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