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Date: Wed, 18 Sep 2002 14:42:07 -0700 (PDT)
From: "George V. Neville-Neil" <gnn@waits.engr.nominum.com>
Reply-To: "George V. Neville-Neil" <gnn@waits.engr.nominum.com>
To: FreeBSD-gnats-submit@FreeBSD.org
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Subject: kern/42937: panic when ARP cache uses up all mbufs
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>Number:         42937
>Category:       kern
>Synopsis:       panic when ARP cache uses up all mbufs
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed Sep 18 14:50:01 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator:     George V. Neville-Neil
>Release:        FreeBSD 4.5-RELEASE i386
>Organization:
Nominum Inc. 
>Environment:
System: FreeBSD waits.engr.nominum.com 4.5-RELEASE FreeBSD 4.5-RELEASE #0: Mon Jun 24 14:33:42 PDT 2002 gnn@waits.engr.nominum.com:/usr/src/sys/compile/WAITS i386

>Description:
	We have an application that can send a ping to many different clients
very quickly (it is a DHCP server).  On FreeBSD each ping causes an ARP entry
to be created and the associated mbuf (for the outgoing ICMP packet) to be
stored with it.  This packet is trapped until the ARP reply comes back or it
is timed out.  The arp cache is timed out every 5 minutes.  It is quite easy
to use up all the mbufs in this time, and then any mbuf allocation that 
panics on failure causes the kernel to die.

>How-To-Repeat:

	Write a program that pings many addresses.
	Watch netstat -m.
	Watch kernel die.

>Fix:
	None known.
>Release-Note:
>Audit-Trail:
>Unformatted:

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