net/ax25/ax25_subr.c



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/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * Copyright (C) Alan Cox GW4PTS (alan@lxorguk.ukuu.org.uk)
 * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
 * Copyright (C) Joerg Reuter DL1BKE (jreuter@yaina.de)
 * Copyright (C) Frederic Rible F1OAT (frible@teaser.fr)
 */
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/kernel.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/slab.h>
#include <net/ax25.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <net/tcp_states.h>
#include <asm/uaccess.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/interrupt.h>

/*
 *	This routine purges all the queues of frames.
 */
void ax25_clear_queues(ax25_cb *ax25)
{
	skb_queue_purge(&ax25->write_queue);
	skb_queue_purge(&ax25->ack_queue);
	skb_queue_purge(&ax25->reseq_queue);
	skb_queue_purge(&ax25->frag_queue);
}

/*
 * This routine purges the input queue of those frames that have been
 * acknowledged. This replaces the boxes labelled "V(a) <- N(r)" on the
 * SDL diagram.
 */
void ax25_frames_acked(ax25_cb *ax25, unsigned short nr)
{
	struct sk_buff *skb;

	/*
	 * Remove all the ack-ed frames from the ack queue.
	 */
	if (ax25->va != nr) {
		while (skb_peek(&ax25->ack_queue) != NULL && ax25->va != nr) {
			skb = skb_dequeue(&ax25->ack_queue);
			kfree_skb(skb);
			ax25->va = (ax25->va + 1) % ax25->modulus;
		}
	}
}

void ax25_requeue_frames(ax25_cb *ax25)
{
	struct sk_buff *skb;

	/*
	 * Requeue all the un-ack-ed frames on the output queue to be picked
	 * up by ax25_kick called from the timer. This arrangement handles the
	 * possibility of an empty output queue.
	 */
	while ((skb = skb_dequeue_tail(&ax25->ack_queue)) != NULL)
		skb_queue_head(&ax25->write_queue, skb);
}

/*
 *	Validate that the value of nr is between va and vs. Return true or
 *	false for testing.
 */
int ax25_validate_nr(ax25_cb *ax25, unsigned short nr)
{
	unsigned short vc = ax25->va;

	while (vc != ax25->vs) {
		if (nr == vc) return 1;
		vc = (vc + 1) % ax25->modulus;
	}

	if (nr == ax25->vs) return 1;

	return 0;
}

/*
 *	This routine is the centralised routine for parsing the control
 *	information for the different frame formats.
 */
int ax25_decode(ax25_cb *ax25, struct sk_buff *skb, int *ns, int *nr, int *pf)
{
	unsigned char *frame;
	int frametype = AX25_ILLEGAL;

	frame = skb->data;
	*ns = *nr = *pf = 0;

	if (ax25->modulus == AX25_MODULUS) {
		if ((frame[0] & AX25_S) == 0) {
			frametype = AX25_I;			/* I frame - carries NR/NS/PF */
			*ns = (frame[0] >> 1) & 0x07;
			*nr = (frame[0] >> 5) & 0x07;
			*pf = frame[0] & AX25_PF;
		} else if ((frame[0] & AX25_U) == 1) { 	/* S frame - take out PF/NR */
			frametype = frame[0] & 0x0F;
			*nr = (frame[0] >> 5) & 0x07;
			*pf = frame[0] & AX25_PF;
		} else if ((frame[0] & AX25_U) == 3) { 	/* U frame - take out PF */
			frametype = frame[0] & ~AX25_PF;
			*pf = frame[0] & AX25_PF;
		}
		skb_pull(skb, 1);
	} else {
		if ((frame[0] & AX25_S) == 0) {
			frametype = AX25_I;			/* I frame - carries NR/NS/PF */