netdev - Re: why some packets lost during transmission?

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Date:	Wed, 15 Jul 2009 19:17:05 +0200 (CEST)
From:	Jesper Dangaard Brouer <hawk@...u.dk>
To:	jon_zhou@...lent.com
Cc:	netdev@...r.kernel.org
Subject: Re: why some packets lost during transmission?

On Wed, 15 Jul 2009, jon_zhou@...lent.com wrote:

> I try to send packets like this:
>
> for (i=0;i<loop;i++)
> {
>    dev->hard_start_xmit(my_skb,dev);
> }
>
> the 'dev' point to network device.
>
> but too many packets lost if the 'loop' is big(i.e. 5000), I suspect the 
> tx buffer of the NIC is full,but the driver does not print any related 
> info.

Hint, look at the return value... it returns NETDEV_TX_OK if its okay.

> how does the upper layer(i.e.arp,qdisc) handle this situation?

Have you looked at pktgen?

Doc:
   Documentation/networking/pktgen.txt

Code:
   net/core/pktgen.c

Look at function pktgen_xmit() and notice that in the latest kernels 
the dev->hard_start_xmit function pointer has been changed to 
dev->netdev_ops->ndo_start_xmit.

Cheers,
   Jesper Brouer

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