Re: tg3 in 2.6.12-rc6 and Cisco PIX SMTP fixup

From: Valdis . Kletnieks
Date: Fri Jun 17 2005 - 08:54:25 EST

On Fri, 17 Jun 2005 07:33:05 MDT, Alejandro Bonilla said:

> So what do we really have here? Problem with Cisco or a problem in the
> driver? Both?

The Cisco PIX is gratuitously clearing the TCP window scaling bits. So if you
have tcp_adv_win_scale set to (for example) 6, you'll send a window advertisement
of (say) 4096, represented as 64 and a "shift left 6 bits". The PIX whacks the
"6 bits" part, and the other end thinks the window is 64 bytes and wedges when
a response is over 64 bytes long.

There was quite a discussion of this on lkml back last July.

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