Re: [PATCH] net: tcp_drop adds `reason` parameter for tracing v2

On Wed, 25 Aug 2021 09:20:37 -0700 Eric Dumazet wrote:

On Wed, Aug 25, 2021 at 9:04 AM Jakub Kicinski [off-list ref] wrote:

quoted

On Wed, 25 Aug 2021 08:47:46 -0700 Eric Dumazet wrote:  

quoted

I'd rather use a string. So that we can more easily identify _why_ the
packet was drop, without looking at the source code
of the exact kernel version to locate line number 1057  

Yeah, the line number seems like a particularly bad idea. Hopefully
strings won't be problematic, given we can expect most serious users
to feed the tracepoints via BPF. enum would be more convenient there,
I'd think.
 

quoted

You can be sure that we will get reports in the future from users of
heavily modified kernels.
Having to download a git tree, or apply semi-private patches is a no go.  

I'm slightly surprised by this angle. Are there downstream kernels with
heavily modified TCP other than Google's?  

Not sure why Google is mentioned here ?
Have you ever received a public report about TCP behavior in a Google kernel ?

That's a rhetorical question quite likely, but to be clear - what 
I meant is that Google is the main contributor to Linux TCP and has 
the expertise to make changes. I don't know of any others hence the
question.

Over the years, we received hundreds of TCP bug reports on
netdev@vger, where users claim to use  kernel version 4.19 (or other),
when in fact they use 4.19.xxx
It takes in general multiple emails exchange before we get a more
realistic version number.
Not to mention distro kernels, or even worse private kernels, which
are not exactly easy to track for us upstream developers.

Right but for backports values come from original patch, enum or string.

I don't mean to dispute your preference tho, if you want strings,
strings it is.