Ping was  broken. 
It always exited with an wrong status. 
It sometimes waited for a timeout due to a race condition.
Both problems are solved by this patch.

Notes:
Sat Nov 12 08:42:42 EST 2005 rsc
    I think I fixed these, albeit in a different way.  Thanks.
    


Reference: /n/sources/patch/applied/pingbroken
Date: Fri Nov 11 13:19:11 CET 2005
Reviewed-by: rsc

--- /sys/src/cmd/ip/ping.c	Fri Nov 11 13:19:01 2005
+++ /sys/src/cmd/ip/ping.c	Fri Nov 11 13:18:59 2005
@@ -81,6 +81,8 @@
 	USED(a);
 	if(strstr(msg, "alarm"))
 		noted(NCONT);
+	else if(strstr(msg, "die"))
+		exits(0);
 	else
 		noted(NDFLT);
 }
@@ -177,7 +179,7 @@
 	ip = (Icmp*)buf;
 	sum = 0;
 
-	while(!done || first != nil){
+	while((!done || first != nil) && nmsg > lostmsgs+rcvdmsgs){
 		alarm((nmsg-lostmsgs-rcvdmsgs)*interval+5000);
 		n = read(fd, buf, sizeof(buf));
 		alarm(0);
@@ -213,7 +215,8 @@
 
 	if(lostmsgs)
 		print("%d out of %d messages lost\n", lostmsgs, lostmsgs+rcvdmsgs);
-	postnote(PNPROC, senderpid, "die");
+	else
+		postnote(PNPROC, senderpid, "die");
 }
 
 void