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Date:      Tue, 9 Mar 2004 06:20:16 -0800 (PST)
From:      ian j hart <ict@cardinalnewman.coventry.sch.uk>
To:        freebsd-bugs@FreeBSD.org
Subject:   kern/63982: em0 hardware checksum offloading causes bogus errors in tcpdump
Message-ID:  <200403091420.i29EKGqj061329@freefall.freebsd.org>

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The following reply was made to PR kern/63982; it has been noted by GNATS.

From: ian j hart <ict@cardinalnewman.coventry.sch.uk>
To: freebsd-gnats-submit@FreeBSD.org
Cc:  
Subject: kern/63982: em0 hardware checksum offloading causes bogus errors in
	tcpdump
Date: Tue, 9 Mar 2004 03:59:05 -0800 (PST)

 >Number:         63982
 >Category:       kern
 >Synopsis:       em0 hardware checksum offloading causes bogus errors in tcpdump
 >Confidential:   no
 >Severity:       non-critical
 >Priority:       low
 >Responsible:    freebsd-bugs
 >State:          open
 >Quarter:        
 >Keywords:       
 >Date-Required:
 >Class:          sw-bug
 >Submitter-Id:   current-users
 >Arrival-Date:   Tue Mar 09 04:00:31 PST 2004
 >Closed-Date:
 >Last-Modified:
 >Originator:     ian j hart
 >Release:        4.9-RELEASEp3
 >Organization:
 Cardinal Newman School
 >Environment:
 backup.cardinalnewman.lan 4.9-RELEASE-p3 FreeBSD 4.9-RELEASE-p3 #12: Tue Mar  9 10:13:10 GMT 2004     root@backup.cardinalnewman.lan:/usr/obj/usr/src/sys/GENERIC  i386
 
 patched with src/sys/dev/em from RELENG_4
 >Description:
       Running tcpdump -v shows many packets marked as having bad
 checksums. The packets are delivered okay with correct checksums. This
 mainly affects UDP.
 
 I booted from disc2.iso for 4.7, 4.8, and 5.2.1RC and confirmed the
 problem there.
 
 One motherboard (GA-7VAXP-A Ultra) DOES work but all others tried so far, fail. Card in different slots, natch`. irq/timing?
 
 >How-To-Repeat:
       tcpdump -v | grep bad
 Then generate some UDP traffic
 >Fix:
       A workaround and proof of the source of the problem is to
 disable the hardware checksum.
 
 /usr/src/sys/dev/em/if_em.h
 #define EM_CHECKSUM_FEATURES            (CSUM_TCP | CSUM_UDP)
 
 Set to zero
 >Release-Note:
 >Audit-Trail:
 >Unformatted:
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