[rancid] Rancid 3.2 RHEL6 compatibilities with Socket module.

[Robert Drake]

Not speaking for anyone but myself.

FWIW, this is code from spamassassin:

my $ip6 = eval {
      require Socket;
      Socket->VERSION(1.95);
      Socket->import( 'inet_pton' );
      1;
} || eval {
      require Socket6;
      Socket6->import( 'inet_pton' );
      1;
};

Normally I would say use NetAddr::IP or another library to avoid the 
inet_pton call, but I found this note:

# ipaddrval(IPaddr) converts and IPv4/v6 address to a string for comparison.
# Some may ask why not use Net::IP; performance.  We tried and it was 
horribly
# slow.

If performance is a major concern I would make minor changes to the 
existing code (sorry for the formatting):

     if ($a =~ /:/) {
     my($l);
     ($a, $l) = split(/\//, $a);   # this split works even if the slash 
isn't there
     $l ||= 128;    # if !defined is faster than if (/\//)

     $norder = inet_pton(AF_INET6, $a);
     return unpack('H128', $norder) . unpack('H', pack('C', $l));
     }

I don't think this sacrifices readability but it improves the 
performance (by about 30-40k calls/s).  The regex and split string 
operations are almost always the most expensive aspect and if there were 
ways to get rid of them then the speed would go way up. Honestly 
inet_pton is low level but it's the best way to get speed out of IP 
operations (because it's just wrapping a C function).

Drawbacks:  RHEL6 (or anything older than 2009 running perl5.10.x) don't 
have inet_pton.   Socket.pm also doesn't support MSWin32 until 2.019, 
which hasn't been shipped yet with any version of perl (so inet_pton 
isn't available on any windows systems without workarounds.  I have no 
idea if anyone runs rancid on windows though, or if that would be possible)

Suggested workarounds:  It's a minor change.  I'm not sure if Redhat 
uses a system like Debian's quilt for maintaining downstream patches, 
but I would just put together a changeset for the 3 lines and repackage 
it rather than forcing the change upstream.  The reason being that 
although this is minor, changing it causes documentation headaches 
(well.. a comment saying why it is the way it is) and doesn't give a 
sunset clause to it.  If it's maintained in downstream then as soon as 
RHEL6 support is dropped the packages stop being produced and that is 
the sunset of the changes.

Yeah, I've probably spent more time whining in this email than it would 
take for whoever to fix it, but what if there are other 5.12 features 
they turn on later and then need to turn off because someone still runs 
5.10?

Robert



On 6/1/2015 4:50 PM, Brown, David M JR wrote:
> We’ve had several requests to get the updated version of rancid on 
> RHEL 6. However, there seems to be some issues getting that to work 
> with the older version of the Socket module.
>
> https://bugzilla.redhat.com/show_bug.cgi?id=1224143
>
> The patch ftp://ftp.shrubbery.net/pub/rancid/rancid-3.2.p3.gz seems to 
> be the supported resolution though it does prevent rancid 3.2 from 
> running on RHEL 6, out of the box.
>
> The patch in the bug suggests using the Socket6 module and pulling the 
> relevant names which seems to have a working version. Would it be 
> possible to use Socket6 instead of Socket for inet_pton()?
>
> Thanks,
> - David Brown
>
>
> _______________________________________________
> Rancid-discuss mailing list
> Rancid-discuss at shrubbery.net
> http://www.shrubbery.net/mailman/listinfo/rancid-discuss

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