hamachi.c

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	 */
	hmp->rx_buf_sz = (dev->mtu <= 1492 ? PKT_BUF_SZ : 
		(((dev->mtu+26+7) & ~7) + 2 + 16));

	/* Initialize all Rx descriptors. */
	for (i = 0; i < RX_RING_SIZE; i++) {
		hmp->rx_ring[i].status_n_length = 0;
		hmp->rx_skbuff[i] = 0;
	}
	/* Fill in the Rx buffers.  Handle allocation failure gracefully. */
	for (i = 0; i < RX_RING_SIZE; i++) {
		struct sk_buff *skb = dev_alloc_skb(hmp->rx_buf_sz);
		hmp->rx_skbuff[i] = skb;
		if (skb == NULL)
			break;
		skb->dev = dev;         /* Mark as being used by this device. */
		skb_reserve(skb, 2); /* 16 byte align the IP header. */
                hmp->rx_ring[i].addr = cpu_to_leXX(pci_map_single(hmp->pci_dev, 
			skb->tail, hmp->rx_buf_sz, PCI_DMA_FROMDEVICE));
		/* -2 because it doesn't REALLY have that first 2 bytes -KDU */
		hmp->rx_ring[i].status_n_length = cpu_to_le32(DescOwn | 
			DescEndPacket | DescIntr | (hmp->rx_buf_sz -2));
	}
	hmp->dirty_rx = (unsigned int)(i - RX_RING_SIZE);
	hmp->rx_ring[RX_RING_SIZE-1].status_n_length |= cpu_to_le32(DescEndRing);

	for (i = 0; i < TX_RING_SIZE; i++) {
		hmp->tx_skbuff[i] = 0;
		hmp->tx_ring[i].status_n_length = 0;
	}
	/* Mark the last entry of the ring */
	hmp->tx_ring[TX_RING_SIZE-1].status_n_length |= cpu_to_le32(DescEndRing);

	return;
}


#ifdef TX_CHECKSUM
#define csum_add(it, val) \
do { \
    it += (u16) (val); \
    if (it & 0xffff0000) { \
	it &= 0xffff; \
	++it; \
    } \
} while (0)
    /* printk("add %04x --> %04x\n", val, it); \ */

/* uh->len already network format, do not swap */
#define pseudo_csum_udp(sum,ih,uh) do { \
    sum = 0; \
    csum_add(sum, (ih)->saddr >> 16); \
    csum_add(sum, (ih)->saddr & 0xffff); \
    csum_add(sum, (ih)->daddr >> 16); \
    csum_add(sum, (ih)->daddr & 0xffff); \
    csum_add(sum, __constant_htons(IPPROTO_UDP)); \
    csum_add(sum, (uh)->len); \
} while (0)

/* swap len */
#define pseudo_csum_tcp(sum,ih,len) do { \
    sum = 0; \
    csum_add(sum, (ih)->saddr >> 16); \
    csum_add(sum, (ih)->saddr & 0xffff); \
    csum_add(sum, (ih)->daddr >> 16); \
    csum_add(sum, (ih)->daddr & 0xffff); \
    csum_add(sum, __constant_htons(IPPROTO_TCP)); \
    csum_add(sum, htons(len)); \
} while (0)
#endif

static int hamachi_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
	struct hamachi_private *hmp = dev->priv;
	unsigned entry;
	u16 status;

	/* Ok, now make sure that the queue has space before trying to 
		add another skbuff.  if we return non-zero the scheduler
		should interpret this as a queue full and requeue the buffer
		for later.
	 */
	if (hmp->tx_full) {
		/* We should NEVER reach this point -KDU */
		printk(KERN_WARNING "%s: Hamachi transmit queue full at slot %d.\n",dev->name, hmp->cur_tx);

		/* Wake the potentially-idle transmit channel. */
		/* If we don't need to read status, DON'T -KDU */
		status=readw(dev->base_addr + TxStatus);
		if( !(status & 0x0001) || (status & 0x0002))
			writew(0x0001, dev->base_addr + TxCmd);
		return 1;
	} 

	/* Caution: the write order is important here, set the field
	   with the "ownership" bits last. */

	/* Calculate the next Tx descriptor entry. */
	entry = hmp->cur_tx % TX_RING_SIZE;

	hmp->tx_skbuff[entry] = skb;

#ifdef TX_CHECKSUM
	{
	    /* tack on checksum tag */
	    u32 tagval = 0;
	    struct ethhdr *eh = (struct ethhdr *)skb->data;
	    if (eh->h_proto == __constant_htons(ETH_P_IP)) {
		struct iphdr *ih = (struct iphdr *)((char *)eh + ETH_HLEN);
		if (ih->protocol == IPPROTO_UDP) {
		    struct udphdr *uh
		      = (struct udphdr *)((char *)ih + ih->ihl*4);
		    u32 offset = ((unsigned char *)uh + 6) - skb->data;
		    u32 pseudo;
		    pseudo_csum_udp(pseudo, ih, uh);
		    pseudo = htons(pseudo);
		    printk("udp cksum was %04x, sending pseudo %04x\n",
		      uh->check, pseudo);
		    uh->check = 0;  /* zero out uh->check before card calc */
		    /*
		     * start at 14 (skip ethhdr), store at offset (uh->check),
		     * use pseudo value given.
		     */
		    tagval = (14 << 24) | (offset << 16) | pseudo;
		} else if (ih->protocol == IPPROTO_TCP) {
		    printk("tcp, no auto cksum\n");
		}
	    }
	    *(u32 *)skb_push(skb, 8) = tagval;
	}
#endif

        hmp->tx_ring[entry].addr = cpu_to_leXX(pci_map_single(hmp->pci_dev, 
		skb->data, skb->len, PCI_DMA_TODEVICE));
    
	/* Hmmmm, could probably put a DescIntr on these, but the way
		the driver is currently coded makes Tx interrupts unnecessary
		since the clearing of the Tx ring is handled by the start_xmit
		routine.  This organization helps mitigate the interrupts a
		bit and probably renders the max_tx_latency param useless.
		
		Update: Putting a DescIntr bit on all of the descriptors and
		mitigating interrupt frequency with the tx_min_pkt parameter. -KDU
	*/
	if (entry >= TX_RING_SIZE-1)		 /* Wrap ring */
		hmp->tx_ring[entry].status_n_length = cpu_to_le32(DescOwn |
			DescEndPacket | DescEndRing | DescIntr | skb->len);
	else
		hmp->tx_ring[entry].status_n_length = cpu_to_le32(DescOwn |
			DescEndPacket | DescIntr | skb->len);
	hmp->cur_tx++;

	/* Non-x86 Todo: explicitly flush cache lines here. */

	/* Wake the potentially-idle transmit channel. */
	/* If we don't need to read status, DON'T -KDU */
	status=readw(dev->base_addr + TxStatus);
	if( !(status & 0x0001) || (status & 0x0002))
		writew(0x0001, dev->base_addr + TxCmd);

	/* Immediately before returning, let's clear as many entries as we can. */
	hamachi_tx(dev);

	/* We should kick the bottom half here, since we are not accepting
	 * interrupts with every packet.  i.e. realize that Gigabit ethernet
	 * can transmit faster than ordinary machines can load packets;
	 * hence, any packet that got put off because we were in the transmit
	 * routine should IMMEDIATELY get a chance to be re-queued. -KDU
	 */
	if ((hmp->cur_tx - hmp->dirty_tx) < (TX_RING_SIZE - 4)) 
		netif_wake_queue(dev);  /* Typical path */
	else {
		hmp->tx_full = 1;
		netif_stop_queue(dev);
	}
	dev->trans_start = jiffies;

	if (hamachi_debug > 4) {
		printk(KERN_DEBUG "%s: Hamachi transmit frame #%d queued in slot %d.\n",
			   dev->name, hmp->cur_tx, entry);
	}
	return 0;
}

/* The interrupt handler does all of the Rx thread work and cleans up
   after the Tx thread. */
static void hamachi_interrupt(int irq, void *dev_instance, struct pt_regs *rgs)
{
	struct net_device *dev = dev_instance;
	struct hamachi_private *hmp;
	long ioaddr, boguscnt = max_interrupt_work;

#ifndef final_version			/* Can never occur. */
	if (dev == NULL) {
		printk (KERN_ERR "hamachi_interrupt(): irq %d for unknown device.\n", irq);
		return;
	}
#endif

	ioaddr = dev->base_addr;
	hmp = dev->priv;
	spin_lock(&hmp->lock);

	do {
		u32 intr_status = readl(ioaddr + InterruptClear);

		if (hamachi_debug > 4)
			printk(KERN_DEBUG "%s: Hamachi interrupt, status %4.4x.\n",
				   dev->name, intr_status);

		if (intr_status == 0)
			break;

		if (intr_status & IntrRxDone)
			hamachi_rx(dev);

		if (intr_status & IntrTxDone){
			/* This code should RARELY need to execute. After all, this is
			 * a gigabit link, it should consume packets as fast as we put
			 * them in AND we clear the Tx ring in hamachi_start_xmit().
			 */ 
			if (hmp->tx_full){
				for (; hmp->cur_tx - hmp->dirty_tx > 0; hmp->dirty_tx++){
					int entry = hmp->dirty_tx % TX_RING_SIZE;
					struct sk_buff *skb;

					if (hmp->tx_ring[entry].status_n_length & cpu_to_le32(DescOwn)) 
						break;
					skb = hmp->tx_skbuff[entry];
					/* Free the original skb. */
					if (skb){
						pci_unmap_single(hmp->pci_dev, 
							hmp->tx_ring[entry].addr, 
							skb->len,
							PCI_DMA_TODEVICE);
						dev_kfree_skb_irq(skb);
						hmp->tx_skbuff[entry] = 0;
					}
					hmp->tx_ring[entry].status_n_length = 0;
					if (entry >= TX_RING_SIZE-1)  
						hmp->tx_ring[TX_RING_SIZE-1].status_n_length |= 
							cpu_to_le32(DescEndRing);
					hmp->stats.tx_packets++;
				}
				if (hmp->cur_tx - hmp->dirty_tx < TX_RING_SIZE - 4){
					/* The ring is no longer full */
					hmp->tx_full = 0;
					netif_wake_queue(dev);
				}
			} else {
				netif_wake_queue(dev);
			}
		}


		/* Abnormal error summary/uncommon events handlers. */
		if (intr_status &
			(IntrTxPCIFault | IntrTxPCIErr | IntrRxPCIFault | IntrRxPCIErr |
			 LinkChange | NegotiationChange | StatsMax))
			hamachi_error(dev, intr_status);

		if (--boguscnt < 0) {
			printk(KERN_WARNING "%s: Too much work at interrupt, status=0x%4.4x.\n",
				   dev->name, intr_status);
			break;
		}
	} while (1);

	if (hamachi_debug > 3)
		printk(KERN_DEBUG "%s: exiting interrupt, status=%#4.4x.\n",
			   dev->name, readl(ioaddr + IntrStatus));

#ifndef final_version
	/* Code that should never be run!  Perhaps remove after testing.. */
	{
		static int stopit = 10;
		if (dev->start == 0  &&  --stopit < 0) {
			printk(KERN_ERR "%s: Emergency stop, looping startup interrupt.\n",
				   dev->name);
			free_irq(irq, dev);
		}
	}
#endif

	spin_unlock(&hmp->lock);
}

#ifdef TX_CHECKSUM
/*
 * Copied from eth_type_trans(), with reduced header, since we don't
 * get it on RX, only on TX.
 */
static unsigned short hamachi_eth_type_trans(struct sk_buff *skb,
  struct net_device *dev)
{
	struct ethhdr *eth;
	unsigned char *rawp;
	
	skb->mac.raw=skb->data;
	skb_pull(skb,dev->hard_header_len-8);  /* artificially enlarged on tx */
	eth= skb->mac.ethernet;
	
	if(*eth->h_dest&1)
	{
		if(memcmp(eth->h_dest,dev->broadcast, ETH_ALEN)==0)
			skb->pkt_type=PACKET_BROADCAST;
		else
			skb->pkt_type=PACKET_MULTICAST;
	}
	
	/*
	 *	This ALLMULTI check should be redundant by 1.4
	 *	so don't forget to remove it.
	 *
	 *	Seems, you forgot to remove it. All silly devices
	 *	seems to set IFF_PROMISC.
	 */
	 
	else if(dev->flags&(IFF_PROMISC/*|IFF_ALLMULTI*/))
	{
		if(memcmp(eth->h_dest,dev->dev_addr, ETH_ALEN))
			skb->pkt_type=PACKET_OTHERHOST;
	}
	
	if (ntohs(eth->h_proto) >= 1536)
		return eth->h_proto;
		
	rawp = skb->data;
	
	/*
	 *	This is a magic hack to spot IPX packets. Older Novell breaks
	 *	the protocol design and runs IPX over 802.3 without an 802.2 LLC
	 *	layer. We look for FFFF which isn't a used 802.2 SSAP/DSAP. This
	 *	won't work for fault tolerant netware but does for the rest.
	 */
	if (*(unsigned short *)rawp == 0xFFFF)
		return htons(ETH_P_802_3);
		
	/*
	 *	Real 802.2 LLC
	 */
	return htons(ETH_P_802_2);
}
#endif  /* TX_CHECKSUM */

/* This routine is logically part of the interrupt handler, but seperated
   for clarity and better register allocation. */
static int hamachi_rx(struct net_device *dev)
{
	struct hamachi_private *hmp = dev->priv;
	int entry = hmp->cur_rx % RX_RING_SIZE;
	int boguscnt = (hmp->dirty_rx + RX_RING_SIZE) - hmp->cur_rx;

	if (hamachi_debug > 4) {
		printk(KERN_DEBUG " In hamachi_rx(), entry %d status %4.4x.\n",
			   entry, hmp->rx_ring[entry].status_n_length);
	}

	/* If EOP is set on the next entry, it's a new packet. Send it up. */
	while (1) {
		struct hamachi_desc *desc = &(hmp->rx_ring[entry]);
		u32 desc_status = le32_to_cpu(desc->status_n_length);
		u16 data_size = desc_status;	/* Implicit truncate */
		u8 *buf_addr; 
		s32 frame_status;
		
		if (desc_status & DescOwn)
			break;
		pci_dma_sync_single(hmp->pci_dev, desc->addr, hmp->rx_buf_sz, 
			PCI_DMA_FROMDEVICE);
		buf_addr = (u8 *)hmp->rx_ring + entry*sizeof(*desc);
		frame_status = le32_to_cpu(get_unaligned((s32*)&(buf_addr[data_size - 12])));
		if (hamachi_debug > 4)
			printk(KERN_DEBUG "  hamachi_rx() status was %8.8x.\n",
				frame_status);
		if (--boguscnt < 0)
			break;
		if ( ! (desc_status & DescEndPacket)) {
			printk(KERN_WARNING "%s: Oversized Ethernet frame spanned "
				   "multiple buffers, entry %#x length %d status %4.4x!\n",
				   dev->name, hmp->cur_rx, data_size, desc_status);
			printk(KERN_WARNING "%s: Oversized Ethernet frame %p vs %p.\n",
				   dev->name, desc, &hmp->rx_ring[hmp->cur_rx % RX_RING_SIZE]);
			printk(KERN_WARNING "%s: Oversized Ethernet frame -- next status %x/%x last status %x.\n",
				   dev->name,
				   hmp->rx_ring[(hmp->cur_rx+1) % RX_RING_SIZE].status_n_length & 0xffff0000,
				   hmp->rx_ring[(hmp->cur_rx+1) % RX_RING_SIZE].status_n_length & 0x0000ffff,
				   hmp->rx_ring[(hmp->cur_rx-1) % RX_RING_SIZE].status_n_length);
			hmp->stats.rx_length_errors++;
		} /* else  Omit for prototype errata??? */
		if (frame_status & 0x00380000) {
			/* There was an error. */