slirp/src/sbuf.c

   1 /* SPDX-License-Identifier: BSD-3-Clause */
   2 /*
   3  * Copyright (c) 1995 Danny Gasparovski.
   4  */
   5
   6 #include "slirp.h"
   7
   8 static void sbappendsb(struct sbuf *sb, struct mbuf *m);
   9
  10 void
  11 sbfree(struct sbuf *sb)
  12 {
  13         free(sb->sb_data);
  14 }
  15
  16 bool
  17 sbdrop(struct sbuf *sb, int num)
  18 {
  19     int limit = sb->sb_datalen / 2;
  20
  21         /*
  22          * We can only drop how much we have
  23          * This should never succeed
  24          */
  25         if(num > sb->sb_cc)
  26                 num = sb->sb_cc;
  27         sb->sb_cc -= num;
  28         sb->sb_rptr += num;
  29         if(sb->sb_rptr >= sb->sb_data + sb->sb_datalen)
  30                 sb->sb_rptr -= sb->sb_datalen;
  31
  32     if (sb->sb_cc < limit && sb->sb_cc + num >= limit) {
  33         return true;
  34     }
  35
  36     return false;
  37 }
  38
  39 void
  40 sbreserve(struct sbuf *sb, int size)
  41 {
  42         if (sb->sb_data) {
  43                 /* Already alloced, realloc if necessary */
  44                 if (sb->sb_datalen != size) {
  45                         sb->sb_wptr = sb->sb_rptr = sb->sb_data = (char *)realloc(sb->sb_data, size);
  46                         sb->sb_cc = 0;
  47                         if (sb->sb_wptr)
  48                            sb->sb_datalen = size;
  49                         else
  50                            sb->sb_datalen = 0;
  51                 }
  52         } else {
  53                 sb->sb_wptr = sb->sb_rptr = sb->sb_data = (char *)malloc(size);
  54                 sb->sb_cc = 0;
  55                 if (sb->sb_wptr)
  56                    sb->sb_datalen = size;
  57                 else
  58                    sb->sb_datalen = 0;
  59         }
  60 }
  61
  62 /*
  63  * Try and write() to the socket, whatever doesn't get written
  64  * append to the buffer... for a host with a fast net connection,
  65  * this prevents an unnecessary copy of the data
  66  * (the socket is non-blocking, so we won't hang)
  67  */
  68 void
  69 sbappend(struct socket *so, struct mbuf *m)
  70 {
  71         int ret = 0;
  72
  73         DEBUG_CALL("sbappend");
  74         DEBUG_ARG("so = %p", so);
  75         DEBUG_ARG("m = %p", m);
  76         DEBUG_ARG("m->m_len = %d", m->m_len);
  77
  78         /* Shouldn't happen, but...  e.g. foreign host closes connection */
  79         if (m->m_len <= 0) {
  80                 m_free(m);
  81                 return;
  82         }
  83
  84         /*
  85          * If there is urgent data, call sosendoob
  86          * if not all was sent, sowrite will take care of the rest
  87          * (The rest of this function is just an optimisation)
  88          */
  89         if (so->so_urgc) {
  90                 sbappendsb(&so->so_rcv, m);
  91                 m_free(m);
  92                 (void)sosendoob(so);
  93                 return;
  94         }
  95
  96         /*
  97          * We only write if there's nothing in the buffer,
  98          * ottherwise it'll arrive out of order, and hence corrupt
  99          */
 100         if (!so->so_rcv.sb_cc)
 101            ret = slirp_send(so, m->m_data, m->m_len, 0);
 102
 103         if (ret <= 0) {
 104                 /*
 105                  * Nothing was written
 106                  * It's possible that the socket has closed, but
 107                  * we don't need to check because if it has closed,
 108                  * it will be detected in the normal way by soread()
 109                  */
 110                 sbappendsb(&so->so_rcv, m);
 111         } else if (ret != m->m_len) {
 112                 /*
 113                  * Something was written, but not everything..
 114                  * sbappendsb the rest
 115                  */
 116                 m->m_len -= ret;
 117                 m->m_data += ret;
 118                 sbappendsb(&so->so_rcv, m);
 119         } /* else */
 120         /* Whatever happened, we free the mbuf */
 121         m_free(m);
 122 }
 123
 124 /*
 125  * Copy the data from m into sb
 126  * The caller is responsible to make sure there's enough room
 127  */
 128 static void
 129 sbappendsb(struct sbuf *sb, struct mbuf *m)
 130 {
 131         int len, n,  nn;
 132
 133         len = m->m_len;
 134
 135         if (sb->sb_wptr < sb->sb_rptr) {
 136                 n = sb->sb_rptr - sb->sb_wptr;
 137                 if (n > len) n = len;
 138                 memcpy(sb->sb_wptr, m->m_data, n);
 139         } else {
 140                 /* Do the right edge first */
 141                 n = sb->sb_data + sb->sb_datalen - sb->sb_wptr;
 142                 if (n > len) n = len;
 143                 memcpy(sb->sb_wptr, m->m_data, n);
 144                 len -= n;
 145                 if (len) {
 146                         /* Now the left edge */
 147                         nn = sb->sb_rptr - sb->sb_data;
 148                         if (nn > len) nn = len;
 149                         memcpy(sb->sb_data,m->m_data+n,nn);
 150                         n += nn;
 151                 }
 152         }
 153
 154         sb->sb_cc += n;
 155         sb->sb_wptr += n;
 156         if (sb->sb_wptr >= sb->sb_data + sb->sb_datalen)
 157                 sb->sb_wptr -= sb->sb_datalen;
 158 }
 159
 160 /*
 161  * Copy data from sbuf to a normal, straight buffer
 162  * Don't update the sbuf rptr, this will be
 163  * done in sbdrop when the data is acked
 164  */
 165 void
 166 sbcopy(struct sbuf *sb, int off, int len, char *to)
 167 {
 168         char *from;
 169
 170         from = sb->sb_rptr + off;
 171         if (from >= sb->sb_data + sb->sb_datalen)
 172                 from -= sb->sb_datalen;
 173
 174         if (from < sb->sb_wptr) {
 175                 if (len > sb->sb_cc) len = sb->sb_cc;
 176                 memcpy(to,from,len);
 177         } else {
 178                 /* re-use off */
 179                 off = (sb->sb_data + sb->sb_datalen) - from;
 180                 if (off > len) off = len;
 181                 memcpy(to,from,off);
 182                 len -= off;
 183                 if (len)
 184                    memcpy(to+off,sb->sb_data,len);
 185         }
 186 }