svn commit: r295136 - in head: sys/kern sys/netinet sys/sys usr.bin/netstat

[Xin LI]

On Tuesday, February 2, 2016, Alfred Perlstein <alfred at freebsd.org> wrote:

>
>
> On 2/2/16 11:39 AM, John Baldwin wrote:
>
>> On Tuesday, February 02, 2016 05:57:59 AM Alfred Perlstein wrote:
>>
>>> Author: alfred
>>> Date: Tue Feb  2 05:57:59 2016
>>> New Revision: 295136
>>> URL: https://svnweb.freebsd.org/changeset/base/295136
>>>
>>> Log:
>>>    Increase max allowed backlog for listen sockets
>>>    from short to int.
>>>       PR: 203922
>>>    Submitted by: White Knight <white_knight at 2ch.net>
>>>    MFC After: 4 weeks
>>>
>> You do realize that this breaks the ABI of the sysctls used to fetch
>> connection lists (and so will break existing binaries like ucd-snmpd,
>> etc.)
>> and thus can't be MFC'd right?
>>
> OK, I will not MFC it.
>
> Is it worthwhile to extend the xsocket to have padding so that in 11.x and
> beyond we can allow for some changes in the structure?
>
> Another idea I had was to include a version number with the sysctl request
> so that we can send back versioned structures, let me know what you think
> about that.
>
> The first idea will take not more than a few days for me to accomplish,
> the second (versioning the sysctl) probably a few more days than that.


We have similar construction (versioned ioctl) in FreeBSD ZFS but the main
goal is to keep system bootable, not to support all functionalities.  Do we
change the structure often and is it important enough to warrant the
complexity?  I think kmem interface have a simple size check to guard
against world/kernel inconsistency.

I would second John's comment on the necessity of the change though, if one
already have 32K of *backlogged* connections, it's probably not very useful
to allow more coming in.  It sounds like the application itself is
seriously broken, and unless expanding the field have some performance
benefit, I don't think it should stay.

-- 
Xin LI <delphij at delphij.net> https://www.delphij.net/
FreeBSD - The Power to Serve! Live free or die