Re: Status of mount.nfs

[Chuck Lever <chuck.lever@oracle.com>]

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Steve Dickson wrote:
> Chuck Lever wrote:
>> I was looking at this yesterday.  The stock timeout for TCP connects 
>> on Linux is 75 seconds.  The version of getport() used in the mount 
>> command might control the TCP connect timeout by using a non-blocking 
>> connect() with a select().  The select() then times out if the 
>> connection doesn't complete.
>>
>> But I'm wondering if we really want to continue using TCP for GETPORT 
>> calls.  Solaris mount appears to use only UDP for GETPORT, for example.

> As as long as the GETPORTs don't use privilege ports I don't think its
> a problem...

Not sure what you mean.  Yesterday you said the TCP connect timeout 
*was* a problem.  I've recommended two ways to address it.

The ephemeral port space is limited too, don't forget.  It's simply a 
somewhat larger space than the privileged port space.  If a large 
network application (say, a web server) is running on the system, that 
space can shrink fairly rapidly, and we're in nearly the same boat as 
with privileged ports.  Using a TCP connection from an ephemeral port 
only mitigates the port space problem, it doesn't really correct it 
entirely.

> plus I don't think one size fixes all.. meaning due to
> different firewalls requirements both udp and tcp GETPORTS will be
> needed... imho...

We say "firewall!" a lot, but I would like to see typical use cases for 
mounting through a firewall so I understand what kind of implementation 
we're aiming for (and maybe even what kind of test cases to build!).  Do 
our users really expect to mount NFS shares through any firewall with 
"-o defaults" ?

I'd like to hear from the distributors what you consider are the use 
cases that absolutely must be supported.  Otherwise we will end up 
standing on our left big toenail to support stuff that isn't worth the 
pain or is never used.

And can anyone shed some light on why Solaris uses only UDP for GETPORT 
requests at mount time?  Does it ever fall back to try GETPORT on a TCP 
connection?  How do Solaris users mount through a firewall?  Come on all 
you Solaris NFS guys out there, I know you're lurking.

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