1 /* 2 * This program is free software; you can redistribute it and/or modify 3 * it under the terms of the GNU General Public License as published by 4 * the Free Software Foundation; either version 2 of the License, or 5 * (at your option) any later version. 6 * 7 * Copyright (C) Alan Cox GW4PTS (alan@lxorguk.ukuu.org.uk) 8 * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk) 9 * Copyright (C) Joerg Reuter DL1BKE (jreuter@yaina.de) 10 * Copyright (C) Frederic Rible F1OAT (frible@teaser.fr) 11 */ 12 #include <linux/errno.h> 13 #include <linux/types.h> 14 #include <linux/socket.h> 15 #include <linux/in.h> 16 #include <linux/kernel.h> 17 #include <linux/timer.h> 18 #include <linux/string.h> 19 #include <linux/sockios.h> 20 #include <linux/net.h> 21 #include <net/ax25.h> 22 #include <linux/inet.h> 23 #include <linux/netdevice.h> 24 #include <linux/skbuff.h> 25 #include <net/sock.h> 26 #include <net/tcp_states.h> 27 #include <asm/uaccess.h> 28 #include <asm/system.h> 29 #include <linux/fcntl.h> 30 #include <linux/mm.h> 31 #include <linux/interrupt.h> 32 33 /* 34 * This routine purges all the queues of frames. 35 */ 36 void ax25_clear_queues(ax25_cb *ax25) 37 { 38 skb_queue_purge(&ax25->write_queue); 39 skb_queue_purge(&ax25->ack_queue); 40 skb_queue_purge(&ax25->reseq_queue); 41 skb_queue_purge(&ax25->frag_queue); 42 } 43 44 /* 45 * This routine purges the input queue of those frames that have been 46 * acknowledged. This replaces the boxes labelled "V(a) <- N(r)" on the 47 * SDL diagram. 48 */ 49 void ax25_frames_acked(ax25_cb *ax25, unsigned short nr) 50 { 51 struct sk_buff *skb; 52 53 /* 54 * Remove all the ack-ed frames from the ack queue. 55 */ 56 if (ax25->va != nr) { 57 while (skb_peek(&ax25->ack_queue) != NULL && ax25->va != nr) { 58 skb = skb_dequeue(&ax25->ack_queue); 59 kfree_skb(skb); 60 ax25->va = (ax25->va + 1) % ax25->modulus; 61 } 62 } 63 } 64 65 void ax25_requeue_frames(ax25_cb *ax25) 66 { 67 struct sk_buff *skb, *skb_prev = NULL; 68 69 /* 70 * Requeue all the un-ack-ed frames on the output queue to be picked 71 * up by ax25_kick called from the timer. This arrangement handles the 72 * possibility of an empty output queue. 73 */ 74 while ((skb = skb_dequeue(&ax25->ack_queue)) != NULL) { 75 if (skb_prev == NULL) 76 skb_queue_head(&ax25->write_queue, skb); 77 else 78 skb_append(skb_prev, skb, &ax25->write_queue); 79 skb_prev = skb; 80 } 81 } 82 83 /* 84 * Validate that the value of nr is between va and vs. Return true or 85 * false for testing. 86 */ 87 int ax25_validate_nr(ax25_cb *ax25, unsigned short nr) 88 { 89 unsigned short vc = ax25->va; 90 91 while (vc != ax25->vs) { 92 if (nr == vc) return 1; 93 vc = (vc + 1) % ax25->modulus; 94 } 95 96 if (nr == ax25->vs) return 1; 97 98 return 0; 99 } 100 101 /* 102 * This routine is the centralised routine for parsing the control 103 * information for the different frame formats. 104 */ 105 int ax25_decode(ax25_cb *ax25, struct sk_buff *skb, int *ns, int *nr, int *pf) 106 { 107 unsigned char *frame; 108 int frametype = AX25_ILLEGAL; 109 110 frame = skb->data; 111 *ns = *nr = *pf = 0; 112 113 if (ax25->modulus == AX25_MODULUS) { 114 if ((frame[0] & AX25_S) == 0) { 115 frametype = AX25_I; /* I frame - carries NR/NS/PF */ 116 *ns = (frame[0] >> 1) & 0x07; 117 *nr = (frame[0] >> 5) & 0x07; 118 *pf = frame[0] & AX25_PF; 119 } else if ((frame[0] & AX25_U) == 1) { /* S frame - take out PF/NR */ 120 frametype = frame[0] & 0x0F; 121 *nr = (frame[0] >> 5) & 0x07; 122 *pf = frame[0] & AX25_PF; 123 } else if ((frame[0] & AX25_U) == 3) { /* U frame - take out PF */ 124 frametype = frame[0] & ~AX25_PF; 125 *pf = frame[0] & AX25_PF; 126 } 127 skb_pull(skb, 1); 128 } else { 129 if ((frame[0] & AX25_S) == 0) { 130 frametype = AX25_I; /* I frame - carries NR/NS/PF */ 131 *ns = (frame[0] >> 1) & 0x7F; 132 *nr = (frame[1] >> 1) & 0x7F; 133 *pf = frame[1] & AX25_EPF; 134 skb_pull(skb, 2); 135 } else if ((frame[0] & AX25_U) == 1) { /* S frame - take out PF/NR */ 136 frametype = frame[0] & 0x0F; 137 *nr = (frame[1] >> 1) & 0x7F; 138 *pf = frame[1] & AX25_EPF; 139 skb_pull(skb, 2); 140 } else if ((frame[0] & AX25_U) == 3) { /* U frame - take out PF */ 141 frametype = frame[0] & ~AX25_PF; 142 *pf = frame[0] & AX25_PF; 143 skb_pull(skb, 1); 144 } 145 } 146 147 return frametype; 148 } 149 150 /* 151 * This routine is called when the HDLC layer internally generates a 152 * command or response for the remote machine ( eg. RR, UA etc. ). 153 * Only supervisory or unnumbered frames are processed. 154 */ 155 void ax25_send_control(ax25_cb *ax25, int frametype, int poll_bit, int type) 156 { 157 struct sk_buff *skb; 158 unsigned char *dptr; 159 160 if ((skb = alloc_skb(ax25->ax25_dev->dev->hard_header_len + 2, GFP_ATOMIC)) == NULL) 161 return; 162 163 skb_reserve(skb, ax25->ax25_dev->dev->hard_header_len); 164 165 skb_reset_network_header(skb); 166 167 /* Assume a response - address structure for DTE */ 168 if (ax25->modulus == AX25_MODULUS) { 169 dptr = skb_put(skb, 1); 170 *dptr = frametype; 171 *dptr |= (poll_bit) ? AX25_PF : 0; 172 if ((frametype & AX25_U) == AX25_S) /* S frames carry NR */ 173 *dptr |= (ax25->vr << 5); 174 } else { 175 if ((frametype & AX25_U) == AX25_U) { 176 dptr = skb_put(skb, 1); 177 *dptr = frametype; 178 *dptr |= (poll_bit) ? AX25_PF : 0; 179 } else { 180 dptr = skb_put(skb, 2); 181 dptr[0] = frametype; 182 dptr[1] = (ax25->vr << 1); 183 dptr[1] |= (poll_bit) ? AX25_EPF : 0; 184 } 185 } 186 187 ax25_transmit_buffer(ax25, skb, type); 188 } 189 190 /* 191 * Send a 'DM' to an unknown connection attempt, or an invalid caller. 192 * 193 * Note: src here is the sender, thus it's the target of the DM 194 */ 195 void ax25_return_dm(struct net_device *dev, ax25_address *src, ax25_address *dest, ax25_digi *digi) 196 { 197 struct sk_buff *skb; 198 char *dptr; 199 ax25_digi retdigi; 200 201 if (dev == NULL) 202 return; 203 204 if ((skb = alloc_skb(dev->hard_header_len + 1, GFP_ATOMIC)) == NULL) 205 return; /* Next SABM will get DM'd */ 206 207 skb_reserve(skb, dev->hard_header_len); 208 skb_reset_network_header(skb); 209 210 ax25_digi_invert(digi, &retdigi); 211 212 dptr = skb_put(skb, 1); 213 214 *dptr = AX25_DM | AX25_PF; 215 216 /* 217 * Do the address ourselves 218 */ 219 dptr = skb_push(skb, ax25_addr_size(digi)); 220 dptr += ax25_addr_build(dptr, dest, src, &retdigi, AX25_RESPONSE, AX25_MODULUS); 221 222 ax25_queue_xmit(skb, dev); 223 } 224 225 /* 226 * Exponential backoff for AX.25 227 */ 228 void ax25_calculate_t1(ax25_cb *ax25) 229 { 230 int n, t = 2; 231 232 switch (ax25->backoff) { 233 case 0: 234 break; 235 236 case 1: 237 t += 2 * ax25->n2count; 238 break; 239 240 case 2: 241 for (n = 0; n < ax25->n2count; n++) 242 t *= 2; 243 if (t > 8) t = 8; 244 break; 245 } 246 247 ax25->t1 = t * ax25->rtt; 248 } 249 250 /* 251 * Calculate the Round Trip Time 252 */ 253 void ax25_calculate_rtt(ax25_cb *ax25) 254 { 255 if (ax25->backoff == 0) 256 return; 257 258 if (ax25_t1timer_running(ax25) && ax25->n2count == 0) 259 ax25->rtt = (9 * ax25->rtt + ax25->t1 - ax25_display_timer(&ax25->t1timer)) / 10; 260 261 if (ax25->rtt < AX25_T1CLAMPLO) 262 ax25->rtt = AX25_T1CLAMPLO; 263 264 if (ax25->rtt > AX25_T1CLAMPHI) 265 ax25->rtt = AX25_T1CLAMPHI; 266 } 267 268 void ax25_disconnect(ax25_cb *ax25, int reason) 269 { 270 ax25_clear_queues(ax25); 271 272 ax25_stop_t1timer(ax25); 273 ax25_stop_t2timer(ax25); 274 ax25_stop_t3timer(ax25); 275 ax25_stop_idletimer(ax25); 276 277 ax25->state = AX25_STATE_0; 278 279 ax25_link_failed(ax25, reason); 280 281 if (ax25->sk != NULL) { 282 bh_lock_sock(ax25->sk); 283 ax25->sk->sk_state = TCP_CLOSE; 284 ax25->sk->sk_err = reason; 285 ax25->sk->sk_shutdown |= SEND_SHUTDOWN; 286 if (!sock_flag(ax25->sk, SOCK_DEAD)) { 287 ax25->sk->sk_state_change(ax25->sk); 288 sock_set_flag(ax25->sk, SOCK_DEAD); 289 } 290 bh_unlock_sock(ax25->sk); 291 } 292 } 293