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 "qemu/osdep.h"
  19 #include "slirp.h"
  20
  21 #define MBUF_THRESH 30
  22
  23 /*
  24  * Find a nice value for msize
  25  */
  26 #define SLIRP_MSIZE\
  27     (offsetof(struct mbuf, m_dat) + IF_MAXLINKHDR + TCPIPHDR_DELTA + IF_MTU)
  28
  29 void
  30 m_init(Slirp *slirp)
  31 {
  32     slirp->m_freelist.qh_link = slirp->m_freelist.qh_rlink = &slirp->m_freelist;
  33     slirp->m_usedlist.qh_link = slirp->m_usedlist.qh_rlink = &slirp->m_usedlist;
  34 }
  35
  36 void m_cleanup(Slirp *slirp)
  37 {
  38     struct mbuf *m, *next;
  39
  40     m = (struct mbuf *) slirp->m_usedlist.qh_link;
  41     while ((struct quehead *) m != &slirp->m_usedlist) {
  42         next = m->m_next;
  43         if (m->m_flags & M_EXT) {
  44             g_free(m->m_ext);
  45         }
  46         g_free(m);
  47         m = next;
  48     }
  49     m = (struct mbuf *) slirp->m_freelist.qh_link;
  50     while ((struct quehead *) m != &slirp->m_freelist) {
  51         next = m->m_next;
  52         g_free(m);
  53         m = next;
  54     }
  55 }
  56
  57 /*
  58  * Get an mbuf from the free list, if there are none
  59  * allocate one
  60  *
  61  * Because fragmentation can occur if we alloc new mbufs and
  62  * free old mbufs, we mark all mbufs above mbuf_thresh as M_DOFREE,
  63  * which tells m_free to actually g_free() it
  64  */
  65 struct mbuf *
  66 m_get(Slirp *slirp)
  67 {
  68         register struct mbuf *m;
  69         int flags = 0;
  70
  71         DEBUG_CALL("m_get");
  72
  73         if (slirp->m_freelist.qh_link == &slirp->m_freelist) {
  74                 m = g_malloc(SLIRP_MSIZE);
  75                 slirp->mbuf_alloced++;
  76                 if (slirp->mbuf_alloced > MBUF_THRESH)
  77                         flags = M_DOFREE;
  78                 m->slirp = slirp;
  79         } else {
  80                 m = (struct mbuf *) slirp->m_freelist.qh_link;
  81                 remque(m);
  82         }
  83
  84         /* Insert it in the used list */
  85         insque(m,&slirp->m_usedlist);
  86         m->m_flags = (flags | M_USEDLIST);
  87
  88         /* Initialise it */
  89         m->m_size = SLIRP_MSIZE - offsetof(struct mbuf, m_dat);
  90         m->m_data = m->m_dat;
  91         m->m_len = 0;
  92         m->m_nextpkt = NULL;
  93         m->m_prevpkt = NULL;
  94         m->resolution_requested = false;
  95         m->expiration_date = (uint64_t)-1;
  96         DEBUG_ARG("m = %p", m);
  97         return m;
  98 }
  99
 100 void
 101 m_free(struct mbuf *m)
 102 {
 103
 104   DEBUG_CALL("m_free");
 105   DEBUG_ARG("m = %p", m);
 106
 107   if(m) {
 108         /* Remove from m_usedlist */
 109         if (m->m_flags & M_USEDLIST)
 110            remque(m);
 111
 112         /* If it's M_EXT, free() it */
 113         if (m->m_flags & M_EXT) {
 114                 g_free(m->m_ext);
 115         }
 116         /*
 117          * Either free() it or put it on the free list
 118          */
 119         if (m->m_flags & M_DOFREE) {
 120                 m->slirp->mbuf_alloced--;
 121                 g_free(m);
 122         } else if ((m->m_flags & M_FREELIST) == 0) {
 123                 insque(m,&m->slirp->m_freelist);
 124                 m->m_flags = M_FREELIST; /* Clobber other flags */
 125         }
 126   } /* if(m) */
 127 }
 128
 129 /*
 130  * Copy data from one mbuf to the end of
 131  * the other.. if result is too big for one mbuf, allocate
 132  * an M_EXT data segment
 133  */
 134 void
 135 m_cat(struct mbuf *m, struct mbuf *n)
 136 {
 137         /*
 138          * If there's no room, realloc
 139          */
 140         if (M_FREEROOM(m) < n->m_len)
 141                 m_inc(m, m->m_len + n->m_len);
 142
 143         memcpy(m->m_data+m->m_len, n->m_data, n->m_len);
 144         m->m_len += n->m_len;
 145
 146         m_free(n);
 147 }
 148
 149
 150 /* make m 'size' bytes large from m_data */
 151 void
 152 m_inc(struct mbuf *m, int size)
 153 {
 154         int datasize;
 155
 156         /* some compiles throw up on gotos.  This one we can fake. */
 157         if(m->m_size>size) return;
 158
 159         if (m->m_flags & M_EXT) {
 160           datasize = m->m_data - m->m_ext;
 161           m->m_ext = g_realloc(m->m_ext, size + datasize);
 162           m->m_data = m->m_ext + datasize;
 163         } else {
 164           char *dat;
 165           datasize = m->m_data - m->m_dat;
 166           dat = g_malloc(size + datasize);
 167           memcpy(dat, m->m_dat, m->m_size);
 168
 169           m->m_ext = dat;
 170           m->m_data = m->m_ext + datasize;
 171           m->m_flags |= M_EXT;
 172         }
 173
 174         m->m_size = size + datasize;
 175 }
 176
 177
 178
 179 void
 180 m_adj(struct mbuf *m, int len)
 181 {
 182         if (m == NULL)
 183                 return;
 184         if (len >= 0) {
 185                 /* Trim from head */
 186                 m->m_data += len;
 187                 m->m_len -= len;
 188         } else {
 189                 /* Trim from tail */
 190                 len = -len;
 191                 m->m_len -= len;
 192         }
 193 }
 194
 195
 196 /*
 197  * Copy len bytes from m, starting off bytes into n
 198  */
 199 int
 200 m_copy(struct mbuf *n, struct mbuf *m, int off, int len)
 201 {
 202         if (len > M_FREEROOM(n))
 203                 return -1;
 204
 205         memcpy((n->m_data + n->m_len), (m->m_data + off), len);
 206         n->m_len += len;
 207         return 0;
 208 }
 209
 210
 211 /*
 212  * Given a pointer into an mbuf, return the mbuf
 213  * XXX This is a kludge, I should eliminate the need for it
 214  * Fortunately, it's not used often
 215  */
 216 struct mbuf *
 217 dtom(Slirp *slirp, void *dat)
 218 {
 219         struct mbuf *m;
 220
 221         DEBUG_CALL("dtom");
 222         DEBUG_ARG("dat = %p", dat);
 223
 224         /* bug corrected for M_EXT buffers */
 225         for (m = (struct mbuf *) slirp->m_usedlist.qh_link;
 226              (struct quehead *) m != &slirp->m_usedlist;
 227              m = m->m_next) {
 228           if (m->m_flags & M_EXT) {
 229             if( (char *)dat>=m->m_ext && (char *)dat<(m->m_ext + m->m_size) )
 230               return m;
 231           } else {
 232             if( (char *)dat >= m->m_dat && (char *)dat<(m->m_dat + m->m_size) )
 233               return m;
 234           }
 235         }
 236
 237         DEBUG_ERROR((dfd, "dtom failed"));
 238
 239         return (struct mbuf *)0;
 240 }