On Tuesday 03 November 2009 4:26:48 pm Bjoern A. Zeeb wrote: > On Tue, 3 Nov 2009, John Baldwin wrote: > > > Several years ago Dillon added a feature to TCP that casued soreceive() to > > send an ACK right away if data was drained from a TCP socket that had > > previously advertised a zero-sized window. The current code requires the > > receive window to be exactly zero for this to kick in. If window scaling is > > enabled and the window is smaller than the scale, then the effective window > > that is advertised is zero. However, in that case the zero-sized window > > handling is not enabled because the window is not exactly zero. The patch > > below changes the code to check the raw window value against zero. Arguably > > it could check 'th_win' directly instead if folks would prefer that. > > hmm, looking a few lines up, there is a htons() there as well; > obviously doesn't matter for 0. th_win is set to something different > for SYNs. I guess what you are doing is ok, and even though it is not > needed, I feel that it would be easier to read it with an extra pair > of ().
How about using 'if (th->th_win == htons(0))' for the condition? > > Index: tcp_output.c > > =================================================================== > > --- tcp_output.c (revision 198794) > > +++ tcp_output.c (working copy) > > @@ -992,7 +992,7 @@ > > * to read more data than can be buffered prior to transmitting on > > * the connection. > > */ > > - if (recwin == 0) > > + if (recwin >> tp->rcv_scale == 0) > > tp->t_flags |= TF_RXWIN0SENT; > > else > > tp->t_flags &= ~TF_RXWIN0SENT; > > > > > > -- > Bjoern A. Zeeb It will not break if you know what you are doing. > -- John Baldwin _______________________________________________ freebsd-net@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "freebsd-net-unsubscr...@freebsd.org"
