# TSO for IPv6 traffic



## shreyasbforu (Oct 21, 2010)

Looking at the FreeBSD networking stack, TSO is not asked for outgoing IPv6 packets
http://fxr.watson.org/fxr/source/netinet/tcp_output.c#L1075

CSUM_TSO is not set for IPv6 packets going out even when driver advertises IFCAP_TSO6. Any reasons why TSO over IPv6 is not supported ? 
OR
Any idea as to what work is involved in making this happen ?

Thanks in advance.
->Shreyas


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## SirDice (Oct 21, 2010)

> Andre wrote that TSO for IPv4 and IPv6 is always enabled or disabled together. But IPv6 currently lacks a pseudo-header checksum function and thus doesn't support TSO yet.


http://www.bsdunix.ch/serendipity/i...-segmentation-offload-in-FreeBSD-Current.html


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## phoenix (Oct 21, 2010)

Search the freebsd-current mailing list for this week, specifically a thread with subject "IPV6 Checksum offload and TSO6", for a dicsussion of this topic.  It appears that hardware is available that supports these functions (Intel), but the network stack doesn't support the features yet.  A couple of coders are considering working on this in November.


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## acheron (Oct 21, 2010)

See this fresh thread : http://lists.freebsd.org/pipermail/freebsd-net/2010-October/026775.html


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