1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  *
4  * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
5  */
6 #include <linux/errno.h>
7 #include <linux/types.h>
8 #include <linux/socket.h>
9 #include <linux/in.h>
10 #include <linux/kernel.h>
11 #include <linux/timer.h>
12 #include <linux/string.h>
13 #include <linux/sockios.h>
14 #include <linux/net.h>
15 #include <linux/gfp.h>
16 #include <net/ax25.h>
17 #include <linux/inet.h>
18 #include <linux/netdevice.h>
19 #include <linux/skbuff.h>
20 #include <net/sock.h>
21 #include <linux/fcntl.h>
22 #include <linux/mm.h>
23 #include <linux/interrupt.h>
24 #include <net/rose.h>
25 
26 /*
27  *	This procedure is passed a buffer descriptor for an iframe. It builds
28  *	the rest of the control part of the frame and then writes it out.
29  */
rose_send_iframe(struct sock * sk,struct sk_buff * skb)30 static void rose_send_iframe(struct sock *sk, struct sk_buff *skb)
31 {
32 	struct rose_sock *rose = rose_sk(sk);
33 
34 	if (skb == NULL)
35 		return;
36 
37 	skb->data[2] |= (rose->vr << 5) & 0xE0;
38 	skb->data[2] |= (rose->vs << 1) & 0x0E;
39 
40 	rose_start_idletimer(sk);
41 
42 	rose_transmit_link(skb, rose->neighbour);
43 }
44 
rose_kick(struct sock * sk)45 void rose_kick(struct sock *sk)
46 {
47 	struct rose_sock *rose = rose_sk(sk);
48 	struct sk_buff *skb, *skbn;
49 	unsigned short start, end;
50 
51 	if (rose->state != ROSE_STATE_3)
52 		return;
53 
54 	if (rose->condition & ROSE_COND_PEER_RX_BUSY)
55 		return;
56 
57 	if (!skb_peek(&sk->sk_write_queue))
58 		return;
59 
60 	start = (skb_peek(&rose->ack_queue) == NULL) ? rose->va : rose->vs;
61 	end   = (rose->va + sysctl_rose_window_size) % ROSE_MODULUS;
62 
63 	if (start == end)
64 		return;
65 
66 	rose->vs = start;
67 
68 	/*
69 	 * Transmit data until either we're out of data to send or
70 	 * the window is full.
71 	 */
72 
73 	skb  = skb_dequeue(&sk->sk_write_queue);
74 
75 	do {
76 		if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
77 			skb_queue_head(&sk->sk_write_queue, skb);
78 			break;
79 		}
80 
81 		skb_set_owner_w(skbn, sk);
82 
83 		/*
84 		 * Transmit the frame copy.
85 		 */
86 		rose_send_iframe(sk, skbn);
87 
88 		rose->vs = (rose->vs + 1) % ROSE_MODULUS;
89 
90 		/*
91 		 * Requeue the original data frame.
92 		 */
93 		skb_queue_tail(&rose->ack_queue, skb);
94 
95 	} while (rose->vs != end &&
96 		 (skb = skb_dequeue(&sk->sk_write_queue)) != NULL);
97 
98 	rose->vl         = rose->vr;
99 	rose->condition &= ~ROSE_COND_ACK_PENDING;
100 
101 	rose_stop_timer(sk);
102 }
103 
104 /*
105  * The following routines are taken from page 170 of the 7th ARRL Computer
106  * Networking Conference paper, as is the whole state machine.
107  */
108 
rose_enquiry_response(struct sock * sk)109 void rose_enquiry_response(struct sock *sk)
110 {
111 	struct rose_sock *rose = rose_sk(sk);
112 
113 	if (rose->condition & ROSE_COND_OWN_RX_BUSY)
114 		rose_write_internal(sk, ROSE_RNR);
115 	else
116 		rose_write_internal(sk, ROSE_RR);
117 
118 	rose->vl         = rose->vr;
119 	rose->condition &= ~ROSE_COND_ACK_PENDING;
120 
121 	rose_stop_timer(sk);
122 }
123