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 void m_cleanup(Slirp *slirp)
  36 {
  37     struct mbuf *m, *next;
  38
  39     m = slirp->m_usedlist.m_next;
  40     while (m != &slirp->m_usedlist) {
  41         next = m->m_next;
  42         if (m->m_flags & M_EXT) {
  43             free(m->m_ext);
  44         }
  45         free(m);
  46         m = next;
  47     }
  48     m = slirp->m_freelist.m_next;
  49     while (m != &slirp->m_freelist) {
  50         next = m->m_next;
  51         free(m);
  52         m = next;
  53     }
  54 }
  55
  56 /*
  57  * Get an mbuf from the free list, if there are none
  58  * malloc 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 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.m_next == &slirp->m_freelist) {
  73                 m = (struct mbuf *)malloc(SLIRP_MSIZE);
  74                 if (m == NULL) goto end_error;
  75                 slirp->mbuf_alloced++;
  76                 if (slirp->mbuf_alloced > MBUF_THRESH)
  77                         flags = M_DOFREE;
  78                 m->slirp = slirp;
  79         } else {
  80                 m = slirp->m_freelist.m_next;
  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 end_error:
  97         DEBUG_ARG("m = %p", m);
  98         return m;
  99 }
 100
 101 void
 102 m_free(struct mbuf *m)
 103 {
 104
 105   DEBUG_CALL("m_free");
 106   DEBUG_ARG("m = %p", m);
 107
 108   if(m) {
 109         /* Remove from m_usedlist */
 110         if (m->m_flags & M_USEDLIST)
 111            remque(m);
 112
 113         /* If it's M_EXT, free() it */
 114         if (m->m_flags & M_EXT)
 115            free(m->m_ext);
 116
 117         /*
 118          * Either free() it or put it on the free list
 119          */
 120         if (m->m_flags & M_DOFREE) {
 121                 m->slirp->mbuf_alloced--;
 122                 free(m);
 123         } else if ((m->m_flags & M_FREELIST) == 0) {
 124                 insque(m,&m->slirp->m_freelist);
 125                 m->m_flags = M_FREELIST; /* Clobber other flags */
 126         }
 127   } /* if(m) */
 128 }
 129
 130 /*
 131  * Copy data from one mbuf to the end of
 132  * the other.. if result is too big for one mbuf, malloc()
 133  * an M_EXT data segment
 134  */
 135 void
 136 m_cat(struct mbuf *m, struct mbuf *n)
 137 {
 138         /*
 139          * If there's no room, realloc
 140          */
 141         if (M_FREEROOM(m) < n->m_len)
 142                 m_inc(m,m->m_size+MINCSIZE);
 143
 144         memcpy(m->m_data+m->m_len, n->m_data, n->m_len);
 145         m->m_len += n->m_len;
 146
 147         m_free(n);
 148 }
 149
 150
 151 /* make m size bytes large */
 152 void
 153 m_inc(struct mbuf *m, int size)
 154 {
 155         int datasize;
 156
 157         /* some compiles throw up on gotos.  This one we can fake. */
 158         if(m->m_size>size) return;
 159
 160         if (m->m_flags & M_EXT) {
 161           datasize = m->m_data - m->m_ext;
 162           m->m_ext = (char *)realloc(m->m_ext,size);
 163           m->m_data = m->m_ext + datasize;
 164         } else {
 165           char *dat;
 166           datasize = m->m_data - m->m_dat;
 167           dat = (char *)malloc(size);
 168           memcpy(dat, m->m_dat, m->m_size);
 169
 170           m->m_ext = dat;
 171           m->m_data = m->m_ext + datasize;
 172           m->m_flags |= M_EXT;
 173         }
 174
 175         m->m_size = size;
 176
 177 }
 178
 179
 180
 181 void
 182 m_adj(struct mbuf *m, int len)
 183 {
 184         if (m == NULL)
 185                 return;
 186         if (len >= 0) {
 187                 /* Trim from head */
 188                 m->m_data += len;
 189                 m->m_len -= len;
 190         } else {
 191                 /* Trim from tail */
 192                 len = -len;
 193                 m->m_len -= len;
 194         }
 195 }
 196
 197
 198 /*
 199  * Copy len bytes from m, starting off bytes into n
 200  */
 201 int
 202 m_copy(struct mbuf *n, struct mbuf *m, int off, int len)
 203 {
 204         if (len > M_FREEROOM(n))
 205                 return -1;
 206
 207         memcpy((n->m_data + n->m_len), (m->m_data + off), len);
 208         n->m_len += len;
 209         return 0;
 210 }
 211
 212
 213 /*
 214  * Given a pointer into an mbuf, return the mbuf
 215  * XXX This is a kludge, I should eliminate the need for it
 216  * Fortunately, it's not used often
 217  */
 218 struct mbuf *
 219 dtom(Slirp *slirp, void *dat)
 220 {
 221         struct mbuf *m;
 222
 223         DEBUG_CALL("dtom");
 224         DEBUG_ARG("dat = %p", dat);
 225
 226         /* bug corrected for M_EXT buffers */
 227         for (m = slirp->m_usedlist.m_next; m != &slirp->m_usedlist;
 228              m = m->m_next) {
 229           if (m->m_flags & M_EXT) {
 230             if( (char *)dat>=m->m_ext && (char *)dat<(m->m_ext + m->m_size) )
 231               return m;
 232           } else {
 233             if( (char *)dat >= m->m_dat && (char *)dat<(m->m_dat + m->m_size) )
 234               return m;
 235           }
 236         }
 237
 238         DEBUG_ERROR((dfd, "dtom failed"));
 239
 240         return (struct mbuf *)0;
 241 }