xref: /freebsd/sys/sys/mbuf.h (revision c4f02a891fe62fe1277c89859922804ea2c27bcd)
1 /*-
2  * Copyright (c) 1982, 1986, 1988, 1993
3  *	The Regents of the University of California.  All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. All advertising materials mentioning features or use of this software
14  *    must display the following acknowledgement:
15  *	This product includes software developed by the University of
16  *	California, Berkeley and its contributors.
17  * 4. Neither the name of the University 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 REGENTS 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 REGENTS 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  *	@(#)mbuf.h	8.5 (Berkeley) 2/19/95
34  * $FreeBSD$
35  */
36 
37 #ifndef _SYS_MBUF_H_
38 #define	_SYS_MBUF_H_
39 
40 #include <sys/queue.h>
41 
42 /*
43  * Mbufs are of a single size, MSIZE (sys/param.h), which
44  * includes overhead.  An mbuf may add a single "mbuf cluster" of size
45  * MCLBYTES (also in sys/param.h), which has no additional overhead
46  * and is used instead of the internal data area; this is done when
47  * at least MINCLSIZE of data must be stored.  Additionally, it is possible
48  * to allocate a separate buffer externally and attach it to the mbuf in
49  * a way similar to that of mbuf clusters.
50  */
51 #define	MLEN		(MSIZE - sizeof(struct m_hdr))	/* normal data len */
52 #define	MHLEN		(MLEN - sizeof(struct pkthdr))	/* data len w/pkthdr */
53 #define	MINCLSIZE	(MHLEN + 1)	/* smallest amount to put in cluster */
54 #define	M_MAXCOMPRESS	(MHLEN / 2)	/* max amount to copy for compression */
55 
56 #ifdef _KERNEL
57 /*-
58  * Macros for type conversion:
59  * mtod(m, t)	-- Convert mbuf pointer to data pointer of correct type.
60  * dtom(x)	-- Convert data pointer within mbuf to mbuf pointer (XXX).
61  */
62 #define	mtod(m, t)	((t)((m)->m_data))
63 #define	dtom(x)		((struct mbuf *)((intptr_t)(x) & ~(MSIZE-1)))
64 #endif /* _KERNEL */
65 
66 /*
67  * Header present at the beginning of every mbuf.
68  */
69 struct m_hdr {
70 	struct	mbuf *mh_next;		/* next buffer in chain */
71 	struct	mbuf *mh_nextpkt;	/* next chain in queue/record */
72 	caddr_t	mh_data;		/* location of data */
73 	int	mh_len;			/* amount of data in this mbuf */
74 	int	mh_flags;		/* flags; see below */
75 	short	mh_type;		/* type of data in this mbuf */
76 };
77 
78 /*
79  * Packet tag structure (see below for details).
80  */
81 struct m_tag {
82 	SLIST_ENTRY(m_tag)	m_tag_link;	/* List of packet tags */
83 	u_int16_t		m_tag_id;	/* Tag ID */
84 	u_int16_t		m_tag_len;	/* Length of data */
85 	u_int32_t		m_tag_cookie;	/* ABI/Module ID */
86 };
87 
88 /*
89  * Record/packet header in first mbuf of chain; valid only if M_PKTHDR is set.
90  */
91 struct pkthdr {
92 	struct	ifnet *rcvif;		/* rcv interface */
93 	int	len;			/* total packet length */
94 	/* variables for ip and tcp reassembly */
95 	void	*header;		/* pointer to packet header */
96 	/* variables for hardware checksum */
97 	int	csum_flags;		/* flags regarding checksum */
98 	int	csum_data;		/* data field used by csum routines */
99 	SLIST_HEAD(packet_tags, m_tag) tags; /* list of packet tags */
100 };
101 
102 /*
103  * Description of external storage mapped into mbuf; valid only if M_EXT is set.
104  */
105 struct m_ext {
106 	caddr_t	ext_buf;		/* start of buffer */
107 	void	(*ext_free)		/* free routine if not the usual */
108 		    (void *, void *);
109 	void	*ext_args;		/* optional argument pointer */
110 	u_int	ext_size;		/* size of buffer, for ext_free */
111 	u_int	*ref_cnt;		/* pointer to ref count info */
112 	int	ext_type;		/* type of external storage */
113 };
114 
115 /*
116  * The core of the mbuf object along with some shortcut defines for
117  * practical purposes.
118  */
119 struct mbuf {
120 	struct	m_hdr m_hdr;
121 	union {
122 		struct {
123 			struct	pkthdr MH_pkthdr;	/* M_PKTHDR set */
124 			union {
125 				struct	m_ext MH_ext;	/* M_EXT set */
126 				char	MH_databuf[MHLEN];
127 			} MH_dat;
128 		} MH;
129 		char	M_databuf[MLEN];		/* !M_PKTHDR, !M_EXT */
130 	} M_dat;
131 };
132 #define	m_next		m_hdr.mh_next
133 #define	m_len		m_hdr.mh_len
134 #define	m_data		m_hdr.mh_data
135 #define	m_type		m_hdr.mh_type
136 #define	m_flags		m_hdr.mh_flags
137 #define	m_nextpkt	m_hdr.mh_nextpkt
138 #define	m_act		m_nextpkt
139 #define	m_pkthdr	M_dat.MH.MH_pkthdr
140 #define	m_ext		M_dat.MH.MH_dat.MH_ext
141 #define	m_pktdat	M_dat.MH.MH_dat.MH_databuf
142 #define	m_dat		M_dat.M_databuf
143 
144 /*
145  * mbuf flags.
146  */
147 #define	M_EXT		0x0001	/* has associated external storage */
148 #define	M_PKTHDR	0x0002	/* start of record */
149 #define	M_EOR		0x0004	/* end of record */
150 #define	M_RDONLY	0x0008	/* associated data is marked read-only */
151 #define	M_PROTO1	0x0010	/* protocol-specific */
152 #define	M_PROTO2	0x0020	/* protocol-specific */
153 #define	M_PROTO3	0x0040	/* protocol-specific */
154 #define	M_PROTO4	0x0080	/* protocol-specific */
155 #define	M_PROTO5	0x0100	/* protocol-specific */
156 #define	M_FREELIST	0x8000	/* mbuf is on the free list */
157 
158 /*
159  * mbuf pkthdr flags (also stored in m_flags).
160  */
161 #define	M_BCAST		0x0200	/* send/received as link-level broadcast */
162 #define	M_MCAST		0x0400	/* send/received as link-level multicast */
163 #define	M_FRAG		0x0800	/* packet is a fragment of a larger packet */
164 #define	M_FIRSTFRAG	0x1000	/* packet is first fragment */
165 #define	M_LASTFRAG	0x2000	/* packet is last fragment */
166 
167 /*
168  * External buffer types: identify ext_buf type.
169  */
170 #define	EXT_CLUSTER	1	/* mbuf cluster */
171 #define	EXT_SFBUF	2	/* sendfile(2)'s sf_bufs */
172 #define	EXT_NET_DRV	100	/* custom ext_buf provided by net driver(s) */
173 #define	EXT_MOD_TYPE	200	/* custom module's ext_buf type */
174 #define	EXT_DISPOSABLE	300	/* can throw this buffer away w/page flipping */
175 #define	EXT_EXTREF	400	/* has externally maintained ref_cnt ptr*/
176 
177 /*
178  * Flags copied when copying m_pkthdr.
179  */
180 #define	M_COPYFLAGS	(M_PKTHDR|M_EOR|M_RDONLY|M_PROTO1|M_PROTO1|M_PROTO2|\
181 			    M_PROTO3|M_PROTO4|M_PROTO5|M_BCAST|M_MCAST|\
182 			    M_FRAG|M_FIRSTFRAG|M_LASTFRAG)
183 
184 /*
185  * Flags indicating hw checksum support and sw checksum requirements.
186  */
187 #define	CSUM_IP			0x0001		/* will csum IP */
188 #define	CSUM_TCP		0x0002		/* will csum TCP */
189 #define	CSUM_UDP		0x0004		/* will csum UDP */
190 #define	CSUM_IP_FRAGS		0x0008		/* will csum IP fragments */
191 #define	CSUM_FRAGMENT		0x0010		/* will do IP fragmentation */
192 
193 #define	CSUM_IP_CHECKED		0x0100		/* did csum IP */
194 #define	CSUM_IP_VALID		0x0200		/*   ... the csum is valid */
195 #define	CSUM_DATA_VALID		0x0400		/* csum_data field is valid */
196 #define	CSUM_PSEUDO_HDR		0x0800		/* csum_data has pseudo hdr */
197 
198 #define	CSUM_DELAY_DATA		(CSUM_TCP | CSUM_UDP)
199 #define	CSUM_DELAY_IP		(CSUM_IP)	/* XXX add ipv6 here too? */
200 
201 /*
202  * mbuf types.
203  */
204 #define	MT_NOTMBUF	0	/* USED INTERNALLY ONLY! Object is not mbuf */
205 #define	MT_DATA		1	/* dynamic (data) allocation */
206 #define	MT_HEADER	2	/* packet header */
207 #if 0
208 #define	MT_SOCKET	3	/* socket structure */
209 #define	MT_PCB		4	/* protocol control block */
210 #define	MT_RTABLE	5	/* routing tables */
211 #define	MT_HTABLE	6	/* IMP host tables */
212 #define	MT_ATABLE	7	/* address resolution tables */
213 #endif
214 #define	MT_SONAME	8	/* socket name */
215 #if 0
216 #define	MT_SOOPTS	10	/* socket options */
217 #endif
218 #define	MT_FTABLE	11	/* fragment reassembly header */
219 #if 0
220 #define	MT_RIGHTS	12	/* access rights */
221 #define	MT_IFADDR	13	/* interface address */
222 #endif
223 #define	MT_TAG		13	/* volatile metadata associated to pkts */
224 #define	MT_CONTROL	14	/* extra-data protocol message */
225 #define	MT_OOBDATA	15	/* expedited data  */
226 #define	MT_NTYPES	16	/* number of mbuf types for mbtypes[] */
227 
228 /*
229  * Mbuf and cluster allocation statistics PCPU structure.
230  */
231 struct mbpstat {
232 	u_long	mb_mbfree;
233 	u_long	mb_mbbucks;
234 	u_long	mb_clfree;
235 	u_long	mb_clbucks;
236 	long	mb_mbtypes[MT_NTYPES];
237 	short	mb_active;
238 };
239 
240 /*
241  * General mbuf allocator statistics structure.
242  * XXX: Modifications of these are not protected by any mutex locks nor by
243  * any atomic() manipulations.  As a result, we may occasionally lose
244  * a count or two.  Luckily, not all of these fields are modified at all
245  * and remain static, and those that are manipulated are only manipulated
246  * in failure situations, which do not occur (hopefully) very often.
247  */
248 struct mbstat {
249 	u_long	m_drops;	/* times failed to allocate */
250 	u_long	m_wait;		/* times succesfully returned from wait */
251 	u_long	m_drain;	/* times drained protocols for space */
252 	u_long	m_mcfail;	/* XXX: times m_copym failed */
253 	u_long	m_mpfail;	/* XXX: times m_pullup failed */
254 	u_long	m_msize;	/* length of an mbuf */
255 	u_long	m_mclbytes;	/* length of an mbuf cluster */
256 	u_long	m_minclsize;	/* min length of data to allocate a cluster */
257 	u_long	m_mlen;		/* length of data in an mbuf */
258 	u_long	m_mhlen;	/* length of data in a header mbuf */
259 	u_int	m_mbperbuck;	/* number of mbufs per "bucket" */
260 	u_int	m_clperbuck;	/* number of clusters per "bucket" */
261 	/* Number of mbtypes (gives # elems in mbpstat's mb_mbtypes[] array: */
262 	short	m_numtypes;
263 };
264 
265 /*
266  * Flags specifying how an allocation should be made.
267  * M_DONTWAIT means "don't block if nothing is available" whereas
268  * M_TRYWAIT means "block for mbuf_wait ticks at most if nothing is
269  * available."
270  */
271 #define	M_DONTWAIT	0x4		/* don't conflict with M_NOWAIT */
272 #define	M_TRYWAIT	0x8		/* or M_WAITOK */
273 #define	M_WAIT		M_TRYWAIT	/* XXX: Deprecated. */
274 #define	MBTOM(how)	((how) & M_TRYWAIT ? M_WAITOK : M_NOWAIT)
275 
276 #ifdef _KERNEL
277 /*-
278  * mbuf external reference count management macros.
279  *
280  * MEXT_IS_REF(m): true if (m) is not the only mbuf referencing
281  *     the external buffer ext_buf.
282  *
283  * MEXT_REM_REF(m): remove reference to m_ext object.
284  *
285  * MEXT_ADD_REF(m): add reference to m_ext object already
286  *     referred to by (m).
287  */
288 #define	MEXT_IS_REF(m)	(*((m)->m_ext.ref_cnt) > 1)
289 
290 #define	MEXT_REM_REF(m) do {						\
291 	KASSERT(*((m)->m_ext.ref_cnt) > 0, ("m_ext refcnt < 0"));	\
292 	atomic_subtract_int((m)->m_ext.ref_cnt, 1);			\
293 } while(0)
294 
295 #define	MEXT_ADD_REF(m)	atomic_add_int((m)->m_ext.ref_cnt, 1)
296 
297 /*
298  * mbuf, cluster, and external object allocation macros
299  * (for compatibility purposes).
300  */
301 /* NB: M_COPY_PKTHDR is deprecated, use M_MOVE_PKTHDR or m_dup_pktdr */
302 #define	M_MOVE_PKTHDR(to, from)	m_move_pkthdr((to), (from))
303 #define	m_getclr(how, type)	m_get_clrd((how), (type))
304 #define	MGET(m, how, type)	((m) = m_get((how), (type)))
305 #define	MGETHDR(m, how, type)	((m) = m_gethdr((how), (type)))
306 #define	MCLGET(m, how)		m_clget((m), (how))
307 #define	MEXTADD(m, buf, size, free, args, flags, type) 			\
308     m_extadd((m), (caddr_t)(buf), (size), (free), (args), (flags), (type))
309 
310 /*
311  * MEXTFREE(m): disassociate (and possibly free) an external object from (m).
312  *
313  * If the atomic_cmpset_int() returns 0, then we effectively do nothing
314  * in terms of "cleaning up" (freeing the ext buf and ref. counter) as
315  * this means that either there are still references, or another thread
316  * is taking care of the clean-up.
317  */
318 #define	MEXTFREE(m) do {						\
319 	struct mbuf *_mb = (m);						\
320 									\
321 	MEXT_REM_REF(_mb);						\
322 	if (atomic_cmpset_int(_mb->m_ext.ref_cnt, 0, 1))		\
323 		_mext_free(_mb);					\
324 	_mb->m_flags &= ~M_EXT;						\
325 } while (0)
326 
327 /*
328  * Evaluate TRUE if it's safe to write to the mbuf m's data region (this
329  * can be both the local data payload, or an external buffer area,
330  * depending on whether M_EXT is set).
331  */
332 #define	M_WRITABLE(m)	(!((m)->m_flags & M_RDONLY) && (!((m)->m_flags  \
333 			    & M_EXT) || !MEXT_IS_REF(m)))
334 
335 /*
336  * Check if the supplied mbuf has a packet header, or else panic.
337  */
338 #define M_ASSERTPKTHDR(m)				\
339 	KASSERT(m != NULL && m->m_flags & M_PKTHDR,	\
340 		("%s: no mbuf packet header!", __func__))
341 
342 /*
343  * Set the m_data pointer of a newly-allocated mbuf (m_get/MGET) to place
344  * an object of the specified size at the end of the mbuf, longword aligned.
345  */
346 #define	M_ALIGN(m, len) do {						\
347 	(m)->m_data += (MLEN - (len)) & ~(sizeof(long) - 1);		\
348 } while (0)
349 
350 /*
351  * As above, for mbufs allocated with m_gethdr/MGETHDR
352  * or initialized by M_COPY_PKTHDR.
353  */
354 #define	MH_ALIGN(m, len) do {						\
355 	(m)->m_data += (MHLEN - (len)) & ~(sizeof(long) - 1);		\
356 } while (0)
357 
358 /*
359  * Compute the amount of space available
360  * before the current start of data in an mbuf.
361  *
362  * The M_WRITABLE() is a temporary, conservative safety measure: the burden
363  * of checking writability of the mbuf data area rests solely with the caller.
364  */
365 #define	M_LEADINGSPACE(m)						\
366 	((m)->m_flags & M_EXT ?						\
367 	    (M_WRITABLE(m) ? (m)->m_data - (m)->m_ext.ext_buf : 0):	\
368 	    (m)->m_flags & M_PKTHDR ? (m)->m_data - (m)->m_pktdat :	\
369 	    (m)->m_data - (m)->m_dat)
370 
371 /*
372  * Compute the amount of space available
373  * after the end of data in an mbuf.
374  *
375  * The M_WRITABLE() is a temporary, conservative safety measure: the burden
376  * of checking writability of the mbuf data area rests solely with the caller.
377  */
378 #define	M_TRAILINGSPACE(m)						\
379 	((m)->m_flags & M_EXT ?						\
380 	    (M_WRITABLE(m) ? (m)->m_ext.ext_buf + (m)->m_ext.ext_size	\
381 		- ((m)->m_data + (m)->m_len) : 0) :			\
382 	    &(m)->m_dat[MLEN] - ((m)->m_data + (m)->m_len))
383 
384 /*
385  * Arrange to prepend space of size plen to mbuf m.
386  * If a new mbuf must be allocated, how specifies whether to wait.
387  * If the allocation fails, the original mbuf chain is freed and m is
388  * set to NULL.
389  */
390 #define	M_PREPEND(m, plen, how) do {					\
391 	struct mbuf **_mmp = &(m);					\
392 	struct mbuf *_mm = *_mmp;					\
393 	int _mplen = (plen);						\
394 	int __mhow = (how);						\
395 									\
396 	if (M_LEADINGSPACE(_mm) >= _mplen) {				\
397 		_mm->m_data -= _mplen;					\
398 		_mm->m_len += _mplen;					\
399 	} else								\
400 		_mm = m_prepend(_mm, _mplen, __mhow);			\
401 	if (_mm != NULL && _mm->m_flags & M_PKTHDR)			\
402 		_mm->m_pkthdr.len += _mplen;				\
403 	*_mmp = _mm;							\
404 } while (0)
405 
406 /*
407  * Change mbuf to new type.
408  * This is a relatively expensive operation and should be avoided.
409  */
410 #define	MCHTYPE(m, t)	m_chtype((m), (t))
411 
412 /* Length to m_copy to copy all. */
413 #define	M_COPYALL	1000000000
414 
415 /* Compatibility with 4.3. */
416 #define	m_copy(m, o, l)	m_copym((m), (o), (l), M_DONTWAIT)
417 
418 extern	int max_datalen;		/* MHLEN - max_hdr */
419 extern	int max_hdr;			/* Largest link + protocol header */
420 extern	int max_linkhdr;		/* Largest link-level header */
421 extern	int max_protohdr;		/* Largest protocol header */
422 extern	struct mbstat mbstat;		/* General mbuf stats/infos */
423 extern	int nmbclusters;		/* Maximum number of clusters */
424 extern	int nmbcnt;			/* Scale kmem_map for counter space */
425 extern	int nmbufs;			/* Maximum number of mbufs */
426 extern	int nsfbufs;			/* Number of sendfile(2) bufs */
427 
428 void		 _mext_free(struct mbuf *);
429 void		 m_adj(struct mbuf *, int);
430 void		 m_cat(struct mbuf *, struct mbuf *);
431 void		 m_chtype(struct mbuf *, short);
432 void		 m_clget(struct mbuf *, int);
433 void		 m_extadd(struct mbuf *, caddr_t, u_int,
434 		    void (*)(void *, void *), void *, int, int);
435 void		 m_copyback(struct mbuf *, int, int, caddr_t);
436 void		 m_copydata(const struct mbuf *, int, int, caddr_t);
437 struct	mbuf	*m_copym(struct mbuf *, int, int, int);
438 struct	mbuf	*m_copypacket(struct mbuf *, int);
439 void		 m_copy_pkthdr(struct mbuf *, struct mbuf *);
440 struct	mbuf	*m_defrag(struct mbuf *, int);
441 struct	mbuf	*m_devget(char *, int, int, struct ifnet *,
442 		    void (*)(char *, caddr_t, u_int));
443 struct	mbuf	*m_dup(struct mbuf *, int);
444 int		 m_dup_pkthdr(struct mbuf *, struct mbuf *, int);
445 u_int		 m_fixhdr(struct mbuf *);
446 struct	mbuf	*m_fragment(struct mbuf *, int, int);
447 struct	mbuf	*m_free(struct mbuf *);
448 void		 m_freem(struct mbuf *);
449 struct	mbuf	*m_get(int, short);
450 struct	mbuf	*m_get_clrd(int, short);
451 struct	mbuf	*m_getcl(int, short, int);
452 struct	mbuf	*m_gethdr(int, short);
453 struct	mbuf	*m_gethdr_clrd(int, short);
454 struct	mbuf	*m_getm(struct mbuf *, int, int, short);
455 u_int		 m_length(struct mbuf *, struct mbuf **);
456 void		 m_move_pkthdr(struct mbuf *, struct mbuf *);
457 struct	mbuf	*m_prepend(struct mbuf *, int, int);
458 void		 m_print(const struct mbuf *);
459 struct	mbuf	*m_pulldown(struct mbuf *, int, int, int *);
460 struct	mbuf	*m_pullup(struct mbuf *, int);
461 struct	mbuf	*m_split(struct mbuf *, int, int);
462 
463 /*
464  * Packets may have annotations attached by affixing a list
465  * of "packet tags" to the pkthdr structure.  Packet tags are
466  * dynamically allocated semi-opaque data structures that have
467  * a fixed header (struct m_tag) that specifies the size of the
468  * memory block and a <cookie,type> pair that identifies it.
469  * The cookie is a 32-bit unique unsigned value used to identify
470  * a module or ABI.  By convention this value is chose as the
471  * date+time that the module is created, expressed as the number of
472  * seconds since the epoch (e.g. using date -u +'%s').  The type value
473  * is an ABI/module-specific value that identifies a particular annotation
474  * and is private to the module.  For compatibility with systems
475  * like openbsd that define packet tags w/o an ABI/module cookie,
476  * the value PACKET_ABI_COMPAT is used to implement m_tag_get and
477  * m_tag_find compatibility shim functions and several tag types are
478  * defined below.  Users that do not require compatibility should use
479  * a private cookie value so that packet tag-related definitions
480  * can be maintained privately.
481  *
482  * Note that the packet tag returned by m_tag_allocate has the default
483  * memory alignment implemented by malloc.  To reference private data
484  * one can use a construct like:
485  *
486  *	struct m_tag *mtag = m_tag_allocate(...);
487  *	struct foo *p = (struct foo *)(mtag+1);
488  *
489  * if the alignment of struct m_tag is sufficient for referencing members
490  * of struct foo.  Otherwise it is necessary to embed struct m_tag within
491  * the private data structure to insure proper alignment; e.g.
492  *
493  *	struct foo {
494  *		struct m_tag	tag;
495  *		...
496  *	};
497  *	struct foo *p = (struct foo *) m_tag_allocate(...);
498  *	struct m_tag *mtag = &p->tag;
499  */
500 
501 #define	PACKET_TAG_NONE				0  /* Nadda */
502 
503 /* Packet tag for use with PACKET_ABI_COMPAT */
504 #define	PACKET_TAG_IPSEC_IN_DONE		1  /* IPsec applied, in */
505 #define	PACKET_TAG_IPSEC_OUT_DONE		2  /* IPsec applied, out */
506 #define	PACKET_TAG_IPSEC_IN_CRYPTO_DONE		3  /* NIC IPsec crypto done */
507 #define	PACKET_TAG_IPSEC_OUT_CRYPTO_NEEDED	4  /* NIC IPsec crypto req'ed */
508 #define	PACKET_TAG_IPSEC_IN_COULD_DO_CRYPTO	5  /* NIC notifies IPsec */
509 #define	PACKET_TAG_IPSEC_PENDING_TDB		6  /* Reminder to do IPsec */
510 #define	PACKET_TAG_BRIDGE			7  /* Bridge processing done */
511 #define	PACKET_TAG_GIF				8  /* GIF processing done */
512 #define	PACKET_TAG_GRE				9  /* GRE processing done */
513 #define	PACKET_TAG_IN_PACKET_CHECKSUM		10 /* NIC checksumming done */
514 #define	PACKET_TAG_ENCAP			11 /* Encap.  processing */
515 #define	PACKET_TAG_IPSEC_SOCKET			12 /* IPSEC socket ref */
516 #define	PACKET_TAG_IPSEC_HISTORY		13 /* IPSEC history */
517 #define	PACKET_TAG_IPV6_INPUT			14 /* IPV6 input processing */
518 
519 /*
520  * As a temporary and low impact solution to replace the even uglier
521  * approach used so far in some parts of the network stack (which relies
522  * on global variables), packet tag-like annotations are stored in MT_TAG
523  * mbufs (or lookalikes) prepended to the actual mbuf chain.
524  *
525  *	m_type	= MT_TAG
526  *	m_flags = m_tag_id
527  *	m_next	= next buffer in chain.
528  *
529  * BE VERY CAREFUL not to pass these blocks to the mbuf handling routines.
530  */
531 #define	_m_tag_id	m_hdr.mh_flags
532 
533 /* Packet tags used in the FreeBSD network stack */
534 #define	PACKET_TAG_DUMMYNET			15 /* dummynet info */
535 #define	PACKET_TAG_IPFW				16 /* ipfw classification */
536 #define	PACKET_TAG_DIVERT			17 /* divert info */
537 #define	PACKET_TAG_IPFORWARD			18 /* ipforward info */
538 #define	PACKET_TAG_MACLABEL			19 /* MAC label */
539 
540 /* Packet tag routines */
541 struct	m_tag 	*m_tag_alloc(u_int32_t, int, int, int);
542 void		 m_tag_free(struct m_tag *);
543 void		 m_tag_prepend(struct mbuf *, struct m_tag *);
544 void		 m_tag_unlink(struct mbuf *, struct m_tag *);
545 void		 m_tag_delete(struct mbuf *, struct m_tag *);
546 void		 m_tag_delete_chain(struct mbuf *, struct m_tag *);
547 struct	m_tag	*m_tag_locate(struct mbuf *, u_int32_t, int, struct m_tag *);
548 struct	m_tag	*m_tag_copy(struct m_tag *, int);
549 int		 m_tag_copy_chain(struct mbuf *, struct mbuf *, int);
550 void		 m_tag_init(struct mbuf *);
551 struct	m_tag	*m_tag_first(struct mbuf *);
552 struct	m_tag	*m_tag_next(struct mbuf *, struct m_tag *);
553 
554 /* these are for openbsd compatibility */
555 #define	MTAG_ABI_COMPAT		0		/* compatibility ABI */
556 
557 static __inline struct m_tag *
558 m_tag_get(int type, int length, int wait)
559 {
560 	return m_tag_alloc(MTAG_ABI_COMPAT, type, length, wait);
561 }
562 
563 static __inline struct m_tag *
564 m_tag_find(struct mbuf *m, int type, struct m_tag *start)
565 {
566 	return m_tag_locate(m, MTAG_ABI_COMPAT, type, start);
567 }
568 #endif /* _KERNEL */
569 
570 #endif /* !_SYS_MBUF_H_ */
571