Re: [Xen-devel] Understanding netback packet transmission code

[Kaushik Kumar Ram <kaushik@xxxxxxxx>]

On Oct 27, 2009, at 10:47 AM, Micky Kay wrote:

> I figured that the net_tx_action function is the one that schedules  
> packet transmission. I understood a fair portion of the code but for  
> the call to netif_rx (netback.c:1454) after scheduling the  
> tx_response and the update of the rx stats in the transmission  
> function.
When netif_rx is called, the packet is queued to be picked by the  
software Ethernet bridge. netif_rx is called in the transmit path  
since the packet
is being "received" from the bridge's perspective.

> I also noticed that netif_be_start_xmit function queues the sk_buff  
> passed to it in the receive queue (rx_queue) and schedules the  
> net_rx_tasklet (netback.c:336).
netif_be_start_xmit is called by the bridge code and this eventually  
leads to the packet being received by netback. netif_be_start_xmit is  
called in
receive path since the packet is being "transmitted" from the bridge's  
perspective.
> Could someone demystify all of this please? Thanks much.
-Kaushik

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