FreeBSD/Linux Kernel Cross Reference
sys/kern/uipc_mbuf2.c
1 /* $FreeBSD: releng/5.0/sys/kern/uipc_mbuf2.c 107283 2002-11-26 17:59:16Z sam $ */
2 /* $KAME: uipc_mbuf2.c,v 1.31 2001/11/28 11:08:53 itojun Exp $ */
3 /* $NetBSD: uipc_mbuf.c,v 1.40 1999/04/01 00:23:25 thorpej Exp $ */
4
5 /*
6 * Copyright (C) 1999 WIDE Project.
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 * 3. Neither the name of the project nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34 /*
35 * Copyright (c) 1982, 1986, 1988, 1991, 1993
36 * The Regents of the University of California. All rights reserved.
37 *
38 * Redistribution and use in source and binary forms, with or without
39 * modification, are permitted provided that the following conditions
40 * are met:
41 * 1. Redistributions of source code must retain the above copyright
42 * notice, this list of conditions and the following disclaimer.
43 * 2. Redistributions in binary form must reproduce the above copyright
44 * notice, this list of conditions and the following disclaimer in the
45 * documentation and/or other materials provided with the distribution.
46 * 3. All advertising materials mentioning features or use of this software
47 * must display the following acknowledgement:
48 * This product includes software developed by the University of
49 * California, Berkeley and its contributors.
50 * 4. Neither the name of the University nor the names of its contributors
51 * may be used to endorse or promote products derived from this software
52 * without specific prior written permission.
53 *
54 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
55 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
56 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
57 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
58 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
59 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
60 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
61 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
62 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
63 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
64 * SUCH DAMAGE.
65 *
66 * @(#)uipc_mbuf.c 8.4 (Berkeley) 2/14/95
67 */
68
69 /*#define PULLDOWN_DEBUG*/
70
71 #include <sys/param.h>
72 #include <sys/systm.h>
73 #include <sys/kernel.h>
74 #include <sys/lock.h>
75 #include <sys/malloc.h>
76 #include <sys/mbuf.h>
77 #include <sys/mutex.h>
78
79 MALLOC_DEFINE(M_PACKET_TAGS, "tag", "packet-attached information");
80
81 /* can't call it m_dup(), as freebsd[34] uses m_dup() with different arg */
82 static struct mbuf *m_dup1(struct mbuf *, int, int, int);
83
84 /*
85 * ensure that [off, off + len) is contiguous on the mbuf chain "m".
86 * packet chain before "off" is kept untouched.
87 * if offp == NULL, the target will start at <retval, 0> on resulting chain.
88 * if offp != NULL, the target will start at <retval, *offp> on resulting chain.
89 *
90 * on error return (NULL return value), original "m" will be freed.
91 *
92 * XXX: M_TRAILINGSPACE/M_LEADINGSPACE only permitted on writable ext_buf.
93 */
94 struct mbuf *
95 m_pulldown(struct mbuf *m, int off, int len, int *offp)
96 {
97 struct mbuf *n, *o;
98 int hlen, tlen, olen;
99 int writable;
100
101 /* check invalid arguments. */
102 if (m == NULL)
103 panic("m == NULL in m_pulldown()");
104 if (len > MCLBYTES) {
105 m_freem(m);
106 return NULL; /* impossible */
107 }
108
109 #ifdef PULLDOWN_DEBUG
110 {
111 struct mbuf *t;
112 printf("before:");
113 for (t = m; t; t = t->m_next)
114 printf(" %d", t->m_len);
115 printf("\n");
116 }
117 #endif
118 n = m;
119 while (n != NULL && off > 0) {
120 if (n->m_len > off)
121 break;
122 off -= n->m_len;
123 n = n->m_next;
124 }
125 /* be sure to point non-empty mbuf */
126 while (n != NULL && n->m_len == 0)
127 n = n->m_next;
128 if (!n) {
129 m_freem(m);
130 return NULL; /* mbuf chain too short */
131 }
132
133 /*
134 * XXX: This code is flawed because it considers a "writable" mbuf
135 * data region to require all of the following:
136 * (i) mbuf _has_ to have M_EXT set; if it is just a regular
137 * mbuf, it is still not considered "writable."
138 * (ii) since mbuf has M_EXT, the ext_type _has_ to be
139 * EXT_CLUSTER. Anything else makes it non-writable.
140 * (iii) M_WRITABLE() must evaluate true.
141 * Ideally, the requirement should only be (iii).
142 *
143 * If we're writable, we're sure we're writable, because the ref. count
144 * cannot increase from 1, as that would require posession of mbuf
145 * n by someone else (which is impossible). However, if we're _not_
146 * writable, we may eventually become writable )if the ref. count drops
147 * to 1), but we'll fail to notice it unless we re-evaluate
148 * M_WRITABLE(). For now, we only evaluate once at the beginning and
149 * live with this.
150 */
151 /*
152 * XXX: This is dumb. If we're just a regular mbuf with no M_EXT,
153 * then we're not "writable," according to this code.
154 */
155 writable = 0;
156 if ((n->m_flags & M_EXT) == 0 ||
157 (n->m_ext.ext_type == EXT_CLUSTER && M_WRITABLE(n)))
158 writable = 1;
159
160 /*
161 * the target data is on <n, off>.
162 * if we got enough data on the mbuf "n", we're done.
163 */
164 if ((off == 0 || offp) && len <= n->m_len - off && writable)
165 goto ok;
166
167 /*
168 * when len <= n->m_len - off and off != 0, it is a special case.
169 * len bytes from <n, off> sits in single mbuf, but the caller does
170 * not like the starting position (off).
171 * chop the current mbuf into two pieces, set off to 0.
172 */
173 if (len <= n->m_len - off) {
174 o = m_dup1(n, off, n->m_len - off, M_DONTWAIT);
175 if (o == NULL) {
176 m_freem(m);
177 return NULL; /* ENOBUFS */
178 }
179 n->m_len = off;
180 o->m_next = n->m_next;
181 n->m_next = o;
182 n = n->m_next;
183 off = 0;
184 goto ok;
185 }
186
187 /*
188 * we need to take hlen from <n, off> and tlen from <n->m_next, 0>,
189 * and construct contiguous mbuf with m_len == len.
190 * note that hlen + tlen == len, and tlen > 0.
191 */
192 hlen = n->m_len - off;
193 tlen = len - hlen;
194
195 /*
196 * ensure that we have enough trailing data on mbuf chain.
197 * if not, we can do nothing about the chain.
198 */
199 olen = 0;
200 for (o = n->m_next; o != NULL; o = o->m_next)
201 olen += o->m_len;
202 if (hlen + olen < len) {
203 m_freem(m);
204 return NULL; /* mbuf chain too short */
205 }
206
207 /*
208 * easy cases first.
209 * we need to use m_copydata() to get data from <n->m_next, 0>.
210 */
211 if ((off == 0 || offp) && M_TRAILINGSPACE(n) >= tlen
212 && writable) {
213 m_copydata(n->m_next, 0, tlen, mtod(n, caddr_t) + n->m_len);
214 n->m_len += tlen;
215 m_adj(n->m_next, tlen);
216 goto ok;
217 }
218 if ((off == 0 || offp) && M_LEADINGSPACE(n->m_next) >= hlen
219 && writable) {
220 n->m_next->m_data -= hlen;
221 n->m_next->m_len += hlen;
222 bcopy(mtod(n, caddr_t) + off, mtod(n->m_next, caddr_t), hlen);
223 n->m_len -= hlen;
224 n = n->m_next;
225 off = 0;
226 goto ok;
227 }
228
229 /*
230 * now, we need to do the hard way. don't m_copy as there's no room
231 * on both end.
232 */
233 MGET(o, M_DONTWAIT, m->m_type);
234 if (o && len > MLEN) {
235 MCLGET(o, M_DONTWAIT);
236 if ((o->m_flags & M_EXT) == 0) {
237 m_free(o);
238 o = NULL;
239 }
240 }
241 if (!o) {
242 m_freem(m);
243 return NULL; /* ENOBUFS */
244 }
245 /* get hlen from <n, off> into <o, 0> */
246 o->m_len = hlen;
247 bcopy(mtod(n, caddr_t) + off, mtod(o, caddr_t), hlen);
248 n->m_len -= hlen;
249 /* get tlen from <n->m_next, 0> into <o, hlen> */
250 m_copydata(n->m_next, 0, tlen, mtod(o, caddr_t) + o->m_len);
251 o->m_len += tlen;
252 m_adj(n->m_next, tlen);
253 o->m_next = n->m_next;
254 n->m_next = o;
255 n = o;
256 off = 0;
257
258 ok:
259 #ifdef PULLDOWN_DEBUG
260 {
261 struct mbuf *t;
262 printf("after:");
263 for (t = m; t; t = t->m_next)
264 printf("%c%d", t == n ? '*' : ' ', t->m_len);
265 printf(" (off=%d)\n", off);
266 }
267 #endif
268 if (offp)
269 *offp = off;
270 return n;
271 }
272
273 static struct mbuf *
274 m_dup1(struct mbuf *m, int off, int len, int wait)
275 {
276 struct mbuf *n;
277 int l;
278 int copyhdr;
279
280 if (len > MCLBYTES)
281 return NULL;
282 if (off == 0 && (m->m_flags & M_PKTHDR) != 0) {
283 copyhdr = 1;
284 MGETHDR(n, wait, m->m_type);
285 l = MHLEN;
286 } else {
287 copyhdr = 0;
288 MGET(n, wait, m->m_type);
289 l = MLEN;
290 }
291 if (n && len > l) {
292 MCLGET(n, wait);
293 if ((n->m_flags & M_EXT) == 0) {
294 m_free(n);
295 n = NULL;
296 }
297 }
298 if (!n)
299 return NULL;
300
301 if (copyhdr)
302 M_COPY_PKTHDR(n, m);
303 m_copydata(m, off, len, mtod(n, caddr_t));
304 return n;
305 }
306
307 /* Get a packet tag structure along with specified data following. */
308 struct m_tag *
309 m_tag_alloc(u_int32_t cookie, int type, int len, int wait)
310 {
311 struct m_tag *t;
312
313 if (len < 0)
314 return NULL;
315 t = malloc(len + sizeof(struct m_tag), M_PACKET_TAGS, wait);
316 if (t == NULL)
317 return NULL;
318 t->m_tag_id = type;
319 t->m_tag_len = len;
320 t->m_tag_cookie = cookie;
321 return t;
322 }
323
324 /* Free a packet tag. */
325 void
326 m_tag_free(struct m_tag *t)
327 {
328 free(t, M_PACKET_TAGS);
329 }
330
331 /* Prepend a packet tag. */
332 void
333 m_tag_prepend(struct mbuf *m, struct m_tag *t)
334 {
335 KASSERT(m && t, ("m_tag_prepend: null argument, m %p t %p", m, t));
336 SLIST_INSERT_HEAD(&m->m_pkthdr.tags, t, m_tag_link);
337 }
338
339 /* Unlink a packet tag. */
340 void
341 m_tag_unlink(struct mbuf *m, struct m_tag *t)
342 {
343 KASSERT(m && t, ("m_tag_unlink: null argument, m %p t %p", m, t));
344 SLIST_REMOVE(&m->m_pkthdr.tags, t, m_tag, m_tag_link);
345 }
346
347 /* Unlink and free a packet tag. */
348 void
349 m_tag_delete(struct mbuf *m, struct m_tag *t)
350 {
351 KASSERT(m && t, ("m_tag_delete: null argument, m %p t %p", m, t));
352 m_tag_unlink(m, t);
353 m_tag_free(t);
354 }
355
356 /* Unlink and free a packet tag chain, starting from given tag. */
357 void
358 m_tag_delete_chain(struct mbuf *m, struct m_tag *t)
359 {
360 struct m_tag *p, *q;
361
362 KASSERT(m, ("m_tag_delete_chain: null mbuf"));
363 if (t != NULL)
364 p = t;
365 else
366 p = SLIST_FIRST(&m->m_pkthdr.tags);
367 if (p == NULL)
368 return;
369 while ((q = SLIST_NEXT(p, m_tag_link)) != NULL)
370 m_tag_delete(m, q);
371 m_tag_delete(m, p);
372 }
373
374 /* Find a tag, starting from a given position. */
375 struct m_tag *
376 m_tag_locate(struct mbuf *m, u_int32_t cookie, int type, struct m_tag *t)
377 {
378 struct m_tag *p;
379
380 KASSERT(m, ("m_tag_locate: null mbuf"));
381 if (t == NULL)
382 p = SLIST_FIRST(&m->m_pkthdr.tags);
383 else
384 p = SLIST_NEXT(t, m_tag_link);
385 while (p != NULL) {
386 if (p->m_tag_cookie == cookie && p->m_tag_id == type)
387 return p;
388 p = SLIST_NEXT(p, m_tag_link);
389 }
390 return NULL;
391 }
392
393 /* Copy a single tag. */
394 struct m_tag *
395 m_tag_copy(struct m_tag *t)
396 {
397 struct m_tag *p;
398
399 KASSERT(t, ("m_tag_copy: null tag"));
400 p = m_tag_alloc(t->m_tag_cookie, t->m_tag_id, t->m_tag_len, M_NOWAIT);
401 if (p == NULL)
402 return (NULL);
403 bcopy(t + 1, p + 1, t->m_tag_len); /* Copy the data */
404 return p;
405 }
406
407 /*
408 * Copy two tag chains. The destination mbuf (to) loses any attached
409 * tags even if the operation fails. This should not be a problem, as
410 * m_tag_copy_chain() is typically called with a newly-allocated
411 * destination mbuf.
412 */
413 int
414 m_tag_copy_chain(struct mbuf *to, struct mbuf *from)
415 {
416 struct m_tag *p, *t, *tprev = NULL;
417
418 KASSERT(to && from,
419 ("m_tag_copy_chain: null argument, to %p from %p", to, from));
420 m_tag_delete_chain(to, NULL);
421 SLIST_FOREACH(p, &from->m_pkthdr.tags, m_tag_link) {
422 t = m_tag_copy(p);
423 if (t == NULL) {
424 m_tag_delete_chain(to, NULL);
425 return 0;
426 }
427 if (tprev == NULL)
428 SLIST_INSERT_HEAD(&to->m_pkthdr.tags, t, m_tag_link);
429 else {
430 SLIST_INSERT_AFTER(tprev, t, m_tag_link);
431 tprev = t;
432 }
433 }
434 return 1;
435 }
436
437 /* Initialize tags on an mbuf. */
438 void
439 m_tag_init(struct mbuf *m)
440 {
441 SLIST_INIT(&m->m_pkthdr.tags);
442 }
443
444 /* Get first tag in chain. */
445 struct m_tag *
446 m_tag_first(struct mbuf *m)
447 {
448 return SLIST_FIRST(&m->m_pkthdr.tags);
449 }
450
451 /* Get next tag in chain. */
452 struct m_tag *
453 m_tag_next(struct mbuf *m, struct m_tag *t)
454 {
455 return SLIST_NEXT(t, m_tag_link);
456 }
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