[httperf] fd-unavail non-null

[Rick Jones]

> *) I'll try that but i'm not sure how the OS will behave when assigning 
> multiple IPs to a single NIC

It should behave just fine.  Support for multiple IPs per NIC has been in almost 
every TCP/IP stack out there for years.

> *) I fear that assigning more than one IP to a single NIC on the server 
> will stress the network load-balancing algorithm of the OS too much

How so?

> actually I tuned TCP parameters for my tests, and after chechking that 
> it turns out that TIME_WAIT is dramatically reduced to 1sec in my 
> configuration, so I'm surprised this problem arises this fast (seems to 
> be any rate above 1000sess/sec).

rick jones