slirp/mbuf.c

   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 struct  mbuf *mbutl;
  21 char    *mclrefcnt;
  22 int mbuf_alloced = 0;
  23 struct mbuf m_freelist, m_usedlist;
  24 #define MBUF_THRESH 30
  25 int mbuf_max = 0;
  26
  27 /*
  28  * Find a nice value for msize
  29  * XXX if_maxlinkhdr already in mtu
  30  */
  31 #define MSIZE (IF_MTU + IF_MAXLINKHDR + sizeof(struct m_hdr ) + 6)
  32
  33 void
  34 m_init()
  35 {
  36         m_freelist.m_next = m_freelist.m_prev = &m_freelist;
  37         m_usedlist.m_next = m_usedlist.m_prev = &m_usedlist;
  38 }
  39
  40 /*
  41  * Get an mbuf from the free list, if there are none
  42  * malloc one
  43  *
  44  * Because fragmentation can occur if we alloc new mbufs and
  45  * free old mbufs, we mark all mbufs above mbuf_thresh as M_DOFREE,
  46  * which tells m_free to actually free() it
  47  */
  48 struct mbuf *
  49 m_get()
  50 {
  51         register struct mbuf *m;
  52         int flags = 0;
  53
  54         DEBUG_CALL("m_get");
  55
  56         if (m_freelist.m_next == &m_freelist) {
  57                 m = (struct mbuf *)malloc(MSIZE);
  58                 if (m == NULL) goto end_error;
  59                 mbuf_alloced++;
  60                 if (mbuf_alloced > MBUF_THRESH)
  61                         flags = M_DOFREE;
  62                 if (mbuf_alloced > mbuf_max)
  63                         mbuf_max = mbuf_alloced;
  64         } else {
  65                 m = m_freelist.m_next;
  66                 remque(m);
  67         }
  68
  69         /* Insert it in the used list */
  70         insque(m,&m_usedlist);
  71         m->m_flags = (flags | M_USEDLIST);
  72
  73         /* Initialise it */
  74         m->m_size = MSIZE - sizeof(struct m_hdr);
  75         m->m_data = m->m_dat;
  76         m->m_len = 0;
  77         m->m_nextpkt = 0;
  78         m->m_prevpkt = 0;
  79 end_error:
  80         DEBUG_ARG("m = %lx", (long )m);
  81         return m;
  82 }
  83
  84 void
  85 m_free(m)
  86         struct mbuf *m;
  87 {
  88
  89   DEBUG_CALL("m_free");
  90   DEBUG_ARG("m = %lx", (long )m);
  91
  92   if(m) {
  93         /* Remove from m_usedlist */
  94         if (m->m_flags & M_USEDLIST)
  95            remque(m);
  96
  97         /* If it's M_EXT, free() it */
  98         if (m->m_flags & M_EXT)
  99            free(m->m_ext);
 100
 101         /*
 102          * Either free() it or put it on the free list
 103          */
 104         if (m->m_flags & M_DOFREE) {
 105                 free(m);
 106                 mbuf_alloced--;
 107         } else if ((m->m_flags & M_FREELIST) == 0) {
 108                 insque(m,&m_freelist);
 109                 m->m_flags = M_FREELIST; /* Clobber other flags */
 110         }
 111   } /* if(m) */
 112 }
 113
 114 /*
 115  * Copy data from one mbuf to the end of
 116  * the other.. if result is too big for one mbuf, malloc()
 117  * an M_EXT data segment
 118  */
 119 void
 120 m_cat(m, n)
 121         register struct mbuf *m, *n;
 122 {
 123         /*
 124          * If there's no room, realloc
 125          */
 126         if (M_FREEROOM(m) < n->m_len)
 127                 m_inc(m,m->m_size+MINCSIZE);
 128
 129         memcpy(m->m_data+m->m_len, n->m_data, n->m_len);
 130         m->m_len += n->m_len;
 131
 132         m_free(n);
 133 }
 134
 135
 136 /* make m size bytes large */
 137 void
 138 m_inc(m, size)
 139         struct mbuf *m;
 140         int size;
 141 {
 142         int datasize;
 143
 144         /* some compiles throw up on gotos.  This one we can fake. */
 145         if(m->m_size>size) return;
 146
 147         if (m->m_flags & M_EXT) {
 148           datasize = m->m_data - m->m_ext;
 149           m->m_ext = (char *)realloc(m->m_ext,size);
 150 /*              if (m->m_ext == NULL)
 151  *                      return (struct mbuf *)NULL;
 152  */
 153           m->m_data = m->m_ext + datasize;
 154         } else {
 155           char *dat;
 156           datasize = m->m_data - m->m_dat;
 157           dat = (char *)malloc(size);
 158 /*              if (dat == NULL)
 159  *                      return (struct mbuf *)NULL;
 160  */
 161           memcpy(dat, m->m_dat, m->m_size);
 162
 163           m->m_ext = dat;
 164           m->m_data = m->m_ext + datasize;
 165           m->m_flags |= M_EXT;
 166         }
 167
 168         m->m_size = size;
 169
 170 }
 171
 172
 173
 174 void
 175 m_adj(m, len)
 176         struct mbuf *m;
 177         int len;
 178 {
 179         if (m == NULL)
 180                 return;
 181         if (len >= 0) {
 182                 /* Trim from head */
 183                 m->m_data += len;
 184                 m->m_len -= len;
 185         } else {
 186                 /* Trim from tail */
 187                 len = -len;
 188                 m->m_len -= len;
 189         }
 190 }
 191
 192
 193 /*
 194  * Copy len bytes from m, starting off bytes into n
 195  */
 196 int
 197 m_copy(n, m, off, len)
 198         struct mbuf *n, *m;
 199         int off, len;
 200 {
 201         if (len > M_FREEROOM(n))
 202                 return -1;
 203
 204         memcpy((n->m_data + n->m_len), (m->m_data + off), len);
 205         n->m_len += len;
 206         return 0;
 207 }
 208
 209
 210 /*
 211  * Given a pointer into an mbuf, return the mbuf
 212  * XXX This is a kludge, I should eliminate the need for it
 213  * Fortunately, it's not used often
 214  */
 215 struct mbuf *
 216 dtom(dat)
 217         void *dat;
 218 {
 219         struct mbuf *m;
 220
 221         DEBUG_CALL("dtom");
 222         DEBUG_ARG("dat = %lx", (long )dat);
 223
 224         /* bug corrected for M_EXT buffers */
 225         for (m = m_usedlist.m_next; m != &m_usedlist; m = m->m_next) {
 226           if (m->m_flags & M_EXT) {
 227             if( (char *)dat>=m->m_ext && (char *)dat<(m->m_ext + m->m_size) )
 228               return m;
 229           } else {
 230             if( (char *)dat >= m->m_dat && (char *)dat<(m->m_dat + m->m_size) )
 231               return m;
 232           }
 233         }
 234
 235         DEBUG_ERROR((dfd, "dtom failed"));
 236
 237         return (struct mbuf *)0;
 238 }
 239