xref: /freebsd/sys/sys/mbuf.h (revision d2387d42b8da231a5b95cbc313825fb2aadf26f6)
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 	void			(*m_tag_free)(struct m_tag *);
87 };
88 
89 /*
90  * Record/packet header in first mbuf of chain; valid only if M_PKTHDR is set.
91  */
92 struct pkthdr {
93 	struct	ifnet *rcvif;		/* rcv interface */
94 	int	len;			/* total packet length */
95 	/* variables for ip and tcp reassembly */
96 	void	*header;		/* pointer to packet header */
97 	/* variables for hardware checksum */
98 	int	csum_flags;		/* flags regarding checksum */
99 	int	csum_data;		/* data field used by csum routines */
100 	SLIST_HEAD(packet_tags, m_tag) tags; /* list of packet tags */
101 };
102 
103 /*
104  * Description of external storage mapped into mbuf; valid only if M_EXT is set.
105  */
106 struct m_ext {
107 	caddr_t	ext_buf;		/* start of buffer */
108 	void	(*ext_free)		/* free routine if not the usual */
109 		    (void *, void *);
110 	void	*ext_args;		/* optional argument pointer */
111 	u_int	ext_size;		/* size of buffer, for ext_free */
112 	u_int	*ref_cnt;		/* pointer to ref count info */
113 	int	ext_type;		/* type of external storage */
114 };
115 
116 /*
117  * The core of the mbuf object along with some shortcut defines for
118  * practical purposes.
119  */
120 struct mbuf {
121 	struct	m_hdr m_hdr;
122 	union {
123 		struct {
124 			struct	pkthdr MH_pkthdr;	/* M_PKTHDR set */
125 			union {
126 				struct	m_ext MH_ext;	/* M_EXT set */
127 				char	MH_databuf[MHLEN];
128 			} MH_dat;
129 		} MH;
130 		char	M_databuf[MLEN];		/* !M_PKTHDR, !M_EXT */
131 	} M_dat;
132 };
133 #define	m_next		m_hdr.mh_next
134 #define	m_len		m_hdr.mh_len
135 #define	m_data		m_hdr.mh_data
136 #define	m_type		m_hdr.mh_type
137 #define	m_flags		m_hdr.mh_flags
138 #define	m_nextpkt	m_hdr.mh_nextpkt
139 #define	m_act		m_nextpkt
140 #define	m_pkthdr	M_dat.MH.MH_pkthdr
141 #define	m_ext		M_dat.MH.MH_dat.MH_ext
142 #define	m_pktdat	M_dat.MH.MH_dat.MH_databuf
143 #define	m_dat		M_dat.M_databuf
144 
145 /*
146  * mbuf flags.
147  */
148 #define	M_EXT		0x0001	/* has associated external storage */
149 #define	M_PKTHDR	0x0002	/* start of record */
150 #define	M_EOR		0x0004	/* end of record */
151 #define	M_RDONLY	0x0008	/* associated data is marked read-only */
152 #define	M_PROTO1	0x0010	/* protocol-specific */
153 #define	M_PROTO2	0x0020	/* protocol-specific */
154 #define	M_PROTO3	0x0040	/* protocol-specific */
155 #define	M_PROTO4	0x0080	/* protocol-specific */
156 #define	M_PROTO5	0x0100	/* protocol-specific */
157 #define M_PROTO6	0x4000	/* protocol-specific (avoid M_BCAST conflict) */
158 #define	M_FREELIST	0x8000	/* mbuf is on the free list */
159 
160 /*
161  * mbuf pkthdr flags (also stored in m_flags).
162  */
163 #define	M_BCAST		0x0200	/* send/received as link-level broadcast */
164 #define	M_MCAST		0x0400	/* send/received as link-level multicast */
165 #define	M_FRAG		0x0800	/* packet is a fragment of a larger packet */
166 #define	M_FIRSTFRAG	0x1000	/* packet is first fragment */
167 #define	M_LASTFRAG	0x2000	/* packet is last fragment */
168 
169 /*
170  * External buffer types: identify ext_buf type.
171  */
172 #define	EXT_CLUSTER	1	/* mbuf cluster */
173 #define	EXT_SFBUF	2	/* sendfile(2)'s sf_bufs */
174 #define	EXT_NET_DRV	100	/* custom ext_buf provided by net driver(s) */
175 #define	EXT_MOD_TYPE	200	/* custom module's ext_buf type */
176 #define	EXT_DISPOSABLE	300	/* can throw this buffer away w/page flipping */
177 #define	EXT_EXTREF	400	/* has externally maintained ref_cnt ptr*/
178 
179 /*
180  * Flags copied when copying m_pkthdr.
181  */
182 #define	M_COPYFLAGS	(M_PKTHDR|M_EOR|M_RDONLY|M_PROTO1|M_PROTO1|M_PROTO2|\
183 			    M_PROTO3|M_PROTO4|M_PROTO5|M_PROTO6|\
184 			    M_BCAST|M_MCAST|M_FRAG|M_FIRSTFRAG|M_LASTFRAG)
185 
186 /*
187  * Flags indicating hw checksum support and sw checksum requirements.
188  */
189 #define	CSUM_IP			0x0001		/* will csum IP */
190 #define	CSUM_TCP		0x0002		/* will csum TCP */
191 #define	CSUM_UDP		0x0004		/* will csum UDP */
192 #define	CSUM_IP_FRAGS		0x0008		/* will csum IP fragments */
193 #define	CSUM_FRAGMENT		0x0010		/* will do IP fragmentation */
194 
195 #define	CSUM_IP_CHECKED		0x0100		/* did csum IP */
196 #define	CSUM_IP_VALID		0x0200		/*   ... the csum is valid */
197 #define	CSUM_DATA_VALID		0x0400		/* csum_data field is valid */
198 #define	CSUM_PSEUDO_HDR		0x0800		/* csum_data has pseudo hdr */
199 
200 #define	CSUM_DELAY_DATA		(CSUM_TCP | CSUM_UDP)
201 #define	CSUM_DELAY_IP		(CSUM_IP)	/* XXX add ipv6 here too? */
202 
203 /*
204  * mbuf types.
205  */
206 #define	MT_NOTMBUF	0	/* USED INTERNALLY ONLY! Object is not mbuf */
207 #define	MT_DATA		1	/* dynamic (data) allocation */
208 #define	MT_HEADER	2	/* packet header */
209 #if 0
210 #define	MT_SOCKET	3	/* socket structure */
211 #define	MT_PCB		4	/* protocol control block */
212 #define	MT_RTABLE	5	/* routing tables */
213 #define	MT_HTABLE	6	/* IMP host tables */
214 #define	MT_ATABLE	7	/* address resolution tables */
215 #endif
216 #define	MT_SONAME	8	/* socket name */
217 #if 0
218 #define	MT_SOOPTS	10	/* socket options */
219 #endif
220 #define	MT_FTABLE	11	/* fragment reassembly header */
221 #if 0
222 #define	MT_RIGHTS	12	/* access rights */
223 #define	MT_IFADDR	13	/* interface address */
224 #endif
225 #define	MT_CONTROL	14	/* extra-data protocol message */
226 #define	MT_OOBDATA	15	/* expedited data  */
227 #define	MT_NTYPES	16	/* number of mbuf types for mbtypes[] */
228 
229 /*
230  * Mbuf and cluster allocation statistics PCPU structure.
231  */
232 struct mbpstat {
233 	u_long	mb_mbfree;
234 	u_long	mb_mbbucks;
235 	u_long	mb_clfree;
236 	u_long	mb_clbucks;
237 	long	mb_mbtypes[MT_NTYPES];
238 	short	mb_active;
239 };
240 
241 /*
242  * General mbuf allocator statistics structure.
243  * XXX: Modifications of these are not protected by any mutex locks nor by
244  * any atomic() manipulations.  As a result, we may occasionally lose
245  * a count or two.  Luckily, not all of these fields are modified at all
246  * and remain static, and those that are manipulated are only manipulated
247  * in failure situations, which do not occur (hopefully) very often.
248  */
249 struct mbstat {
250 	u_long	m_drops;	/* times failed to allocate */
251 	u_long	m_wait;		/* times succesfully returned from wait */
252 	u_long	m_drain;	/* times drained protocols for space */
253 	u_long	m_mcfail;	/* XXX: times m_copym failed */
254 	u_long	m_mpfail;	/* XXX: times m_pullup failed */
255 	u_long	m_msize;	/* length of an mbuf */
256 	u_long	m_mclbytes;	/* length of an mbuf cluster */
257 	u_long	m_minclsize;	/* min length of data to allocate a cluster */
258 	u_long	m_mlen;		/* length of data in an mbuf */
259 	u_long	m_mhlen;	/* length of data in a header mbuf */
260 	u_int	m_mbperbuck;	/* number of mbufs per "bucket" */
261 	u_int	m_clperbuck;	/* number of clusters per "bucket" */
262 	/* Number of mbtypes (gives # elems in mbpstat's mb_mbtypes[] array: */
263 	short	m_numtypes;
264 	/* XXX: Sendfile stats should eventually move to their own struct */
265 	u_long	sf_iocnt;	/* times sendfile had to do disk I/O */
266 	u_long	sf_allocfail;	/* times sfbuf allocation failed */
267 	u_long	sf_allocwait;	/* times sfbuf allocation had to wait */
268 };
269 
270 /*
271  * Flags specifying how an allocation should be made.
272  * M_DONTWAIT means "don't block if nothing is available" whereas
273  * M_TRYWAIT means "block for mbuf_wait ticks at most if nothing is
274  * available."
275  */
276 #define	M_DONTWAIT	0x4		/* don't conflict with M_NOWAIT */
277 #define	M_TRYWAIT	0x8		/* or M_WAITOK */
278 #define	M_WAIT		M_TRYWAIT	/* XXX: deprecated */
279 #define	MBTOM(how)	((how) & M_TRYWAIT ? M_WAITOK : M_NOWAIT)
280 
281 #ifdef _KERNEL
282 /*-
283  * mbuf external reference count management macros.
284  *
285  * MEXT_IS_REF(m): true if (m) is not the only mbuf referencing
286  *     the external buffer ext_buf.
287  *
288  * MEXT_REM_REF(m): remove reference to m_ext object.
289  *
290  * MEXT_ADD_REF(m): add reference to m_ext object already
291  *     referred to by (m).
292  */
293 #define	MEXT_IS_REF(m)	(*((m)->m_ext.ref_cnt) > 1)
294 
295 #define	MEXT_REM_REF(m) do {						\
296 	KASSERT(*((m)->m_ext.ref_cnt) > 0, ("m_ext refcnt < 0"));	\
297 	atomic_subtract_int((m)->m_ext.ref_cnt, 1);			\
298 } while(0)
299 
300 #define	MEXT_ADD_REF(m)	atomic_add_int((m)->m_ext.ref_cnt, 1)
301 
302 /*
303  * mbuf, cluster, and external object allocation macros
304  * (for compatibility purposes).
305  */
306 /* NB: M_COPY_PKTHDR is deprecated.  Use M_MOVE_PKTHDR or m_dup_pktdr. */
307 #define	M_MOVE_PKTHDR(to, from)	m_move_pkthdr((to), (from))
308 #define	m_getclr(how, type)	m_get_clrd((how), (type))
309 #define	MGET(m, how, type)	((m) = m_get((how), (type)))
310 #define	MGETHDR(m, how, type)	((m) = m_gethdr((how), (type)))
311 #define	MCLGET(m, how)		m_clget((m), (how))
312 #define	MEXTADD(m, buf, size, free, args, flags, type) 			\
313     m_extadd((m), (caddr_t)(buf), (size), (free), (args), (flags), (type))
314 
315 /*
316  * MEXTFREE(m): disassociate (and possibly free) an external object from (m).
317  *
318  * If the atomic_cmpset_int() returns 0, then we effectively do nothing
319  * in terms of "cleaning up" (freeing the ext buf and ref. counter) as
320  * this means that either there are still references, or another thread
321  * is taking care of the clean-up.
322  */
323 #define	MEXTFREE(m) do {						\
324 	struct mbuf *_mb = (m);						\
325 									\
326 	MEXT_REM_REF(_mb);						\
327 	if (atomic_cmpset_int(_mb->m_ext.ref_cnt, 0, 1))		\
328 		_mext_free(_mb);					\
329 	_mb->m_flags &= ~M_EXT;						\
330 } while (0)
331 
332 /*
333  * Evaluate TRUE if it's safe to write to the mbuf m's data region (this
334  * can be both the local data payload, or an external buffer area,
335  * depending on whether M_EXT is set).
336  */
337 #define	M_WRITABLE(m)	(!((m)->m_flags & M_RDONLY) && (!((m)->m_flags  \
338 			    & M_EXT) || !MEXT_IS_REF(m)))
339 
340 /*
341  * Check if the supplied mbuf has a packet header, or else panic.
342  */
343 #define M_ASSERTPKTHDR(m)				\
344 	KASSERT(m != NULL && m->m_flags & M_PKTHDR,	\
345 		("%s: no mbuf packet header!", __func__))
346 
347 /*
348  * Ensure that the supplied mbuf is a valid, non-free mbuf.
349  */
350 #define M_ASSERTVALID(m)					\
351 	KASSERT((((struct mbuf *)m)->m_flags & M_FREELIST) == 0,			\
352 		("%s: attempted use of a free mbuf!", __func__))
353 
354 /*
355  * Set the m_data pointer of a newly-allocated mbuf (m_get/MGET) to place
356  * an object of the specified size at the end of the mbuf, longword aligned.
357  */
358 #define	M_ALIGN(m, len) do {						\
359 	(m)->m_data += (MLEN - (len)) & ~(sizeof(long) - 1);		\
360 } while (0)
361 
362 /*
363  * As above, for mbufs allocated with m_gethdr/MGETHDR
364  * or initialized by M_COPY_PKTHDR.
365  */
366 #define	MH_ALIGN(m, len) do {						\
367 	(m)->m_data += (MHLEN - (len)) & ~(sizeof(long) - 1);		\
368 } while (0)
369 
370 /*
371  * Compute the amount of space available
372  * before the current start of data in an mbuf.
373  *
374  * The M_WRITABLE() is a temporary, conservative safety measure: the burden
375  * of checking writability of the mbuf data area rests solely with the caller.
376  */
377 #define	M_LEADINGSPACE(m)						\
378 	((m)->m_flags & M_EXT ?						\
379 	    (M_WRITABLE(m) ? (m)->m_data - (m)->m_ext.ext_buf : 0):	\
380 	    (m)->m_flags & M_PKTHDR ? (m)->m_data - (m)->m_pktdat :	\
381 	    (m)->m_data - (m)->m_dat)
382 
383 /*
384  * Compute the amount of space available
385  * after the end of data in an mbuf.
386  *
387  * The M_WRITABLE() is a temporary, conservative safety measure: the burden
388  * of checking writability of the mbuf data area rests solely with the caller.
389  */
390 #define	M_TRAILINGSPACE(m)						\
391 	((m)->m_flags & M_EXT ?						\
392 	    (M_WRITABLE(m) ? (m)->m_ext.ext_buf + (m)->m_ext.ext_size	\
393 		- ((m)->m_data + (m)->m_len) : 0) :			\
394 	    &(m)->m_dat[MLEN] - ((m)->m_data + (m)->m_len))
395 
396 /*
397  * Arrange to prepend space of size plen to mbuf m.
398  * If a new mbuf must be allocated, how specifies whether to wait.
399  * If the allocation fails, the original mbuf chain is freed and m is
400  * set to NULL.
401  */
402 #define	M_PREPEND(m, plen, how) do {					\
403 	struct mbuf **_mmp = &(m);					\
404 	struct mbuf *_mm = *_mmp;					\
405 	int _mplen = (plen);						\
406 	int __mhow = (how);						\
407 									\
408 	if (M_LEADINGSPACE(_mm) >= _mplen) {				\
409 		_mm->m_data -= _mplen;					\
410 		_mm->m_len += _mplen;					\
411 	} else								\
412 		_mm = m_prepend(_mm, _mplen, __mhow);			\
413 	if (_mm != NULL && _mm->m_flags & M_PKTHDR)			\
414 		_mm->m_pkthdr.len += _mplen;				\
415 	*_mmp = _mm;							\
416 } while (0)
417 
418 /*
419  * Change mbuf to new type.
420  * This is a relatively expensive operation and should be avoided.
421  */
422 #define	MCHTYPE(m, t)	m_chtype((m), (t))
423 
424 /* Length to m_copy to copy all. */
425 #define	M_COPYALL	1000000000
426 
427 /* Compatibility with 4.3. */
428 #define	m_copy(m, o, l)	m_copym((m), (o), (l), M_DONTWAIT)
429 
430 extern	int max_datalen;		/* MHLEN - max_hdr */
431 extern	int max_hdr;			/* Largest link + protocol header */
432 extern	int max_linkhdr;		/* Largest link-level header */
433 extern	int max_protohdr;		/* Largest protocol header */
434 extern	struct mbstat mbstat;		/* General mbuf stats/infos */
435 extern	int nmbclusters;		/* Maximum number of clusters */
436 extern	int nmbcnt;			/* Scale kmem_map for counter space */
437 extern	int nmbufs;			/* Maximum number of mbufs */
438 
439 struct	uio;
440 
441 void		 _mext_free(struct mbuf *);
442 void		 m_adj(struct mbuf *, int);
443 int		 m_apply(struct mbuf *, int, int,
444 		 int (*)(void *, void *, unsigned int), void *);
445 void		 m_cat(struct mbuf *, struct mbuf *);
446 void		 m_chtype(struct mbuf *, short);
447 void		 m_clget(struct mbuf *, int);
448 void		 m_extadd(struct mbuf *, caddr_t, u_int,
449 		    void (*)(void *, void *), void *, int, int);
450 void		 m_copyback(struct mbuf *, int, int, caddr_t);
451 void		 m_copydata(const struct mbuf *, int, int, caddr_t);
452 struct	mbuf	*m_copym(struct mbuf *, int, int, int);
453 struct	mbuf	*m_copypacket(struct mbuf *, int);
454 void		 m_copy_pkthdr(struct mbuf *, struct mbuf *);
455 struct	mbuf	*m_defrag(struct mbuf *, int);
456 struct	mbuf	*m_devget(char *, int, int, struct ifnet *,
457 		    void (*)(char *, caddr_t, u_int));
458 struct	mbuf	*m_dup(struct mbuf *, int);
459 int		 m_dup_pkthdr(struct mbuf *, struct mbuf *, int);
460 u_int		 m_fixhdr(struct mbuf *);
461 struct	mbuf	*m_fragment(struct mbuf *, int, int);
462 struct	mbuf	*m_free(struct mbuf *);
463 void		 m_freem(struct mbuf *);
464 struct	mbuf	*m_get(int, short);
465 struct	mbuf	*m_get_clrd(int, short);
466 struct	mbuf	*m_getcl(int, short, int);
467 struct	mbuf	*m_gethdr(int, short);
468 struct	mbuf	*m_gethdr_clrd(int, short);
469 struct	mbuf	*m_getm(struct mbuf *, int, int, short);
470 struct	mbuf	*m_getptr(struct mbuf *, int, int *);
471 u_int		 m_length(struct mbuf *, struct mbuf **);
472 void		 m_move_pkthdr(struct mbuf *, struct mbuf *);
473 struct	mbuf	*m_prepend(struct mbuf *, int, int);
474 void		 m_print(const struct mbuf *);
475 struct	mbuf	*m_pulldown(struct mbuf *, int, int, int *);
476 struct	mbuf	*m_pullup(struct mbuf *, int);
477 struct	mbuf	*m_split(struct mbuf *, int, int);
478 struct	mbuf *
479 	m_uiotombuf(struct uio *uio, int how, int len);
480 
481 /*
482  * Packets may have annotations attached by affixing a list
483  * of "packet tags" to the pkthdr structure.  Packet tags are
484  * dynamically allocated semi-opaque data structures that have
485  * a fixed header (struct m_tag) that specifies the size of the
486  * memory block and a <cookie,type> pair that identifies it.
487  * The cookie is a 32-bit unique unsigned value used to identify
488  * a module or ABI.  By convention this value is chose as the
489  * date+time that the module is created, expressed as the number of
490  * seconds since the epoch (e.g., using date -u +'%s').  The type value
491  * is an ABI/module-specific value that identifies a particular annotation
492  * and is private to the module.  For compatibility with systems
493  * like OpenBSD that define packet tags w/o an ABI/module cookie,
494  * the value PACKET_ABI_COMPAT is used to implement m_tag_get and
495  * m_tag_find compatibility shim functions and several tag types are
496  * defined below.  Users that do not require compatibility should use
497  * a private cookie value so that packet tag-related definitions
498  * can be maintained privately.
499  *
500  * Note that the packet tag returned by m_tag_allocate has the default
501  * memory alignment implemented by malloc.  To reference private data
502  * one can use a construct like:
503  *
504  *	struct m_tag *mtag = m_tag_allocate(...);
505  *	struct foo *p = (struct foo *)(mtag+1);
506  *
507  * if the alignment of struct m_tag is sufficient for referencing members
508  * of struct foo.  Otherwise it is necessary to embed struct m_tag within
509  * the private data structure to insure proper alignment; e.g.,
510  *
511  *	struct foo {
512  *		struct m_tag	tag;
513  *		...
514  *	};
515  *	struct foo *p = (struct foo *) m_tag_allocate(...);
516  *	struct m_tag *mtag = &p->tag;
517  */
518 
519 /*
520  * Persistent tags stay with an mbuf until the mbuf is reclaimed.
521  * Otherwise tags are expected to ``vanish'' when they pass through
522  * a network interface.  For most interfaces this happens normally
523  * as the tags are reclaimed when the mbuf is free'd.  However in
524  * some special cases reclaiming must be done manually.  An example
525  * is packets that pass through the loopback interface.  Also, one
526  * must be careful to do this when ``turning around'' packets (e.g.,
527  * icmp_reflect).
528  *
529  * To mark a tag persistent bit-or this flag in when defining the
530  * tag id.  The tag will then be treated as described above.
531  */
532 #define	MTAG_PERSISTENT				0x800
533 
534 #define	PACKET_TAG_NONE				0  /* Nadda */
535 
536 /* Packet tag for use with PACKET_ABI_COMPAT. */
537 #define	PACKET_TAG_IPSEC_IN_DONE		1  /* IPsec applied, in */
538 #define	PACKET_TAG_IPSEC_OUT_DONE		2  /* IPsec applied, out */
539 #define	PACKET_TAG_IPSEC_IN_CRYPTO_DONE		3  /* NIC IPsec crypto done */
540 #define	PACKET_TAG_IPSEC_OUT_CRYPTO_NEEDED	4  /* NIC IPsec crypto req'ed */
541 #define	PACKET_TAG_IPSEC_IN_COULD_DO_CRYPTO	5  /* NIC notifies IPsec */
542 #define	PACKET_TAG_IPSEC_PENDING_TDB		6  /* Reminder to do IPsec */
543 #define	PACKET_TAG_BRIDGE			7  /* Bridge processing done */
544 #define	PACKET_TAG_GIF				8  /* GIF processing done */
545 #define	PACKET_TAG_GRE				9  /* GRE processing done */
546 #define	PACKET_TAG_IN_PACKET_CHECKSUM		10 /* NIC checksumming done */
547 #define	PACKET_TAG_ENCAP			11 /* Encap.  processing */
548 #define	PACKET_TAG_IPSEC_SOCKET			12 /* IPSEC socket ref */
549 #define	PACKET_TAG_IPSEC_HISTORY		13 /* IPSEC history */
550 #define	PACKET_TAG_IPV6_INPUT			14 /* IPV6 input processing */
551 #define	PACKET_TAG_DUMMYNET			15 /* dummynet info */
552 #define	PACKET_TAG_DIVERT			17 /* divert info */
553 #define	PACKET_TAG_IPFORWARD			18 /* ipforward info */
554 #define	PACKET_TAG_MACLABEL	(19 | MTAG_PERSISTENT) /* MAC label */
555 #define	PACKET_TAG_PF_GENERATED	(20 | MTAG_PERSISTENT) /* PF, pass always */
556 #define	PACKET_TAG_PF_ROUTED			21 /* PF routed, avoid loops */
557 #define	PACKET_TAG_PF_FRAGCACHE			22 /* PF fragment cached */
558 #define	PACKET_TAG_PF_QID			23 /* PF ALTQ queue id */
559 #define	PACKET_TAG_PF_TAG			24 /* PF tagged */
560 
561 /* Packet tag routines. */
562 struct	m_tag 	*m_tag_alloc(u_int32_t, int, int, int);
563 void		 m_tag_delete(struct mbuf *, struct m_tag *);
564 void		 m_tag_delete_chain(struct mbuf *, struct m_tag *);
565 struct	m_tag	*m_tag_locate(struct mbuf *, u_int32_t, int, struct m_tag *);
566 struct	m_tag	*m_tag_copy(struct m_tag *, int);
567 int		 m_tag_copy_chain(struct mbuf *, struct mbuf *, int);
568 void		 m_tag_delete_nonpersistent(struct mbuf *);
569 
570 /*
571  * Initialize the list of tags associated with an mbuf.
572  */
573 static __inline void
574 m_tag_init(struct mbuf *m)
575 {
576 	SLIST_INIT(&m->m_pkthdr.tags);
577 }
578 
579 /*
580  * Setup the contents of a tag.  Note that this does not
581  * fillin the free method; the caller is expected to do that.
582  *
583  * XXX probably should be called m_tag_init; but that was
584  * already taken.
585  */
586 static __inline void
587 m_tag_setup(struct m_tag *t, u_int32_t cookie, int type, int len)
588 {
589 	t->m_tag_id = type;
590 	t->m_tag_len = len;
591 	t->m_tag_cookie = cookie;
592 }
593 
594 /*
595  * Reclaim resources associated with a tag.
596  */
597 static __inline void
598 m_tag_free(struct m_tag *t)
599 {
600 	(*t->m_tag_free)(t);
601 }
602 
603 /*
604  * Return the first tag associated with an mbuf.
605  */
606 static __inline struct m_tag *
607 m_tag_first(struct mbuf *m)
608 {
609 	return SLIST_FIRST(&m->m_pkthdr.tags);
610 }
611 
612 /*
613  * Return the next tag in the list of tags associated with an mbuf.
614  */
615 static __inline struct m_tag *
616 m_tag_next(struct mbuf *m, struct m_tag *t)
617 {
618 	return SLIST_NEXT(t, m_tag_link);
619 }
620 
621 /*
622  * Prepend a tag to the list of tags associated with an mbuf.
623  */
624 static __inline void
625 m_tag_prepend(struct mbuf *m, struct m_tag *t)
626 {
627 	SLIST_INSERT_HEAD(&m->m_pkthdr.tags, t, m_tag_link);
628 }
629 
630 /*
631  * Unlink a tag from the list of tags associated with an mbuf.
632  */
633 static __inline void
634 m_tag_unlink(struct mbuf *m, struct m_tag *t)
635 {
636 	SLIST_REMOVE(&m->m_pkthdr.tags, t, m_tag, m_tag_link);
637 }
638 
639 /* These are for OpenBSD compatibility. */
640 #define	MTAG_ABI_COMPAT		0		/* compatibility ABI */
641 
642 static __inline struct m_tag *
643 m_tag_get(int type, int length, int wait)
644 {
645 	return m_tag_alloc(MTAG_ABI_COMPAT, type, length, wait);
646 }
647 
648 static __inline struct m_tag *
649 m_tag_find(struct mbuf *m, int type, struct m_tag *start)
650 {
651 	return SLIST_EMPTY(&m->m_pkthdr.tags) ?
652 		NULL : m_tag_locate(m, MTAG_ABI_COMPAT, type, start);
653 }
654 #endif /* _KERNEL */
655 
656 #endif /* !_SYS_MBUF_H_ */
657