Re: 2.6.17: networking bug??

[Mark Lord]

Mark Lord wrote:
> ..
> > The site www.everymac.com is still not browseable until
> > setting /proc/sys/net/ipv4/tcp_window_scaling===0.
> >
> > There's one other difference I see in the tcpdump traces.
> > The first packets from each trace below show different
> > values for "wscale".  The old (working) kernels use "wscale 2",
> > whereas 2.6.17 uses "wscale 6".  In both cases, the value
> > seen in /proc/sys/net/ipv4/tcp_adv_win_scale is 2.
>
> Okay.  More progress here.  The calculation of the "wscale" values
> is based on the "tcp_rmem" sysctl numbers.
>
> The defaults for these *differ* between 2.6.16.18 and 2.6.17-rc*.
>
> 2.6.16: 4096    87380    174760
> 2.6.17: 4096    87380   2097152
>
> If I change the tcp_rmem setting on 2.6.17 to match the old value,
> then the website www.everymac.com becomes accessible again:
>
> echo 4096 87380 174760 > /proc/sys/net/ipv4/tcp_rmem
>
> Looking at diffs between 2.6.16 and 2.6.17, I see a big rework
> of the tcp_rmem code in linux/net/ipv4/tcp.c
>
> Looks like something got broken there, or possibly the wscale
> calculations have a bug that is only triggered by the new rmem values ??

Okay, here's the blob that broke it.

> [TCP]: Set default max buffers from memory pool size
> author	John Heffner <jheffner@xxxxxxx>
> 	Sat, 25 Mar 2006 09:34:07 +0000 (01:34 -0800)
> committer	David S. Miller <davem@xxxxxxxxxxxxx>
> 	Sat, 25 Mar 2006 09:34:07 +0000 (01:34 -0800)
> commit	7b4f4b5ebceab67ce440a61081a69f0265e17c2a
> tree	ac02c685ce23f2440fecbebaa5b55cd47947c03e	tree
> parent	2babf9daae4a3561f3264638a22ac7d0b14a6f52	commit | commitdiff
> [TCP]: Set default max buffers from memory pool size
>
> This patch sets the maximum TCP buffer sizes (available to automatic
> buffer tuning, not to setsockopt) based on the TCP memory pool size.
> The maximum sndbuf and rcvbuf each will be up to 4 MB, but no more
> than 1/128 of the memory pressure threshold.
>
> Signed-off-by: John Heffner <jheffner@xxxxxxx>
> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>

John / David:  Any ideas on what's gone awry here?



-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/