Hi Elad, I am using the Intel 8280 ethernet card. Here is an output from lspci: 05:08.0 Ethernet controller: Intel Corporation 82801DB PRO/100 VM (LOM) Ethernet Controller (rev 81) I tried to use the ethtool to check whether it has TCP checksum offload capabilities or not but didn't get much info. Here is the output: [root@gdev26 ~]# ethtool -k eth0 Offload parameters for eth0: Cannot get device rx csum settings: Operation not supported Cannot get device tx csum settings: Operation not supported Cannot get device scatter-gather settings: Operation not supported Cannot get device tcp segmentation offload settings: Operation not supported no offload info available -- Regards, Gaurav Aggarwal On 10/27/07, Elad Lahav <elad_lahav@xxxxxxxxxxxxxxxxxxxxx> wrote: > TCP checksum may actually be computed in hardware, so that the value you > see in the packet may not be the final checksum value. > Which NIC are you using? You can use ethtool to check whether it has TCP > offload capabilities. > > Elad > > > Gaurav Aggarwal wrote: > > Hi All, > > > > I wrote a program where I am using the nfnetlink and netfilter_queue > > model to capture the packet. After that I just change the destination > > address of the packet and insert it back into the ip stack. Now > > instead of calculating the TCP checksum from scratch, I was just > > recalculating it by using incremental update mechanism as mentioned in > > RFC 1624. Good thing is that I was able to get the correct IP header > > checksum but packet's TCP checksum value is corrupted. Interesting > > thing is, the difference in checksum is exactly the same as that of > > difference in original and modified packet header. What I mean to say > > is that I was changing the destination IP from "10.102.35.22" to > > "10.102.35.24" and the difference in tcp checksum (expected and > > computed) is coming as 0x02. Attached is the source code and tcpdump. > > Any help will be really appreciated. > > > > > > > -- > To unsubscribe from this list: send an email with > "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx > Please read the FAQ at http://kernelnewbies.org/FAQ > > -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
