1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 *
4 * Copyright Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
5 * Copyright Darryl Miles G7LED (dlm@g7led.demon.co.uk)
6 */
7 #include <linux/errno.h>
8 #include <linux/types.h>
9 #include <linux/socket.h>
10 #include <linux/in.h>
11 #include <linux/kernel.h>
12 #include <linux/timer.h>
13 #include <linux/string.h>
14 #include <linux/sockios.h>
15 #include <linux/net.h>
16 #include <linux/slab.h>
17 #include <net/ax25.h>
18 #include <linux/inet.h>
19 #include <linux/netdevice.h>
20 #include <linux/skbuff.h>
21 #include <net/sock.h>
22 #include <linux/uaccess.h>
23 #include <linux/fcntl.h>
24 #include <linux/mm.h>
25 #include <linux/interrupt.h>
26 #include <net/netrom.h>
27
28 /*
29 * This is where all NET/ROM frames pass, except for IP-over-NET/ROM which
30 * cannot be fragmented in this manner.
31 */
32 void nr_output(struct sock *sk, struct sk_buff *skb)
33 {
34 struct sk_buff *skbn;
35 unsigned char transport[NR_TRANSPORT_LEN];
36 int err, frontlen, len;
37
38 if (skb->len - NR_TRANSPORT_LEN > NR_MAX_PACKET_SIZE) {
39 /* Save a copy of the Transport Header */
40 skb_copy_from_linear_data(skb, transport, NR_TRANSPORT_LEN);
41 skb_pull(skb, NR_TRANSPORT_LEN);
42
43 frontlen = skb_headroom(skb);
44
45 while (skb->len > 0) {
46 if ((skbn = sock_alloc_send_skb(sk, frontlen + NR_MAX_PACKET_SIZE, 0, &err)) == NULL)
47 return;
48
49 skb_reserve(skbn, frontlen);
50
51 len = (NR_MAX_PACKET_SIZE > skb->len) ? skb->len : NR_MAX_PACKET_SIZE;
52
53 /* Copy the user data */
54 skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
55 skb_pull(skb, len);
56
57 /* Duplicate the Transport Header */
58 skb_push(skbn, NR_TRANSPORT_LEN);
59 skb_copy_to_linear_data(skbn, transport,
60 NR_TRANSPORT_LEN);
61 if (skb->len > 0)
62 skbn->data[4] |= NR_MORE_FLAG;
63
64 skb_queue_tail(&sk->sk_write_queue, skbn); /* Throw it on the queue */
65 }
66
67 kfree_skb(skb);
68 } else {
69 skb_queue_tail(&sk->sk_write_queue, skb); /* Throw it on the queue */
70 }
71
72 nr_kick(sk);
73 }
74
75 /*
76 * This procedure is passed a buffer descriptor for an iframe. It builds
77 * the rest of the control part of the frame and then writes it out.
78 */
79 static void nr_send_iframe(struct sock *sk, struct sk_buff *skb)
80 {
81 struct nr_sock *nr = nr_sk(sk);
82
83 if (skb == NULL)
84 return;
85
86 skb->data[2] = nr->vs;
87 skb->data[3] = nr->vr;
88
89 if (nr->condition & NR_COND_OWN_RX_BUSY)
90 skb->data[4] |= NR_CHOKE_FLAG;
91
92 nr_start_idletimer(sk);
93
94 nr_transmit_buffer(sk, skb);
95 }
96
97 void nr_send_nak_frame(struct sock *sk)
98 {
99 struct sk_buff *skb, *skbn;
100 struct nr_sock *nr = nr_sk(sk);
101
102 if ((skb = skb_peek(&nr->ack_queue)) == NULL)
103 return;
104
105 if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL)
106 return;
107
108 skbn->data[2] = nr->va;
109 skbn->data[3] = nr->vr;
110
111 if (nr->condition & NR_COND_OWN_RX_BUSY)
112 skbn->data[4] |= NR_CHOKE_FLAG;
113
114 nr_transmit_buffer(sk, skbn);
115
116 nr->condition &= ~NR_COND_ACK_PENDING;
117 nr->vl = nr->vr;
118
119 nr_stop_t1timer(sk);
120 }
121
122 void nr_kick(struct sock *sk)
123 {
124 struct nr_sock *nr = nr_sk(sk);
125 struct sk_buff *skb, *skbn;
126 unsigned short start, end;
127
128 if (nr->state != NR_STATE_3)
129 return;
130
131 if (nr->condition & NR_COND_PEER_RX_BUSY)
132 return;
133
134 if (!skb_peek(&sk->sk_write_queue))
135 return;
136
137 start = (skb_peek(&nr->ack_queue) == NULL) ? nr->va : nr->vs;
138 end = (nr->va + nr->window) % NR_MODULUS;
139
140 if (start == end)
141 return;
142
143 nr->vs = start;
144
145 /*
146 * Transmit data until either we're out of data to send or
147 * the window is full.
148 */
149
150 /*
151 * Dequeue the frame and copy it.
152 */
153 skb = skb_dequeue(&sk->sk_write_queue);
154
155 do {
156 if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
157 skb_queue_head(&sk->sk_write_queue, skb);
158 break;
159 }
160
161 skb_set_owner_w(skbn, sk);
162
163 /*
164 * Transmit the frame copy.
165 */
166 nr_send_iframe(sk, skbn);
167
168 nr->vs = (nr->vs + 1) % NR_MODULUS;
169
170 /*
171 * Requeue the original data frame.
172 */
173 skb_queue_tail(&nr->ack_queue, skb);
174
175 } while (nr->vs != end &&
176 (skb = skb_dequeue(&sk->sk_write_queue)) != NULL);
177
178 nr->vl = nr->vr;
179 nr->condition &= ~NR_COND_ACK_PENDING;
180
181 if (!nr_t1timer_running(sk))
182 nr_start_t1timer(sk);
183 }
184
185 void nr_transmit_buffer(struct sock *sk, struct sk_buff *skb)
186 {
187 struct nr_sock *nr = nr_sk(sk);
188 unsigned char *dptr;
189
190 /*
191 * Add the protocol byte and network header.
192 */
193 dptr = skb_push(skb, NR_NETWORK_LEN);
194
195 memcpy(dptr, &nr->source_addr, AX25_ADDR_LEN);
196 dptr[6] &= ~AX25_CBIT;
197 dptr[6] &= ~AX25_EBIT;
198 dptr[6] |= AX25_SSSID_SPARE;
199 dptr += AX25_ADDR_LEN;
200
201 memcpy(dptr, &nr->dest_addr, AX25_ADDR_LEN);
202 dptr[6] &= ~AX25_CBIT;
203 dptr[6] |= AX25_EBIT;
204 dptr[6] |= AX25_SSSID_SPARE;
205 dptr += AX25_ADDR_LEN;
206
207 *dptr++ = READ_ONCE(sysctl_netrom_network_ttl_initialiser);
208
209 if (!nr_route_frame(skb, NULL)) {
210 kfree_skb(skb);
211 nr_disconnect(sk, ENETUNREACH);
212 }
213 }
214
215 /*
216 * The following routines are taken from page 170 of the 7th ARRL Computer
217 * Networking Conference paper, as is the whole state machine.
218 */
219
220 void nr_establish_data_link(struct sock *sk)
221 {
222 struct nr_sock *nr = nr_sk(sk);
223
224 nr->condition = 0x00;
225 nr->n2count = 0;
226
227 nr_write_internal(sk, NR_CONNREQ);
228
229 nr_stop_t2timer(sk);
230 nr_stop_t4timer(sk);
231 nr_stop_idletimer(sk);
232 nr_start_t1timer(sk);
233 }
234
235 /*
236 * Never send a NAK when we are CHOKEd.
237 */
238 void nr_enquiry_response(struct sock *sk)
239 {
240 struct nr_sock *nr = nr_sk(sk);
241 int frametype = NR_INFOACK;
242
243 if (nr->condition & NR_COND_OWN_RX_BUSY) {
244 frametype |= NR_CHOKE_FLAG;
245 } else {
246 if (skb_peek(&nr->reseq_queue) != NULL)
247 frametype |= NR_NAK_FLAG;
248 }
249
250 nr_write_internal(sk, frametype);
251
252 nr->vl = nr->vr;
253 nr->condition &= ~NR_COND_ACK_PENDING;
254 }
255
256 void nr_check_iframes_acked(struct sock *sk, unsigned short nr)
257 {
258 struct nr_sock *nrom = nr_sk(sk);
259
260 if (nrom->vs == nr) {
261 nr_frames_acked(sk, nr);
262 nr_stop_t1timer(sk);
263 nrom->n2count = 0;
264 } else {
265 if (nrom->va != nr) {
266 nr_frames_acked(sk, nr);
267 nr_start_t1timer(sk);
268 }
269 }
270 }
271
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