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 Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
8 * Copyright Darryl Miles G7LED (dlm@g7led.demon.co.uk)
9 */
10#include <linux/errno.h>
11#include <linux/types.h>
12#include <linux/socket.h>
13#include <linux/in.h>
14#include <linux/kernel.h>
15#include <linux/timer.h>
16#include <linux/string.h>
17#include <linux/sockios.h>
18#include <linux/net.h>
19#include <linux/slab.h>
20#include <net/ax25.h>
21#include <linux/inet.h>
22#include <linux/netdevice.h>
23#include <linux/skbuff.h>
24#include <net/sock.h>
25#include <linux/uaccess.h>
26#include <linux/fcntl.h>
27#include <linux/mm.h>
28#include <linux/interrupt.h>
29#include <net/netrom.h>
30
31/*
32 *	This is where all NET/ROM frames pass, except for IP-over-NET/ROM which
33 *	cannot be fragmented in this manner.
34 */
35void nr_output(struct sock *sk, struct sk_buff *skb)
36{
37	struct sk_buff *skbn;
38	unsigned char transport[NR_TRANSPORT_LEN];
39	int err, frontlen, len;
40
41	if (skb->len - NR_TRANSPORT_LEN > NR_MAX_PACKET_SIZE) {
42		/* Save a copy of the Transport Header */
43		skb_copy_from_linear_data(skb, transport, NR_TRANSPORT_LEN);
44		skb_pull(skb, NR_TRANSPORT_LEN);
45
46		frontlen = skb_headroom(skb);
47
48		while (skb->len > 0) {
49			if ((skbn = sock_alloc_send_skb(sk, frontlen + NR_MAX_PACKET_SIZE, 0, &err)) == NULL)
50				return;
51
52			skb_reserve(skbn, frontlen);
53
54			len = (NR_MAX_PACKET_SIZE > skb->len) ? skb->len : NR_MAX_PACKET_SIZE;
55
56			/* Copy the user data */
57			skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
58			skb_pull(skb, len);
59
60			/* Duplicate the Transport Header */
61			skb_push(skbn, NR_TRANSPORT_LEN);
62			skb_copy_to_linear_data(skbn, transport,
63						NR_TRANSPORT_LEN);
64			if (skb->len > 0)
65				skbn->data[4] |= NR_MORE_FLAG;
66
67			skb_queue_tail(&sk->sk_write_queue, skbn); /* Throw it on the queue */
68		}
69
70		kfree_skb(skb);
71	} else {
72		skb_queue_tail(&sk->sk_write_queue, skb);		/* Throw it on the queue */
73	}
74
75	nr_kick(sk);
76}
77
78/*
79 *	This procedure is passed a buffer descriptor for an iframe. It builds
80 *	the rest of the control part of the frame and then writes it out.
81 */
82static void nr_send_iframe(struct sock *sk, struct sk_buff *skb)
83{
84	struct nr_sock *nr = nr_sk(sk);
85
86	if (skb == NULL)
87		return;
88
89	skb->data[2] = nr->vs;
90	skb->data[3] = nr->vr;
91
92	if (nr->condition & NR_COND_OWN_RX_BUSY)
93		skb->data[4] |= NR_CHOKE_FLAG;
94
95	nr_start_idletimer(sk);
96
97	nr_transmit_buffer(sk, skb);
98}
99
100void nr_send_nak_frame(struct sock *sk)
101{
102	struct sk_buff *skb, *skbn;
103	struct nr_sock *nr = nr_sk(sk);
104
105	if ((skb = skb_peek(&nr->ack_queue)) == NULL)
106		return;
107
108	if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL)
109		return;
110
111	skbn->data[2] = nr->va;
112	skbn->data[3] = nr->vr;
113
114	if (nr->condition & NR_COND_OWN_RX_BUSY)
115		skbn->data[4] |= NR_CHOKE_FLAG;
116
117	nr_transmit_buffer(sk, skbn);
118
119	nr->condition &= ~NR_COND_ACK_PENDING;
120	nr->vl         = nr->vr;
121
122	nr_stop_t1timer(sk);
123}
124
125void nr_kick(struct sock *sk)
126{
127	struct nr_sock *nr = nr_sk(sk);
128	struct sk_buff *skb, *skbn;
129	unsigned short start, end;
130
131	if (nr->state != NR_STATE_3)
132		return;
133
134	if (nr->condition & NR_COND_PEER_RX_BUSY)
135		return;
136
137	if (!skb_peek(&sk->sk_write_queue))
138		return;
139
140	start = (skb_peek(&nr->ack_queue) == NULL) ? nr->va : nr->vs;
141	end   = (nr->va + nr->window) % NR_MODULUS;
142
143	if (start == end)
144		return;
145
146	nr->vs = start;
147
148	/*
149	 * Transmit data until either we're out of data to send or
150	 * the window is full.
151	 */
152
153	/*
154	 * Dequeue the frame and copy it.
155	 */
156	skb = skb_dequeue(&sk->sk_write_queue);
157
158	do {
159		if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
160			skb_queue_head(&sk->sk_write_queue, skb);
161			break;
162		}
163
164		skb_set_owner_w(skbn, sk);
165
166		/*
167		 * Transmit the frame copy.
168		 */
169		nr_send_iframe(sk, skbn);
170
171		nr->vs = (nr->vs + 1) % NR_MODULUS;
172
173		/*
174		 * Requeue the original data frame.
175		 */
176		skb_queue_tail(&nr->ack_queue, skb);
177
178	} while (nr->vs != end &&
179		 (skb = skb_dequeue(&sk->sk_write_queue)) != NULL);
180
181	nr->vl         = nr->vr;
182	nr->condition &= ~NR_COND_ACK_PENDING;
183
184	if (!nr_t1timer_running(sk))
185		nr_start_t1timer(sk);
186}
187
188void nr_transmit_buffer(struct sock *sk, struct sk_buff *skb)
189{
190	struct nr_sock *nr = nr_sk(sk);
191	unsigned char *dptr;
192
193	/*
194	 *	Add the protocol byte and network header.
195	 */
196	dptr = skb_push(skb, NR_NETWORK_LEN);
197
198	memcpy(dptr, &nr->source_addr, AX25_ADDR_LEN);
199	dptr[6] &= ~AX25_CBIT;
200	dptr[6] &= ~AX25_EBIT;
201	dptr[6] |= AX25_SSSID_SPARE;
202	dptr += AX25_ADDR_LEN;
203
204	memcpy(dptr, &nr->dest_addr, AX25_ADDR_LEN);
205	dptr[6] &= ~AX25_CBIT;
206	dptr[6] |= AX25_EBIT;
207	dptr[6] |= AX25_SSSID_SPARE;
208	dptr += AX25_ADDR_LEN;
209
210	*dptr++ = sysctl_netrom_network_ttl_initialiser;
211
212	if (!nr_route_frame(skb, NULL)) {
213		kfree_skb(skb);
214		nr_disconnect(sk, ENETUNREACH);
215	}
216}
217
218/*
219 * The following routines are taken from page 170 of the 7th ARRL Computer
220 * Networking Conference paper, as is the whole state machine.
221 */
222
223void nr_establish_data_link(struct sock *sk)
224{
225	struct nr_sock *nr = nr_sk(sk);
226
227	nr->condition = 0x00;
228	nr->n2count   = 0;
229
230	nr_write_internal(sk, NR_CONNREQ);
231
232	nr_stop_t2timer(sk);
233	nr_stop_t4timer(sk);
234	nr_stop_idletimer(sk);
235	nr_start_t1timer(sk);
236}
237
238/*
239 * Never send a NAK when we are CHOKEd.
240 */
241void nr_enquiry_response(struct sock *sk)
242{
243	struct nr_sock *nr = nr_sk(sk);
244	int frametype = NR_INFOACK;
245
246	if (nr->condition & NR_COND_OWN_RX_BUSY) {
247		frametype |= NR_CHOKE_FLAG;
248	} else {
249		if (skb_peek(&nr->reseq_queue) != NULL)
250			frametype |= NR_NAK_FLAG;
251	}
252
253	nr_write_internal(sk, frametype);
254
255	nr->vl         = nr->vr;
256	nr->condition &= ~NR_COND_ACK_PENDING;
257}
258
259void nr_check_iframes_acked(struct sock *sk, unsigned short nr)
260{
261	struct nr_sock *nrom = nr_sk(sk);
262
263	if (nrom->vs == nr) {
264		nr_frames_acked(sk, nr);
265		nr_stop_t1timer(sk);
266		nrom->n2count = 0;
267	} else {
268		if (nrom->va != nr) {
269			nr_frames_acked(sk, nr);
270			nr_start_t1timer(sk);
271		}
272	}
273}
274