extra paranoia if multipile ips are found.

Reference: /n/sources/patch/applied/ipv6on
Date: Fri Jul 20 00:50:25 CES 2007
Signed-off-by: quanstro@speakeasy.net

--- /rc/bin/ipv6on	Fri Jul 20 00:49:44 2007
+++ /rc/bin/ipv6on	Fri Jul 20 00:49:43 2007
@@ -29,11 +29,15 @@
 	xdir=(-x $netdir)
 }
 
-fn nonnil {	# name ip
-	if (~ $#2 0) {
+fn nonnil {
+	if (~ $#$1 0) {
 		echo no ip for $1
 		exit no-ip
 	}
+	if (! ~ $#$1 1) {
+		echo multiple ips for $1
+		exit multiple-ips
+	}
 }
 
 #
@@ -48,7 +52,7 @@
 
 # for testing
 mylnk=`{ip/linklocal `{cat $netdir/ether?/addr}}
-nonnil mylnk $mylnk
+nonnil mylnk
 
 if (~ $#gw 1) {
 	if (~ $gw [0-9]*.[0-9]*.[0-9]*.[0-9]*)
@@ -64,12 +68,12 @@
 		sleep 3					# wait for ping
 
 		gweth=`{grep '* '^$gwv4^' ' $netdir/arp | awk '{print $4}' }
-		nonnil gweth $gweth
+		nonnil gweth
 		gwlnk=`{ip/linklocal $gweth}
-		nonnil gwlnk $gwlnk
+		nonnil gwlnk
 	}
 }
-nonnil mev6 $mev6
+nonnil mev6
 #
 # configure my global v6 addresses
 #
@@ -79,7 +83,7 @@
 if (~ $#gw 1) {
 	if (~ $#gwv6 0 || ~ $gwv6 '')
 		gwv6=`{ip/linklocal $gweth}
-	nonnil gwv6 $gwv6
+	nonnil gwv6
 	#
 	# add default v6 route to v6 addr of v4 gw
 	#