I'm trying to do tcp segmentation in my network driver in order to pack IO buffers sent to the hardware more efficiently and, thus, save IO. What I do is to set the NETIF_F_TSO flag on my netdevice. Then I get large packets from the stack. I fragment the packet according to MSS, i.e. split tcp payload, put modified tcp and ip headers at the start of each segment and send the segments out. However, in the following example I have the problem that the Linux stack retransmits the first segment: I send 2000 bytes using a simple tcp client server program. I get the whole packet in my driver. I create two segments (1440 and 560 bytes + headers) and send them. On the receiver side the packets look as if they had been segmented by the stack. On the sender side, however, Linux retransmits the first 1440 (+headers). Also, I never get an ACK for the second segment from the receiver. Is there any data in the Linux tcp/ip stack I have to adjust when I do tcp segmentation in my driver? I suppose there is nothing to be done. If I was using real hardware TSO the hardware could not adjust data in the Linux stack either. Any ideas? Regards, Thomas. - : send the line "unsubscribe linux-net" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
