slirp/src/mbuf.c

   1 /* SPDX-License-Identifier: BSD-3-Clause */
   2 /*
   3  * Copyright (c) 1995 Danny Gasparovski
   4  */
   5
   6 /*
   7  * mbuf's in SLiRP are much simpler than the real mbufs in
   8  * FreeBSD.  They are fixed size, determined by the MTU,
   9  * so that one whole packet can fit.  Mbuf's cannot be
  10  * chained together.  If there's more data than the mbuf
  11  * could hold, an external g_malloced buffer is pointed to
  12  * by m_ext (and the data pointers) and M_EXT is set in
  13  * the flags
  14  */
  15
  16 #include "slirp.h"
  17
  18 #define MBUF_THRESH 30
  19
  20 /*
  21  * Find a nice value for msize
  22  */
  23 #define SLIRP_MSIZE\
  24     (offsetof(struct mbuf, m_dat) + IF_MAXLINKHDR + TCPIPHDR_DELTA + IF_MTU)
  25
  26 void
  27 m_init(Slirp *slirp)
  28 {
  29     slirp->m_freelist.qh_link = slirp->m_freelist.qh_rlink = &slirp->m_freelist;
  30     slirp->m_usedlist.qh_link = slirp->m_usedlist.qh_rlink = &slirp->m_usedlist;
  31 }
  32
  33 void m_cleanup(Slirp *slirp)
  34 {
  35     struct mbuf *m, *next;
  36
  37     m = (struct mbuf *) slirp->m_usedlist.qh_link;
  38     while ((struct quehead *) m != &slirp->m_usedlist) {
  39         next = m->m_next;
  40         if (m->m_flags & M_EXT) {
  41             g_free(m->m_ext);
  42         }
  43         g_free(m);
  44         m = next;
  45     }
  46     m = (struct mbuf *) slirp->m_freelist.qh_link;
  47     while ((struct quehead *) m != &slirp->m_freelist) {
  48         next = m->m_next;
  49         g_free(m);
  50         m = next;
  51     }
  52 }
  53
  54 /*
  55  * Get an mbuf from the free list, if there are none
  56  * allocate one
  57  *
  58  * Because fragmentation can occur if we alloc new mbufs and
  59  * free old mbufs, we mark all mbufs above mbuf_thresh as M_DOFREE,
  60  * which tells m_free to actually g_free() it
  61  */
  62 struct mbuf *
  63 m_get(Slirp *slirp)
  64 {
  65         register struct mbuf *m;
  66         int flags = 0;
  67
  68         DEBUG_CALL("m_get");
  69
  70         if (slirp->m_freelist.qh_link == &slirp->m_freelist) {
  71                 m = g_malloc(SLIRP_MSIZE);
  72                 slirp->mbuf_alloced++;
  73                 if (slirp->mbuf_alloced > MBUF_THRESH)
  74                         flags = M_DOFREE;
  75                 m->slirp = slirp;
  76         } else {
  77                 m = (struct mbuf *) slirp->m_freelist.qh_link;
  78                 remque(m);
  79         }
  80
  81         /* Insert it in the used list */
  82         insque(m,&slirp->m_usedlist);
  83         m->m_flags = (flags | M_USEDLIST);
  84
  85         /* Initialise it */
  86         m->m_size = SLIRP_MSIZE - offsetof(struct mbuf, m_dat);
  87         m->m_data = m->m_dat;
  88         m->m_len = 0;
  89         m->m_nextpkt = NULL;
  90         m->m_prevpkt = NULL;
  91         m->resolution_requested = false;
  92         m->expiration_date = (uint64_t)-1;
  93         DEBUG_ARG("m = %p", m);
  94         return m;
  95 }
  96
  97 void
  98 m_free(struct mbuf *m)
  99 {
 100
 101   DEBUG_CALL("m_free");
 102   DEBUG_ARG("m = %p", m);
 103
 104   if(m) {
 105         /* Remove from m_usedlist */
 106         if (m->m_flags & M_USEDLIST)
 107            remque(m);
 108
 109         /* If it's M_EXT, free() it */
 110         if (m->m_flags & M_EXT) {
 111                 g_free(m->m_ext);
 112         }
 113         /*
 114          * Either free() it or put it on the free list
 115          */
 116         if (m->m_flags & M_DOFREE) {
 117                 m->slirp->mbuf_alloced--;
 118                 g_free(m);
 119         } else if ((m->m_flags & M_FREELIST) == 0) {
 120                 insque(m,&m->slirp->m_freelist);
 121                 m->m_flags = M_FREELIST; /* Clobber other flags */
 122         }
 123   } /* if(m) */
 124 }
 125
 126 /*
 127  * Copy data from one mbuf to the end of
 128  * the other.. if result is too big for one mbuf, allocate
 129  * an M_EXT data segment
 130  */
 131 void
 132 m_cat(struct mbuf *m, struct mbuf *n)
 133 {
 134         /*
 135          * If there's no room, realloc
 136          */
 137         if (M_FREEROOM(m) < n->m_len)
 138                 m_inc(m, m->m_len + n->m_len);
 139
 140         memcpy(m->m_data+m->m_len, n->m_data, n->m_len);
 141         m->m_len += n->m_len;
 142
 143         m_free(n);
 144 }
 145
 146
 147 /* make m 'size' bytes large from m_data */
 148 void
 149 m_inc(struct mbuf *m, int size)
 150 {
 151     int gapsize;
 152
 153     /* some compilers throw up on gotos.  This one we can fake. */
 154     if (M_ROOM(m) > size) {
 155         return;
 156     }
 157
 158     if (m->m_flags & M_EXT) {
 159         gapsize = m->m_data - m->m_ext;
 160         m->m_ext = g_realloc(m->m_ext, size + gapsize);
 161     } else {
 162         gapsize = m->m_data - m->m_dat;
 163         m->m_ext = g_malloc(size + gapsize);
 164         memcpy(m->m_ext, m->m_dat, m->m_size);
 165         m->m_flags |= M_EXT;
 166     }
 167
 168     m->m_data = m->m_ext + gapsize;
 169     m->m_size = size + gapsize;
 170 }
 171
 172
 173
 174 void
 175 m_adj(struct mbuf *m, int len)
 176 {
 177         if (m == NULL)
 178                 return;
 179         if (len >= 0) {
 180                 /* Trim from head */
 181                 m->m_data += len;
 182                 m->m_len -= len;
 183         } else {
 184                 /* Trim from tail */
 185                 len = -len;
 186                 m->m_len -= len;
 187         }
 188 }
 189
 190
 191 /*
 192  * Copy len bytes from m, starting off bytes into n
 193  */
 194 int
 195 m_copy(struct mbuf *n, struct mbuf *m, int off, int len)
 196 {
 197         if (len > M_FREEROOM(n))
 198                 return -1;
 199
 200         memcpy((n->m_data + n->m_len), (m->m_data + off), len);
 201         n->m_len += len;
 202         return 0;
 203 }
 204
 205
 206 /*
 207  * Given a pointer into an mbuf, return the mbuf
 208  * XXX This is a kludge, I should eliminate the need for it
 209  * Fortunately, it's not used often
 210  */
 211 struct mbuf *
 212 dtom(Slirp *slirp, void *dat)
 213 {
 214         struct mbuf *m;
 215
 216         DEBUG_CALL("dtom");
 217         DEBUG_ARG("dat = %p", dat);
 218
 219         /* bug corrected for M_EXT buffers */
 220         for (m = (struct mbuf *) slirp->m_usedlist.qh_link;
 221              (struct quehead *) m != &slirp->m_usedlist;
 222              m = m->m_next) {
 223           if (m->m_flags & M_EXT) {
 224             if( (char *)dat>=m->m_ext && (char *)dat<(m->m_ext + m->m_size) )
 225               return m;
 226           } else {
 227             if( (char *)dat >= m->m_dat && (char *)dat<(m->m_dat + m->m_size) )
 228               return m;
 229           }
 230         }
 231
 232         DEBUG_ERROR("dtom failed");
 233
 234         return (struct mbuf *)0;
 235 }