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