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