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  */
  21
  22 #include <linux/kernel.h>
  23 #include <linux/string.h>
  24 #include <linux/skbuff.h>
  25 #include <net/sock.h>
  26 #include <net/x25.h>
  27
  28 /*
  29  *      Parse a set of facilities into the facilities structure. Unrecognised
  30  *      facilities are written to the debug log file.
  31  */
  32 int x25_parse_facilities(struct sk_buff *skb,
  33                          struct x25_facilities *facilities,
  34                          unsigned long *vc_fac_mask)
  35 {
  36         unsigned char *p = skb->data;
  37         unsigned int len = *p++;
  38
  39         *vc_fac_mask = 0;
  40
  41         while (len > 0) {
  42                 switch (*p & X25_FAC_CLASS_MASK) {
  43                 case X25_FAC_CLASS_A:
  44                         switch (*p) {
  45                         case X25_FAC_REVERSE:
  46                                 facilities->reverse = p[1] & 0x01;
  47                                 *vc_fac_mask |= X25_MASK_REVERSE;
  48                                 break;
  49                         case X25_FAC_THROUGHPUT:
  50                                 facilities->throughput = p[1];
  51                                 *vc_fac_mask |= X25_MASK_THROUGHPUT;
  52                                 break;
  53                         default:
  54                                 printk(KERN_DEBUG "X.25: unknown facility "
  55                                        "%02X, value %02X\n",
  56                                        p[0], p[1]);
  57                                 break;
  58                         }
  59                         p   += 2;
  60                         len -= 2;
  61                         break;
  62                 case X25_FAC_CLASS_B:
  63                         switch (*p) {
  64                         case X25_FAC_PACKET_SIZE:
  65                                 facilities->pacsize_in  = p[1];
  66                                 facilities->pacsize_out = p[2];
  67                                 *vc_fac_mask |= X25_MASK_PACKET_SIZE;
  68                                 break;
  69                         case X25_FAC_WINDOW_SIZE:
  70                                 facilities->winsize_in  = p[1];
  71                                 facilities->winsize_out = p[2];
  72                                 *vc_fac_mask |= X25_MASK_WINDOW_SIZE;
  73                                 break;
  74                         default:
  75                                 printk(KERN_DEBUG "X.25: unknown facility "
  76                                        "%02X, values %02X, %02X\n",
  77                                        p[0], p[1], p[2]);
  78                                 break;
  79                         }
  80                         p   += 3;
  81                         len -= 3;
  82                         break;
  83                 case X25_FAC_CLASS_C:
  84                         printk(KERN_DEBUG "X.25: unknown facility %02X, "
  85                                "values %02X, %02X, %02X\n",
  86                                p[0], p[1], p[2], p[3]);
  87                         p   += 4;
  88                         len -= 4;
  89                         break;
  90                 case X25_FAC_CLASS_D:
  91                         printk(KERN_DEBUG "X.25: unknown facility %02X, "
  92                                "length %d, values %02X, %02X, %02X, %02X\n",
  93                                p[0], p[1], p[2], p[3], p[4], p[5]);
  94                         len -= p[1] + 2;
  95                         p   += p[1] + 2;
  96                         break;
  97                 }
  98         }
  99
 100         return p - skb->data;
 101 }
 102
 103 /*
 104  *      Create a set of facilities.
 105  */
 106 int x25_create_facilities(unsigned char *buffer,
 107                           struct x25_facilities *facilities,
 108                           unsigned long facil_mask)
 109 {
 110         unsigned char *p = buffer + 1;
 111         int len;
 112
 113         if (!facil_mask) {
 114                 /*
 115                  * Length of the facilities field in call_req or
 116                  * call_accept packets
 117                  */
 118                 buffer[0] = 0;
 119                 len = 1; /* 1 byte for the length field */
 120                 return len;
 121         }
 122
 123         if (facilities->reverse && (facil_mask & X25_MASK_REVERSE)) {
 124                 *p++ = X25_FAC_REVERSE;
 125                 *p++ = !!facilities->reverse;
 126         }
 127
 128         if (facilities->throughput && (facil_mask & X25_MASK_THROUGHPUT)) {
 129                 *p++ = X25_FAC_THROUGHPUT;
 130                 *p++ = facilities->throughput;
 131         }
 132
 133         if ((facilities->pacsize_in || facilities->pacsize_out) &&
 134             (facil_mask & X25_MASK_PACKET_SIZE)) {
 135                 *p++ = X25_FAC_PACKET_SIZE;
 136                 *p++ = facilities->pacsize_in ? : facilities->pacsize_out;
 137                 *p++ = facilities->pacsize_out ? : facilities->pacsize_in;
 138         }
 139
 140         if ((facilities->winsize_in || facilities->winsize_out) &&
 141             (facil_mask & X25_MASK_WINDOW_SIZE)) {
 142                 *p++ = X25_FAC_WINDOW_SIZE;
 143                 *p++ = facilities->winsize_in ? : facilities->winsize_out;
 144                 *p++ = facilities->winsize_out ? : facilities->winsize_in;
 145         }
 146
 147         len       = p - buffer;
 148         buffer[0] = len - 1;
 149
 150         return len;
 151 }
 152
 153 /*
 154  *      Try to reach a compromise on a set of facilities.
 155  *
 156  *      The only real problem is with reverse charging.
 157  */
 158 int x25_negotiate_facilities(struct sk_buff *skb, struct sock *sk,
 159                              struct x25_facilities *new)
 160 {
 161         struct x25_sock *x25 = x25_sk(sk);
 162         struct x25_facilities *ours = &x25->facilities;
 163         struct x25_facilities theirs;
 164         int len;
 165
 166         memset(&theirs, 0, sizeof(theirs));
 167         memcpy(new, ours, sizeof(*new));
 168
 169         len = x25_parse_facilities(skb, &theirs, &x25->vc_facil_mask);
 170
 171         /*
 172          *      They want reverse charging, we won't accept it.
 173          */
 174         if (theirs.reverse && ours->reverse) {
 175                 SOCK_DEBUG(sk, "X.25: rejecting reverse charging request");
 176                 return -1;
 177         }
 178
 179         new->reverse = theirs.reverse;
 180
 181         if (theirs.throughput) {
 182                 if (theirs.throughput < ours->throughput) {
 183                         SOCK_DEBUG(sk, "X.25: throughput negotiated down");
 184                         new->throughput = theirs.throughput;
 185                 }
 186         }
 187
 188         if (theirs.pacsize_in && theirs.pacsize_out) {
 189                 if (theirs.pacsize_in < ours->pacsize_in) {
 190                         SOCK_DEBUG(sk, "X.25: packet size inwards negotiated down");
 191                         new->pacsize_in = theirs.pacsize_in;
 192                 }
 193                 if (theirs.pacsize_out < ours->pacsize_out) {
 194                         SOCK_DEBUG(sk, "X.25: packet size outwards negotiated down");
 195                         new->pacsize_out = theirs.pacsize_out;
 196                 }
 197         }
 198
 199         if (theirs.winsize_in && theirs.winsize_out) {
 200                 if (theirs.winsize_in < ours->winsize_in) {
 201                         SOCK_DEBUG(sk, "X.25: window size inwards negotiated down");
 202                         new->winsize_in = theirs.winsize_in;
 203                 }
 204                 if (theirs.winsize_out < ours->winsize_out) {
 205                         SOCK_DEBUG(sk, "X.25: window size outwards negotiated down");
 206                         new->winsize_out = theirs.winsize_out;
 207                 }
 208         }
 209
 210         return len;
 211 }
 212
 213 /*
 214  *      Limit values of certain facilities according to the capability of the
 215  *      currently attached x25 link.
 216  */
 217 void x25_limit_facilities(struct x25_facilities *facilities,
 218                           struct x25_neigh *nb)
 219 {
 220
 221         if (!nb->extended) {
 222                 if (facilities->winsize_in  > 7) {
 223                         printk(KERN_DEBUG "X.25: incoming winsize limited to 7\n");
 224                         facilities->winsize_in = 7;
 225                 }
 226                 if (facilities->winsize_out > 7) {
 227                         facilities->winsize_out = 7;
 228                         printk( KERN_DEBUG "X.25: outgoing winsize limited to 7\n");
 229                 }
 230         }
 231 }