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 int mbuf_thresh = 30;
  25 int mbuf_max = 0;
  26 int msize;
  27
  28 void
  29 m_init()
  30 {
  31         m_freelist.m_next = m_freelist.m_prev = &m_freelist;
  32         m_usedlist.m_next = m_usedlist.m_prev = &m_usedlist;
  33         msize_init();
  34 }
  35
  36 void
  37 msize_init()
  38 {
  39         /*
  40          * Find a nice value for msize
  41          * XXX if_maxlinkhdr already in mtu
  42          */
  43         msize = (if_mtu>if_mru?if_mtu:if_mru) +
  44                         if_maxlinkhdr + sizeof(struct m_hdr ) + 6;
  45 }
  46
  47 /*
  48  * Get an mbuf from the free list, if there are none
  49  * malloc one
  50  *
  51  * Because fragmentation can occur if we alloc new mbufs and
  52  * free old mbufs, we mark all mbufs above mbuf_thresh as M_DOFREE,
  53  * which tells m_free to actually free() it
  54  */
  55 struct mbuf *
  56 m_get()
  57 {
  58         register struct mbuf *m;
  59         int flags = 0;
  60
  61         DEBUG_CALL("m_get");
  62
  63         if (m_freelist.m_next == &m_freelist) {
  64                 m = (struct mbuf *)malloc(msize);
  65                 if (m == NULL) goto end_error;
  66                 mbuf_alloced++;
  67                 if (mbuf_alloced > mbuf_thresh)
  68                         flags = M_DOFREE;
  69                 if (mbuf_alloced > mbuf_max)
  70                         mbuf_max = mbuf_alloced;
  71         } else {
  72                 m = m_freelist.m_next;
  73                 remque(m);
  74         }
  75
  76         /* Insert it in the used list */
  77         insque(m,&m_usedlist);
  78         m->m_flags = (flags | M_USEDLIST);
  79
  80         /* Initialise it */
  81         m->m_size = msize - sizeof(struct m_hdr);
  82         m->m_data = m->m_dat;
  83         m->m_len = 0;
  84         m->m_nextpkt = 0;
  85         m->m_prevpkt = 0;
  86 end_error:
  87         DEBUG_ARG("m = %lx", (long )m);
  88         return m;
  89 }
  90
  91 void
  92 m_free(m)
  93         struct mbuf *m;
  94 {
  95
  96   DEBUG_CALL("m_free");
  97   DEBUG_ARG("m = %lx", (long )m);
  98
  99   if(m) {
 100         /* Remove from m_usedlist */
 101         if (m->m_flags & M_USEDLIST)
 102            remque(m);
 103
 104         /* If it's M_EXT, free() it */
 105         if (m->m_flags & M_EXT)
 106            free(m->m_ext);
 107
 108         /*
 109          * Either free() it or put it on the free list
 110          */
 111         if (m->m_flags & M_DOFREE) {
 112                 free(m);
 113                 mbuf_alloced--;
 114         } else if ((m->m_flags & M_FREELIST) == 0) {
 115                 insque(m,&m_freelist);
 116                 m->m_flags = M_FREELIST; /* Clobber other flags */
 117         }
 118   } /* if(m) */
 119 }
 120
 121 /*
 122  * Copy data from one mbuf to the end of
 123  * the other.. if result is too big for one mbuf, malloc()
 124  * an M_EXT data segment
 125  */
 126 void
 127 m_cat(m, n)
 128         register struct mbuf *m, *n;
 129 {
 130         /*
 131          * If there's no room, realloc
 132          */
 133         if (M_FREEROOM(m) < n->m_len)
 134                 m_inc(m,m->m_size+MINCSIZE);
 135
 136         memcpy(m->m_data+m->m_len, n->m_data, n->m_len);
 137         m->m_len += n->m_len;
 138
 139         m_free(n);
 140 }
 141
 142
 143 /* make m size bytes large */
 144 void
 145 m_inc(m, size)
 146         struct mbuf *m;
 147         int size;
 148 {
 149         int datasize;
 150
 151         /* some compiles throw up on gotos.  This one we can fake. */
 152         if(m->m_size>size) return;
 153
 154         if (m->m_flags & M_EXT) {
 155           datasize = m->m_data - m->m_ext;
 156           m->m_ext = (char *)realloc(m->m_ext,size);
 157 /*              if (m->m_ext == NULL)
 158  *                      return (struct mbuf *)NULL;
 159  */
 160           m->m_data = m->m_ext + datasize;
 161         } else {
 162           char *dat;
 163           datasize = m->m_data - m->m_dat;
 164           dat = (char *)malloc(size);
 165 /*              if (dat == NULL)
 166  *                      return (struct mbuf *)NULL;
 167  */
 168           memcpy(dat, m->m_dat, m->m_size);
 169
 170           m->m_ext = dat;
 171           m->m_data = m->m_ext + datasize;
 172           m->m_flags |= M_EXT;
 173         }
 174
 175         m->m_size = size;
 176
 177 }
 178
 179
 180
 181 void
 182 m_adj(m, len)
 183         struct mbuf *m;
 184         int len;
 185 {
 186         if (m == NULL)
 187                 return;
 188         if (len >= 0) {
 189                 /* Trim from head */
 190                 m->m_data += len;
 191                 m->m_len -= len;
 192         } else {
 193                 /* Trim from tail */
 194                 len = -len;
 195                 m->m_len -= len;
 196         }
 197 }
 198
 199
 200 /*
 201  * Copy len bytes from m, starting off bytes into n
 202  */
 203 int
 204 m_copy(n, m, off, len)
 205         struct mbuf *n, *m;
 206         int off, len;
 207 {
 208         if (len > M_FREEROOM(n))
 209                 return -1;
 210
 211         memcpy((n->m_data + n->m_len), (m->m_data + off), len);
 212         n->m_len += len;
 213         return 0;
 214 }
 215
 216
 217 /*
 218  * Given a pointer into an mbuf, return the mbuf
 219  * XXX This is a kludge, I should eliminate the need for it
 220  * Fortunately, it's not used often
 221  */
 222 struct mbuf *
 223 dtom(dat)
 224         void *dat;
 225 {
 226         struct mbuf *m;
 227
 228         DEBUG_CALL("dtom");
 229         DEBUG_ARG("dat = %lx", (long )dat);
 230
 231         /* bug corrected for M_EXT buffers */
 232         for (m = m_usedlist.m_next; m != &m_usedlist; m = m->m_next) {
 233           if (m->m_flags & M_EXT) {
 234             if( (char *)dat>=m->m_ext && (char *)dat<(m->m_ext + m->m_size) )
 235               return m;
 236           } else {
 237             if( (char *)dat >= m->m_dat && (char *)dat<(m->m_dat + m->m_size) )
 238               return m;
 239           }
 240         }
 241
 242         DEBUG_ERROR((dfd, "dtom failed"));
 243
 244         return (struct mbuf *)0;
 245 }
 246