Re: [PATCH v5 1/2] tcp: Add TCP_INFO counter for packets received out-of-order

[Thomas Higdon <tph@fb.com>]

On Sat, Sep 14, 2019 at 11:43:25AM -0400, Neal Cardwell wrote:
> On Fri, Sep 13, 2019 at 7:23 PM Thomas Higdon <tph@fb.com> wrote:
> >
> > For receive-heavy cases on the server-side, we want to track the
> > connection quality for individual client IPs. This counter, similar to
> > the existing system-wide TCPOFOQueue counter in /proc/net/netstat,
> > tracks out-of-order packet reception. By providing this counter in
> > TCP_INFO, it will allow understanding to what degree receive-heavy
> > sockets are experiencing out-of-order delivery and packet drops
> > indicating congestion.
> >
> > Please note that this is similar to the counter in NetBSD TCP_INFO, and
> > has the same name.
> >
> > Also note that we avoid increasing the size of the tcp_sock struct by
> > taking advantage of a hole.
> >
> > Signed-off-by: Thomas Higdon <tph@fb.com>
> > ---
> > changes since v4:
> >  - optimize placement of rcv_ooopack to avoid increasing tcp_sock struct
> >    size
> 
> 
> Acked-by: Neal Cardwell <ncardwell@google.com>
> 
> Thanks, Thomas, for adding this!
> 
> After this is merged, would you mind sending a patch to add support to
> the "ss" command line tool to print these 2 new fields?
> 
> My favorite recent example of such a patch to ss is Eric's change:
>   https://git.kernel.org/pub/scm/network/iproute2/iproute2.git/commit/misc/ss.c?id=5eead6270a19f00464052d4084f32182cfe027ff

Yes, and thank you for the help in getting this into a good state!

From looking at that "ss" patch, it seems like we would need to wait
until iproute2-next's include/uapi/linux/tcp.h has received a merge from
kernel net-next before we'd be able to apply a patch for "ss" that uses
the new fields.

In the meantime, as you've asked, I will go ahead and send a patch for
iproute2-next's "ss" with the assumption that these tcpinfo changes have
already been merged.