1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 *	X.25 Packet Layer release 002
4 *
5 *	This is ALPHA test software. This code may break your machine, randomly fail to work with new
6 *	releases, misbehave and/or generally screw up. It might even work.
7 *
8 *	This code REQUIRES 2.1.15 or higher
9 *
10 *	History
11 *	X.25 001	Jonathan Naylor	Started coding.
12 *      2000-09-04	Henner Eisen	Prevent freeing a dangling skb.
13 */
14
15#define pr_fmt(fmt) "X25: " fmt
16
17#include <linux/kernel.h>
18#include <linux/netdevice.h>
19#include <linux/skbuff.h>
20#include <linux/slab.h>
21#include <net/sock.h>
22#include <linux/if_arp.h>
23#include <net/x25.h>
24#include <net/x25device.h>
25
26static int x25_receive_data(struct sk_buff *skb, struct x25_neigh *nb)
27{
28	struct sock *sk;
29	unsigned short frametype;
30	unsigned int lci;
31
32	if (!pskb_may_pull(skb, X25_STD_MIN_LEN))
33		return 0;
34
35	frametype = skb->data[2];
36	lci = ((skb->data[0] << 8) & 0xF00) + ((skb->data[1] << 0) & 0x0FF);
37
38	/*
39	 *	LCI of zero is always for us, and its always a link control
40	 *	frame.
41	 */
42	if (lci == 0) {
43		x25_link_control(skb, nb, frametype);
44		return 0;
45	}
46
47	/*
48	 *	Find an existing socket.
49	 */
50	if ((sk = x25_find_socket(lci, nb)) != NULL) {
51		int queued = 1;
52
53		skb_reset_transport_header(skb);
54		bh_lock_sock(sk);
55		if (!sock_owned_by_user(sk)) {
56			queued = x25_process_rx_frame(sk, skb);
57		} else {
58			queued = !sk_add_backlog(sk, skb, READ_ONCE(sk->sk_rcvbuf));
59		}
60		bh_unlock_sock(sk);
61		sock_put(sk);
62		return queued;
63	}
64
65	/*
66	 *	Is is a Call Request ? if so process it.
67	 */
68	if (frametype == X25_CALL_REQUEST)
69		return x25_rx_call_request(skb, nb, lci);
70
71	/*
72	 * 	Its not a Call Request, nor is it a control frame.
73	 *	Can we forward it?
74	 */
75
76	if (x25_forward_data(lci, nb, skb)) {
77		if (frametype == X25_CLEAR_CONFIRMATION) {
78			x25_clear_forward_by_lci(lci);
79		}
80		kfree_skb(skb);
81		return 1;
82	}
83
84/*
85	x25_transmit_clear_request(nb, lci, 0x0D);
86*/
87
88	if (frametype != X25_CLEAR_CONFIRMATION)
89		pr_debug("x25_receive_data(): unknown frame type %2x\n",frametype);
90
91	return 0;
92}
93
94int x25_lapb_receive_frame(struct sk_buff *skb, struct net_device *dev,
95			   struct packet_type *ptype, struct net_device *orig_dev)
96{
97	struct sk_buff *nskb;
98	struct x25_neigh *nb;
99
100	if (!net_eq(dev_net(dev), &init_net))
101		goto drop;
102
103	nskb = skb_copy(skb, GFP_ATOMIC);
104	if (!nskb)
105		goto drop;
106	kfree_skb(skb);
107	skb = nskb;
108
109	/*
110	 * Packet received from unrecognised device, throw it away.
111	 */
112	nb = x25_get_neigh(dev);
113	if (!nb) {
114		pr_debug("unknown neighbour - %s\n", dev->name);
115		goto drop;
116	}
117
118	if (!pskb_may_pull(skb, 1)) {
119		x25_neigh_put(nb);
120		goto drop;
121	}
122
123	switch (skb->data[0]) {
124
125	case X25_IFACE_DATA:
126		skb_pull(skb, 1);
127		if (x25_receive_data(skb, nb)) {
128			x25_neigh_put(nb);
129			goto out;
130		}
131		break;
132
133	case X25_IFACE_CONNECT:
134		x25_link_established(nb);
135		break;
136
137	case X25_IFACE_DISCONNECT:
138		x25_link_terminated(nb);
139		break;
140	}
141	x25_neigh_put(nb);
142drop:
143	kfree_skb(skb);
144out:
145	return 0;
146}
147
148void x25_establish_link(struct x25_neigh *nb)
149{
150	struct sk_buff *skb;
151	unsigned char *ptr;
152
153	switch (nb->dev->type) {
154	case ARPHRD_X25:
155		if ((skb = alloc_skb(1, GFP_ATOMIC)) == NULL) {
156			pr_err("x25_dev: out of memory\n");
157			return;
158		}
159		ptr  = skb_put(skb, 1);
160		*ptr = X25_IFACE_CONNECT;
161		break;
162
163	default:
164		return;
165	}
166
167	skb->protocol = htons(ETH_P_X25);
168	skb->dev      = nb->dev;
169
170	dev_queue_xmit(skb);
171}
172
173void x25_terminate_link(struct x25_neigh *nb)
174{
175	struct sk_buff *skb;
176	unsigned char *ptr;
177
178	if (nb->dev->type != ARPHRD_X25)
179		return;
180
181	skb = alloc_skb(1, GFP_ATOMIC);
182	if (!skb) {
183		pr_err("x25_dev: out of memory\n");
184		return;
185	}
186
187	ptr  = skb_put(skb, 1);
188	*ptr = X25_IFACE_DISCONNECT;
189
190	skb->protocol = htons(ETH_P_X25);
191	skb->dev      = nb->dev;
192	dev_queue_xmit(skb);
193}
194
195void x25_send_frame(struct sk_buff *skb, struct x25_neigh *nb)
196{
197	unsigned char *dptr;
198
199	skb_reset_network_header(skb);
200
201	switch (nb->dev->type) {
202	case ARPHRD_X25:
203		dptr  = skb_push(skb, 1);
204		*dptr = X25_IFACE_DATA;
205		break;
206
207	default:
208		kfree_skb(skb);
209		return;
210	}
211
212	skb->protocol = htons(ETH_P_X25);
213	skb->dev      = nb->dev;
214
215	dev_queue_xmit(skb);
216}
217