Jeff Garzik [off-list ref] wrote:

Please help me understand:  why add all this TSO code (zerocopy), if you 
 are adding memcpy() under the hood?

 Was this reviewed on netdev?  or by any network developer?

 Overall this patch adds a whole lot of code that must be VERY intimate 
 with the net stack, a huge maintenance burden that is likely to be rife 
 with out-of-date code and bugs over time.

There was some dicussion on linux-net last Thursday.