I see the receiving side also .Packets are not assembled by ip-defrag . now where packets are assembled at transport layer ? if yes then how they are assembled ?
On Tue, Jun 4, 2013 at 7:24 PM, Craig Jackson <cjack...@ebscohost.com>wrote: > > -----Original Message----- > > From: Varun Sharma [mailto:vsd...@gmail.com] > > Sent: Tuesday, June 04, 2013 2:45 AM > > To: Craig Jackson; kernelnewbies@kernelnewbies.org; > > valdis.kletni...@vt.edu > > Subject: Re: assembly of packets > > > > On receving side upto tcp layer skb->len=1480 now where is packet > > assembled on tcp layer ? > > or it is directly copies into user space buffer. > > > > I am sending len = 10000 in send system call. > > > >> On Mon, Jun 3, 2013 at 9:45 PM, Craig Jackson <cjack...@ebscohost.com> > >> wrote: > >> In my experience, the second paragraph isn't quite true. What you see > >> with TSO is the pre-segmentation "packet", up to 65k. (By this I mean > >> the set of data which is given to the offload hardware to segment.) So > >> you need to make sure that your "-s" value is big enough to see > >> everything. > >> > >> (Speaking as someone who was bitten by bugs in the early versions of > >> TSO.) > >> > >> Craig > > > >>> -----Original Message----- > >>> From: kernelnewbies-bounces+cjackson=ebscohost....@kernelnewbies.org > >>> [mailto:kernelnewbies-bounces+cjackson=ebscohost....@kernelnewbies.org > ] > >>> On Behalf Of valdis.kletni...@vt.edu > >>> Sent: Monday, June 03, 2013 12:03 PM > >>> To: Varun Sharma > >>> Cc: kernelnewbies@kernelnewbies.org > >>> Subject: Re: assembly of packets > >>> > >>> 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. > > Sorry for top-posting before. It's incredibly hard to get Outlook 2007 to > do things right. > > Varun, I now see we may not have answered the question you have. TSO (TCP > Segementation Offload) > is associated with sending packets, not receiving them. They are > re-assembled at the receiving > end in the standard manner. > > Are you actually thinking of GRO (Generic Receive Offload)? > > Craig >
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