed
121*91df013fSAsim Jamshed<p><b>EBADF</b></p></td>
122*91df013fSAsim Jamshed<td width="3%"></td>
123*91df013fSAsim Jamshed<td width="74%">
124*91df013fSAsim Jamshed
125*91df013fSAsim Jamshed
126*91df013fSAsim Jamshed<p>The socket descriptor <i>sockid</i> is invalid.</p></td></tr>
127*91df013fSAsim Jamshed<tr valign="top" align="left">
128*91df013fSAsim Jamshed<td width="11%"></td>
129*91df013fSAsim Jamshed<td width="12%">
130*91df013fSAsim Jamshed
131*91df013fSAsim Jamshed
132*91df013fSAsim Jamshed<p><b>EINVAL</b></p></td>
133*91df013fSAsim Jamshed<td width="3%"></td>
134*91df013fSAsim Jamshed<td width="74%">
135*91df013fSAsim Jamshed
136*91df013fSAsim Jamshed
137*91df013fSAsim Jamshed<p>The buffer management of the monitoring socket with
138*91df013fSAsim Jamshed<i>sockid</i> was already disabled.</p></td></tr>
139*91df013fSAsim Jamshed<tr valign="top" align="left">
140*91df013fSAsim Jamshed<td width="11%"></td>
141*91df013fSAsim Jamshed<td width="12%">
142*91df013fSAsim Jamshed
143*91df013fSAsim Jamshed
144*91df013fSAsim Jamshed<p><b>ENOTSOCK</b></p></td>
145*91df013fSAsim Jamshed<td width="3%"></td>
146*91df013fSAsim Jamshed<td width="74%">
147*91df013fSAsim Jamshed
148*91df013fSAsim Jamshed
149*91df013fSAsim Jamshed<p>The socket referred to by <i>sockid</i> has invalid
150*91df013fSAsim Jamshed<i>type</i></p> </td></tr>
151*91df013fSAsim Jamshed<tr valign="top" align="left">
152*91df013fSAsim Jamshed<td width="11%"></td>
153*91df013fSAsim Jamshed<td width="12%">
154*91df013fSAsim Jamshed
155*91df013fSAsim Jamshed
156*91df013fSAsim Jamshed<p><b>ENOTCONN</b></p></td>
157*91df013fSAsim Jamshed<td width="3%"></td>
158*91df013fSAsim Jamshed<td width="74%">
159*91df013fSAsim Jamshed
160*91df013fSAsim Jamshed
161*91df013fSAsim Jamshed<p>Th socket referred to by <i>sockid</i> is in a TCP state
162*91df013fSAsim Jamshedthat disallows read operations.</p></td></tr>
163*91df013fSAsim Jamshed<tr valign="top" align="left">
164*91df013fSAsim Jamshed<td width="11%"></td>
165*91df013fSAsim Jamshed<td width="12%">
166*91df013fSAsim Jamshed
167*91df013fSAsim Jamshed
168*91df013fSAsim Jamshed<p><b>ENODATA</b></p></td>
169*91df013fSAsim Jamshed<td width="3%"></td>
170*91df013fSAsim Jamshed<td width="74%">
171*91df013fSAsim Jamshed
172*91df013fSAsim Jamshed
173*91df013fSAsim Jamshed<p>The socket referred to by <i>sockid</i> does not have
174*91df013fSAsim Jamshedany available bytes in its buffer for reading.</p></td></tr>
175*91df013fSAsim Jamshed<tr valign="top" align="left">
176*91df013fSAsim Jamshed<td width="11%"></td>
177*91df013fSAsim Jamshed<td width="12%">
178*91df013fSAsim Jamshed
179*91df013fSAsim Jamshed
180*91df013fSAsim Jamshed<p><b>EPERM</b></p></td>
181*91df013fSAsim Jamshed<td width="3%"></td>
182*91df013fSAsim Jamshed<td width="74%">
183*91df013fSAsim Jamshed
184*91df013fSAsim Jamshed
185*91df013fSAsim Jamshed<p>The caller is not permitted to access this function.</p></td></tr>
186*91df013fSAsim Jamshed</table>
187*91df013fSAsim Jamshed
188*91df013fSAsim Jamshed<h2>NOTES
189*91df013fSAsim Jamshed<a name="NOTES"></a>
190*91df013fSAsim Jamshed</h2>
191*91df013fSAsim Jamshed
192*91df013fSAsim Jamshed
193*91df013fSAsim Jamshed<p style="margin-left:11%; margin-top: 1em">Since TCP flow
194*91df013fSAsim Jamshedcontrol applies between end-hosts, the receive buffer
195*91df013fSAsim Jamshedmanaged by mOS can become full while new packets continue to
196*91df013fSAsim Jamshedarrive. Silent TCP ring buffer overwriting is undesirable
197*91df013fSAsim Jamshedsince the application may not notice the buffer overflow.
198*91df013fSAsim JamshedInstead, mOS raises an error event to explicitly notify the
199*91df013fSAsim Jamshedapplication about the buffer overflow. The application can
200*91df013fSAsim Jamshedeither drain the buffer by reading the data (by calling
201*91df013fSAsim Jamshed<b>mtcp_peek())</b> or enlarge the buffer (by calling
202*91df013fSAsim Jamshed<b>mtcp_setsockopt()).</b> Otherwise, the stack overwrites
203*91df013fSAsim Jamshedthe buffer with the new data, and adjusts the internal peek
204*91df013fSAsim Jamshedpointer. To notify the application about the overwriting,
205*91df013fSAsim Jamshed<b>mtcp_peek()</b> fails right after overwriting. Subsequent
206*91df013fSAsim Jamshedfunction calls continue to read the data from the new
207*91df013fSAsim Jamshedposition.</p>
208*91df013fSAsim Jamshed
209*91df013fSAsim Jamshed<h2>AUTHORS
210*91df013fSAsim Jamshed<a name="AUTHORS"></a>
211*91df013fSAsim Jamshed</h2>
212*91df013fSAsim Jamshed
213*91df013fSAsim Jamshed
214*91df013fSAsim Jamshed<p style="margin-left:11%; margin-top: 1em">mOS development
215*91df013fSAsim Jamshedteam &lt;[email protected]&gt;</p>
216*91df013fSAsim Jamshed
217*91df013fSAsim Jamshed<h2>SEE ALSO
218*91df013fSAsim Jamshed<a name="SEE ALSO"></a>
219*91df013fSAsim Jamshed</h2>
220*91df013fSAsim Jamshed
221*91df013fSAsim Jamshed
222*91df013fSAsim Jamshed
223*91df013fSAsim Jamshed<p style="margin-left:11%; margin-top: 1em"><b>mtcp_ppeek</b>(),
224*91df013fSAsim Jamshed<b>mtcp_socket</b>(), <b>mtcp_getsockopt</b>()</p>
225*91df013fSAsim Jamshed
226*91df013fSAsim Jamshed<h2>COLOPHON
227*91df013fSAsim Jamshed<a name="COLOPHON"></a>
228*91df013fSAsim Jamshed</h2>
229*91df013fSAsim Jamshed
230*91df013fSAsim Jamshed
231*91df013fSAsim Jamshed<p style="margin-left:11%; margin-top: 1em">This page is
232*91df013fSAsim Jamshedpart of mOS release 0.3 <i>docs</i> section. A description
233*91df013fSAsim Jamshedof the project, and information about reporting bugs, can be
234*91df013fSAsim Jamshedfound at http://mos.kaist.edu/.</p>
235*91df013fSAsim Jamshed<hr>
236*91df013fSAsim Jamshed</body>
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