1 /* SPDX-License-Identifier: BSD-3-Clause */
2 /*
3  * Copyright (c) 1982, 1986, 1988, 1993
4  *	The Regents of the University of California.  All rights reserved.
5  *
6  * Redistribution and use in source and binary forms, with or without
7  * modification, are permitted provided that the following conditions
8  * are met:
9  * 1. Redistributions of source code must retain the above copyright
10  *    notice, this list of conditions and the following disclaimer.
11  * 2. Redistributions in binary form must reproduce the above copyright
12  *    notice, this list of conditions and the following disclaimer in the
13  *    documentation and/or other materials provided with the distribution.
14  * 3. Neither the name of the University nor the names of its contributors
15  *    may be used to endorse or promote products derived from this software
16  *    without specific prior written permission.
17  *
18  * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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  *	@(#)mbuf.h	8.3 (Berkeley) 1/21/94
31  * mbuf.h,v 1.9 1994/11/14 13:54:20 bde Exp
32  */
33 
34 #ifndef MBUF_H
35 #define MBUF_H
36 
37 /*
38  * Macros for type conversion
39  * mtod(m,t) -	convert mbuf pointer to data pointer of correct type
40  */
41 #define mtod(m, t) ((t)(m)->m_data)
42 
43 /* XXX About mbufs for slirp:
44  * Only one mbuf is ever used in a chain, for each "cell" of data.
45  * m_nextpkt points to the next packet, if fragmented.
46  * If the data is too large, the M_EXT is used, and a larger block
47  * is alloced.  Therefore, m_free[m] must check for M_EXT and if set
48  * free the m_ext.  This is inefficient memory-wise, but who cares.
49  */
50 
51 /*
52  * mbufs allow to have a gap between the start of the allocated buffer (m_ext if
53  * M_EXT is set, m_dat otherwise) and the in-use data:
54  *
55  *  |--gapsize----->|---m_len------->
56  *  |----------m_size------------------------------>
57  *                  |----M_ROOM-------------------->
58  *                                   |-M_FREEROOM-->
59  *
60  *  ^               ^                               ^
61  *  m_dat/m_ext     m_data                          end of buffer
62  */
63 
64 /*
65  * How much room is in the mbuf, from m_data to the end of the mbuf
66  */
67 #define M_ROOM(m)                                                        \
68     ((m->m_flags & M_EXT) ? (((m)->m_ext + (m)->m_size) - (m)->m_data) : \
69                             (((m)->m_dat + (m)->m_size) - (m)->m_data))
70 
71 /*
72  * How much free room there is
73  */
74 #define M_FREEROOM(m) (M_ROOM(m) - (m)->m_len)
75 
76 /*
77  * How much free room there is before m_data
78  */
79 #define M_ROOMBEFORE(m) \
80     (((m)->m_flags & M_EXT) ? (m)->m_data - (m)->m_ext \
81                             : (m)->m_data - (m)->m_dat)
82 
83 struct mbuf {
84     /* XXX should union some of these! */
85     /* header at beginning of each mbuf: */
86     struct mbuf *m_next; /* Linked list of mbufs */
87     struct mbuf *m_prev;
88     struct mbuf *m_nextpkt; /* Next packet in queue/record */
89     struct mbuf *m_prevpkt; /* Flags aren't used in the output queue */
90     int m_flags; /* Misc flags */
91 
92     int m_size; /* Size of mbuf, from m_dat or m_ext */
93     struct socket *m_so;
94 
95     char *m_data; /* Current location of data */
96     int m_len; /* Amount of data in this mbuf, from m_data */
97 
98     Slirp *slirp;
99     bool resolution_requested;
100     uint64_t expiration_date;
101     char *m_ext;
102     /* start of dynamic buffer area, must be last element */
103     char m_dat[];
104 };
105 
106 #define ifq_prev m_prev
107 #define ifq_next m_next
108 #define ifs_prev m_prevpkt
109 #define ifs_next m_nextpkt
110 #define ifq_so m_so
111 
112 #define M_EXT 0x01 /* m_ext points to more (malloced) data */
113 #define M_FREELIST 0x02 /* mbuf is on free list */
114 #define M_USEDLIST 0x04 /* XXX mbuf is on used list (for dtom()) */
115 #define M_DOFREE                                      \
116     0x08 /* when m_free is called on the mbuf, free() \
117           * it rather than putting it on the free list */
118 
119 void m_init(Slirp *);
120 void m_cleanup(Slirp *slirp);
121 struct mbuf *m_get(Slirp *);
122 void m_free(struct mbuf *);
123 void m_cat(register struct mbuf *, register struct mbuf *);
124 void m_inc(struct mbuf *, int);
125 void m_adj(struct mbuf *, int);
126 int m_copy(struct mbuf *, struct mbuf *, int, int);
127 struct mbuf *m_dup(Slirp *slirp, struct mbuf *m, bool copy_header, size_t header_size);
128 struct mbuf *dtom(Slirp *, void *);
129 void *mtod_check(struct mbuf *, size_t len);
130 void *m_end(struct mbuf *);
131 
ifs_init(struct mbuf * ifm)132 static inline void ifs_init(struct mbuf *ifm)
133 {
134     ifm->ifs_next = ifm->ifs_prev = ifm;
135 }
136 
137 #ifdef DEBUG
138 #  define MBUF_DEBUG 1
139 #else
140 #  ifdef HAVE_VALGRIND
141 #    include <valgrind/valgrind.h>
142 #    define MBUF_DEBUG RUNNING_ON_VALGRIND
143 #  else
144 #    define MBUF_DEBUG 0
145 #  endif
146 #endif
147 
148 /*
149  * When a function is given an mbuf as well as the responsibility to free it, we
150  * want valgrind etc. to properly identify the new responsible for the
151  * free. Achieve this by making a new copy. For instance:
152  *
153  * f0(void) {
154  *   struct mbuf *m = m_get(slirp);
155  *   [...]
156  *   switch (something) {
157  *   case 1:
158  *     f1(m);
159  *     break;
160  *   case 2:
161  *     f2(m);
162  *     break;
163  *   [...]
164  *   }
165  * }
166  *
167  * f1(struct mbuf *m) {
168  *   M_DUP_DEBUG(m->slirp, m);
169  *   [...]
170  *   m_free(m); // but author of f1 might be forgetting this
171  * }
172  *
173  * f0 transfers the freeing responsibility to f1, f2, etc.  Without the
174  * M_DUP_DEBUG call in f1, valgrind would tell us that it is f0 where the buffer
175  * was allocated, but it's difficult to know whether a leak is actually in f0,
176  * or in f1, or in f2, etc.  Duplicating the mbuf in M_DUP_DEBUG each time the
177  * responsibility is transferred allows to immediately know where the leak
178  * actually is.
179  */
180 #define M_DUP_DEBUG(slirp, m, copy_header, header_size) do { \
181     if (MBUF_DEBUG) { \
182         struct mbuf *__n; \
183         __n = m_dup((slirp), (m), (copy_header), (header_size)); \
184         m_free(m); \
185         (m) = __n; \
186     } else { \
187         (void) (slirp); (void) (copy_header); \
188         g_assert(M_ROOMBEFORE(m) >= (header_size)); \
189     } \
190 } while(0)
191 
192 #endif
193