dn_nsp_out.c

嵌入式系统设计与实验教材二源码linux内核移植与编译

/*
 * DECnet       An implementation of the DECnet protocol suite for the LINUX
 *              operating system.  DECnet is implemented using the  BSD Socket
 *              interface as the means of communication with the user level.
 *
 *              DECnet Network Services Protocol (Output)
 *
 * Author:      Eduardo Marcelo Serrat <[e-mail]>
 *
 * Changes:
 *
 *    Steve Whitehouse:  Split into dn_nsp_in.c and dn_nsp_out.c from
 *                       original dn_nsp.c.
 *    Steve Whitehouse:  Updated to work with my new routing architecture.
 *    Steve Whitehouse:  Added changes from Eduardo Serrat's patches.
 *    Steve Whitehouse:  Now conninits have the "return" bit set.
 *    Steve Whitehouse:  Fixes to check alloc'd skbs are non NULL!
 *                       Moved output state machine into one function
 *    Steve Whitehouse:  New output state machine
 *         Paul Koning:  Connect Confirm message fix.
 *      Eduardo Serrat:  Fix to stop dn_nsp_do_disc() sending malformed packets.
 *    Steve Whitehouse:  dn_nsp_output() and friends needed a spring clean
 */

/******************************************************************************
    (c) 1995-1998 E.M. Serrat		[e-mail]
    
    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
    any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.
*******************************************************************************/

#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/netdevice.h>
#include <linux/inet.h>
#include <linux/route.h>
#include <net/sock.h>
#include <asm/segment.h>
#include <asm/system.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/termios.h>      
#include <linux/interrupt.h>
#include <linux/proc_fs.h>
#include <linux/stat.h>
#include <linux/init.h>
#include <linux/poll.h>
#include <linux/if_packet.h>
#include <net/neighbour.h>
#include <net/dst.h>
#include <net/dn_nsp.h>
#include <net/dn_dev.h>
#include <net/dn_route.h>


static int nsp_backoff[NSP_MAXRXTSHIFT + 1] = { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };

/*
 * If sk == NULL, then we assume that we are supposed to be making
 * a routing layer skb. If sk != NULL, then we are supposed to be
 * creating an skb for the NSP layer.
 *
 * The eventual aim is for each socket to have a cached header size
 * for its outgoing packets, and to set hdr from this when sk != NULL.
 */
struct sk_buff *dn_alloc_skb(struct sock *sk, int size, int pri)
{
	struct sk_buff *skb;
	int hdr = 64;

	if ((skb = alloc_skb(size + hdr, pri)) == NULL)
		return NULL;

	skb->protocol = __constant_htons(ETH_P_DNA_RT);
	skb->pkt_type = PACKET_OUTGOING;

	if (sk)
		skb_set_owner_w(skb, sk);

	skb_reserve(skb, hdr);

	return skb;
}

/*
 * Wrapper for the above, for allocs of data skbs. We try and get the
 * whole size thats been asked for (plus 11 bytes of header). If this
 * fails, then we try for any size over 16 bytes for SOCK_STREAMS.
 */
struct sk_buff *dn_alloc_send_skb(struct sock *sk, int *size, int noblock, int *err)
{
	int space;
	int len;
	struct sk_buff *skb = NULL;

	*err = 0;

	while(skb == NULL) {
		if (signal_pending(current)) {
			*err = ERESTARTSYS;
			break;
		}

		if (sk->shutdown & SEND_SHUTDOWN) {
			*err = EINVAL;
			break;
		}

		if (sk->err)
			break;

		len = *size + 11;
		space = sk->sndbuf - atomic_read(&sk->wmem_alloc);

		if (space < len) {
			if ((sk->socket->type == SOCK_STREAM) && (space >= (16 + 11)))
				len = space;
		}

		if (space < len) {
			set_bit(SOCK_ASYNC_NOSPACE, &sk->socket->flags);
			if (noblock) {
				*err = EWOULDBLOCK;
				break;
			}

			clear_bit(SOCK_ASYNC_WAITDATA, &sk->socket->flags);
			SOCK_SLEEP_PRE(sk)

			if ((sk->sndbuf - atomic_read(&sk->wmem_alloc)) < len)
				schedule();

			SOCK_SLEEP_POST(sk)
			continue;
		}

		if ((skb = dn_alloc_skb(sk, len, sk->allocation)) == NULL)
			continue;

		*size = len - 11;
	}

	return skb;
}

/*
 * Calculate persist timer based upon the smoothed round
 * trip time and the variance. Backoff according to the
 * nsp_backoff[] array.
 */
unsigned long dn_nsp_persist(struct sock *sk)
{
	struct dn_scp *scp = DN_SK(sk);

	unsigned long t = ((scp->nsp_srtt >> 2) + scp->nsp_rttvar) >> 1;

	t *= nsp_backoff[scp->nsp_rxtshift];

	if (t < HZ) t = HZ;
	if (t > (600*HZ)) t = (600*HZ);

	if (scp->nsp_rxtshift < NSP_MAXRXTSHIFT)
		scp->nsp_rxtshift++;

	/* printk(KERN_DEBUG "rxtshift %lu, t=%lu\n", scp->nsp_rxtshift, t); */

	return t;
}

/*
 * This is called each time we get an estimate for the rtt
 * on the link.
 */
static void dn_nsp_rtt(struct sock *sk, long rtt)
{
	struct dn_scp *scp = DN_SK(sk);
	long srtt = (long)scp->nsp_srtt;
	long rttvar = (long)scp->nsp_rttvar;
	long delta;

	/*
	 * If the jiffies clock flips over in the middle of timestamp
	 * gathering this value might turn out negative, so we make sure
	 * that is it always positive here.
	 */
	if (rtt < 0) 
		rtt = -rtt;
	/*
	 * Add new rtt to smoothed average
	 */
	delta = ((rtt << 3) - srtt);
	srtt += (delta >> 3);
	if (srtt >= 1) 
		scp->nsp_srtt = (unsigned long)srtt;
	else
		scp->nsp_srtt = 1;

	/*
	 * Add new rtt varience to smoothed varience
	 */
	delta >>= 1;
	rttvar += ((((delta>0)?(delta):(-delta)) - rttvar) >> 2);
	if (rttvar >= 1) 
		scp->nsp_rttvar = (unsigned long)rttvar;
	else
		scp->nsp_rttvar = 1;

	/* printk(KERN_DEBUG "srtt=%lu rttvar=%lu\n", scp->nsp_srtt, scp->nsp_rttvar); */
}

/**
 * dn_nsp_clone_and_send - Send a data packet by cloning it
 * @skb: The packet to clone and transmit
 * @gfp: memory allocation flag
 *
 * Clone a queued data or other data packet and transmit it.
 *
 * Returns: The number of times the packet has been sent previously
 */
static inline unsigned dn_nsp_clone_and_send(struct sk_buff *skb, int gfp)
{
	struct dn_skb_cb *cb = DN_SKB_CB(skb);
	struct sk_buff *skb2;
	int ret = 0;

	if ((skb2 = skb_clone(skb, gfp)) != NULL) {
		ret = cb->xmit_count;
		cb->xmit_count++;
		cb->stamp = jiffies;
		skb2->sk = skb->sk;
		dn_nsp_send(skb2);
	}

	return ret;
}

/**
 * dn_nsp_output - Try and send something from socket queues
 * @sk: The socket whose queues are to be investigated
 * @gfp: The memory allocation flags
 *
 * Try and send the packet on the end of the data and other data queues.
 * Other data gets priority over data, and if we retransmit a packet we
 * reduce the window by dividing it in two.
 *
 */
void dn_nsp_output(struct sock *sk)
{
	struct dn_scp *scp = DN_SK(sk);
	struct sk_buff *skb;
	unsigned reduce_win = 0;

	/*
	 * First we check for otherdata/linkservice messages
	 */
	if ((skb = skb_peek(&scp->other_xmit_queue)) != NULL)
		reduce_win = dn_nsp_clone_and_send(skb, GFP_ATOMIC);

	/*
	 * If we may not send any data, we don't.
	 * If we are still trying to get some other data down the
	 * channel, we don't try and send any data.
	 */
	if (reduce_win || (scp->flowrem_sw != DN_SEND))
		goto recalc_window;

	if ((skb = skb_peek(&scp->data_xmit_queue)) != NULL)
		reduce_win = dn_nsp_clone_and_send(skb, GFP_ATOMIC);

	/*
	 * If we've sent any frame more than once, we cut the
	 * send window size in half. There is always a minimum
	 * window size of one available.
	 */
recalc_window:
	if (reduce_win) {
		scp->snd_window >>= 1;
		if (scp->snd_window < NSP_MIN_WINDOW)
			scp->snd_window = NSP_MIN_WINDOW;
	}
}

int dn_nsp_xmit_timeout(struct sock *sk)
{
	struct dn_scp *scp = DN_SK(sk);

	dn_nsp_output(sk);

	if (skb_queue_len(&scp->data_xmit_queue) || skb_queue_len(&scp->other_xmit_queue))
		scp->persist = dn_nsp_persist(sk);

	return 0;
}

static inline unsigned char *dn_mk_common_header(struct dn_scp *scp, struct sk_buff *skb, unsigned char msgflag, int len)
{
	unsigned char *ptr = skb_push(skb, len);

	if (len < 5)
		BUG();

	*ptr++ = msgflag;
	*((unsigned short *)ptr) = scp->addrrem;
	ptr += 2;
	*((unsigned short *)ptr) = scp->addrloc;
	ptr += 2;
	return ptr;
}

static unsigned short *dn_mk_ack_header(struct sock *sk, struct sk_buff *skb, unsigned char msgflag, int hlen, int other)
{
	struct dn_scp *scp = DN_SK(sk);
	unsigned short acknum = scp->numdat_rcv & 0x0FFF;
	unsigned short ackcrs = scp->numoth_rcv & 0x0FFF;
	unsigned short *ptr;

	if (hlen < 9)
		BUG();

	scp->ackxmt_dat = acknum;
	scp->ackxmt_oth = ackcrs;
	acknum |= 0x8000;
	ackcrs |= 0x8000;

	/* If this is an "other data/ack" message, swap acknum and ackcrs */
	if (other) {
		unsigned short tmp = acknum;
		acknum = ackcrs;
		ackcrs = tmp;
	}

	/* Set "cross subchannel" bit in ackcrs */
	ackcrs |= 0x2000;

	ptr = (unsigned short *)dn_mk_common_header(scp, skb, msgflag, hlen);

	*ptr++ = dn_htons(acknum);
	*ptr++ = dn_htons(ackcrs);

	return ptr;
}

void dn_nsp_queue_xmit(struct sock *sk, struct sk_buff *skb, int gfp, int oth)
{
	struct dn_scp *scp = DN_SK(sk);
	struct dn_skb_cb *cb = DN_SKB_CB(skb);
	unsigned long t = ((scp->nsp_srtt >> 2) + scp->nsp_rttvar) >> 1;

	/*
	 * Slow start: If we have been idle for more than