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 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
  32 m_init()
  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 *
  47 m_get()
  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 = 0;
  76         m->m_prevpkt = 0;
  77 end_error:
  78         DEBUG_ARG("m = %lx", (long )m);
  79         return m;
  80 }
  81
  82 void
  83 m_free(m)
  84         struct mbuf *m;
  85 {
  86
  87   DEBUG_CALL("m_free");
  88   DEBUG_ARG("m = %lx", (long )m);
  89
  90   if(m) {
  91         /* Remove from m_usedlist */
  92         if (m->m_flags & M_USEDLIST)
  93            remque(m);
  94
  95         /* If it's M_EXT, free() it */
  96         if (m->m_flags & M_EXT)
  97            free(m->m_ext);
  98
  99         /*
 100          * Either free() it or put it on the free list
 101          */
 102         if (m->m_flags & M_DOFREE) {
 103                 free(m);
 104                 mbuf_alloced--;
 105         } else if ((m->m_flags & M_FREELIST) == 0) {
 106                 insque(m,&m_freelist);
 107                 m->m_flags = M_FREELIST; /* Clobber other flags */
 108         }
 109   } /* if(m) */
 110 }
 111
 112 /*
 113  * Copy data from one mbuf to the end of
 114  * the other.. if result is too big for one mbuf, malloc()
 115  * an M_EXT data segment
 116  */
 117 void
 118 m_cat(m, n)
 119         register struct mbuf *m, *n;
 120 {
 121         /*
 122          * If there's no room, realloc
 123          */
 124         if (M_FREEROOM(m) < n->m_len)
 125                 m_inc(m,m->m_size+MINCSIZE);
 126
 127         memcpy(m->m_data+m->m_len, n->m_data, n->m_len);
 128         m->m_len += n->m_len;
 129
 130         m_free(n);
 131 }
 132
 133
 134 /* make m size bytes large */
 135 void
 136 m_inc(m, size)
 137         struct mbuf *m;
 138         int size;
 139 {
 140         int datasize;
 141
 142         /* some compiles throw up on gotos.  This one we can fake. */
 143         if(m->m_size>size) return;
 144
 145         if (m->m_flags & M_EXT) {
 146           datasize = m->m_data - m->m_ext;
 147           m->m_ext = (char *)realloc(m->m_ext,size);
 148 /*              if (m->m_ext == NULL)
 149  *                      return (struct mbuf *)NULL;
 150  */
 151           m->m_data = m->m_ext + datasize;
 152         } else {
 153           char *dat;
 154           datasize = m->m_data - m->m_dat;
 155           dat = (char *)malloc(size);
 156 /*              if (dat == NULL)
 157  *                      return (struct mbuf *)NULL;
 158  */
 159           memcpy(dat, m->m_dat, m->m_size);
 160
 161           m->m_ext = dat;
 162           m->m_data = m->m_ext + datasize;
 163           m->m_flags |= M_EXT;
 164         }
 165
 166         m->m_size = size;
 167
 168 }
 169
 170
 171
 172 void
 173 m_adj(m, len)
 174         struct mbuf *m;
 175         int len;
 176 {
 177         if (m == NULL)
 178                 return;
 179         if (len >= 0) {
 180                 /* Trim from head */
 181                 m->m_data += len;
 182                 m->m_len -= len;
 183         } else {
 184                 /* Trim from tail */
 185                 len = -len;
 186                 m->m_len -= len;
 187         }
 188 }
 189
 190
 191 /*
 192  * Copy len bytes from m, starting off bytes into n
 193  */
 194 int
 195 m_copy(n, m, off, len)
 196         struct mbuf *n, *m;
 197         int off, len;
 198 {
 199         if (len > M_FREEROOM(n))
 200                 return -1;
 201
 202         memcpy((n->m_data + n->m_len), (m->m_data + off), len);
 203         n->m_len += len;
 204         return 0;
 205 }
 206
 207
 208 /*
 209  * Given a pointer into an mbuf, return the mbuf
 210  * XXX This is a kludge, I should eliminate the need for it
 211  * Fortunately, it's not used often
 212  */
 213 struct mbuf *
 214 dtom(dat)
 215         void *dat;
 216 {
 217         struct mbuf *m;
 218
 219         DEBUG_CALL("dtom");
 220         DEBUG_ARG("dat = %lx", (long )dat);
 221
 222         /* bug corrected for M_EXT buffers */
 223         for (m = m_usedlist.m_next; m != &m_usedlist; m = m->m_next) {
 224           if (m->m_flags & M_EXT) {
 225             if( (char *)dat>=m->m_ext && (char *)dat<(m->m_ext + m->m_size) )
 226               return m;
 227           } else {
 228             if( (char *)dat >= m->m_dat && (char *)dat<(m->m_dat + m->m_size) )
 229               return m;
 230           }
 231         }
 232
 233         DEBUG_ERROR((dfd, "dtom failed"));
 234
 235         return (struct mbuf *)0;
 236 }
 237