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

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.


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