[Openswan dev] Small optimisation for lots of interfaces

[D. Hugh Redelmeier]

| From: David McCullough <davidm at snapgear.com>
| 
| If you have a box with 100's of interfaces,  processing ifconfig
| output to find the configured ipsec interfaces is a little expensive,
| so this patch changes it to use /proc/net/ipsec_tncfg.

This surprises me.  Is the ifconfig command slow, or is the time spent
somewhere else?  How bad does it actually get?

I would be interested in the output of
	time ifconfig >/dev/null
	time grep -sv NULL /proc/net/ipsec_tncfg >/dev/null

I'd actually expect some of the code in Pluto for discovering
interfaces to be a worse problem when there are a lot of interfaces.