assembly of packets

Valdis.Kletnieks at Valdis.Kletnieks at
Mon Jun 3 12:02:45 EDT 2013

On Mon, 03 Jun 2013 14:48:41 +0530, Varun Sharma said:

> If TSO(tcp segmentation offload ) is enabled then nic card handle
> segmentation then where is assembly of packets happens ? Is it
> tcp_rcv_established function ?

The whole *point* of TSO is so the NIC does all the segmentation
reassembly and DMA, and wake the kernel up when all the data is already
stashed in buffers fully processed.

Incidentally, this is why if you run tcpdump on an interface that has TSO
enabled, you'll only see the first 3 handshaking packets and the final
FIN packets - the other packets wake up the TCP stack at a point after
where tcpdump's tap would have seen the packet.
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