1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * X.25 Packet Layer release 002 4 * 5 * This is ALPHA test software. This code may break your machine, 6 * randomly fail to work with new releases, misbehave and/or generally 7 * screw up. It might even work. 8 * 9 * This code REQUIRES 2.1.15 or higher 10 * 11 * History 12 * X.25 001 Jonathan Naylor Started coding. 13 * X.25 002 Jonathan Naylor New timer architecture. 14 * 2000-09-04 Henner Eisen Prevented x25_output() skb leakage. 15 * 2000-10-27 Henner Eisen MSG_DONTWAIT for fragment allocation. 16 * 2000-11-10 Henner Eisen x25_send_iframe(): re-queued frames 17 * needed cleaned seq-number fields. 18 */ 19 20 #include <linux/slab.h> 21 #include <linux/socket.h> 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 static int x25_pacsize_to_bytes(unsigned int pacsize) 29 { 30 int bytes = 1; 31 32 if (!pacsize) 33 return 128; 34 35 while (pacsize-- > 0) 36 bytes *= 2; 37 38 return bytes; 39 } 40 41 /* 42 * This is where all X.25 information frames pass. 43 * 44 * Returns the amount of user data bytes sent on success 45 * or a negative error code on failure. 46 */ 47 int x25_output(struct sock *sk, struct sk_buff *skb) 48 { 49 struct sk_buff *skbn; 50 unsigned char header[X25_EXT_MIN_LEN]; 51 int err, frontlen, len; 52 int sent=0, noblock = X25_SKB_CB(skb)->flags & MSG_DONTWAIT; 53 struct x25_sock *x25 = x25_sk(sk); 54 int header_len = x25->neighbour->extended ? X25_EXT_MIN_LEN : 55 X25_STD_MIN_LEN; 56 int max_len = x25_pacsize_to_bytes(x25->facilities.pacsize_out); 57 58 if (skb->len - header_len > max_len) { 59 /* Save a copy of the Header */ 60 skb_copy_from_linear_data(skb, header, header_len); 61 skb_pull(skb, header_len); 62 63 frontlen = skb_headroom(skb); 64 65 while (skb->len > 0) { 66 release_sock(sk); 67 skbn = sock_alloc_send_skb(sk, frontlen + max_len, 68 noblock, &err); 69 lock_sock(sk); 70 if (!skbn) { 71 if (err == -EWOULDBLOCK && noblock){ 72 kfree_skb(skb); 73 return sent; 74 } 75 net_dbg_ratelimited("x25_output: fragment alloc" 76 " failed, err=%d, %d bytes " 77 "sent\n", err, sent); 78 return err; 79 } 80 81 skb_reserve(skbn, frontlen); 82 83 len = max_len > skb->len ? skb->len : max_len; 84 85 /* Copy the user data */ 86 skb_copy_from_linear_data(skb, skb_put(skbn, len), len); 87 skb_pull(skb, len); 88 89 /* Duplicate the Header */ 90 skb_push(skbn, header_len); 91 skb_copy_to_linear_data(skbn, header, header_len); 92 93 if (skb->len > 0) { 94 if (x25->neighbour->extended) 95 skbn->data[3] |= X25_EXT_M_BIT; 96 else 97 skbn->data[2] |= X25_STD_M_BIT; 98 } 99 100 skb_queue_tail(&sk->sk_write_queue, skbn); 101 sent += len; 102 } 103 104 kfree_skb(skb); 105 } else { 106 skb_queue_tail(&sk->sk_write_queue, skb); 107 sent = skb->len - header_len; 108 } 109 return sent; 110 } 111 112 /* 113 * This procedure is passed a buffer descriptor for an iframe. It builds 114 * the rest of the control part of the frame and then writes it out. 115 */ 116 static void x25_send_iframe(struct sock *sk, struct sk_buff *skb) 117 { 118 struct x25_sock *x25 = x25_sk(sk); 119 120 if (!skb) 121 return; 122 123 if (x25->neighbour->extended) { 124 skb->data[2] = (x25->vs << 1) & 0xFE; 125 skb->data[3] &= X25_EXT_M_BIT; 126 skb->data[3] |= (x25->vr << 1) & 0xFE; 127 } else { 128 skb->data[2] &= X25_STD_M_BIT; 129 skb->data[2] |= (x25->vs << 1) & 0x0E; 130 skb->data[2] |= (x25->vr << 5) & 0xE0; 131 } 132 133 x25_transmit_link(skb, x25->neighbour); 134 } 135 136 void x25_kick(struct sock *sk) 137 { 138 struct sk_buff *skb, *skbn; 139 unsigned short start, end; 140 int modulus; 141 struct x25_sock *x25 = x25_sk(sk); 142 143 if (x25->state != X25_STATE_3) 144 return; 145 146 /* 147 * Transmit interrupt data. 148 */ 149 if (skb_peek(&x25->interrupt_out_queue) != NULL && 150 !test_and_set_bit(X25_INTERRUPT_FLAG, &x25->flags)) { 151 152 skb = skb_dequeue(&x25->interrupt_out_queue); 153 x25_transmit_link(skb, x25->neighbour); 154 } 155 156 if (x25->condition & X25_COND_PEER_RX_BUSY) 157 return; 158 159 if (!skb_peek(&sk->sk_write_queue)) 160 return; 161 162 modulus = x25->neighbour->extended ? X25_EMODULUS : X25_SMODULUS; 163 164 start = skb_peek(&x25->ack_queue) ? x25->vs : x25->va; 165 end = (x25->va + x25->facilities.winsize_out) % modulus; 166 167 if (start == end) 168 return; 169 170 x25->vs = start; 171 172 /* 173 * Transmit data until either we're out of data to send or 174 * the window is full. 175 */ 176 177 skb = skb_dequeue(&sk->sk_write_queue); 178 179 do { 180 if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) { 181 skb_queue_head(&sk->sk_write_queue, skb); 182 break; 183 } 184 185 skb_set_owner_w(skbn, sk); 186 187 /* 188 * Transmit the frame copy. 189 */ 190 x25_send_iframe(sk, skbn); 191 192 x25->vs = (x25->vs + 1) % modulus; 193 194 /* 195 * Requeue the original data frame. 196 */ 197 skb_queue_tail(&x25->ack_queue, skb); 198 199 } while (x25->vs != end && 200 (skb = skb_dequeue(&sk->sk_write_queue)) != NULL); 201 202 x25->vl = x25->vr; 203 x25->condition &= ~X25_COND_ACK_PENDING; 204 205 x25_stop_timer(sk); 206 } 207 208 /* 209 * The following routines are taken from page 170 of the 7th ARRL Computer 210 * Networking Conference paper, as is the whole state machine. 211 */ 212 213 void x25_enquiry_response(struct sock *sk) 214 { 215 struct x25_sock *x25 = x25_sk(sk); 216 217 if (x25->condition & X25_COND_OWN_RX_BUSY) 218 x25_write_internal(sk, X25_RNR); 219 else 220 x25_write_internal(sk, X25_RR); 221 222 x25->vl = x25->vr; 223 x25->condition &= ~X25_COND_ACK_PENDING; 224 225 x25_stop_timer(sk); 226 } 227