net/x25/x25_facilities.c

   1 /*
   2  *      X.25 Packet Layer release 002
   3  *
   4  *      This is ALPHA test software. This code may break your machine,
   5  *      randomly fail to work with new releases, misbehave and/or generally
   6  *      screw up. It might even work.
   7  *
   8  *      This code REQUIRES 2.1.15 or higher
   9  *
  10  *      This module:
  11  *              This module is free software; you can redistribute it and/or
  12  *              modify it under the terms of the GNU General Public License
  13  *              as published by the Free Software Foundation; either version
  14  *              2 of the License, or (at your option) any later version.
  15  *
  16  *      History
  17  *      X.25 001        Split from x25_subr.c
  18  *      mar/20/00       Daniela Squassoni Disabling/enabling of facilities
  19  *                                        negotiation.
  20  *      apr/14/05       Shaun Pereira - Allow fast select with no restriction
  21  *                                      on response.
  22  */
  23
  24 #include <linux/kernel.h>
  25 #include <linux/string.h>
  26 #include <linux/skbuff.h>
  27 #include <net/sock.h>
  28 #include <net/x25.h>
  29
  30 /*
  31  *      Parse a set of facilities into the facilities structure. Unrecognised
  32  *      facilities are written to the debug log file.
  33  */
  34 int x25_parse_facilities(struct sk_buff *skb,
  35                          struct x25_facilities *facilities,
  36                          unsigned long *vc_fac_mask)
  37 {
  38         unsigned char *p = skb->data;
  39         unsigned int len = *p++;
  40
  41         *vc_fac_mask = 0;
  42
  43         while (len > 0) {
  44                 switch (*p & X25_FAC_CLASS_MASK) {
  45                 case X25_FAC_CLASS_A:
  46                         switch (*p) {
  47                         case X25_FAC_REVERSE:
  48                                 if((p[1] & 0x81) == 0x81) {
  49                                         facilities->reverse = p[1] & 0x81;
  50                                         *vc_fac_mask |= X25_MASK_REVERSE;
  51                                         break;
  52                                 }
  53
  54                                 if((p[1] & 0x01) == 0x01) {
  55                                         facilities->reverse = p[1] & 0x01;
  56                                         *vc_fac_mask |= X25_MASK_REVERSE;
  57                                         break;
  58                                 }
  59
  60                                 if((p[1] & 0x80) == 0x80) {
  61                                         facilities->reverse = p[1] & 0x80;
  62                                         *vc_fac_mask |= X25_MASK_REVERSE;
  63                                         break;
  64                                 }
  65
  66                                 if(p[1] == 0x00) {
  67                                         facilities->reverse
  68                                                 = X25_DEFAULT_REVERSE;
  69                                         *vc_fac_mask |= X25_MASK_REVERSE;
  70                                         break;
  71                                 }
  72
  73                         case X25_FAC_THROUGHPUT:
  74                                 facilities->throughput = p[1];
  75                                 *vc_fac_mask |= X25_MASK_THROUGHPUT;
  76                                 break;
  77                         default:
  78                                 printk(KERN_DEBUG "X.25: unknown facility "
  79                                        "%02X, value %02X\n",
  80                                        p[0], p[1]);
  81                                 break;
  82                         }
  83                         p   += 2;
  84                         len -= 2;
  85                         break;
  86                 case X25_FAC_CLASS_B:
  87                         switch (*p) {
  88                         case X25_FAC_PACKET_SIZE:
  89                                 facilities->pacsize_in  = p[1];
  90                                 facilities->pacsize_out = p[2];
  91                                 *vc_fac_mask |= X25_MASK_PACKET_SIZE;
  92                                 break;
  93                         case X25_FAC_WINDOW_SIZE:
  94                                 facilities->winsize_in  = p[1];
  95                                 facilities->winsize_out = p[2];
  96                                 *vc_fac_mask |= X25_MASK_WINDOW_SIZE;
  97                                 break;
  98                         default:
  99                                 printk(KERN_DEBUG "X.25: unknown facility "
 100                                        "%02X, values %02X, %02X\n",
 101                                        p[0], p[1], p[2]);
 102                                 break;
 103                         }
 104                         p   += 3;
 105                         len -= 3;
 106                         break;
 107                 case X25_FAC_CLASS_C:
 108                         printk(KERN_DEBUG "X.25: unknown facility %02X, "
 109                                "values %02X, %02X, %02X\n",
 110                                p[0], p[1], p[2], p[3]);
 111                         p   += 4;
 112                         len -= 4;
 113                         break;
 114                 case X25_FAC_CLASS_D:
 115                         printk(KERN_DEBUG "X.25: unknown facility %02X, "
 116                                "length %d, values %02X, %02X, %02X, %02X\n",
 117                                p[0], p[1], p[2], p[3], p[4], p[5]);
 118                         len -= p[1] + 2;
 119                         p   += p[1] + 2;
 120                         break;
 121                 }
 122         }
 123
 124         return p - skb->data;
 125 }
 126
 127 /*
 128  *      Create a set of facilities.
 129  */
 130 int x25_create_facilities(unsigned char *buffer,
 131                           struct x25_facilities *facilities,
 132                           unsigned long facil_mask)
 133 {
 134         unsigned char *p = buffer + 1;
 135         int len;
 136
 137         if (!facil_mask) {
 138                 /*
 139                  * Length of the facilities field in call_req or
 140                  * call_accept packets
 141                  */
 142                 buffer[0] = 0;
 143                 len = 1; /* 1 byte for the length field */
 144                 return len;
 145         }
 146
 147         if (facilities->reverse && (facil_mask & X25_MASK_REVERSE)) {
 148                 *p++ = X25_FAC_REVERSE;
 149                 *p++ = facilities->reverse;
 150         }
 151
 152         if (facilities->throughput && (facil_mask & X25_MASK_THROUGHPUT)) {
 153                 *p++ = X25_FAC_THROUGHPUT;
 154                 *p++ = facilities->throughput;
 155         }
 156
 157         if ((facilities->pacsize_in || facilities->pacsize_out) &&
 158             (facil_mask & X25_MASK_PACKET_SIZE)) {
 159                 *p++ = X25_FAC_PACKET_SIZE;
 160                 *p++ = facilities->pacsize_in ? : facilities->pacsize_out;
 161                 *p++ = facilities->pacsize_out ? : facilities->pacsize_in;
 162         }
 163
 164         if ((facilities->winsize_in || facilities->winsize_out) &&
 165             (facil_mask & X25_MASK_WINDOW_SIZE)) {
 166                 *p++ = X25_FAC_WINDOW_SIZE;
 167                 *p++ = facilities->winsize_in ? : facilities->winsize_out;
 168                 *p++ = facilities->winsize_out ? : facilities->winsize_in;
 169         }
 170
 171         len       = p - buffer;
 172         buffer[0] = len - 1;
 173
 174         return len;
 175 }
 176
 177 /*
 178  *      Try to reach a compromise on a set of facilities.
 179  *
 180  *      The only real problem is with reverse charging.
 181  */
 182 int x25_negotiate_facilities(struct sk_buff *skb, struct sock *sk,
 183                              struct x25_facilities *new)
 184 {
 185         struct x25_sock *x25 = x25_sk(sk);
 186         struct x25_facilities *ours = &x25->facilities;
 187         struct x25_facilities theirs;
 188         int len;
 189
 190         memset(&theirs, 0, sizeof(theirs));
 191         memcpy(new, ours, sizeof(*new));
 192
 193         len = x25_parse_facilities(skb, &theirs, &x25->vc_facil_mask);
 194
 195         /*
 196          *      They want reverse charging, we won't accept it.
 197          */
 198         if ((theirs.reverse & 0x01 ) && (ours->reverse & 0x01)) {
 199                 SOCK_DEBUG(sk, "X.25: rejecting reverse charging request");
 200                 return -1;
 201         }
 202
 203         new->reverse = theirs.reverse;
 204
 205         if (theirs.throughput) {
 206                 if (theirs.throughput < ours->throughput) {
 207                         SOCK_DEBUG(sk, "X.25: throughput negotiated down");
 208                         new->throughput = theirs.throughput;
 209                 }
 210         }
 211
 212         if (theirs.pacsize_in && theirs.pacsize_out) {
 213                 if (theirs.pacsize_in < ours->pacsize_in) {
 214                         SOCK_DEBUG(sk, "X.25: packet size inwards negotiated down");
 215                         new->pacsize_in = theirs.pacsize_in;
 216                 }
 217                 if (theirs.pacsize_out < ours->pacsize_out) {
 218                         SOCK_DEBUG(sk, "X.25: packet size outwards negotiated down");
 219                         new->pacsize_out = theirs.pacsize_out;
 220                 }
 221         }
 222
 223         if (theirs.winsize_in && theirs.winsize_out) {
 224                 if (theirs.winsize_in < ours->winsize_in) {
 225                         SOCK_DEBUG(sk, "X.25: window size inwards negotiated down");
 226                         new->winsize_in = theirs.winsize_in;
 227                 }
 228                 if (theirs.winsize_out < ours->winsize_out) {
 229                         SOCK_DEBUG(sk, "X.25: window size outwards negotiated down");
 230                         new->winsize_out = theirs.winsize_out;
 231                 }
 232         }
 233
 234         return len;
 235 }
 236
 237 /*
 238  *      Limit values of certain facilities according to the capability of the
 239  *      currently attached x25 link.
 240  */
 241 void x25_limit_facilities(struct x25_facilities *facilities,
 242                           struct x25_neigh *nb)
 243 {
 244
 245         if (!nb->extended) {
 246                 if (facilities->winsize_in  > 7) {
 247                         printk(KERN_DEBUG "X.25: incoming winsize limited to 7\n");
 248                         facilities->winsize_in = 7;
 249                 }
 250                 if (facilities->winsize_out > 7) {
 251                         facilities->winsize_out = 7;
 252                         printk( KERN_DEBUG "X.25: outgoing winsize limited to 7\n");
 253                 }
 254         }
 255 }