1 /*
2 * Copyright (c) 1995 Danny Gasparovski
3 *
4 * Please read the file COPYRIGHT for the
5 * terms and conditions of the copyright.
6 */
7
8 /*
9 * mbuf's in SLiRP are much simpler than the real mbufs in
10 * FreeBSD. They are fixed size, determined by the MTU,
11 * so that one whole packet can fit. Mbuf's cannot be
12 * chained together. If there's more data than the mbuf
13 * could hold, an external malloced buffer is pointed to
14 * by m_ext (and the data pointers) and M_EXT is set in
15 * the flags
16 */
17
18 #include <slirp.h>
19
20 int mbuf_alloced = 0;
21 struct mbuf m_freelist, m_usedlist;
22 #define MBUF_THRESH 30
23 int mbuf_max = 0;
24
25 /*
26 * Find a nice value for msize
27 * XXX if_maxlinkhdr already in mtu
28 */
29 #define SLIRP_MSIZE (IF_MTU + IF_MAXLINKHDR + sizeof(struct m_hdr ) + 6)
30
31 void
m_init(void)32 m_init(void)
33 {
34 m_freelist.m_next = m_freelist.m_prev = &m_freelist;
35 m_usedlist.m_next = m_usedlist.m_prev = &m_usedlist;
36 }
37
38 /*
39 * Get an mbuf from the free list, if there are none
40 * malloc one
41 *
42 * Because fragmentation can occur if we alloc new mbufs and
43 * free old mbufs, we mark all mbufs above mbuf_thresh as M_DOFREE,
44 * which tells m_free to actually free() it
45 */
46 struct mbuf *
m_get(void)47 m_get(void)
48 {
49 register struct mbuf *m;
50 int flags = 0;
51
52 DEBUG_CALL("m_get");
53
54 if (m_freelist.m_next == &m_freelist) {
55 m = (struct mbuf *)malloc(SLIRP_MSIZE);
56 if (m == NULL) goto end_error;
57 mbuf_alloced++;
58 if (mbuf_alloced > MBUF_THRESH)
59 flags = M_DOFREE;
60 if (mbuf_alloced > mbuf_max)
61 mbuf_max = mbuf_alloced;
62 } else {
63 m = m_freelist.m_next;
64 remque(m);
65 }
66
67 /* Insert it in the used list */
68 insque(m,&m_usedlist);
69 m->m_flags = (flags | M_USEDLIST);
70
71 /* Initialise it */
72 m->m_size = SLIRP_MSIZE - sizeof(struct m_hdr);
73 m->m_data = m->m_dat;
74 m->m_len = 0;
75 m->m_nextpkt = NULL;
76 m->m_prevpkt = NULL;
77 end_error:
78 DEBUG_ARG("m = %lx", (long )m);
79 return m;
80 }
81
82 void
m_free(struct mbuf * m)83 m_free(struct mbuf *m)
84 {
85
86 DEBUG_CALL("m_free");
87 DEBUG_ARG("m = %lx", (long )m);
88
89 if(m) {
90 /* Remove from m_usedlist */
91 if (m->m_flags & M_USEDLIST)
92 remque(m);
93
94 /* If it's M_EXT, free() it */
95 if (m->m_flags & M_EXT)
96 free(m->m_ext);
97
98 /*
99 * Either free() it or put it on the free list
100 */
101 if (m->m_flags & M_DOFREE) {
102 free(m);
103 mbuf_alloced--;
104 } else if ((m->m_flags & M_FREELIST) == 0) {
105 insque(m,&m_freelist);
106 m->m_flags = M_FREELIST; /* Clobber other flags */
107 }
108 } /* if(m) */
109 }
110
111 /*
112 * Copy data from one mbuf to the end of
113 * the other.. if result is too big for one mbuf, malloc()
114 * an M_EXT data segment
115 */
116 void
m_cat(struct mbuf * m,struct mbuf * n)117 m_cat(struct mbuf *m, struct mbuf *n)
118 {
119 /*
120 * If there's no room, realloc
121 */
122 if (M_FREEROOM(m) < n->m_len)
123 m_inc(m,m->m_size+MINCSIZE);
124
125 memcpy(m->m_data+m->m_len, n->m_data, n->m_len);
126 m->m_len += n->m_len;
127
128 m_free(n);
129 }
130
131
132 /* make m size bytes large */
133 void
m_inc(struct mbuf * m,int size)134 m_inc(struct mbuf *m, int size)
135 {
136 int datasize;
137
138 /* some compiles throw up on gotos. This one we can fake. */
139 if(m->m_size>size) return;
140
141 if (m->m_flags & M_EXT) {
142 datasize = m->m_data - m->m_ext;
143 m->m_ext = (char *)realloc(m->m_ext,size);
144 /* if (m->m_ext == NULL)
145 * return (struct mbuf *)NULL;
146 */
147 m->m_data = m->m_ext + datasize;
148 } else {
149 char *dat;
150 datasize = m->m_data - m->m_dat;
151 dat = (char *)malloc(size);
152 /* if (dat == NULL)
153 * return (struct mbuf *)NULL;
154 */
155 memcpy(dat, m->m_dat, m->m_size);
156
157 m->m_ext = dat;
158 m->m_data = m->m_ext + datasize;
159 m->m_flags |= M_EXT;
160 }
161
162 m->m_size = size;
163
164 }
165
166
167
168 void
m_adj(struct mbuf * m,int len)169 m_adj(struct mbuf *m, int len)
170 {
171 if (m == NULL)
172 return;
173 if (len >= 0) {
174 /* Trim from head */
175 m->m_data += len;
176 m->m_len -= len;
177 } else {
178 /* Trim from tail */
179 len = -len;
180 m->m_len -= len;
181 }
182 }
183
184
185 /*
186 * Copy len bytes from m, starting off bytes into n
187 */
188 int
m_copy(struct mbuf * n,struct mbuf * m,int off,int len)189 m_copy(struct mbuf *n, struct mbuf *m, int off, int len)
190 {
191 if (len > M_FREEROOM(n))
192 return -1;
193
194 memcpy((n->m_data + n->m_len), (m->m_data + off), len);
195 n->m_len += len;
196 return 0;
197 }
198
199
200 /*
201 * Given a pointer into an mbuf, return the mbuf
202 * XXX This is a kludge, I should eliminate the need for it
203 * Fortunately, it's not used often
204 */
205 struct mbuf *
dtom(void * dat)206 dtom(void *dat)
207 {
208 struct mbuf *m;
209
210 DEBUG_CALL("dtom");
211 DEBUG_ARG("dat = %lx", (long )dat);
212
213 /* bug corrected for M_EXT buffers */
214 for (m = m_usedlist.m_next; m != &m_usedlist; m = m->m_next) {
215 if (m->m_flags & M_EXT) {
216 if( (char *)dat>=m->m_ext && (char *)dat<(m->m_ext + m->m_size) )
217 return m;
218 } else {
219 if( (char *)dat >= m->m_dat && (char *)dat<(m->m_dat + m->m_size) )
220 return m;
221 }
222 }
223
224 DEBUG_ERROR((dfd, "dtom failed"));
225
226 return (struct mbuf *)0;
227 }
228