nr_out.c

  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, 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				kfree_skb(skb);
 48				return;
 49			}
 50
 51			skb_reserve(skbn, 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, skb_put(skbn, len), len);
 57			skb_pull(skb, len);
 58
 59			/* Duplicate the Transport Header */
 60			skb_push(skbn, NR_TRANSPORT_LEN);
 61			skb_copy_to_linear_data(skbn, transport,
 62						NR_TRANSPORT_LEN);
 63			if (skb->len > 0)
 64				skbn->data[4] |= NR_MORE_FLAG;
 65
 66			skb_queue_tail(&sk->sk_write_queue, skbn); /* Throw it on the queue */
 67		}
 68
 69		kfree_skb(skb);
 70	} else {
 71		skb_queue_tail(&sk->sk_write_queue, 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(&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(&sk->sk_write_queue))
137		return;
138
139	start = (skb_peek(&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(&sk->sk_write_queue);
156
157	do {
158		if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
159			skb_queue_head(&sk->sk_write_queue, skb);
160			break;
161		}
162
163		skb_set_owner_w(skbn, sk);
164
165		/*
166		 * Transmit the frame copy.
167		 */
168		nr_send_iframe(sk, skbn);
169
170		nr->vs = (nr->vs + 1) % NR_MODULUS;
171
172		/*
173		 * Requeue the original data frame.
174		 */
175		skb_queue_tail(&nr->ack_queue, skb);
176
177	} while (nr->vs != end &&
178		 (skb = skb_dequeue(&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(&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}