Question regarding do_tcp_sendpages, tcp_current_mss and eff_sacks

[Ashvin Goel]

I am trying to use do_tcp_sendpages() to stream some data from within 
the Linux Redhat kernel 2.4.20 (it is an smp kernel running on a 
uniprocessor). After a while this function returns an error value of 
-512. This error value makes no sense to me. A little debugging showed 
that tcp_current_mss() returns negative values. In particular, for the 
socket to which do_tcp_sendpages() is sending data, tp->eff_sacks has 
the value 200. This makes the value returned by tcp_current_mss be -156 
(1448 - 4 - 200 * 8). Is this value reasonable? I think this value is 
causing do_tcp_sendpages() to return a large negative value.

Thanks for any help/suggestions. Please CC your post to me personally.

Thanks
Ashvin Goel
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