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 g_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  */
  25 #define SLIRP_MSIZE\
  26     (offsetof(struct mbuf, m_dat) + IF_MAXLINKHDR + TCPIPHDR_DELTA + IF_MTU)
  27
  28 void
  29 m_init(Slirp *slirp)
  30 {
  31     slirp->m_freelist.qh_link = slirp->m_freelist.qh_rlink = &slirp->m_freelist;
  32     slirp->m_usedlist.qh_link = slirp->m_usedlist.qh_rlink = &slirp->m_usedlist;
  33 }
  34
  35 void m_cleanup(Slirp *slirp)
  36 {
  37     struct mbuf *m, *next;
  38
  39     m = (struct mbuf *) slirp->m_usedlist.qh_link;
  40     while ((struct quehead *) m != &slirp->m_usedlist) {
  41         next = m->m_next;
  42         if (m->m_flags & M_EXT) {
  43             g_free(m->m_ext);
  44         }
  45         g_free(m);
  46         m = next;
  47     }
  48     m = (struct mbuf *) slirp->m_freelist.qh_link;
  49     while ((struct quehead *) m != &slirp->m_freelist) {
  50         next = m->m_next;
  51         g_free(m);
  52         m = next;
  53     }
  54 }
  55
  56 /*
  57  * Get an mbuf from the free list, if there are none
  58  * allocate one
  59  *
  60  * Because fragmentation can occur if we alloc new mbufs and
  61  * free old mbufs, we mark all mbufs above mbuf_thresh as M_DOFREE,
  62  * which tells m_free to actually g_free() it
  63  */
  64 struct mbuf *
  65 m_get(Slirp *slirp)
  66 {
  67         register struct mbuf *m;
  68         int flags = 0;
  69
  70         DEBUG_CALL("m_get");
  71
  72         if (slirp->m_freelist.qh_link == &slirp->m_freelist) {
  73                 m = g_malloc(SLIRP_MSIZE);
  74                 slirp->mbuf_alloced++;
  75                 if (slirp->mbuf_alloced > MBUF_THRESH)
  76                         flags = M_DOFREE;
  77                 m->slirp = slirp;
  78         } else {
  79                 m = (struct mbuf *) slirp->m_freelist.qh_link;
  80                 remque(m);
  81         }
  82
  83         /* Insert it in the used list */
  84         insque(m,&slirp->m_usedlist);
  85         m->m_flags = (flags | M_USEDLIST);
  86
  87         /* Initialise it */
  88         m->m_size = SLIRP_MSIZE - offsetof(struct mbuf, m_dat);
  89         m->m_data = m->m_dat;
  90         m->m_len = 0;
  91         m->m_nextpkt = NULL;
  92         m->m_prevpkt = NULL;
  93         m->resolution_requested = false;
  94         m->expiration_date = (uint64_t)-1;
  95         DEBUG_ARG("m = %p", m);
  96         return m;
  97 }
  98
  99 void
 100 m_free(struct mbuf *m)
 101 {
 102
 103   DEBUG_CALL("m_free");
 104   DEBUG_ARG("m = %p", m);
 105
 106   if(m) {
 107         /* Remove from m_usedlist */
 108         if (m->m_flags & M_USEDLIST)
 109            remque(m);
 110
 111         /* If it's M_EXT, free() it */
 112         if (m->m_flags & M_EXT) {
 113                 g_free(m->m_ext);
 114         }
 115         /*
 116          * Either free() it or put it on the free list
 117          */
 118         if (m->m_flags & M_DOFREE) {
 119                 m->slirp->mbuf_alloced--;
 120                 g_free(m);
 121         } else if ((m->m_flags & M_FREELIST) == 0) {
 122                 insque(m,&m->slirp->m_freelist);
 123                 m->m_flags = M_FREELIST; /* Clobber other flags */
 124         }
 125   } /* if(m) */
 126 }
 127
 128 /*
 129  * Copy data from one mbuf to the end of
 130  * the other.. if result is too big for one mbuf, allocate
 131  * an M_EXT data segment
 132  */
 133 void
 134 m_cat(struct mbuf *m, struct mbuf *n)
 135 {
 136         /*
 137          * If there's no room, realloc
 138          */
 139         if (M_FREEROOM(m) < n->m_len)
 140                 m_inc(m, m->m_len + n->m_len);
 141
 142         memcpy(m->m_data+m->m_len, n->m_data, n->m_len);
 143         m->m_len += n->m_len;
 144
 145         m_free(n);
 146 }
 147
 148
 149 /* make m 'size' bytes large from m_data */
 150 void
 151 m_inc(struct mbuf *m, int size)
 152 {
 153     int gapsize;
 154
 155     /* some compilers throw up on gotos.  This one we can fake. */
 156     if (M_ROOM(m) > size) {
 157         return;
 158     }
 159
 160     if (m->m_flags & M_EXT) {
 161         gapsize = m->m_data - m->m_ext;
 162         m->m_ext = g_realloc(m->m_ext, size + gapsize);
 163     } else {
 164         gapsize = m->m_data - m->m_dat;
 165         m->m_ext = g_malloc(size + gapsize);
 166         memcpy(m->m_ext, m->m_dat, m->m_size);
 167         m->m_flags |= M_EXT;
 168     }
 169
 170     m->m_data = m->m_ext + gapsize;
 171     m->m_size = size + gapsize;
 172 }
 173
 174
 175
 176 void
 177 m_adj(struct mbuf *m, 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(struct mbuf *n, struct mbuf *m, int off, int 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(Slirp *slirp, void *dat)
 215 {
 216         struct mbuf *m;
 217
 218         DEBUG_CALL("dtom");
 219         DEBUG_ARG("dat = %p", dat);
 220
 221         /* bug corrected for M_EXT buffers */
 222         for (m = (struct mbuf *) slirp->m_usedlist.qh_link;
 223              (struct quehead *) m != &slirp->m_usedlist;
 224              m = m->m_next) {
 225           if (m->m_flags & M_EXT) {
 226             if( (char *)dat>=m->m_ext && (char *)dat<(m->m_ext + m->m_size) )
 227               return m;
 228           } else {
 229             if( (char *)dat >= m->m_dat && (char *)dat<(m->m_dat + m->m_size) )
 230               return m;
 231           }
 232         }
 233
 234         DEBUG_ERROR("dtom failed");
 235
 236         return (struct mbuf *)0;
 237 }