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