xref: /freebsd/sys/kern/uipc_accf.c (revision c1d255d3)
1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3  *
4  * Copyright (c) 2000 Paycounter, Inc.
5  * Copyright (c) 2005 Robert N. M. Watson
6  * Author: Alfred Perlstein <alfred@paycounter.com>, <alfred@FreeBSD.org>
7  * All rights reserved.
8  *
9  * Redistribution and use in source and binary forms, with or without
10  * modification, are permitted provided that the following conditions
11  * are met:
12  * 1. Redistributions of source code must retain the above copyright
13  *    notice, this list of conditions and the following disclaimer.
14  * 2. Redistributions in binary form must reproduce the above copyright
15  *    notice, this list of conditions and the following disclaimer in the
16  *    documentation and/or other materials provided with the distribution.
17  *
18  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
19  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
22  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28  * SUCH DAMAGE.
29  */
30 
31 #include <sys/cdefs.h>
32 __FBSDID("$FreeBSD$");
33 
34 #define ACCEPT_FILTER_MOD
35 
36 #include "opt_param.h"
37 #include <sys/param.h>
38 #include <sys/systm.h>
39 #include <sys/domain.h>
40 #include <sys/kernel.h>
41 #include <sys/lock.h>
42 #include <sys/malloc.h>
43 #include <sys/mbuf.h>
44 #include <sys/module.h>
45 #include <sys/mutex.h>
46 #include <sys/protosw.h>
47 #include <sys/sysctl.h>
48 #include <sys/socket.h>
49 #include <sys/socketvar.h>
50 #include <sys/queue.h>
51 
52 static struct mtx accept_filter_mtx;
53 MTX_SYSINIT(accept_filter, &accept_filter_mtx, "accept_filter_mtx",
54 	MTX_DEF);
55 #define	ACCEPT_FILTER_LOCK()	mtx_lock(&accept_filter_mtx)
56 #define	ACCEPT_FILTER_UNLOCK()	mtx_unlock(&accept_filter_mtx)
57 
58 static SLIST_HEAD(, accept_filter) accept_filtlsthd =
59 	SLIST_HEAD_INITIALIZER(accept_filtlsthd);
60 
61 MALLOC_DEFINE(M_ACCF, "accf", "accept filter data");
62 
63 static int unloadable = 0;
64 
65 SYSCTL_NODE(_net, OID_AUTO, accf, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
66     "Accept filters");
67 SYSCTL_INT(_net_accf, OID_AUTO, unloadable, CTLFLAG_RW, &unloadable, 0,
68 	"Allow unload of accept filters (not recommended)");
69 
70 /*
71  * Must be passed a malloc'd structure so we don't explode if the kld is
72  * unloaded, we leak the struct on deallocation to deal with this, but if a
73  * filter is loaded with the same name as a leaked one we re-use the entry.
74  */
75 int
76 accept_filt_add(struct accept_filter *filt)
77 {
78 	struct accept_filter *p;
79 
80 	ACCEPT_FILTER_LOCK();
81 	SLIST_FOREACH(p, &accept_filtlsthd, accf_next)
82 		if (strcmp(p->accf_name, filt->accf_name) == 0)  {
83 			if (p->accf_callback != NULL) {
84 				ACCEPT_FILTER_UNLOCK();
85 				return (EEXIST);
86 			} else {
87 				p->accf_callback = filt->accf_callback;
88 				ACCEPT_FILTER_UNLOCK();
89 				free(filt, M_ACCF);
90 				return (0);
91 			}
92 		}
93 
94 	if (p == NULL)
95 		SLIST_INSERT_HEAD(&accept_filtlsthd, filt, accf_next);
96 	ACCEPT_FILTER_UNLOCK();
97 	return (0);
98 }
99 
100 int
101 accept_filt_del(char *name)
102 {
103 	struct accept_filter *p;
104 
105 	p = accept_filt_get(name);
106 	if (p == NULL)
107 		return (ENOENT);
108 
109 	p->accf_callback = NULL;
110 	return (0);
111 }
112 
113 struct accept_filter *
114 accept_filt_get(char *name)
115 {
116 	struct accept_filter *p;
117 
118 	ACCEPT_FILTER_LOCK();
119 	SLIST_FOREACH(p, &accept_filtlsthd, accf_next)
120 		if (strcmp(p->accf_name, name) == 0)
121 			break;
122 	ACCEPT_FILTER_UNLOCK();
123 
124 	return (p);
125 }
126 
127 int
128 accept_filt_generic_mod_event(module_t mod, int event, void *data)
129 {
130 	struct accept_filter *p;
131 	struct accept_filter *accfp = (struct accept_filter *) data;
132 	int error;
133 
134 	switch (event) {
135 	case MOD_LOAD:
136 		p = malloc(sizeof(*p), M_ACCF, M_WAITOK);
137 		bcopy(accfp, p, sizeof(*p));
138 		error = accept_filt_add(p);
139 		break;
140 
141 	case MOD_UNLOAD:
142 		/*
143 		 * Do not support unloading yet. we don't keep track of
144 		 * refcounts and unloading an accept filter callback and then
145 		 * having it called is a bad thing.  A simple fix would be to
146 		 * track the refcount in the struct accept_filter.
147 		 */
148 		if (unloadable != 0) {
149 			error = accept_filt_del(accfp->accf_name);
150 		} else
151 			error = EOPNOTSUPP;
152 		break;
153 
154 	case MOD_SHUTDOWN:
155 		error = 0;
156 		break;
157 
158 	default:
159 		error = EOPNOTSUPP;
160 		break;
161 	}
162 
163 	return (error);
164 }
165 
166 int
167 accept_filt_getopt(struct socket *so, struct sockopt *sopt)
168 {
169 	struct accept_filter_arg *afap;
170 	int error;
171 
172 	error = 0;
173 	afap = malloc(sizeof(*afap), M_TEMP, M_WAITOK | M_ZERO);
174 	SOCK_LOCK(so);
175 	if (!SOLISTENING(so)) {
176 		error = EINVAL;
177 		goto out;
178 	}
179 	if (so->sol_accept_filter == NULL) {
180 		error = EINVAL;
181 		goto out;
182 	}
183 	strcpy(afap->af_name, so->sol_accept_filter->accf_name);
184 	if (so->sol_accept_filter_str != NULL)
185 		strcpy(afap->af_arg, so->sol_accept_filter_str);
186 out:
187 	SOCK_UNLOCK(so);
188 	if (error == 0)
189 		error = sooptcopyout(sopt, afap, sizeof(*afap));
190 	free(afap, M_TEMP);
191 	return (error);
192 }
193 
194 int
195 accept_filt_setopt(struct socket *so, struct sockopt *sopt)
196 {
197 	struct accept_filter_arg *afap;
198 	struct accept_filter *afp;
199 	char *accept_filter_str = NULL;
200 	void *accept_filter_arg = NULL;
201 	int error;
202 
203 	/*
204 	 * Handle the simple delete case first.
205 	 */
206 	if (sopt == NULL || sopt->sopt_val == NULL) {
207 		struct socket *sp, *sp1;
208 		int wakeup;
209 
210 		SOCK_LOCK(so);
211 		if (!SOLISTENING(so)) {
212 			SOCK_UNLOCK(so);
213 			return (EINVAL);
214 		}
215 		if (so->sol_accept_filter == NULL) {
216 			SOCK_UNLOCK(so);
217 			return (0);
218 		}
219 		if (so->sol_accept_filter->accf_destroy != NULL)
220 			so->sol_accept_filter->accf_destroy(so);
221 		if (so->sol_accept_filter_str != NULL)
222 			free(so->sol_accept_filter_str, M_ACCF);
223 		so->sol_accept_filter = NULL;
224 		so->sol_accept_filter_arg = NULL;
225 		so->sol_accept_filter_str = NULL;
226 		so->so_options &= ~SO_ACCEPTFILTER;
227 
228 		/*
229 		 * Move from incomplete queue to complete only those
230 		 * connections, that are blocked by us.
231 		 */
232 		wakeup = 0;
233 		TAILQ_FOREACH_SAFE(sp, &so->sol_incomp, so_list, sp1) {
234 			SOCK_LOCK(sp);
235 			if (sp->so_options & SO_ACCEPTFILTER) {
236 				TAILQ_REMOVE(&so->sol_incomp, sp, so_list);
237 				TAILQ_INSERT_TAIL(&so->sol_comp, sp, so_list);
238 				sp->so_qstate = SQ_COMP;
239 				sp->so_options &= ~SO_ACCEPTFILTER;
240 				so->sol_incqlen--;
241 				so->sol_qlen++;
242 				wakeup = 1;
243 			}
244 			SOCK_UNLOCK(sp);
245 		}
246 		if (wakeup)
247 			solisten_wakeup(so);  /* unlocks */
248 		else
249 			SOLISTEN_UNLOCK(so);
250 		return (0);
251 	}
252 
253 	/*
254 	 * Pre-allocate any memory we may need later to avoid blocking at
255 	 * untimely moments.  This does not optimize for invalid arguments.
256 	 */
257 	afap = malloc(sizeof(*afap), M_TEMP, M_WAITOK);
258 	error = sooptcopyin(sopt, afap, sizeof *afap, sizeof *afap);
259 	afap->af_name[sizeof(afap->af_name)-1] = '\0';
260 	afap->af_arg[sizeof(afap->af_arg)-1] = '\0';
261 	if (error) {
262 		free(afap, M_TEMP);
263 		return (error);
264 	}
265 	afp = accept_filt_get(afap->af_name);
266 	if (afp == NULL) {
267 		free(afap, M_TEMP);
268 		return (ENOENT);
269 	}
270 	if (afp->accf_create != NULL && afap->af_name[0] != '\0') {
271 		size_t len = strlen(afap->af_name) + 1;
272 		accept_filter_str = malloc(len, M_ACCF, M_WAITOK);
273 		strcpy(accept_filter_str, afap->af_name);
274 	}
275 
276 	/*
277 	 * Require a listen socket; don't try to replace an existing filter
278 	 * without first removing it.
279 	 */
280 	SOCK_LOCK(so);
281 	if (!SOLISTENING(so) || so->sol_accept_filter != NULL) {
282 		error = EINVAL;
283 		goto out;
284 	}
285 
286 	/*
287 	 * Invoke the accf_create() method of the filter if required.  The
288 	 * socket mutex is held over this call, so create methods for filters
289 	 * can't block.
290 	 */
291 	if (afp->accf_create != NULL) {
292 		accept_filter_arg = afp->accf_create(so, afap->af_arg);
293 		if (accept_filter_arg == NULL) {
294 			error = EINVAL;
295 			goto out;
296 		}
297 	}
298 	so->sol_accept_filter = afp;
299 	so->sol_accept_filter_arg = accept_filter_arg;
300 	so->sol_accept_filter_str = accept_filter_str;
301 	accept_filter_str = NULL;
302 	so->so_options |= SO_ACCEPTFILTER;
303 out:
304 	SOCK_UNLOCK(so);
305 	if (accept_filter_str != NULL)
306 		free(accept_filter_str, M_ACCF);
307 	free(afap, M_TEMP);
308 	return (error);
309 }
310