net/x25/x25_facilities.c

0001 // SPDX-License-Identifier: GPL-2.0-or-later
0002 /*
0003  *  X.25 Packet Layer release 002
0004  *
0005  *  This is ALPHA test software. This code may break your machine,
0006  *  randomly fail to work with new releases, misbehave and/or generally
0007  *  screw up. It might even work.
0008  *
0009  *  This code REQUIRES 2.1.15 or higher
0010  *
0011  *  History
0012  *  X.25 001    Split from x25_subr.c
0013  *  mar/20/00   Daniela Squassoni Disabling/enabling of facilities
0014  *                    negotiation.
0015  *  apr/14/05   Shaun Pereira - Allow fast select with no restriction
0016  *                  on response.
0017  */
0018
0019 #define pr_fmt(fmt) "X25: " fmt
0020
0021 #include <linux/kernel.h>
0022 #include <linux/string.h>
0023 #include <linux/skbuff.h>
0024 #include <net/sock.h>
0025 #include <net/x25.h>
0026
0027 /**
0028  * x25_parse_facilities - Parse facilities from skb into the facilities structs
0029  *
0030  * @skb: sk_buff to parse
0031  * @facilities: Regular facilities, updated as facilities are found
0032  * @dte_facs: ITU DTE facilities, updated as DTE facilities are found
0033  * @vc_fac_mask: mask is updated with all facilities found
0034  *
0035  * Return codes:
0036  *  -1 - Parsing error, caller should drop call and clean up
0037  *   0 - Parse OK, this skb has no facilities
0038  *  >0 - Parse OK, returns the length of the facilities header
0039  *
0040  */
0041 int x25_parse_facilities(struct sk_buff *skb, struct x25_facilities *facilities,
0042         struct x25_dte_facilities *dte_facs, unsigned long *vc_fac_mask)
0043 {
0044     unsigned char *p;
0045     unsigned int len;
0046
0047     *vc_fac_mask = 0;
0048
0049     /*
0050      * The kernel knows which facilities were set on an incoming call but
0051      * currently this information is not available to userspace.  Here we
0052      * give userspace who read incoming call facilities 0 length to indicate
0053      * it wasn't set.
0054      */
0055     dte_facs->calling_len = 0;
0056     dte_facs->called_len = 0;
0057     memset(dte_facs->called_ae, '\0', sizeof(dte_facs->called_ae));
0058     memset(dte_facs->calling_ae, '\0', sizeof(dte_facs->calling_ae));
0059
0060     if (!pskb_may_pull(skb, 1))
0061         return 0;
0062
0063     len = skb->data[0];
0064
0065     if (!pskb_may_pull(skb, 1 + len))
0066         return -1;
0067
0068     p = skb->data + 1;
0069
0070     while (len > 0) {
0071         switch (*p & X25_FAC_CLASS_MASK) {
0072         case X25_FAC_CLASS_A:
0073             if (len < 2)
0074                 return -1;
0075             switch (*p) {
0076             case X25_FAC_REVERSE:
0077                 if((p[1] & 0x81) == 0x81) {
0078                     facilities->reverse = p[1] & 0x81;
0079                     *vc_fac_mask |= X25_MASK_REVERSE;
0080                     break;
0081                 }
0082
0083                 if((p[1] & 0x01) == 0x01) {
0084                     facilities->reverse = p[1] & 0x01;
0085                     *vc_fac_mask |= X25_MASK_REVERSE;
0086                     break;
0087                 }
0088
0089                 if((p[1] & 0x80) == 0x80) {
0090                     facilities->reverse = p[1] & 0x80;
0091                     *vc_fac_mask |= X25_MASK_REVERSE;
0092                     break;
0093                 }
0094
0095                 if(p[1] == 0x00) {
0096                     facilities->reverse
0097                         = X25_DEFAULT_REVERSE;
0098                     *vc_fac_mask |= X25_MASK_REVERSE;
0099                     break;
0100                 }
0101                 fallthrough;
0102             case X25_FAC_THROUGHPUT:
0103                 facilities->throughput = p[1];
0104                 *vc_fac_mask |= X25_MASK_THROUGHPUT;
0105                 break;
0106             case X25_MARKER:
0107                 break;
0108             default:
0109                 pr_debug("unknown facility "
0110                        "%02X, value %02X\n",
0111                        p[0], p[1]);
0112                 break;
0113             }
0114             p   += 2;
0115             len -= 2;
0116             break;
0117         case X25_FAC_CLASS_B:
0118             if (len < 3)
0119                 return -1;
0120             switch (*p) {
0121             case X25_FAC_PACKET_SIZE:
0122                 facilities->pacsize_in  = p[1];
0123                 facilities->pacsize_out = p[2];
0124                 *vc_fac_mask |= X25_MASK_PACKET_SIZE;
0125                 break;
0126             case X25_FAC_WINDOW_SIZE:
0127                 facilities->winsize_in  = p[1];
0128                 facilities->winsize_out = p[2];
0129                 *vc_fac_mask |= X25_MASK_WINDOW_SIZE;
0130                 break;
0131             default:
0132                 pr_debug("unknown facility "
0133                        "%02X, values %02X, %02X\n",
0134                        p[0], p[1], p[2]);
0135                 break;
0136             }
0137             p   += 3;
0138             len -= 3;
0139             break;
0140         case X25_FAC_CLASS_C:
0141             if (len < 4)
0142                 return -1;
0143             pr_debug("unknown facility %02X, "
0144                    "values %02X, %02X, %02X\n",
0145                    p[0], p[1], p[2], p[3]);
0146             p   += 4;
0147             len -= 4;
0148             break;
0149         case X25_FAC_CLASS_D:
0150             if (len < p[1] + 2)
0151                 return -1;
0152             switch (*p) {
0153             case X25_FAC_CALLING_AE:
0154                 if (p[1] > X25_MAX_DTE_FACIL_LEN || p[1] <= 1)
0155                     return -1;
0156                 if (p[2] > X25_MAX_AE_LEN)
0157                     return -1;
0158                 dte_facs->calling_len = p[2];
0159                 memcpy(dte_facs->calling_ae, &p[3], p[1] - 1);
0160                 *vc_fac_mask |= X25_MASK_CALLING_AE;
0161                 break;
0162             case X25_FAC_CALLED_AE:
0163                 if (p[1] > X25_MAX_DTE_FACIL_LEN || p[1] <= 1)
0164                     return -1;
0165                 if (p[2] > X25_MAX_AE_LEN)
0166                     return -1;
0167                 dte_facs->called_len = p[2];
0168                 memcpy(dte_facs->called_ae, &p[3], p[1] - 1);
0169                 *vc_fac_mask |= X25_MASK_CALLED_AE;
0170                 break;
0171             default:
0172                 pr_debug("unknown facility %02X,"
0173                     "length %d\n", p[0], p[1]);
0174                 break;
0175             }
0176             len -= p[1] + 2;
0177             p += p[1] + 2;
0178             break;
0179         }
0180     }
0181
0182     return p - skb->data;
0183 }
0184
0185 /*
0186  *  Create a set of facilities.
0187  */
0188 int x25_create_facilities(unsigned char *buffer,
0189         struct x25_facilities *facilities,
0190         struct x25_dte_facilities *dte_facs, unsigned long facil_mask)
0191 {
0192     unsigned char *p = buffer + 1;
0193     int len;
0194
0195     if (!facil_mask) {
0196         /*
0197          * Length of the facilities field in call_req or
0198          * call_accept packets
0199          */
0200         buffer[0] = 0;
0201         len = 1; /* 1 byte for the length field */
0202         return len;
0203     }
0204
0205     if (facilities->reverse && (facil_mask & X25_MASK_REVERSE)) {
0206         *p++ = X25_FAC_REVERSE;
0207         *p++ = facilities->reverse;
0208     }
0209
0210     if (facilities->throughput && (facil_mask & X25_MASK_THROUGHPUT)) {
0211         *p++ = X25_FAC_THROUGHPUT;
0212         *p++ = facilities->throughput;
0213     }
0214
0215     if ((facilities->pacsize_in || facilities->pacsize_out) &&
0216         (facil_mask & X25_MASK_PACKET_SIZE)) {
0217         *p++ = X25_FAC_PACKET_SIZE;
0218         *p++ = facilities->pacsize_in ? : facilities->pacsize_out;
0219         *p++ = facilities->pacsize_out ? : facilities->pacsize_in;
0220     }
0221
0222     if ((facilities->winsize_in || facilities->winsize_out) &&
0223         (facil_mask & X25_MASK_WINDOW_SIZE)) {
0224         *p++ = X25_FAC_WINDOW_SIZE;
0225         *p++ = facilities->winsize_in ? : facilities->winsize_out;
0226         *p++ = facilities->winsize_out ? : facilities->winsize_in;
0227     }
0228
0229     if (facil_mask & (X25_MASK_CALLING_AE|X25_MASK_CALLED_AE)) {
0230         *p++ = X25_MARKER;
0231         *p++ = X25_DTE_SERVICES;
0232     }
0233
0234     if (dte_facs->calling_len && (facil_mask & X25_MASK_CALLING_AE)) {
0235         unsigned int bytecount = (dte_facs->calling_len + 1) >> 1;
0236         *p++ = X25_FAC_CALLING_AE;
0237         *p++ = 1 + bytecount;
0238         *p++ = dte_facs->calling_len;
0239         memcpy(p, dte_facs->calling_ae, bytecount);
0240         p += bytecount;
0241     }
0242
0243     if (dte_facs->called_len && (facil_mask & X25_MASK_CALLED_AE)) {
0244         unsigned int bytecount = (dte_facs->called_len % 2) ?
0245         dte_facs->called_len / 2 + 1 :
0246         dte_facs->called_len / 2;
0247         *p++ = X25_FAC_CALLED_AE;
0248         *p++ = 1 + bytecount;
0249         *p++ = dte_facs->called_len;
0250         memcpy(p, dte_facs->called_ae, bytecount);
0251         p+=bytecount;
0252     }
0253
0254     len       = p - buffer;
0255     buffer[0] = len - 1;
0256
0257     return len;
0258 }
0259
0260 /*
0261  *  Try to reach a compromise on a set of facilities.
0262  *
0263  *  The only real problem is with reverse charging.
0264  */
0265 int x25_negotiate_facilities(struct sk_buff *skb, struct sock *sk,
0266         struct x25_facilities *new, struct x25_dte_facilities *dte)
0267 {
0268     struct x25_sock *x25 = x25_sk(sk);
0269     struct x25_facilities *ours = &x25->facilities;
0270     struct x25_facilities theirs;
0271     int len;
0272
0273     memset(&theirs, 0, sizeof(theirs));
0274     memcpy(new, ours, sizeof(*new));
0275     memset(dte, 0, sizeof(*dte));
0276
0277     len = x25_parse_facilities(skb, &theirs, dte, &x25->vc_facil_mask);
0278     if (len < 0)
0279         return len;
0280
0281     /*
0282      *  They want reverse charging, we won't accept it.
0283      */
0284     if ((theirs.reverse & 0x01 ) && (ours->reverse & 0x01)) {
0285         SOCK_DEBUG(sk, "X.25: rejecting reverse charging request\n");
0286         return -1;
0287     }
0288
0289     new->reverse = theirs.reverse;
0290
0291     if (theirs.throughput) {
0292         int theirs_in =  theirs.throughput & 0x0f;
0293         int theirs_out = theirs.throughput & 0xf0;
0294         int ours_in  = ours->throughput & 0x0f;
0295         int ours_out = ours->throughput & 0xf0;
0296         if (!ours_in || theirs_in < ours_in) {
0297             SOCK_DEBUG(sk, "X.25: inbound throughput negotiated\n");
0298             new->throughput = (new->throughput & 0xf0) | theirs_in;
0299         }
0300         if (!ours_out || theirs_out < ours_out) {
0301             SOCK_DEBUG(sk,
0302                 "X.25: outbound throughput negotiated\n");
0303             new->throughput = (new->throughput & 0x0f) | theirs_out;
0304         }
0305     }
0306
0307     if (theirs.pacsize_in && theirs.pacsize_out) {
0308         if (theirs.pacsize_in < ours->pacsize_in) {
0309             SOCK_DEBUG(sk, "X.25: packet size inwards negotiated down\n");
0310             new->pacsize_in = theirs.pacsize_in;
0311         }
0312         if (theirs.pacsize_out < ours->pacsize_out) {
0313             SOCK_DEBUG(sk, "X.25: packet size outwards negotiated down\n");
0314             new->pacsize_out = theirs.pacsize_out;
0315         }
0316     }
0317
0318     if (theirs.winsize_in && theirs.winsize_out) {
0319         if (theirs.winsize_in < ours->winsize_in) {
0320             SOCK_DEBUG(sk, "X.25: window size inwards negotiated down\n");
0321             new->winsize_in = theirs.winsize_in;
0322         }
0323         if (theirs.winsize_out < ours->winsize_out) {
0324             SOCK_DEBUG(sk, "X.25: window size outwards negotiated down\n");
0325             new->winsize_out = theirs.winsize_out;
0326         }
0327     }
0328
0329     return len;
0330 }
0331
0332 /*
0333  *  Limit values of certain facilities according to the capability of the
0334  *      currently attached x25 link.
0335  */
0336 void x25_limit_facilities(struct x25_facilities *facilities,
0337               struct x25_neigh *nb)
0338 {
0339
0340     if (!nb->extended) {
0341         if (facilities->winsize_in  > 7) {
0342             pr_debug("incoming winsize limited to 7\n");
0343             facilities->winsize_in = 7;
0344         }
0345         if (facilities->winsize_out > 7) {
0346             facilities->winsize_out = 7;
0347             pr_debug("outgoing winsize limited to 7\n");
0348         }
0349     }
0350 }