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 "qemu/osdep.h"
  19 #include <slirp.h>
  20
  21 #define MBUF_THRESH 30
  22
  23 /*
  24  * Find a nice value for msize
  25  * XXX if_maxlinkhdr already in mtu
  26  */
  27 #define SLIRP_MSIZE (IF_MTU + IF_MAXLINKHDR + offsetof(struct mbuf, m_dat) + 6)
  28
  29 void
  30 m_init(Slirp *slirp)
  31 {
  32     slirp->m_freelist.m_next = slirp->m_freelist.m_prev = &slirp->m_freelist;
  33     slirp->m_usedlist.m_next = slirp->m_usedlist.m_prev = &slirp->m_usedlist;
  34 }
  35
  36 void m_cleanup(Slirp *slirp)
  37 {
  38     struct mbuf *m, *next;
  39
  40     m = slirp->m_usedlist.m_next;
  41     while (m != &slirp->m_usedlist) {
  42         next = m->m_next;
  43         if (m->m_flags & M_EXT) {
  44             free(m->m_ext);
  45         }
  46         free(m);
  47         m = next;
  48     }
  49     m = slirp->m_freelist.m_next;
  50     while (m != &slirp->m_freelist) {
  51         next = m->m_next;
  52         free(m);
  53         m = next;
  54     }
  55 }
  56
  57 /*
  58  * Get an mbuf from the free list, if there are none
  59  * malloc 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 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.m_next == &slirp->m_freelist) {
  74                 m = (struct mbuf *)malloc(SLIRP_MSIZE);
  75                 if (m == NULL) goto end_error;
  76                 slirp->mbuf_alloced++;
  77                 if (slirp->mbuf_alloced > MBUF_THRESH)
  78                         flags = M_DOFREE;
  79                 m->slirp = slirp;
  80         } else {
  81                 m = slirp->m_freelist.m_next;
  82                 remque(m);
  83         }
  84
  85         /* Insert it in the used list */
  86         insque(m,&slirp->m_usedlist);
  87         m->m_flags = (flags | M_USEDLIST);
  88
  89         /* Initialise it */
  90         m->m_size = SLIRP_MSIZE - offsetof(struct mbuf, m_dat);
  91         m->m_data = m->m_dat;
  92         m->m_len = 0;
  93         m->m_nextpkt = NULL;
  94         m->m_prevpkt = NULL;
  95         m->resolution_requested = false;
  96         m->expiration_date = (uint64_t)-1;
  97 end_error:
  98         DEBUG_ARG("m = %p", m);
  99         return m;
 100 }
 101
 102 void
 103 m_free(struct mbuf *m)
 104 {
 105
 106   DEBUG_CALL("m_free");
 107   DEBUG_ARG("m = %p", m);
 108
 109   if(m) {
 110         /* Remove from m_usedlist */
 111         if (m->m_flags & M_USEDLIST)
 112            remque(m);
 113
 114         /* If it's M_EXT, free() it */
 115         if (m->m_flags & M_EXT)
 116            free(m->m_ext);
 117
 118         /*
 119          * Either free() it or put it on the free list
 120          */
 121         if (m->m_flags & M_DOFREE) {
 122                 m->slirp->mbuf_alloced--;
 123                 free(m);
 124         } else if ((m->m_flags & M_FREELIST) == 0) {
 125                 insque(m,&m->slirp->m_freelist);
 126                 m->m_flags = M_FREELIST; /* Clobber other flags */
 127         }
 128   } /* if(m) */
 129 }
 130
 131 /*
 132  * Copy data from one mbuf to the end of
 133  * the other.. if result is too big for one mbuf, malloc()
 134  * an M_EXT data segment
 135  */
 136 void
 137 m_cat(struct mbuf *m, struct mbuf *n)
 138 {
 139         /*
 140          * If there's no room, realloc
 141          */
 142         if (M_FREEROOM(m) < n->m_len)
 143                 m_inc(m,m->m_size+MINCSIZE);
 144
 145         memcpy(m->m_data+m->m_len, n->m_data, n->m_len);
 146         m->m_len += n->m_len;
 147
 148         m_free(n);
 149 }
 150
 151
 152 /* make m size bytes large */
 153 void
 154 m_inc(struct mbuf *m, int size)
 155 {
 156         int datasize;
 157
 158         /* some compiles throw up on gotos.  This one we can fake. */
 159         if(m->m_size>size) return;
 160
 161         if (m->m_flags & M_EXT) {
 162           datasize = m->m_data - m->m_ext;
 163           m->m_ext = (char *)realloc(m->m_ext,size);
 164           m->m_data = m->m_ext + datasize;
 165         } else {
 166           char *dat;
 167           datasize = m->m_data - m->m_dat;
 168           dat = (char *)malloc(size);
 169           memcpy(dat, m->m_dat, m->m_size);
 170
 171           m->m_ext = dat;
 172           m->m_data = m->m_ext + datasize;
 173           m->m_flags |= M_EXT;
 174         }
 175
 176         m->m_size = size;
 177
 178 }
 179
 180
 181
 182 void
 183 m_adj(struct mbuf *m, int len)
 184 {
 185         if (m == NULL)
 186                 return;
 187         if (len >= 0) {
 188                 /* Trim from head */
 189                 m->m_data += len;
 190                 m->m_len -= len;
 191         } else {
 192                 /* Trim from tail */
 193                 len = -len;
 194                 m->m_len -= len;
 195         }
 196 }
 197
 198
 199 /*
 200  * Copy len bytes from m, starting off bytes into n
 201  */
 202 int
 203 m_copy(struct mbuf *n, struct mbuf *m, int off, int len)
 204 {
 205         if (len > M_FREEROOM(n))
 206                 return -1;
 207
 208         memcpy((n->m_data + n->m_len), (m->m_data + off), len);
 209         n->m_len += len;
 210         return 0;
 211 }
 212
 213
 214 /*
 215  * Given a pointer into an mbuf, return the mbuf
 216  * XXX This is a kludge, I should eliminate the need for it
 217  * Fortunately, it's not used often
 218  */
 219 struct mbuf *
 220 dtom(Slirp *slirp, void *dat)
 221 {
 222         struct mbuf *m;
 223
 224         DEBUG_CALL("dtom");
 225         DEBUG_ARG("dat = %p", dat);
 226
 227         /* bug corrected for M_EXT buffers */
 228         for (m = slirp->m_usedlist.m_next; m != &slirp->m_usedlist;
 229              m = m->m_next) {
 230           if (m->m_flags & M_EXT) {
 231             if( (char *)dat>=m->m_ext && (char *)dat<(m->m_ext + m->m_size) )
 232               return m;
 233           } else {
 234             if( (char *)dat >= m->m_dat && (char *)dat<(m->m_dat + m->m_size) )
 235               return m;
 236           }
 237         }
 238
 239         DEBUG_ERROR((dfd, "dtom failed"));
 240
 241         return (struct mbuf *)0;
 242 }