isdn_ppp.c

讲述linux的初始化过程

	if (is->debug & 0x10) {
		printk(KERN_DEBUG "push, skb %d %04x\n", (int) skb->len, proto);
		isdn_ppp_frame_log("rpush", skb->data, skb->len, 32,is->unit,lp->ppp_slot);
	}
	if (is->compflags & SC_DECOMP_ON) {
		skb = isdn_ppp_decompress(skb, is, mis, &proto);
		if (!skb) // decompression error
  			return;
  	}
	switch (proto) {
		case PPP_IPX:  /* untested */
			if (is->debug & 0x20)
				printk(KERN_DEBUG "isdn_ppp: IPX\n");
			skb->protocol = htons(ETH_P_IPX);
			break;
		case PPP_IP:
			if (is->debug & 0x20)
				printk(KERN_DEBUG "isdn_ppp: IP\n");
			skb->protocol = htons(ETH_P_IP);
			break;
#ifdef CONFIG_ISDN_PPP_VJ
		case PPP_VJC_UNCOMP:
			if (is->debug & 0x20)
				printk(KERN_DEBUG "isdn_ppp: VJC_UNCOMP\n");
			if (slhc_remember(ippp_table[net_dev->local->ppp_slot]->slcomp, skb->data, skb->len) <= 0) {
				printk(KERN_WARNING "isdn_ppp: received illegal VJC_UNCOMP frame!\n");
				goto drop_packet;
			}
			skb->protocol = htons(ETH_P_IP);
			break;
		case PPP_VJC_COMP:
			if (is->debug & 0x20)
				printk(KERN_DEBUG "isdn_ppp: VJC_COMP\n");
			{
				struct sk_buff *skb_old = skb;
				int pkt_len;
				skb = dev_alloc_skb(skb_old->len + 128);

				if (!skb) {
					printk(KERN_WARNING "%s: Memory squeeze, dropping packet.\n", dev->name);
					skb = skb_old;
					goto drop_packet;
				}
				skb_put(skb, skb_old->len + 128);
				memcpy(skb->data, skb_old->data, skb_old->len);
				pkt_len = slhc_uncompress(ippp_table[net_dev->local->ppp_slot]->slcomp,
						skb->data, skb_old->len);
				kfree_skb(skb_old);
				if (pkt_len < 0)
					goto drop_packet;

				skb_trim(skb, pkt_len);
				skb->protocol = htons(ETH_P_IP);
			}
			break;
#endif
		case PPP_CCP:
		case PPP_CCPFRAG:
			isdn_ppp_receive_ccp(net_dev,lp,skb,proto);
			/* Dont pop up ResetReq/Ack stuff to the daemon any
			   longer - the job is done already */
			if(skb->data[0] == CCP_RESETREQ ||
			   skb->data[0] == CCP_RESETACK)
				break;
			/* fall through */
		default:
			isdn_ppp_fill_rq(skb->data, skb->len, proto, lp->ppp_slot);	/* push data to pppd device */
			kfree_skb(skb);
			return;
	}

 	/* Reset hangup-timer */
 	lp->huptimer = 0;

	skb->dev = dev;
	skb->mac.raw = skb->data;
	netif_rx(skb);
	/* net_dev->local->stats.rx_packets++; done in isdn_net.c */
	return;

 drop_packet:
	net_dev->local->stats.rx_dropped++;
	kfree_skb(skb);
}

/*
 * isdn_ppp_skb_push ..
 * checks whether we have enough space at the beginning of the skb
 * and allocs a new SKB if necessary
 */
static unsigned char *isdn_ppp_skb_push(struct sk_buff **skb_p,int len)
{
	struct sk_buff *skb = *skb_p;

	if(skb_headroom(skb) < len) {
		struct sk_buff *nskb = skb_realloc_headroom(skb, len);

		if (!nskb) {
			printk(KERN_ERR "isdn_ppp_skb_push: can't realloc headroom!\n");
			dev_kfree_skb(skb);
			return NULL;
		}
		printk(KERN_DEBUG "isdn_ppp_skb_push:under %d %d\n",skb_headroom(skb),len);
		dev_kfree_skb(skb);
		*skb_p = nskb;
		return skb_push(nskb, len);
	}
	return skb_push(skb,len);
}


/*
 * send ppp frame .. we expect a PIDCOMPressable proto --
 *  (here: currently always PPP_IP,PPP_VJC_COMP,PPP_VJC_UNCOMP)
 *
 * VJ compression may change skb pointer!!! .. requeue with old
 * skb isn't allowed!!
 */

int
isdn_ppp_xmit(struct sk_buff *skb, struct net_device *netdev)
{
	isdn_net_local *lp,*mlp;
	isdn_net_dev *nd;
	unsigned int proto = PPP_IP;     /* 0x21 */
	struct ippp_struct *ipt,*ipts;
	int slot;

	mlp = (isdn_net_local *) (netdev->priv);
	nd = mlp->netdev;       /* get master lp */

	slot = mlp->ppp_slot;
	if (slot < 0 || slot > ISDN_MAX_CHANNELS) {
		printk(KERN_ERR "isdn_ppp_xmit: lp->ppp_slot %d\n", mlp->ppp_slot);
		kfree_skb(skb);
		return 0;
	}
	ipts = ippp_table[slot];

	if (!(ipts->pppcfg & SC_ENABLE_IP)) {	/* PPP connected ? */
		if (ipts->debug & 0x1)
			printk(KERN_INFO "%s: IP frame delayed.\n", netdev->name);
		return 1;
	}

	switch (ntohs(skb->protocol)) {
		case ETH_P_IP:
			proto = PPP_IP;
			break;
		case ETH_P_IPX:
			proto = PPP_IPX;	/* untested */
			break;
		default:
			dev_kfree_skb(skb);
			printk(KERN_ERR "isdn_ppp: skipped unsupported protocol: %#x.\n", 
			       skb->protocol);
			return 0;
	}

	lp = isdn_net_get_locked_lp(nd);
	if (!lp) {
		printk(KERN_WARNING "%s: all channels busy - requeuing!\n", netdev->name);
		return 1;
	}
	/* we have our lp locked from now on */

	slot = lp->ppp_slot;
	if (slot < 0 || slot > ISDN_MAX_CHANNELS) {
		printk(KERN_ERR "isdn_ppp_xmit: lp->ppp_slot %d\n", lp->ppp_slot);
		kfree_skb(skb);
		return 0;
	}
	ipt = ippp_table[slot];
	lp->huptimer = 0;

	/*
	 * after this line .. requeueing in the device queue is no longer allowed!!!
	 */

	/* Pull off the fake header we stuck on earlier to keep
	 * the fragmentation code happy.
	 */
	skb_pull(skb,IPPP_MAX_HEADER);

	if (ipt->debug & 0x4)
		printk(KERN_DEBUG "xmit skb, len %d\n", (int) skb->len);
        if (ipts->debug & 0x40)
                isdn_ppp_frame_log("xmit0", skb->data, skb->len, 32,ipts->unit,lp->ppp_slot);

#ifdef CONFIG_ISDN_PPP_VJ
	if (proto == PPP_IP && ipts->pppcfg & SC_COMP_TCP) {	/* ipts here? probably yes, but check this again */
		struct sk_buff *new_skb;
	        unsigned short hl;
		/*
		 * we need to reserve enought space in front of
		 * sk_buff. old call to dev_alloc_skb only reserved
		 * 16 bytes, now we are looking what the driver want.
		 */
		hl = dev->drv[lp->isdn_device]->interface->hl_hdrlen + IPPP_MAX_HEADER;
		/* 
		 * Note: hl might still be insufficient because the method
		 * above does not account for a possibible MPPP slave channel
		 * which had larger HL header space requirements than the
		 * master.
		 */
		new_skb = alloc_skb(hl+skb->len, GFP_ATOMIC);
		if (new_skb) {
			u_char *buf;
			int pktlen;

			skb_reserve(new_skb, hl);
			new_skb->dev = skb->dev;
			skb_put(new_skb, skb->len);
			buf = skb->data;

			pktlen = slhc_compress(ipts->slcomp, skb->data, skb->len, new_skb->data,
				 &buf, !(ipts->pppcfg & SC_NO_TCP_CCID));

			if (buf != skb->data) {	
				if (new_skb->data != buf)
					printk(KERN_ERR "isdn_ppp: FATAL error after slhc_compress!!\n");
				dev_kfree_skb(skb);
				skb = new_skb;
			} else {
				dev_kfree_skb(new_skb);
			}

			skb_trim(skb, pktlen);
			if (skb->data[0] & SL_TYPE_COMPRESSED_TCP) {	/* cslip? style -> PPP */
				proto = PPP_VJC_COMP;
				skb->data[0] ^= SL_TYPE_COMPRESSED_TCP;
			} else {
				if (skb->data[0] >= SL_TYPE_UNCOMPRESSED_TCP)
					proto = PPP_VJC_UNCOMP;
				skb->data[0] = (skb->data[0] & 0x0f) | 0x40;
			}
		}
	}
#endif

	/*
	 * normal (single link) or bundle compression
	 */
	if(ipts->compflags & SC_COMP_ON)
		skb = isdn_ppp_compress(skb,&proto,ipt,ipts,0);

	if (ipt->debug & 0x24)
		printk(KERN_DEBUG "xmit2 skb, len %d, proto %04x\n", (int) skb->len, proto);

#ifdef CONFIG_ISDN_MPP
	if (ipt->mpppcfg & SC_MP_PROT) {
		/* we get mp_seqno from static isdn_net_local */
		long mp_seqno = ipts->mp_seqno;
		ipts->mp_seqno++;
		if (ipt->mpppcfg & SC_OUT_SHORT_SEQ) {
			unsigned char *data = isdn_ppp_skb_push(&skb, 3);
			if(!data)
				goto unlock;
			mp_seqno &= 0xfff;
			data[0] = MP_BEGIN_FRAG | MP_END_FRAG | ((mp_seqno >> 8) & 0xf);	/* (B)egin & (E)ndbit .. */
			data[1] = mp_seqno & 0xff;
			data[2] = proto;	/* PID compression */
		} else {
			unsigned char *data = isdn_ppp_skb_push(&skb, 5);
			if(!data)
				goto unlock;
			data[0] = MP_BEGIN_FRAG | MP_END_FRAG;	/* (B)egin & (E)ndbit .. */
			data[1] = (mp_seqno >> 16) & 0xff;	/* sequence number: 24bit */
			data[2] = (mp_seqno >> 8) & 0xff;
			data[3] = (mp_seqno >> 0) & 0xff;
			data[4] = proto;	/* PID compression */
		}
		proto = PPP_MP; /* MP Protocol, 0x003d */
	}
#endif

	/*
	 * 'link in bundle' compression  ...
	 */
	if(ipt->compflags & SC_LINK_COMP_ON)
		skb = isdn_ppp_compress(skb,&proto,ipt,ipts,1);

	if( (ipt->pppcfg & SC_COMP_PROT) && (proto <= 0xff) ) {
		unsigned char *data = isdn_ppp_skb_push(&skb,1);
		if(!data)
			goto unlock;
		data[0] = proto & 0xff;
	}
	else {
		unsigned char *data = isdn_ppp_skb_push(&skb,2);
		if(!data)
			goto unlock;
		data[0] = (proto >> 8) & 0xff;
		data[1] = proto & 0xff;
	}
	if(!(ipt->pppcfg & SC_COMP_AC)) {
		unsigned char *data = isdn_ppp_skb_push(&skb,2);
		if(!data)
			goto unlock;
		data[0] = 0xff;    /* All Stations */
		data[1] = 0x03;    /* Unnumbered information */
	}

	/* tx-stats are now updated via BSENT-callback */

	if (ipts->debug & 0x40) {
		printk(KERN_DEBUG "skb xmit: len: %d\n", (int) skb->len);
		isdn_ppp_frame_log("xmit", skb->data, skb->len, 32,ipt->unit,lp->ppp_slot);
	}
	
	isdn_net_writebuf_skb(lp, skb);

 unlock:
	spin_unlock_bh(&lp->xmit_lock);
	return 0;
}

#ifdef CONFIG_ISDN_MPP

/* this is _not_ rfc1990 header, but something we convert both short and long
 * headers to for convinience's sake:
 * 	byte 0 is flags as in rfc1990
 *	bytes 1...4 is 24-bit seqence number converted to host byte order 
 */
#define MP_HEADER_LEN	5

#define MP_LONGSEQ_MASK		0x00ffffff
#define MP_SHORTSEQ_MASK	0x00000fff
#define MP_LONGSEQ_MAX		MP_LONGSEQ_MASK
#define MP_SHORTSEQ_MAX		MP_SHORTSEQ_MASK
#define MP_LONGSEQ_MAXBIT	((MP_LONGSEQ_MASK+1)>>1)
#define MP_SHORTSEQ_MAXBIT	((MP_SHORTSEQ_MASK+1)>>1)

/* sequence-wrap safe comparisions (for long sequence)*/ 
#define MP_LT(a,b)	((a-b)&MP_LONGSEQ_MAXBIT)
#define MP_LE(a,b) 	!((b-a)&MP_LONGSEQ_MAXBIT)
#define MP_GT(a,b) 	((b-a)&MP_LONGSEQ_MAXBIT)
#define MP_GE(a,b)	!((a-b)&MP_LONGSEQ_MAXBIT)

#define MP_SEQ(f)	((*(u32*)(f->data+1)))
#define MP_FLAGS(f)	(f->data[0])

static int isdn_ppp_mp_bundle_array_init(void)
{
	int i;
	int sz = ISDN_MAX_CHANNELS*sizeof(ippp_bundle);
	if( (isdn_ppp_bundle_arr = (ippp_bundle*)kmalloc(sz, 
							GFP_KERNEL)) == NULL )
		return -ENOMEM;
	memset(isdn_ppp_bundle_arr, 0, sz);
	for( i = 0; i < ISDN_MAX_CHANNELS; i++ )
		spin_lock_init(&isdn_ppp_bundle_arr[i].lock);
	return 0;
}

static ippp_bundle * isdn_ppp_mp_bundle_alloc(void)
{
	int i;
	for( i = 0; i < ISDN_MAX_CHANNELS; i++ )
		if (isdn_ppp_bundle_arr[i].ref_ct <= 0)
			return (isdn_ppp_bundle_arr + i);
	return NULL;
}

static int isdn_ppp_mp_init( isdn_net_local * lp, ippp_bundle * add_to )
{
	struct ippp_struct * is = ippp_table[lp->ppp_slot];
   
	if (add_to) {
		if( lp->netdev->pb )
			lp->netdev->pb->ref_ct--;
		lp->netdev->pb = add_to;
	} else {		/* first link in a bundle */
		is->mp_seqno = 0;
		if ((lp->netdev->pb = isdn_ppp_mp_bundle_alloc()) == NULL)
			return -ENOMEM;
		lp->next = lp->last = lp;	/* nobody else in a queue */
		lp->netdev->pb->frags = NULL;
		lp->netdev->pb->frames = 0;
		lp->netdev->pb->seq = LONG_MAX;
	}
	lp->netdev->pb->ref_ct++;
	
	is->last_link_seqno = 0;
	return 0;
}

static u32 isdn_ppp_mp_get_seq( int short_seq, 
					struct sk_buff * skb, u32 last_seq );
static struct sk_buff * isdn_ppp_mp_discard( ippp_bundle * mp,
			struct sk_buff * from, struct sk_buff * to );
static void isdn_ppp_mp_reassembly( isdn_net_dev * net_dev, isdn_net_local * lp,
				struct sk_buff * from, struct sk_buff * to );
static void isdn_ppp_mp_free_skb( ippp_bundle * mp, struct sk_buff * skb );
static void isdn_ppp_mp_print_recv_pkt( int slot, struct sk_buff * skb );

static void isdn_ppp_mp_receive(isdn_net_dev * net_dev, isdn_net_local * lp, 
							struct sk_buff *skb)
{
	struct ippp_struct *is;
	isdn_net_local * lpq;
	ippp_bundle * mp;
	isdn_mppp_stats * stats;
	struct sk_buff * newfrag, * frag, * start, *nextf;
	u32 newseq, minseq, thisseq;
	unsigned long flags;
	int slot;

	spin_lock_irqsave(&net_dev->pb->lock, flags);
    	mp = net_dev->pb;
        stats = &mp->stats;
	slot = lp->ppp_slot;
	if (slot < 0 || slot > ISDN_MAX_CHANNELS) {
		printk(KERN_ERR "isdn_ppp_mp_receive: lp->ppp_slot %d\n", lp->ppp_slot);
		stats->frame_drops++;
		dev_kfree_skb(skb);
		spin_unlock_irqrestore(&mp->lock, flags);
		return;
	}
	is = ippp_table[slot];
    	if( ++mp->frames > stats->max_queue_len )
		stats->max_queue_len = mp->frames;
	
	if (is->debug & 0x8)
		isdn_ppp_mp_print_recv_pkt(lp->ppp_slot, skb);

	newseq = isdn_ppp_mp_get_seq(is->mpppcfg & SC_IN_SHORT_SEQ, 
						skb, is->last_link_seqno);


	/* if this packet seq # is less than last already processed one,
	 * toss it right away, but check for sequence start case first 
	 */
	if( mp->seq > MP_LONGSEQ_MAX && (newseq & MP_LONGSEQ_MAXBIT) ) {
		mp->seq = newseq;	/* the first packet: required for
					 * rfc1990 non-compliant clients --
					 * prevents constant packet toss */
	} else if( MP_LT(newseq, mp->seq) ) {
		stats->frame_drops++;
		isdn_ppp_mp_free_skb(mp, skb);
		spin_unlock_irqrestore(&mp->lock, flags);
		return;
	}
	
	/* find the minimum received sequence number over all links */
	is->last_link_seqno = minseq = newseq;
	for (lpq = net_dev->queue;;) {
		slot = lpq->ppp_slot;
		if (slot < 0 || slot > ISDN_MAX_CHANNELS) {
			printk(KERN_ERR "isdn_ppp_mp_receive: lpq->ppp_slot %d\n", lpq->ppp_slot);
		} else {
			u32 lls = ippp_table[slot]->last_link_seqno;
			if (MP_LT(lls, minseq))
				minseq = lls;
		}
		if ((lpq = lpq->next) == net_dev->queue)
			break;
	}
	if (MP_LT(minseq, mp->seq))
		minseq = mp->seq;	/* can't go beyond already processed
					 * packets */
	newfrag = skb;

  	/* if this new fragment is before the first one, then enqueue it now. */
  	if ((frag = mp->frags) == NULL || MP_LT(newseq, MP_SEQ(frag))) {
		newfrag->next = frag;
    		mp->frags = frag = newfrag;
    		newfrag = NULL;
  	}

  	start = MP_FLAGS(frag) & MP_BEGIN_FRAG &&
				MP_SEQ(frag) == mp->seq ? frag : NULL;

	/* 
	 * main fragment traversing loop
	 *
	 * try to accomplish several tasks:
	 * - insert new fragment into the proper sequence slot (once that's done
	 *   newfrag will be set to NULL)
	 * - reassemble any complete fragment sequence (non-null 'start'
	 *   indicates there is a continguous sequence present)
	 * - discard any incomplete sequences that are below minseq -- due
	 *   to the fact that sender always increment sequence number, if there
	 *   is an incomplete sequence below minseq, no new fragments would
	 *   come to complete such sequence and it should be discarded
	 *
	 * loop completes when we accomplished the following tasks:
	 * - new fragment is inserted in the proper sequence ('newfrag' is 
	 *   set to NULL)
	 * - we hit a gap in the sequence, so no reassembly/processing is