1/*
2 *	X.25 Packet Layer release 002
3 *
4 *	This is ALPHA test software. This code may break your machine, randomly fail to work with new
5 *	releases, misbehave and/or generally screw up. It might even work.
6 *
7 *	This code REQUIRES 2.1.15 or higher
8 *
9 *	This module:
10 *		This module is free software; you can redistribute it and/or
11 *		modify it under the terms of the GNU General Public License
12 *		as published by the Free Software Foundation; either version
13 *		2 of the License, or (at your option) any later version.
14 *
15 *	History
16 *	X.25 001	Jonathan Naylor	Started coding.
17 *      2000-09-04	Henner Eisen	Prevent freeing a dangling skb.
18 */
19
20#define pr_fmt(fmt) "X25: " fmt
21
22#include <linux/kernel.h>
23#include <linux/netdevice.h>
24#include <linux/skbuff.h>
25#include <linux/slab.h>
26#include <net/sock.h>
27#include <linux/if_arp.h>
28#include <net/x25.h>
29#include <net/x25device.h>
30
31static int x25_receive_data(struct sk_buff *skb, struct x25_neigh *nb)
32{
33	struct sock *sk;
34	unsigned short frametype;
35	unsigned int lci;
36
37	if (!pskb_may_pull(skb, X25_STD_MIN_LEN))
38		return 0;
39
40	frametype = skb->data[2];
41	lci = ((skb->data[0] << 8) & 0xF00) + ((skb->data[1] << 0) & 0x0FF);
42
43	/*
44	 *	LCI of zero is always for us, and its always a link control
45	 *	frame.
46	 */
47	if (lci == 0) {
48		x25_link_control(skb, nb, frametype);
49		return 0;
50	}
51
52	/*
53	 *	Find an existing socket.
54	 */
55	if ((sk = x25_find_socket(lci, nb)) != NULL) {
56		int queued = 1;
57
58		skb_reset_transport_header(skb);
59		bh_lock_sock(sk);
60		if (!sock_owned_by_user(sk)) {
61			queued = x25_process_rx_frame(sk, skb);
62		} else {
63			queued = !sk_add_backlog(sk, skb, sk->sk_rcvbuf);
64		}
65		bh_unlock_sock(sk);
66		sock_put(sk);
67		return queued;
68	}
69
70	/*
71	 *	Is is a Call Request ? if so process it.
72	 */
73	if (frametype == X25_CALL_REQUEST)
74		return x25_rx_call_request(skb, nb, lci);
75
76	/*
77	 * 	Its not a Call Request, nor is it a control frame.
78	 *	Can we forward it?
79	 */
80
81	if (x25_forward_data(lci, nb, skb)) {
82		if (frametype == X25_CLEAR_CONFIRMATION) {
83			x25_clear_forward_by_lci(lci);
84		}
85		kfree_skb(skb);
86		return 1;
87	}
88
89/*
90	x25_transmit_clear_request(nb, lci, 0x0D);
91*/
92
93	if (frametype != X25_CLEAR_CONFIRMATION)
94		pr_debug("x25_receive_data(): unknown frame type %2x\n",frametype);
95
96	return 0;
97}
98
99int x25_lapb_receive_frame(struct sk_buff *skb, struct net_device *dev,
100			   struct packet_type *ptype, struct net_device *orig_dev)
101{
102	struct sk_buff *nskb;
103	struct x25_neigh *nb;
104
105	if (!net_eq(dev_net(dev), &init_net))
106		goto drop;
107
108	nskb = skb_copy(skb, GFP_ATOMIC);
109	if (!nskb)
110		goto drop;
111	kfree_skb(skb);
112	skb = nskb;
113
114	/*
115	 * Packet received from unrecognised device, throw it away.
116	 */
117	nb = x25_get_neigh(dev);
118	if (!nb) {
119		pr_debug("unknown neighbour - %s\n", dev->name);
120		goto drop;
121	}
122
123	if (!pskb_may_pull(skb, 1))
124		return 0;
125
126	switch (skb->data[0]) {
127
128	case X25_IFACE_DATA:
129		skb_pull(skb, 1);
130		if (x25_receive_data(skb, nb)) {
131			x25_neigh_put(nb);
132			goto out;
133		}
134		break;
135
136	case X25_IFACE_CONNECT:
137		x25_link_established(nb);
138		break;
139
140	case X25_IFACE_DISCONNECT:
141		x25_link_terminated(nb);
142		break;
143	}
144	x25_neigh_put(nb);
145drop:
146	kfree_skb(skb);
147out:
148	return 0;
149}
150
151void x25_establish_link(struct x25_neigh *nb)
152{
153	struct sk_buff *skb;
154	unsigned char *ptr;
155
156	switch (nb->dev->type) {
157	case ARPHRD_X25:
158		if ((skb = alloc_skb(1, GFP_ATOMIC)) == NULL) {
159			pr_err("x25_dev: out of memory\n");
160			return;
161		}
162		ptr  = skb_put(skb, 1);
163		*ptr = X25_IFACE_CONNECT;
164		break;
165
166#if IS_ENABLED(CONFIG_LLC)
167	case ARPHRD_ETHER:
168		return;
169#endif
170	default:
171		return;
172	}
173
174	skb->protocol = htons(ETH_P_X25);
175	skb->dev      = nb->dev;
176
177	dev_queue_xmit(skb);
178}
179
180void x25_terminate_link(struct x25_neigh *nb)
181{
182	struct sk_buff *skb;
183	unsigned char *ptr;
184
185#if IS_ENABLED(CONFIG_LLC)
186	if (nb->dev->type == ARPHRD_ETHER)
187		return;
188#endif
189	if (nb->dev->type != ARPHRD_X25)
190		return;
191
192	skb = alloc_skb(1, GFP_ATOMIC);
193	if (!skb) {
194		pr_err("x25_dev: out of memory\n");
195		return;
196	}
197
198	ptr  = skb_put(skb, 1);
199	*ptr = X25_IFACE_DISCONNECT;
200
201	skb->protocol = htons(ETH_P_X25);
202	skb->dev      = nb->dev;
203	dev_queue_xmit(skb);
204}
205
206void x25_send_frame(struct sk_buff *skb, struct x25_neigh *nb)
207{
208	unsigned char *dptr;
209
210	skb_reset_network_header(skb);
211
212	switch (nb->dev->type) {
213	case ARPHRD_X25:
214		dptr  = skb_push(skb, 1);
215		*dptr = X25_IFACE_DATA;
216		break;
217
218#if IS_ENABLED(CONFIG_LLC)
219	case ARPHRD_ETHER:
220		kfree_skb(skb);
221		return;
222#endif
223	default:
224		kfree_skb(skb);
225		return;
226	}
227
228	skb->protocol = htons(ETH_P_X25);
229	skb->dev      = nb->dev;
230
231	dev_queue_xmit(skb);
232}
233