1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause
3 *
4 * Copyright (c) 2010-2011 The FreeBSD Foundation
5 * All rights reserved.
6 *
7 * This software was developed at the Centre for Advanced Internet
8 * Architectures, Swinburne University of Technology, Melbourne, Australia by
9 * Lawrence Stewart under sponsorship from the FreeBSD Foundation.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 * notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in the
18 * documentation and/or other materials provided with the distribution.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33 /*
34 * This example Khelp module uses the helper hook points available in the TCP
35 * stack to calculate a per-connection count of inbound and outbound packets
36 * when the connection is in the established state. The code is verbosely
37 * documented in an attempt to explain how everything fits together.
38 */
39
40 #include <sys/param.h>
41 #include <sys/kernel.h>
42 #include <sys/hhook.h>
43 #include <sys/khelp.h>
44 #include <sys/module.h>
45 #include <sys/module_khelp.h>
46 #include <sys/socket.h>
47 #include <sys/socketvar.h>
48
49 #include <netinet/tcp_var.h>
50
51 #include <vm/uma.h>
52
53 /*
54 * Function prototype for our helper hook (man 9 hhook) compatible hook
55 * function.
56 */
57 static int example_hook(int hhook_type, int hhook_id, void *udata,
58 void *ctx_data, void *hdata, struct osd *hosd);
59
60 /*
61 * Our per-connection persistent data storage struct.
62 */
63 struct example {
64 uint32_t est_in_count;
65 uint32_t est_out_count;
66 };
67
68 /*
69 * Fill in the required bits of our module's struct helper (defined in
70 * <sys/module_khelp.h>).
71 *
72 * - Our helper will be storing persistent state for each TCP connection, so we
73 * request the use the Object Specific Data (OSD) feature from the framework by
74 * setting the HELPER_NEEDS_OSD flag.
75 *
76 * - Our helper is related to the TCP subsystem, so tell the Khelp framework
77 * this by setting an appropriate class for the module. When a new TCP
78 * connection is created, the Khelp framework takes care of associating helper
79 * modules of the appropriate class with the new connection.
80 */
81 struct helper example_helper = {
82 .h_flags = HELPER_NEEDS_OSD,
83 .h_classes = HELPER_CLASS_TCP
84 };
85
86 /*
87 * Set which helper hook points our module wants to hook by creating an array of
88 * hookinfo structs (defined in <sys/hhook.h>). We hook the TCP established
89 * inbound/outbound hook points (TCP hhook points are defined in
90 * <netinet/tcp_var.h>) with our example_hook() function. We don't require a user
91 * data pointer to be passed to our hook function when called, so we set it to
92 * NULL.
93 */
94 struct hookinfo example_hooks[] = {
95 {
96 .hook_type = HHOOK_TYPE_TCP,
97 .hook_id = HHOOK_TCP_EST_IN,
98 .hook_udata = NULL,
99 .hook_func = &example_hook
100 },
101 {
102 .hook_type = HHOOK_TYPE_TCP,
103 .hook_id = HHOOK_TCP_EST_OUT,
104 .hook_udata = NULL,
105 .hook_func = &example_hook
106 }
107 };
108
109 /*
110 * Very simple helper hook function. Here's a quick run through the arguments:
111 *
112 * - hhook_type and hhook_id are useful if you use a single function with many
113 * hook points and want to know which hook point called the function.
114 *
115 * - udata will be NULL, because we didn't elect to pass a pointer in either of
116 * the hookinfo structs we instantiated above in the example_hooks array.
117 *
118 * - ctx_data contains context specific data from the hook point call site. The
119 * data type passed is subsystem dependent. In the case of TCP, the hook points
120 * pass a pointer to a "struct tcp_hhook_data" (defined in <netinet/tcp_var.h>).
121 *
122 * - hdata is a pointer to the persistent per-object storage for our module. The
123 * pointer is allocated automagically by the Khelp framework when the connection
124 * is created, and comes from a dedicated UMA zone. It will never be NULL.
125 *
126 * - hosd can be used with the Khelp framework's khelp_get_osd() function to
127 * access data belonging to a different Khelp module.
128 */
129 static int
example_hook(int hhook_type,int hhook_id,void * udata,void * ctx_data,void * hdata,struct osd * hosd)130 example_hook(int hhook_type, int hhook_id, void *udata, void *ctx_data,
131 void *hdata, struct osd *hosd)
132 {
133 struct example *data;
134
135 data = hdata;
136
137 if (hhook_id == HHOOK_TCP_EST_IN)
138 data->est_in_count++;
139 else if (hhook_id == HHOOK_TCP_EST_OUT)
140 data->est_out_count++;
141
142 return (0);
143 }
144
145 /*
146 * We use a convenient macro which handles registering our module with the Khelp
147 * framework. Note that Khelp modules which set the HELPER_NEEDS_OSD flag (i.e.
148 * require persistent per-object storage) must use the KHELP_DECLARE_MOD_UMA()
149 * macro. If you don't require per-object storage, use the KHELP_DECLARE_MOD()
150 * macro instead.
151 */
152 KHELP_DECLARE_MOD_UMA(example, &example_helper, example_hooks, 1,
153 sizeof(struct example), NULL, NULL);
154