net/x25/x25_subr.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    Jonathan Naylor   Started coding.
0013  *  X.25 002    Jonathan Naylor   Centralised disconnection processing.
0014  *  mar/20/00   Daniela Squassoni Disabling/enabling of facilities
0015  *                    negotiation.
0016  *  jun/24/01   Arnaldo C. Melo   use skb_queue_purge, cleanups
0017  *  apr/04/15   Shaun Pereira       Fast select with no
0018  *                      restriction on response.
0019  */
0020
0021 #define pr_fmt(fmt) "X25: " fmt
0022
0023 #include <linux/slab.h>
0024 #include <linux/kernel.h>
0025 #include <linux/string.h>
0026 #include <linux/skbuff.h>
0027 #include <net/sock.h>
0028 #include <net/tcp_states.h>
0029 #include <net/x25.h>
0030
0031 /*
0032  *  This routine purges all of the queues of frames.
0033  */
0034 void x25_clear_queues(struct sock *sk)
0035 {
0036     struct x25_sock *x25 = x25_sk(sk);
0037
0038     skb_queue_purge(&sk->sk_write_queue);
0039     skb_queue_purge(&x25->ack_queue);
0040     skb_queue_purge(&x25->interrupt_in_queue);
0041     skb_queue_purge(&x25->interrupt_out_queue);
0042     skb_queue_purge(&x25->fragment_queue);
0043 }
0044
0045
0046 /*
0047  * This routine purges the input queue of those frames that have been
0048  * acknowledged. This replaces the boxes labelled "V(a) <- N(r)" on the
0049  * SDL diagram.
0050 */
0051 void x25_frames_acked(struct sock *sk, unsigned short nr)
0052 {
0053     struct sk_buff *skb;
0054     struct x25_sock *x25 = x25_sk(sk);
0055     int modulus = x25->neighbour->extended ? X25_EMODULUS : X25_SMODULUS;
0056
0057     /*
0058      * Remove all the ack-ed frames from the ack queue.
0059      */
0060     if (x25->va != nr)
0061         while (skb_peek(&x25->ack_queue) && x25->va != nr) {
0062             skb = skb_dequeue(&x25->ack_queue);
0063             kfree_skb(skb);
0064             x25->va = (x25->va + 1) % modulus;
0065         }
0066 }
0067
0068 void x25_requeue_frames(struct sock *sk)
0069 {
0070     struct sk_buff *skb, *skb_prev = NULL;
0071
0072     /*
0073      * Requeue all the un-ack-ed frames on the output queue to be picked
0074      * up by x25_kick. This arrangement handles the possibility of an empty
0075      * output queue.
0076      */
0077     while ((skb = skb_dequeue(&x25_sk(sk)->ack_queue)) != NULL) {
0078         if (!skb_prev)
0079             skb_queue_head(&sk->sk_write_queue, skb);
0080         else
0081             skb_append(skb_prev, skb, &sk->sk_write_queue);
0082         skb_prev = skb;
0083     }
0084 }
0085
0086 /*
0087  *  Validate that the value of nr is between va and vs. Return true or
0088  *  false for testing.
0089  */
0090 int x25_validate_nr(struct sock *sk, unsigned short nr)
0091 {
0092     struct x25_sock *x25 = x25_sk(sk);
0093     unsigned short vc = x25->va;
0094     int modulus = x25->neighbour->extended ? X25_EMODULUS : X25_SMODULUS;
0095
0096     while (vc != x25->vs) {
0097         if (nr == vc)
0098             return 1;
0099         vc = (vc + 1) % modulus;
0100     }
0101
0102     return nr == x25->vs ? 1 : 0;
0103 }
0104
0105 /*
0106  *  This routine is called when the packet layer internally generates a
0107  *  control frame.
0108  */
0109 void x25_write_internal(struct sock *sk, int frametype)
0110 {
0111     struct x25_sock *x25 = x25_sk(sk);
0112     struct sk_buff *skb;
0113     unsigned char  *dptr;
0114     unsigned char  facilities[X25_MAX_FAC_LEN];
0115     unsigned char  addresses[1 + X25_ADDR_LEN];
0116     unsigned char  lci1, lci2;
0117     /*
0118      *  Default safe frame size.
0119      */
0120     int len = X25_MAX_L2_LEN + X25_EXT_MIN_LEN;
0121
0122     /*
0123      *  Adjust frame size.
0124      */
0125     switch (frametype) {
0126     case X25_CALL_REQUEST:
0127         len += 1 + X25_ADDR_LEN + X25_MAX_FAC_LEN + X25_MAX_CUD_LEN;
0128         break;
0129     case X25_CALL_ACCEPTED: /* fast sel with no restr on resp */
0130         if (x25->facilities.reverse & 0x80) {
0131             len += 1 + X25_MAX_FAC_LEN + X25_MAX_CUD_LEN;
0132         } else {
0133             len += 1 + X25_MAX_FAC_LEN;
0134         }
0135         break;
0136     case X25_CLEAR_REQUEST:
0137     case X25_RESET_REQUEST:
0138         len += 2;
0139         break;
0140     case X25_RR:
0141     case X25_RNR:
0142     case X25_REJ:
0143     case X25_CLEAR_CONFIRMATION:
0144     case X25_INTERRUPT_CONFIRMATION:
0145     case X25_RESET_CONFIRMATION:
0146         break;
0147     default:
0148         pr_err("invalid frame type %02X\n", frametype);
0149         return;
0150     }
0151
0152     if ((skb = alloc_skb(len, GFP_ATOMIC)) == NULL)
0153         return;
0154
0155     /*
0156      *  Space for Ethernet and 802.2 LLC headers.
0157      */
0158     skb_reserve(skb, X25_MAX_L2_LEN);
0159
0160     /*
0161      *  Make space for the GFI and LCI, and fill them in.
0162      */
0163     dptr = skb_put(skb, 2);
0164
0165     lci1 = (x25->lci >> 8) & 0x0F;
0166     lci2 = (x25->lci >> 0) & 0xFF;
0167
0168     if (x25->neighbour->extended) {
0169         *dptr++ = lci1 | X25_GFI_EXTSEQ;
0170         *dptr++ = lci2;
0171     } else {
0172         *dptr++ = lci1 | X25_GFI_STDSEQ;
0173         *dptr++ = lci2;
0174     }
0175
0176     /*
0177      *  Now fill in the frame type specific information.
0178      */
0179     switch (frametype) {
0180
0181         case X25_CALL_REQUEST:
0182             dptr    = skb_put(skb, 1);
0183             *dptr++ = X25_CALL_REQUEST;
0184             len     = x25_addr_aton(addresses, &x25->dest_addr,
0185                         &x25->source_addr);
0186             skb_put_data(skb, addresses, len);
0187             len     = x25_create_facilities(facilities,
0188                     &x25->facilities,
0189                     &x25->dte_facilities,
0190                     x25->neighbour->global_facil_mask);
0191             skb_put_data(skb, facilities, len);
0192             skb_put_data(skb, x25->calluserdata.cuddata,
0193                      x25->calluserdata.cudlength);
0194             x25->calluserdata.cudlength = 0;
0195             break;
0196
0197         case X25_CALL_ACCEPTED:
0198             dptr    = skb_put(skb, 2);
0199             *dptr++ = X25_CALL_ACCEPTED;
0200             *dptr++ = 0x00;     /* Address lengths */
0201             len     = x25_create_facilities(facilities,
0202                             &x25->facilities,
0203                             &x25->dte_facilities,
0204                             x25->vc_facil_mask);
0205             skb_put_data(skb, facilities, len);
0206
0207             /* fast select with no restriction on response
0208                 allows call user data. Userland must
0209                 ensure it is ours and not theirs */
0210             if(x25->facilities.reverse & 0x80) {
0211                 skb_put_data(skb,
0212                          x25->calluserdata.cuddata,
0213                          x25->calluserdata.cudlength);
0214             }
0215             x25->calluserdata.cudlength = 0;
0216             break;
0217
0218         case X25_CLEAR_REQUEST:
0219             dptr    = skb_put(skb, 3);
0220             *dptr++ = frametype;
0221             *dptr++ = x25->causediag.cause;
0222             *dptr++ = x25->causediag.diagnostic;
0223             break;
0224
0225         case X25_RESET_REQUEST:
0226             dptr    = skb_put(skb, 3);
0227             *dptr++ = frametype;
0228             *dptr++ = 0x00;     /* XXX */
0229             *dptr++ = 0x00;     /* XXX */
0230             break;
0231
0232         case X25_RR:
0233         case X25_RNR:
0234         case X25_REJ:
0235             if (x25->neighbour->extended) {
0236                 dptr     = skb_put(skb, 2);
0237                 *dptr++  = frametype;
0238                 *dptr++  = (x25->vr << 1) & 0xFE;
0239             } else {
0240                 dptr     = skb_put(skb, 1);
0241                 *dptr    = frametype;
0242                 *dptr++ |= (x25->vr << 5) & 0xE0;
0243             }
0244             break;
0245
0246         case X25_CLEAR_CONFIRMATION:
0247         case X25_INTERRUPT_CONFIRMATION:
0248         case X25_RESET_CONFIRMATION:
0249             dptr  = skb_put(skb, 1);
0250             *dptr = frametype;
0251             break;
0252     }
0253
0254     x25_transmit_link(skb, x25->neighbour);
0255 }
0256
0257 /*
0258  *  Unpick the contents of the passed X.25 Packet Layer frame.
0259  */
0260 int x25_decode(struct sock *sk, struct sk_buff *skb, int *ns, int *nr, int *q,
0261            int *d, int *m)
0262 {
0263     struct x25_sock *x25 = x25_sk(sk);
0264     unsigned char *frame;
0265
0266     if (!pskb_may_pull(skb, X25_STD_MIN_LEN))
0267         return X25_ILLEGAL;
0268     frame = skb->data;
0269
0270     *ns = *nr = *q = *d = *m = 0;
0271
0272     switch (frame[2]) {
0273     case X25_CALL_REQUEST:
0274     case X25_CALL_ACCEPTED:
0275     case X25_CLEAR_REQUEST:
0276     case X25_CLEAR_CONFIRMATION:
0277     case X25_INTERRUPT:
0278     case X25_INTERRUPT_CONFIRMATION:
0279     case X25_RESET_REQUEST:
0280     case X25_RESET_CONFIRMATION:
0281     case X25_RESTART_REQUEST:
0282     case X25_RESTART_CONFIRMATION:
0283     case X25_REGISTRATION_REQUEST:
0284     case X25_REGISTRATION_CONFIRMATION:
0285     case X25_DIAGNOSTIC:
0286         return frame[2];
0287     }
0288
0289     if (x25->neighbour->extended) {
0290         if (frame[2] == X25_RR  ||
0291             frame[2] == X25_RNR ||
0292             frame[2] == X25_REJ) {
0293             if (!pskb_may_pull(skb, X25_EXT_MIN_LEN))
0294                 return X25_ILLEGAL;
0295             frame = skb->data;
0296
0297             *nr = (frame[3] >> 1) & 0x7F;
0298             return frame[2];
0299         }
0300     } else {
0301         if ((frame[2] & 0x1F) == X25_RR  ||
0302             (frame[2] & 0x1F) == X25_RNR ||
0303             (frame[2] & 0x1F) == X25_REJ) {
0304             *nr = (frame[2] >> 5) & 0x07;
0305             return frame[2] & 0x1F;
0306         }
0307     }
0308
0309     if (x25->neighbour->extended) {
0310         if ((frame[2] & 0x01) == X25_DATA) {
0311             if (!pskb_may_pull(skb, X25_EXT_MIN_LEN))
0312                 return X25_ILLEGAL;
0313             frame = skb->data;
0314
0315             *q  = (frame[0] & X25_Q_BIT) == X25_Q_BIT;
0316             *d  = (frame[0] & X25_D_BIT) == X25_D_BIT;
0317             *m  = (frame[3] & X25_EXT_M_BIT) == X25_EXT_M_BIT;
0318             *nr = (frame[3] >> 1) & 0x7F;
0319             *ns = (frame[2] >> 1) & 0x7F;
0320             return X25_DATA;
0321         }
0322     } else {
0323         if ((frame[2] & 0x01) == X25_DATA) {
0324             *q  = (frame[0] & X25_Q_BIT) == X25_Q_BIT;
0325             *d  = (frame[0] & X25_D_BIT) == X25_D_BIT;
0326             *m  = (frame[2] & X25_STD_M_BIT) == X25_STD_M_BIT;
0327             *nr = (frame[2] >> 5) & 0x07;
0328             *ns = (frame[2] >> 1) & 0x07;
0329             return X25_DATA;
0330         }
0331     }
0332
0333     pr_debug("invalid PLP frame %3ph\n", frame);
0334
0335     return X25_ILLEGAL;
0336 }
0337
0338 void x25_disconnect(struct sock *sk, int reason, unsigned char cause,
0339             unsigned char diagnostic)
0340 {
0341     struct x25_sock *x25 = x25_sk(sk);
0342
0343     x25_clear_queues(sk);
0344     x25_stop_timer(sk);
0345
0346     x25->lci   = 0;
0347     x25->state = X25_STATE_0;
0348
0349     x25->causediag.cause      = cause;
0350     x25->causediag.diagnostic = diagnostic;
0351
0352     sk->sk_state     = TCP_CLOSE;
0353     sk->sk_err       = reason;
0354     sk->sk_shutdown |= SEND_SHUTDOWN;
0355
0356     if (!sock_flag(sk, SOCK_DEAD)) {
0357         sk->sk_state_change(sk);
0358         sock_set_flag(sk, SOCK_DEAD);
0359     }
0360     if (x25->neighbour) {
0361         read_lock_bh(&x25_list_lock);
0362         x25_neigh_put(x25->neighbour);
0363         x25->neighbour = NULL;
0364         read_unlock_bh(&x25_list_lock);
0365     }
0366 }
0367
0368 /*
0369  * Clear an own-rx-busy condition and tell the peer about this, provided
0370  * that there is a significant amount of free receive buffer space available.
0371  */
0372 void x25_check_rbuf(struct sock *sk)
0373 {
0374     struct x25_sock *x25 = x25_sk(sk);
0375
0376     if (atomic_read(&sk->sk_rmem_alloc) < (sk->sk_rcvbuf >> 1) &&
0377         (x25->condition & X25_COND_OWN_RX_BUSY)) {
0378         x25->condition &= ~X25_COND_OWN_RX_BUSY;
0379         x25->condition &= ~X25_COND_ACK_PENDING;
0380         x25->vl         = x25->vr;
0381         x25_write_internal(sk, X25_RR);
0382         x25_stop_timer(sk);
0383     }
0384 }