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 */
32void 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, to: 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, size: frontlen + NR_MAX_PACKET_SIZE, noblock: 0, errcode: &err)) == NULL) {
47 kfree_skb(skb);
48 return;
49 }
50
51 skb_reserve(skb: skbn, len: frontlen);
52
53 len = (NR_MAX_PACKET_SIZE > skb->len) ? skb->len : NR_MAX_PACKET_SIZE;
54
55 /* Copy the user data */
56 skb_copy_from_linear_data(skb, to: skb_put(skb: skbn, len), len);
57 skb_pull(skb, len);
58
59 /* Duplicate the Transport Header */
60 skb_push(skb: skbn, NR_TRANSPORT_LEN);
61 skb_copy_to_linear_data(skb: skbn, from: transport,
62 NR_TRANSPORT_LEN);
63 if (skb->len > 0)
64 skbn->data[4] |= NR_MORE_FLAG;
65
66 skb_queue_tail(list: &sk->sk_write_queue, newsk: skbn); /* Throw it on the queue */
67 }
68
69 kfree_skb(skb);
70 } else {
71 skb_queue_tail(list: &sk->sk_write_queue, newsk: skb); /* Throw it on the queue */
72 }
73
74 nr_kick(sk);
75}
76
77/*
78 * This procedure is passed a buffer descriptor for an iframe. It builds
79 * the rest of the control part of the frame and then writes it out.
80 */
81static void nr_send_iframe(struct sock *sk, struct sk_buff *skb)
82{
83 struct nr_sock *nr = nr_sk(sk);
84
85 if (skb == NULL)
86 return;
87
88 skb->data[2] = nr->vs;
89 skb->data[3] = nr->vr;
90
91 if (nr->condition & NR_COND_OWN_RX_BUSY)
92 skb->data[4] |= NR_CHOKE_FLAG;
93
94 nr_start_idletimer(sk);
95
96 nr_transmit_buffer(sk, skb);
97}
98
99void nr_send_nak_frame(struct sock *sk)
100{
101 struct sk_buff *skb, *skbn;
102 struct nr_sock *nr = nr_sk(sk);
103
104 if ((skb = skb_peek(list_: &nr->ack_queue)) == NULL)
105 return;
106
107 if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL)
108 return;
109
110 skbn->data[2] = nr->va;
111 skbn->data[3] = nr->vr;
112
113 if (nr->condition & NR_COND_OWN_RX_BUSY)
114 skbn->data[4] |= NR_CHOKE_FLAG;
115
116 nr_transmit_buffer(sk, skbn);
117
118 nr->condition &= ~NR_COND_ACK_PENDING;
119 nr->vl = nr->vr;
120
121 nr_stop_t1timer(sk);
122}
123
124void nr_kick(struct sock *sk)
125{
126 struct nr_sock *nr = nr_sk(sk);
127 struct sk_buff *skb, *skbn;
128 unsigned short start, end;
129
130 if (nr->state != NR_STATE_3)
131 return;
132
133 if (nr->condition & NR_COND_PEER_RX_BUSY)
134 return;
135
136 if (!skb_peek(list_: &sk->sk_write_queue))
137 return;
138
139 start = (skb_peek(list_: &nr->ack_queue) == NULL) ? nr->va : nr->vs;
140 end = (nr->va + nr->window) % NR_MODULUS;
141
142 if (start == end)
143 return;
144
145 nr->vs = start;
146
147 /*
148 * Transmit data until either we're out of data to send or
149 * the window is full.
150 */
151
152 /*
153 * Dequeue the frame and copy it.
154 */
155 skb = skb_dequeue(list: &sk->sk_write_queue);
156
157 do {
158 if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
159 skb_queue_head(list: &sk->sk_write_queue, newsk: skb);
160 break;
161 }
162
163 skb_set_owner_w(skb: skbn, sk);
164
165 /*
166 * Transmit the frame copy.
167 */
168 nr_send_iframe(sk, skb: skbn);
169
170 nr->vs = (nr->vs + 1) % NR_MODULUS;
171
172 /*
173 * Requeue the original data frame.
174 */
175 skb_queue_tail(list: &nr->ack_queue, newsk: skb);
176
177 } while (nr->vs != end &&
178 (skb = skb_dequeue(list: &sk->sk_write_queue)) != NULL);
179
180 nr->vl = nr->vr;
181 nr->condition &= ~NR_COND_ACK_PENDING;
182
183 if (!nr_t1timer_running(sk))
184 nr_start_t1timer(sk);
185}
186
187void nr_transmit_buffer(struct sock *sk, struct sk_buff *skb)
188{
189 struct nr_sock *nr = nr_sk(sk);
190 unsigned char *dptr;
191
192 /*
193 * Add the protocol byte and network header.
194 */
195 dptr = skb_push(skb, NR_NETWORK_LEN);
196
197 memcpy(dptr, &nr->source_addr, AX25_ADDR_LEN);
198 dptr[6] &= ~AX25_CBIT;
199 dptr[6] &= ~AX25_EBIT;
200 dptr[6] |= AX25_SSSID_SPARE;
201 dptr += AX25_ADDR_LEN;
202
203 memcpy(dptr, &nr->dest_addr, AX25_ADDR_LEN);
204 dptr[6] &= ~AX25_CBIT;
205 dptr[6] |= AX25_EBIT;
206 dptr[6] |= AX25_SSSID_SPARE;
207 dptr += AX25_ADDR_LEN;
208
209 *dptr++ = READ_ONCE(sysctl_netrom_network_ttl_initialiser);
210
211 if (!nr_route_frame(skb, NULL)) {
212 kfree_skb(skb);
213 nr_disconnect(sk, ENETUNREACH);
214 }
215}
216
217/*
218 * The following routines are taken from page 170 of the 7th ARRL Computer
219 * Networking Conference paper, as is the whole state machine.
220 */
221
222void nr_establish_data_link(struct sock *sk)
223{
224 struct nr_sock *nr = nr_sk(sk);
225
226 nr->condition = 0x00;
227 nr->n2count = 0;
228
229 nr_write_internal(sk, NR_CONNREQ);
230
231 nr_stop_t2timer(sk);
232 nr_stop_t4timer(sk);
233 nr_stop_idletimer(sk);
234 nr_start_t1timer(sk);
235}
236
237/*
238 * Never send a NAK when we are CHOKEd.
239 */
240void nr_enquiry_response(struct sock *sk)
241{
242 struct nr_sock *nr = nr_sk(sk);
243 int frametype = NR_INFOACK;
244
245 if (nr->condition & NR_COND_OWN_RX_BUSY) {
246 frametype |= NR_CHOKE_FLAG;
247 } else {
248 if (skb_peek(list_: &nr->reseq_queue) != NULL)
249 frametype |= NR_NAK_FLAG;
250 }
251
252 nr_write_internal(sk, frametype);
253
254 nr->vl = nr->vr;
255 nr->condition &= ~NR_COND_ACK_PENDING;
256}
257
258void nr_check_iframes_acked(struct sock *sk, unsigned short nr)
259{
260 struct nr_sock *nrom = nr_sk(sk);
261
262 if (nrom->vs == nr) {
263 nr_frames_acked(sk, nr);
264 nr_stop_t1timer(sk);
265 nrom->n2count = 0;
266 } else {
267 if (nrom->va != nr) {
268 nr_frames_acked(sk, nr);
269 nr_start_t1timer(sk);
270 }
271 }
272}
273

source code of linux/net/netrom/nr_out.c