1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
|
<html><head><META http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><title>The Apache Tomcat Connector - AJP Protocol Reference - AJPv13</title><meta name="author" value="danmil@shore.net"><meta name="email" value="danmil@shore.net"><meta name="author" value="Jean-Frederic Clere"><meta name="email" value="jfrederic.clere@fujitsu-siemens.com"><link href="../../style.css" type="text/css" rel="stylesheet"></head><body bgcolor="#ffffff" text="#000000" link="#525D76" alink="#525D76" vlink="#525D76"><table border="0" width="100%" cellspacing="4"><!--PAGE HEADER--><tr><td colspan="2"><!--TOMCAT LOGO--><a href="http://tomcat.apache.org/"><img src="../../images/tomcat.gif" align="left" alt="Apache Tomcat" border="0"></a><!--APACHE LOGO--><a href="http://www.apache.org/"><img src="http://www.apache.org/images/asf-logo.gif" align="right" alt="Apache Logo" border="0"></a></td></tr><!--HEADER SEPARATOR--><tr><td colspan="2"><hr noshade size="1"></td></tr><tr><!--RIGHT SIDE MAIN BODY--><td width="80%" valign="top" align="left"><table border="0" width="100%" cellspacing="4"><tr><td align="left" valign="top"><h1>The Apache Tomcat Connector - AJP Protocol Reference</h1><h2>AJPv13</h2></td><td align="right" valign="top" nowrap="true"><img src="../../images/void.gif" width="1" height="1" vspace="0" hspace="0" border="0"></td></tr></table><table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Intro"><strong>Intro</strong></a></font></td></tr><tr><td><blockquote>
<p>
The original document was written by
Dan Milstein, <author email="danmil@shore.net">danmil@shore.net</author>
on December 2000. The present document is generated out of an xml file
to allow a more easy integration in the Tomcat documentation.
</p>
<p>
This describes the Apache JServ Protocol version 1.3 (hereafter
<b>ajp13</b>). There is, apparently, no current documentation of how the
protocol works. This document is an attempt to remedy that, in order to
make life easier for maintainers of JK, and for anyone who wants to
port the protocol somewhere (into jakarta 4.x, for example).
</p>
</blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="author"><strong>author</strong></a></font></td></tr><tr><td><blockquote>
<p>
I am not one of the designers of this protocol -- I believe that Gal
Shachor was the original designer. Everything in this document is derived
from the actual implementation I found in the tomcat 3.x code. I hope it
is useful, but I can't make any grand claims to perfect accuracy. I also
don't know why certain design decisions were made. Where I was able, I've
offered some possible justifications for certain choices, but those are
only my guesses. In general, the C code which Shachor wrote is very clean
and comprehensible (if almost totally undocumented). I've cleaned up the
Java code, and I think it's reasonably readable.
</p>
</blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Design Goals"><strong>Design Goals</strong></a></font></td></tr><tr><td><blockquote>
<p>
According to email from Gal Shachor to the jakarta-dev mailing list,
the original goals of <b>JK</b> (and thus <b>ajp13</b>) were to extend
<b>mod_jserv</b> and <b>ajp12</b> by (I am only including the goals which
relate to communication between the web server and the servlet container):
<ul>
<li> Increasing performance (speed, specifically). </li>
<li> Adding support for SSL, so that <b class="code">isSecure()</b> and
<b class="code">getScheme()</b> will function correctly within the servlet
container. The client certificates and cipher suite will be
available to servlets as request attributes. </li>
</ul>
</p>
</blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Overview of the protocol"><strong>Overview of the protocol</strong></a></font></td></tr><tr><td><blockquote>
<p>
The <b>ajp13</b> protocol is packet-oriented. A binary format was
presumably chosen over the more readable plain text for reasons of
performance. The web server communicates with the servlet container over
TCP connections. To cut down on the expensive process of socket creation,
the web server will attempt to maintain persistent TCP connections to the
servlet container, and to reuse a connection for multiple request/response
cycles.
</p><p>
Once a connection is assigned to a particular request, it will not be
used for any others until the request-handling cycle has terminated. In
other words, requests are not multiplexed over connections. This makes
for much simpler code at either end of the connection, although it does
cause more connections to be open at once.
</p><p>
Once the web server has opened a connection to the servlet container,
the connection can be in one of the following states:
</p><p>
<ul>
<li> Idle <br> No request is being handled over this connection. </li>
<li> Assigned <br> The connecton is handling a specific request.</li>
</ul>
</p><p>
Once a connection is assigned to handle a particular request, the basic
request informaton (e.g. HTTP headers, etc) is sent over the connection in
a highly condensed form (e.g. common strings are encoded as integers).
Details of that format are below in Request Packet Structure. If there is a
body to the request (content-length > 0), that is sent in a separate
packet immediately after.
</p><p>
At this point, the servlet container is presumably ready to start
processing the request. As it does so, it can send the
following messages back to the web server:
<ul>
<li>SEND_HEADERS <br>Send a set of headers back to the browser.</li>
<li>SEND_BODY_CHUNK <br>Send a chunk of body data back to the browser.</li>
<li>GET_BODY_CHUNK <br>Get further data from the request if it hasn't all
been transferred yet. This is necessary because the packets have a fixed
maximum size and arbitrary amounts of data can be included the body of a
request (for uploaded files, for example). (Note: this is unrelated to
HTTP chunked tranfer).</li>
<li>END_RESPONSE <br> Finish the request-handling cycle.</li>
</ul>
</p><p>
Each message is accompanied by a differently formatted packet of data. See
Response Packet Structures below for details.
</p>
</blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Basic Packet Structure"><strong>Basic Packet Structure</strong></a></font></td></tr><tr><td><blockquote>
<p>
There is a bit of an XDR heritage to this protocol, but it differs in
lots of ways (no 4 byte alignment, for example).
</p><p>
Byte order: I am not clear about the endian-ness of the individual
bytes. I'm guessing the bytes are little-endian, because that's what XDR
specifies, and I'm guessing that sys/socket library is magically making
that so (on the C side). If anyone with a better knowledge of socket calls
can step in, that would be great.
</p><p>
There are four data types in the protocol: bytes, booleans, integers and
strings.
<dl>
<dt><b>Byte</b></dt>
<dd>A single byte.</dd>
<dt><b>Boolean</b></dt>
<dd>A single byte, 1 = true, 0 = false. Using other non-zero values as
true (i.e. C-style) may work in some places, but it won't in
others.</dd>
<dt><b>Integer</b></dt>
<dd>A number in the range of 0 to 2^16 (32768). Stored in 2 bytes with
the high-order byte first.</dd>
<dt><b>String</b></dt>
<dd>A variable-sized string (length bounded by 2^16). Encoded with the
length packed into two bytes first, followed by the string (including the
terminating '\0'). Note that the encoded length does <b>not</b> include
the trailing '\0' -- it is like <b class="code">strlen</b>. This is a touch
confusing on the Java side, which is littered with odd autoincrement
statements to skip over these terminators. I believe the reason this was
done was to allow the C code to be extra efficient when reading strings
which the servlet container is sending back -- with the terminating \0
character, the C code can pass around references into a single buffer,
without copying. If the \0 was missing, the C code would have to copy
things out in order to get its notion of a string. Note a size of -1
(65535) indicates a null string and no data follow the length in this
case.</dd>
</dl>
</p>
<table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Packet Size"><strong>Packet Size</strong></a></font></td></tr><tr><td><blockquote>
<p>
According to much of the code, the max packet
size is 8 * 1024 bytes (8K). The actual length of the packet is encoded in the
header.
</p>
</blockquote></td></tr></table>
<table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Packet Headers"><strong>Packet Headers</strong></a></font></td></tr><tr><td><blockquote>
<p>
Packets sent from the server to the container begin with
<b class="code">0x1234</b>. Packets sent from the container to the server begin
with <b class="code">AB</b> (that's the ASCII code for A followed by the ASCII
code for B). After those first two bytes, there is an integer (encoded as
above) with the length of the payload. Although this might suggest that
the maximum payload could be as large as 2^16, in fact, the code sets the
maximum to be 8K.
<table>
<tr>
<th colspan="6">Packet Format (Server->Container)</th>
</tr>
<tr>
<th>Byte</th>
<td>0</td>
<td>1</td>
<td>2</td>
<td>3</td>
<td>4...(n+3)</td>
</tr>
<tr>
<th>Contents</th>
<td>0x12</td>
<td>0x34</td>
<td colspan="2">Data Length (n)</td>
<td>Data</td>
</tr>
</table>
<table>
<tr>
<th colspan="6"><b>Packet Format (Container->Server)</b></th>
</tr>
<tr>
<th>Byte</th>
<td>0</td>
<td>1</td>
<td>2</td>
<td>3</td>
<td>4...(n+3)</td>
</tr>
<tr>
<th>Contents</th>
<td>A</td>
<td>B</td>
<td colspan="2">Data Length (n)</td>
<td>Data</td>
</tr>
</table>
</p>
<p>
<A NAME="prefix-codes"></A> For most packets, the first byte of the
payload encodes the type of message. The exception is for request body
packets sent from the server to the container -- they are sent with a
standard packet header (0x1234 and then length of the packet), but without
any prefix code after that (this seems like a mistake to me).
</p><p>
The web server can send the following messages to the servlet container:
<table>
<tr>
<th>Code</th>
<th>Type of Packet</th>
<th>Meaning</th>
</tr>
<tr>
<td>2</td>
<td>Forward Request</td>
<td>Begin the request-processing cycle with the following data</td>
</tr>
<tr>
<td>7</td>
<td>Shutdown</td>
<td>The web server asks the container to shut itself down.</td>
</tr>
<tr>
<td>8</td>
<td>Ping</td>
<td>The web server asks the container to take control (secure login phase).</td>
</tr>
<tr>
<td>10</td>
<td>CPing</td>
<td>The web server asks the container to respond quickly with a CPong.</td>
</tr>
<tr>
<td>none</td>
<td>Data</td>
<td>Size (2 bytes) and corresponding body data.</td>
</tr>
</table>
</p>
<p>
To ensure some
basic security, the container will only actually do the <b class="code">Shutdown</b> if the
request comes from the same machine on which it's hosted.
</p>
<p>
The first <b class="code">Data</b> packet is send immediatly after the <b class="code">Forward Request</b> by the web server.
</p>
<p>The servlet container can send the following types of messages to the web
server:
<table>
<tr>
<th>Code</th>
<th>Type of Packet</th>
<th>Meaning</th>
</tr>
<tr>
<td>3</td>
<td>Send Body Chunk</td>
<td>Send a chunk of the body from the servlet container to the web
server (and presumably, onto the browser). </td>
</tr>
<tr>
<td>4</td>
<td>Send Headers</td>
<td>Send the response headers from the servlet container to the web
server (and presumably, onto the browser).</td>
</tr>
<tr>
<td>5</td>
<td>End Response</td>
<td>Marks the end of the response (and thus the request-handling cycle).</td>
</tr>
<tr>
<td>6</td>
<td>Get Body Chunk</td>
<td>Get further data from the request if it hasn't all been transferred
yet.</td>
</tr>
<tr>
<td>9</td>
<td>CPong Reply</td>
<td>The reply to a CPing request</td>
</tr>
</table>
</p>
<p>
Each of the above messages has a different internal structure, detailed below.
</p>
</blockquote></td></tr></table>
</blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Request Packet Structure"><strong>Request Packet Structure</strong></a></font></td></tr><tr><td><blockquote>
<p>
For messages from the server to the container of type "Forward Request":
</p><p>
<div class="example"><pre>
AJP13_FORWARD_REQUEST :=
prefix_code (byte) 0x02 = JK_AJP13_FORWARD_REQUEST
method (byte)
protocol (string)
req_uri (string)
remote_addr (string)
remote_host (string)
server_name (string)
server_port (integer)
is_ssl (boolean)
num_headers (integer)
request_headers *(req_header_name req_header_value)
attributes *(attribut_name attribute_value)
request_terminator (byte) OxFF
</pre></div>
</p><p>
The <b class="code">request_headers</b> have the following structure:
</p><p>
<div class="example"><pre>
req_header_name :=
sc_req_header_name | (string) [see below for how this is parsed]
sc_req_header_name := 0xA0xx (integer)
req_header_value := (string)
</pre></div>
</p><p>
The <b class="code">attributes</b> are optional and have the following structure:
</p><p>
<div class="example"><pre>
attribute_name := sc_a_name | (sc_a_req_attribute string)
attribute_value := (string)
</pre></div>
</p><p>
Not that the all-important header is "content-length', because it
determines whether or not the container looks for another packet
immediately.
</p><p>
Detailed description of the elements of Forward Request.
</p>
<table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="request_prefix"><strong>request_prefix</strong></a></font></td></tr><tr><td><blockquote>
<p>
For all requests, this will be 2.
See above for details on other <A HREF="#prefix-codes">prefix codes</A>.
</p>
</blockquote></td></tr></table>
<table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="method"><strong>method</strong></a></font></td></tr><tr><td><blockquote>
<p>
The HTTP method, encoded as a single byte:
</p>
<p>
<table>
<tr><th>Command Name</th><th>Code</th></tr>
<tr><td>OPTIONS</td><td>1</td></tr>
<tr><td>GET</td><td>2</td></tr>
<tr><td>HEAD</td><td>3</td></tr>
<tr><td>POST</td><td>4</td></tr>
<tr><td>PUT</td><td>5</td></tr>
<tr><td>DELETE</td><td>6</td></tr>
<tr><td>TRACE</td><td>7</td></tr>
<tr><td>PROPFIND</td><td>8</td></tr>
<tr><td>PROPPATCH</td><td>9</td></tr>
<tr><td>MKCOL</td><td>10</td></tr>
<tr><td>COPY</td><td>11</td></tr>
<tr><td>MOVE</td><td>12</td></tr>
<tr><td>LOCK</td><td>13</td></tr>
<tr><td>UNLOCK</td><td>14</td></tr>
<tr><td>ACL</td><td>15</td></tr>
<tr><td>REPORT</td><td>16</td></tr>
<tr><td>VERSION-CONTROL</td><td>17</td></tr>
<tr><td>CHECKIN</td><td>18</td></tr>
<tr><td>CHECKOUT</td><td>19</td></tr>
<tr><td>UNCHECKOUT</td><td>20</td></tr>
<tr><td>SEARCH</td><td>21</td></tr>
<tr><td>MKWORKSPACE</td><td>22</td></tr>
<tr><td>UPDATE</td><td>23</td></tr>
<tr><td>LABEL</td><td>24</td></tr>
<tr><td>MERGE</td><td>25</td></tr>
<tr><td>BASELINE_CONTROL</td><td>26</td></tr>
<tr><td>MKACTIVITY</td><td>27</td></tr>
</table>
</p>
<p>Later version of ajp13, when used with mod_jk2, will transport
additional methods, even if they are not in this list.
</p>
</blockquote></td></tr></table>
<table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="protocol, req_uri, remote_addr, remote_host, server_name, server_port, is_ssl"><strong>protocol, req_uri, remote_addr, remote_host, server_name, server_port, is_ssl</strong></a></font></td></tr><tr><td><blockquote>
<p>
These are all fairly self-explanatory. Each of these is required, and
will be sent for every request.
</p>
</blockquote></td></tr></table>
<table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Headers"><strong>Headers</strong></a></font></td></tr><tr><td><blockquote>
<p>
The structure of <b class="code">request_headers</b> is the following:
First, the number of headers <b class="code">num_headers</b> is encoded.
Then, a series of header name <b class="code">req_header_name</b> / value
<b class="code">req_header_value</b> pairs follows.
Common header names are encoded as integers,
to save space. If the header name is not in the list of basic headers,
it is encoded normally (as a string, with prefixed length). The list of
common headers <b class="code">sc_req_header_name</b>and their codes
is as follows (all are case-sensitive):
</p><p>
<table>
<tr><th>Name</th><th>Code value</th><th>Code name</th></tr>
<tr><td>accept</td><td>0xA001</td><td>SC_REQ_ACCEPT</td></tr>
<tr><td>accept-charset</td><td>0xA002</td><td>SC_REQ_ACCEPT_CHARSET</td></tr>
<tr><td>accept-encoding</td><td>0xA003</td><td>SC_REQ_ACCEPT_ENCODING</td></tr>
<tr><td>accept-language</td><td>0xA004</td><td>SC_REQ_ACCEPT_LANGUAGE</td></tr>
<tr><td>authorization</td><td>0xA005</td><td>SC_REQ_AUTHORIZATION</td></tr>
<tr><td>connection</td><td>0xA006</td><td>SC_REQ_CONNECTION</td></tr>
<tr><td>content-type</td><td>0xA007</td><td>SC_REQ_CONTENT_TYPE</td></tr>
<tr><td>content-length</td><td>0xA008</td><td>SC_REQ_CONTENT_LENGTH</td></tr>
<tr><td>cookie</td><td>0xA009</td><td>SC_REQ_COOKIE</td></tr>
<tr><td>cookie2</td><td>0xA00A</td><td>SC_REQ_COOKIE2</td></tr>
<tr><td>host</td><td>0xA00B</td><td>SC_REQ_HOST</td></tr>
<tr><td>pragma</td><td>0xA00C</td><td>SC_REQ_PRAGMA</td></tr>
<tr><td>referer</td><td>0xA00D</td><td>SC_REQ_REFERER</td></tr>
<tr><td>user-agent</td><td>0xA00E</td><td>SC_REQ_USER_AGENT</td></tr>
</table>
</p><p>
The Java code that reads this grabs the first two-byte integer and if
it sees an <b class="code">'0xA0'</b> in the most significant
byte, it uses the integer in the second byte as an index into an array of
header names. If the first byte is not '0xA0', it assumes that the
two-byte integer is the length of a string, which is then read in.
</p><p>
This works on the assumption that no header names will have length
greater than 0x9999 (==0xA000 - 1), which is perfectly reasonable, though
somewhat arbitrary. (If you, like me, started to think about the cookie
spec here, and about how long headers can get, fear not -- this limit is
on header <b>names</b> not header <b>values</b>. It seems unlikely that
unmanageably huge header names will be showing up in the HTTP spec any time
soon).
</p><p>
<b>Note:</b> The <b class="code">content-length</b> header is extremely
important. If it is present and non-zero, the container assumes that
the request has a body (a POST request, for example), and immediately
reads a separate packet off the input stream to get that body.
</p>
</blockquote></td></tr></table>
<table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Attributes"><strong>Attributes</strong></a></font></td></tr><tr><td><blockquote>
<p>
The attributes prefixed with a <b class="code">?</b>
(e.g. <b class="code">?context</b>) are all optional. For each, there is a
single byte code to indicate the type of attribute, and then a string to
give its value. They can be sent in any order (thogh the C code always
sends them in the order listed below). A special terminating code is
sent to signal the end of the list of optional attributes. The list of
byte codes is:
</p><p>
<table>
<tr><th>Information</th><th>Code Value</th><th>Note</th></tr>
<tr><td>?context</td><td>0x01</td><td>Not currently implemented</td></tr>
<tr><td>?servlet_path</td><td>0x02</td><td>Not currently implemented</td></tr>
<tr><td>?remote_user</td><td>0x03</td><td></td></tr>
<tr><td>?auth_type</td><td>0x04</td><td></td></tr>
<tr><td>?query_string</td><td>0x05</td><td></td></tr>
<tr><td>?route</td><td>0x06</td><td></td></tr>
<tr><td>?ssl_cert</td><td>0x07</td><td></td></tr>
<tr><td>?ssl_cipher</td><td>0x08</td><td></td></tr>
<tr><td>?ssl_session</td><td>0x09</td><td></td></tr>
<tr><td>?req_attribute</td><td>0x0A</td><td>Name (the name of the attribut follows)</td></tr>
<tr><td>?ssl_key_size</td><td>0x0B</td><td></td></tr>
<tr><td>?secret</td><td>0x0C</td><td></td></tr>
<tr><td>?stored_method</td><td>0x0D</td><td></td></tr>
<tr><td>are_done</td><td>0xFF</td><td>request_terminator</td></tr>
</table>
</p><p>
The <b class="code">context</b> and <b class="code">servlet_path</b> are not currently
set by the C code, and most of the Java code completely ignores whatever
is sent over for those fields (and some of it will actually break if a
string is sent along after one of those codes). I don't know if this is
a bug or an unimplemented feature or just vestigial code, but it's
missing from both sides of the connection.
</p><p>
The <b class="code">remote_user</b> and <b class="code">auth_type</b> presumably refer
to HTTP-level authentication, and communicate the remote user's username
and the type of authentication used to establish their identity (e.g. Basic,
Digest). I'm not clear on why the password isn't also sent, but I don't
know HTTP authentication inside and out.
</p><p>
The <b class="code">query_string</b>, <b class="code">ssl_cert</b>,
<b class="code">ssl_cipher</b>, and <b class="code">ssl_session</b> refer to the
corresponding pieces of HTTP and HTTPS.
</p><p>
The <b class="code">route</b>, as I understand it, is used to support sticky
sessions -- associating a user's sesson with a particular Tomcat instance
in the presence of multiple, load-balancing servers. I don't know the
details.
</p><p>
Beyond this list of basic attributes, any number of other attributes can
be sent via the <b class="code">req_attribute</b> code (0x0A). A pair of strings
to represent the attribute name and value are sent immediately after each
instance of that code. Environment values are passed in via this method.
</p><p>
Finally, after all the attributes have been sent, the attribute terminator,
0xFF, is sent. This signals both the end of the list of attributes and
also then end of the Request Packet.
</p>
</blockquote></td></tr></table>
</blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Response Packet Structure"><strong>Response Packet Structure</strong></a></font></td></tr><tr><td><blockquote>
<p>
For messages which the container can send back to the server.
<div class="example"><pre>
AJP13_SEND_BODY_CHUNK :=
prefix_code 3
chunk_length (integer)
chunk *(byte)
AJP13_SEND_HEADERS :=
prefix_code 4
http_status_code (integer)
http_status_msg (string)
num_headers (integer)
response_headers *(res_header_name header_value)
res_header_name :=
sc_res_header_name | (string) [see below for how this is parsed]
sc_res_header_name := 0xA0 (byte)
header_value := (string)
AJP13_END_RESPONSE :=
prefix_code 5
reuse (boolean)
AJP13_GET_BODY_CHUNK :=
prefix_code 6
requested_length (integer)
</pre></div>
</p>
<p>
Details:
</p>
<table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Send Body Chunk"><strong>Send Body Chunk</strong></a></font></td></tr><tr><td><blockquote>
<p>
The chunk is basically binary data, and is sent directly back to the browser.
</p>
</blockquote></td></tr></table>
<table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Send Headers"><strong>Send Headers</strong></a></font></td></tr><tr><td><blockquote>
<p>
The status code and message are the usual HTTP things (e.g. "200" and "OK").
The response header names are encoded the same way the request header names are.
See <A HREF="#header_encoding">above</A> for details about how the the
codes are distinguished from the strings. The codes for common headers are:
</p>
<p>
<table>
<tr><th>Name</th><th>Code value</th></tr>
<tr><td>Content-Type</td><td>0xA001</td></tr>
<tr><td>Content-Language</td><td>0xA002</td></tr>
<tr><td>Content-Length</td><td>0xA003</td></tr>
<tr><td>Date</td><td>0xA004</td></tr>
<tr><td>Last-Modified</td><td>0xA005</td></tr>
<tr><td>Location</td><td>0xA006</td></tr>
<tr><td>Set-Cookie</td><td>0xA007</td></tr>
<tr><td>Set-Cookie2</td><td>0xA008</td></tr>
<tr><td>Servlet-Engine</td><td>0xA009</td></tr>
<tr><td>Status</td><td>0xA00A</td></tr>
<tr><td>WWW-Authenticate</td><td>0xA00B</td></tr>
</table>
</p>
<p>
After the code or the string header name, the header value is immediately
encoded.
</p>
</blockquote></td></tr></table>
<table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="End Response"><strong>End Response</strong></a></font></td></tr><tr><td><blockquote>
<p>
Signals the end of this request-handling cycle. If the
<b class="code">reuse</b> flag is true (==1), this TCP connection can now be used to
handle new incoming requests. If <b class="code">reuse</b> is false (anything
other than 1 in the actual C code), the connection should be closed.
</p>
</blockquote></td></tr></table>
<table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Get Body Chunk"><strong>Get Body Chunk</strong></a></font></td></tr><tr><td><blockquote>
<p>
The container asks for more data from the request (If the body was
too large to fit in the first packet sent over or when the request is
chuncked).
The server will send a body packet back with an amount of data which is
the minimum of the <b class="code">request_length</b>,
the maximum send body size (8186 (8 Kbytes - 6)), and the
number of bytes actually left to send from the request body.
<br>
If there is no more data in the body (i.e. the servlet container is
trying to read past the end of the body), the server will send back an
"empty" packet, which is a body packet with a payload length of 0.
(0x12,0x34,0x00,0x00)
</p>
</blockquote></td></tr></table>
</blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Questions I Have"><strong>Questions I Have</strong></a></font></td></tr><tr><td><blockquote>
<p> What happens if the request headers > max packet size? There is no
provision to send a second packet of request headers in case there are more
than 8K (I think this is correctly handled for response headers, though I'm
not certain). I don't know if there is a way to get more than 8K worth of
data into that initial set of request headers, but I'll bet there is
(combine long cookies with long ssl information and a lot of environment
variables, and you should hit 8K easily). I think the connector would just
fail before trying to send any headers in this case, but I'm not certain.</p>
<p> What about authentication? There doesn't seem to be any authentication
of the connection between the web server and the container. This strikes
me as potentially dangerous.</p>
</blockquote></td></tr></table></td></tr><!--FOOTER SEPARATOR--><tr><td colspan="2"><hr noshade size="1"></td></tr><!--PAGE FOOTER--><tr><td colspan="2"><div align="center"><font color="#525D76" size="-1"><em>
Copyright © 1999-2011, Apache Software Foundation
</em></font></div></td></tr></table></body></html>
|
