ipsec_mbuf.c revision 1.28 
1/*	$NetBSD: ipsec_mbuf.c,v 1.28 2018/05/31 15:34:25 maxv Exp $	*/
2
3/*
4 * Copyright (c) 2002, 2003 Sam Leffler, Errno Consulting
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 *
28 * $FreeBSD: sys/netipsec/ipsec_mbuf.c,v 1.5.2.2 2003/03/28 20:32:53 sam Exp $
29 */
30
31#include <sys/cdefs.h>
32__KERNEL_RCSID(0, "$NetBSD: ipsec_mbuf.c,v 1.28 2018/05/31 15:34:25 maxv Exp $");
33
34/*
35 * IPsec-specific mbuf routines.
36 */
37
38#include <sys/param.h>
39#include <sys/systm.h>
40#include <sys/mbuf.h>
41
42#include <netipsec/ipsec.h>
43#include <netipsec/ipsec_var.h>
44#include <netipsec/ipsec_private.h>
45
46/*
47 * Create a writable copy of the mbuf chain.  While doing this
48 * we compact the chain with a goal of producing a chain with
49 * at most two mbufs.  The second mbuf in this chain is likely
50 * to be a cluster.  The primary purpose of this work is to create
51 * a writable packet for encryption, compression, etc.  The
52 * secondary goal is to linearize the data so the data can be
53 * passed to crypto hardware in the most efficient manner possible.
54 */
55struct mbuf *
56m_clone(struct mbuf *m0)
57{
58	struct mbuf *m, *mprev;
59	struct mbuf *n, *mfirst, *mlast;
60	int len, off;
61
62	KASSERT(m0 != NULL);
63
64	mprev = NULL;
65	for (m = m0; m != NULL; m = mprev->m_next) {
66		/*
67		 * Regular mbufs are ignored unless there's a cluster
68		 * in front of it that we can use to coalesce.
69		 */
70		if ((m->m_flags & M_EXT) == 0) {
71			if (mprev && (mprev->m_flags & M_EXT) &&
72			    m->m_len <= M_TRAILINGSPACE(mprev)) {
73				memcpy(mtod(mprev, char *) + mprev->m_len,
74				    mtod(m, char *), m->m_len);
75				mprev->m_len += m->m_len;
76				mprev->m_next = m_free(m);
77				IPSEC_STATINC(IPSEC_STAT_MBCOALESCED);
78			} else {
79				mprev = m;
80			}
81			continue;
82		}
83
84		/*
85		 * Writable mbufs are left alone.
86		 */
87		if (!M_READONLY(m)) {
88			mprev = m;
89			continue;
90		}
91
92		/*
93		 * Not writable, replace with a copy or coalesce with
94		 * the previous mbuf if possible (since we have to copy
95		 * it anyway, we try to reduce the number of mbufs and
96		 * clusters so that future work is easier).
97		 */
98
99		/* We only coalesce into a cluster. */
100		if (mprev != NULL && (mprev->m_flags & M_EXT) &&
101		    m->m_len <= M_TRAILINGSPACE(mprev)) {
102			memcpy(mtod(mprev, char *) + mprev->m_len,
103			    mtod(m, char *), m->m_len);
104			mprev->m_len += m->m_len;
105			mprev->m_next = m_free(m);
106			IPSEC_STATINC(IPSEC_STAT_CLCOALESCED);
107			continue;
108		}
109
110		/*
111		 * Allocate new space to hold the copy...
112		 */
113		if (mprev == NULL && (m->m_flags & M_PKTHDR)) {
114			MGETHDR(n, M_DONTWAIT, m->m_type);
115			if (n == NULL) {
116				m_freem(m0);
117				return NULL;
118			}
119			M_MOVE_PKTHDR(n, m);
120			MCLGET(n, M_DONTWAIT);
121			if ((n->m_flags & M_EXT) == 0) {
122				m_free(n);
123				m_freem(m0);
124				return NULL;
125			}
126		} else {
127			n = m_getcl(M_DONTWAIT, m->m_type, m->m_flags);
128			if (n == NULL) {
129				m_freem(m0);
130				return NULL;
131			}
132		}
133
134		/*
135		 * ... and copy the data.  We deal with jumbo mbufs
136		 * (i.e. m_len > MCLBYTES) by splitting them into
137		 * clusters.  We could just malloc a buffer and make
138		 * it external but too many device drivers don't know
139		 * how to break up the non-contiguous memory when
140		 * doing DMA.
141		 */
142		len = m->m_len;
143		off = 0;
144		mfirst = n;
145		mlast = NULL;
146		for (;;) {
147			const int cc = min(len, MCLBYTES);
148			memcpy(mtod(n, char *), mtod(m, char *) + off, cc);
149			n->m_len = cc;
150			if (mlast != NULL)
151				mlast->m_next = n;
152			mlast = n;
153			IPSEC_STATINC(IPSEC_STAT_CLCOPIED);
154
155			len -= cc;
156			if (len <= 0)
157				break;
158			off += cc;
159
160			n = m_getcl(M_DONTWAIT, m->m_type, m->m_flags);
161			if (n == NULL) {
162				m_freem(mfirst);
163				m_freem(m0);
164				return NULL;
165			}
166		}
167		n->m_next = m->m_next;
168		if (mprev == NULL)
169			m0 = mfirst;		/* new head of chain */
170		else
171			mprev->m_next = mfirst;	/* replace old mbuf */
172		m_free(m);			/* release old mbuf */
173		mprev = mfirst;
174	}
175
176	return m0;
177}
178
179/*
180 * Make space for a new header of length hlen at skip bytes
181 * into the packet.  When doing this we allocate new mbufs only
182 * when absolutely necessary.  The mbuf where the new header
183 * is to go is returned together with an offset into the mbuf.
184 * If NULL is returned then the mbuf chain may have been modified;
185 * the caller is assumed to always free the chain.
186 */
187struct mbuf *
188m_makespace(struct mbuf *m0, int skip, int hlen, int *off)
189{
190	struct mbuf *m;
191	unsigned remain;
192
193	KASSERT(m0 != NULL);
194	KASSERT(m0->m_flags & M_PKTHDR);
195	KASSERTMSG(hlen < MHLEN, "hlen too big: %u", hlen);
196
197	for (m = m0; m && skip > m->m_len; m = m->m_next)
198		skip -= m->m_len;
199	if (m == NULL)
200		return NULL;
201
202	/*
203	 * At this point skip is the offset into the mbuf m
204	 * where the new header should be placed.  Figure out
205	 * if there's space to insert the new header.  If so,
206	 * and copying the remainder makes sense then do so.
207	 * Otherwise insert a new mbuf in the chain, splitting
208	 * the contents of m as needed.
209	 */
210	remain = m->m_len - skip;		/* data to move */
211	if (hlen > M_TRAILINGSPACE(m)) {
212		struct mbuf *n0, *n, **np;
213		int todo, len, done, alloc;
214
215		n0 = NULL;
216		np = &n0;
217		alloc = 0;
218		done = 0;
219		todo = remain;
220		while (todo > 0) {
221			if (todo > MHLEN) {
222				n = m_getcl(M_DONTWAIT, m->m_type, 0);
223				len = MCLBYTES;
224			} else {
225				n = m_get(M_DONTWAIT, m->m_type);
226				len = MHLEN;
227			}
228			if (n == NULL) {
229				m_freem(n0);
230				return NULL;
231			}
232			*np = n;
233			np = &n->m_next;
234			alloc++;
235			len = min(todo, len);
236			memcpy(n->m_data, mtod(m, char *) + skip + done, len);
237			n->m_len = len;
238			done += len;
239			todo -= len;
240		}
241
242		if (hlen <= M_TRAILINGSPACE(m) + remain) {
243			m->m_len = skip + hlen;
244			*off = skip;
245			if (n0 != NULL) {
246				*np = m->m_next;
247				m->m_next = n0;
248			}
249		} else {
250			n = m_get(M_DONTWAIT, m->m_type);
251			if (n == NULL) {
252				m_freem(n0);
253				return NULL;
254			}
255			alloc++;
256
257			if ((n->m_next = n0) == NULL)
258				np = &n->m_next;
259			n0 = n;
260
261			*np = m->m_next;
262			m->m_next = n0;
263
264			n->m_len = hlen;
265			m->m_len = skip;
266
267			m = n;			/* header is at front ... */
268			*off = 0;		/* ... of new mbuf */
269		}
270
271		IPSEC_STATADD(IPSEC_STAT_MBINSERTED, alloc);
272	} else {
273		/*
274		 * Copy the remainder to the back of the mbuf
275		 * so there's space to write the new header.
276		 */
277		/* XXX can this be memcpy? does it handle overlap? */
278		memmove(mtod(m, char *) + skip + hlen,
279			mtod(m, char *) + skip, remain);
280		m->m_len += hlen;
281		*off = skip;
282	}
283
284	m0->m_pkthdr.len += hlen;		/* adjust packet length */
285	return m;
286}
287
288/*
289 * m_pad(m, n) pads <m> with <n> bytes at the end. The packet header
290 * length is updated, and a pointer to the first byte of the padding
291 * (which is guaranteed to be all in one mbuf) is returned.
292 */
293void *
294m_pad(struct mbuf *m, int n)
295{
296	register struct mbuf *m0, *m1;
297	register int len, pad;
298	void *retval;
299
300	if (__predict_false(n > MLEN)) {
301		panic("%s: %d > MLEN", __func__, n);
302	}
303	KASSERT(m->m_flags & M_PKTHDR);
304
305	len = m->m_pkthdr.len;
306	pad = n;
307	m0 = m;
308
309	while (m0->m_len < len) {
310		KASSERTMSG(m0->m_next != NULL,
311		    "m0 null, len %u m_len %u", len, m0->m_len);
312		len -= m0->m_len;
313		m0 = m0->m_next;
314	}
315
316	if (m0->m_len != len) {
317		IPSECLOG(LOG_DEBUG,
318		    "length mismatch (should be %d instead of %d)\n",
319		    m->m_pkthdr.len, m->m_pkthdr.len + m0->m_len - len);
320		m_freem(m);
321		return NULL;
322	}
323
324	/* Check for zero-length trailing mbufs, and find the last one. */
325	for (m1 = m0; m1->m_next; m1 = m1->m_next) {
326		if (m1->m_next->m_len != 0) {
327			IPSECLOG(LOG_DEBUG,
328			    "length mismatch (should be %d instead of %d)\n",
329			    m->m_pkthdr.len,
330			    m->m_pkthdr.len + m1->m_next->m_len);
331			m_freem(m);
332			return NULL;
333		}
334
335		m0 = m1->m_next;
336	}
337
338	if (pad > M_TRAILINGSPACE(m0)) {
339		/* Add an mbuf to the chain. */
340		MGET(m1, M_DONTWAIT, MT_DATA);
341		if (m1 == NULL) {
342			m_freem(m);
343			IPSECLOG(LOG_DEBUG, "unable to get extra mbuf\n");
344			return NULL;
345		}
346
347		m0->m_next = m1;
348		m0 = m1;
349		m0->m_len = 0;
350	}
351
352	retval = m0->m_data + m0->m_len;
353	m0->m_len += pad;
354	m->m_pkthdr.len += pad;
355
356	return retval;
357}
358
359/*
360 * Remove hlen data at offset skip in the packet.  This is used by
361 * the protocols strip protocol headers and associated data (e.g. IV,
362 * authenticator) on input.
363 */
364int
365m_striphdr(struct mbuf *m, int skip, int hlen)
366{
367	struct mbuf *m1;
368	int roff;
369
370	KASSERT(m->m_flags & M_PKTHDR);
371
372	/* Find beginning of header */
373	m1 = m_getptr(m, skip, &roff);
374	if (m1 == NULL)
375		return EINVAL;
376
377	/* Remove the header and associated data from the mbuf. */
378	if (roff == 0) {
379		/* The header was at the beginning of the mbuf */
380		IPSEC_STATINC(IPSEC_STAT_INPUT_FRONT);
381		m_adj(m1, hlen);
382		if (m1 != m)
383			m->m_pkthdr.len -= hlen;
384	} else if (roff + hlen >= m1->m_len) {
385		struct mbuf *mo;
386		int adjlen;
387
388		/*
389		 * Part or all of the header is at the end of this mbuf,
390		 * so first let's remove the remainder of the header from
391		 * the beginning of the remainder of the mbuf chain, if any.
392		 */
393		IPSEC_STATINC(IPSEC_STAT_INPUT_END);
394		if (roff + hlen > m1->m_len) {
395			adjlen = roff + hlen - m1->m_len;
396
397			/* Adjust the next mbuf by the remainder */
398			m_adj(m1->m_next, adjlen);
399
400			/* The second mbuf is guaranteed not to have a pkthdr... */
401			m->m_pkthdr.len -= adjlen;
402		}
403
404		/* Now, let's unlink the mbuf chain for a second...*/
405		mo = m1->m_next;
406		m1->m_next = NULL;
407
408		/* ...and trim the end of the first part of the chain...sick */
409		adjlen = m1->m_len - roff;
410		m_adj(m1, -adjlen);
411		if (m1 != m)
412			m->m_pkthdr.len -= adjlen;
413
414		/* Finally, let's relink */
415		m1->m_next = mo;
416	} else {
417		/*
418		 * The header lies in the "middle" of the mbuf; copy
419		 * the remainder of the mbuf down over the header.
420		 */
421		IPSEC_STATINC(IPSEC_STAT_INPUT_MIDDLE);
422		memmove(mtod(m1, u_char *) + roff,
423		      mtod(m1, u_char *) + roff + hlen,
424		      m1->m_len - (roff + hlen));
425		m1->m_len -= hlen;
426		m->m_pkthdr.len -= hlen;
427	}
428
429	return 0;
430}
431