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 Jonathan Naylor Started coding. 18 * X.25 002 Jonathan Naylor New timer architecture. 19 * 2000-09-04 Henner Eisen Prevented x25_output() skb leakage. 20 * 2000-10-27 Henner Eisen MSG_DONTWAIT for fragment allocation. 21 * 2000-11-10 Henner Eisen x25_send_iframe(): re-queued frames 22 * needed cleaned seq-number fields. 23 */ 24 25 #include <linux/slab.h> 26 #include <linux/socket.h> 27 #include <linux/kernel.h> 28 #include <linux/string.h> 29 #include <linux/skbuff.h> 30 #include <net/sock.h> 31 #include <net/x25.h> 32 33 static int x25_pacsize_to_bytes(unsigned int pacsize) 34 { 35 int bytes = 1; 36 37 if (!pacsize) 38 return 128; 39 40 while (pacsize-- > 0) 41 bytes *= 2; 42 43 return bytes; 44 } 45 46 /* 47 * This is where all X.25 information frames pass. 48 * 49 * Returns the amount of user data bytes sent on success 50 * or a negative error code on failure. 51 */ 52 int x25_output(struct sock *sk, struct sk_buff *skb) 53 { 54 struct sk_buff *skbn; 55 unsigned char header[X25_EXT_MIN_LEN]; 56 int err, frontlen, len; 57 int sent=0, noblock = X25_SKB_CB(skb)->flags & MSG_DONTWAIT; 58 struct x25_sock *x25 = x25_sk(sk); 59 int header_len = x25->neighbour->extended ? X25_EXT_MIN_LEN : 60 X25_STD_MIN_LEN; 61 int max_len = x25_pacsize_to_bytes(x25->facilities.pacsize_out); 62 63 if (skb->len - header_len > max_len) { 64 /* Save a copy of the Header */ 65 skb_copy_from_linear_data(skb, header, header_len); 66 skb_pull(skb, header_len); 67 68 frontlen = skb_headroom(skb); 69 70 while (skb->len > 0) { 71 release_sock(sk); 72 skbn = sock_alloc_send_skb(sk, frontlen + max_len, 73 noblock, &err); 74 lock_sock(sk); 75 if (!skbn) { 76 if (err == -EWOULDBLOCK && noblock){ 77 kfree_skb(skb); 78 return sent; 79 } 80 SOCK_DEBUG(sk, "x25_output: fragment alloc" 81 " failed, err=%d, %d bytes " 82 "sent\n", err, sent); 83 return err; 84 } 85 86 skb_reserve(skbn, frontlen); 87 88 len = max_len > skb->len ? skb->len : max_len; 89 90 /* Copy the user data */ 91 skb_copy_from_linear_data(skb, skb_put(skbn, len), len); 92 skb_pull(skb, len); 93 94 /* Duplicate the Header */ 95 skb_push(skbn, header_len); 96 skb_copy_to_linear_data(skbn, header, header_len); 97 98 if (skb->len > 0) { 99 if (x25->neighbour->extended) 100 skbn->data[3] |= X25_EXT_M_BIT; 101 else 102 skbn->data[2] |= X25_STD_M_BIT; 103 } 104 105 skb_queue_tail(&sk->sk_write_queue, skbn); 106 sent += len; 107 } 108 109 kfree_skb(skb); 110 } else { 111 skb_queue_tail(&sk->sk_write_queue, skb); 112 sent = skb->len - header_len; 113 } 114 return sent; 115 } 116 117 /* 118 * This procedure is passed a buffer descriptor for an iframe. It builds 119 * the rest of the control part of the frame and then writes it out. 120 */ 121 static void x25_send_iframe(struct sock *sk, struct sk_buff *skb) 122 { 123 struct x25_sock *x25 = x25_sk(sk); 124 125 if (!skb) 126 return; 127 128 if (x25->neighbour->extended) { 129 skb->data[2] = (x25->vs << 1) & 0xFE; 130 skb->data[3] &= X25_EXT_M_BIT; 131 skb->data[3] |= (x25->vr << 1) & 0xFE; 132 } else { 133 skb->data[2] &= X25_STD_M_BIT; 134 skb->data[2] |= (x25->vs << 1) & 0x0E; 135 skb->data[2] |= (x25->vr << 5) & 0xE0; 136 } 137 138 x25_transmit_link(skb, x25->neighbour); 139 } 140 141 void x25_kick(struct sock *sk) 142 { 143 struct sk_buff *skb, *skbn; 144 unsigned short start, end; 145 int modulus; 146 struct x25_sock *x25 = x25_sk(sk); 147 148 if (x25->state != X25_STATE_3) 149 return; 150 151 /* 152 * Transmit interrupt data. 153 */ 154 if (skb_peek(&x25->interrupt_out_queue) != NULL && 155 !test_and_set_bit(X25_INTERRUPT_FLAG, &x25->flags)) { 156 157 skb = skb_dequeue(&x25->interrupt_out_queue); 158 x25_transmit_link(skb, x25->neighbour); 159 } 160 161 if (x25->condition & X25_COND_PEER_RX_BUSY) 162 return; 163 164 if (!skb_peek(&sk->sk_write_queue)) 165 return; 166 167 modulus = x25->neighbour->extended ? X25_EMODULUS : X25_SMODULUS; 168 169 start = skb_peek(&x25->ack_queue) ? x25->vs : x25->va; 170 end = (x25->va + x25->facilities.winsize_out) % modulus; 171 172 if (start == end) 173 return; 174 175 x25->vs = start; 176 177 /* 178 * Transmit data until either we're out of data to send or 179 * the window is full. 180 */ 181 182 skb = skb_dequeue(&sk->sk_write_queue); 183 184 do { 185 if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) { 186 skb_queue_head(&sk->sk_write_queue, skb); 187 break; 188 } 189 190 skb_set_owner_w(skbn, sk); 191 192 /* 193 * Transmit the frame copy. 194 */ 195 x25_send_iframe(sk, skbn); 196 197 x25->vs = (x25->vs + 1) % modulus; 198 199 /* 200 * Requeue the original data frame. 201 */ 202 skb_queue_tail(&x25->ack_queue, skb); 203 204 } while (x25->vs != end && 205 (skb = skb_dequeue(&sk->sk_write_queue)) != NULL); 206 207 x25->vl = x25->vr; 208 x25->condition &= ~X25_COND_ACK_PENDING; 209 210 x25_stop_timer(sk); 211 } 212 213 /* 214 * The following routines are taken from page 170 of the 7th ARRL Computer 215 * Networking Conference paper, as is the whole state machine. 216 */ 217 218 void x25_enquiry_response(struct sock *sk) 219 { 220 struct x25_sock *x25 = x25_sk(sk); 221 222 if (x25->condition & X25_COND_OWN_RX_BUSY) 223 x25_write_internal(sk, X25_RNR); 224 else 225 x25_write_internal(sk, X25_RR); 226 227 x25->vl = x25->vr; 228 x25->condition &= ~X25_COND_ACK_PENDING; 229 230 x25_stop_timer(sk); 231 } 232