Subject: Re: Bugfix in arch/ppc/8260_io/fcc_enet.c linux-2.4.17

From: "Amit D. Chaudhary" <[email-masked]>
Date: Fri, 08 Mar 2002 16:26:34 -0800

David,

Is there an impact of your change on the board doing a netboot and
loading the rootfs from a nfs mount?

Thanks
Amit

David Ashley wrote:
> I found a bug which was manifest when linux boots and lots of ethernet
> packets are coming in. I think the problem is because the fcc_enet.c
> adds the network device in very early during the boot, and the driver is
> happily calling netif_rx() on the received packets even though the interface
> isn't officially "up". Linux appears not to like this, and would crash
> sporadically, or predictibly if I have a program on another computer running
> just blasting packets at the first one.
>
> The fix is to just put an if around this section in fcc_enet_rx:
> 		skb = dev_alloc_skb(pkt_len-4);
>
> 		if (skb == NULL) {
> 			printk("%s: Memory squeeze, dropping packet.\n", dev->name);
> 			cep->stats.rx_dropped++;
> 		}
> 		else {
> 			skb->dev = dev;
> 			skb_put(skb,pkt_len-4);	/* Make room */
> 			eth_copy_and_sum(skb,
> 				(unsigned char *)__va(bdp->cbd_bufaddr),
> 				pkt_len-4, 0);
> 			skb->protocol=eth_type_trans(skb,dev);
> 			netif_rx(skb);
> 		}
>
> So it becomes:
> 		if(dev->flags & IFF_UP) { /* only do if iface is up */
> 	                skb = dev_alloc_skb(pkt_len-4);
>
> 	                if (skb == NULL) {
> 	                        printk("%s: Memory squeeze, dropping packet.\n", dev->name);
> 	                        cep->stats.rx_dropped++;
> 	                }
> 	                else {
> 	                        skb->dev = dev;
> 	                        skb_put(skb,pkt_len-4); /* Make room */
> 	                        eth_copy_and_sum(skb,
> 	                                (unsigned char *)__va(bdp->cbd_bufaddr),
> 	                                pkt_len-4, 0);
> 	                        skb->protocol=eth_type_trans(skb,dev);
> 	                        netif_rx(skb);
> 	                }
> 		}
>
> This fixes the crash bug.
>
> -Dave
>
>
>
>
>

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