Date: Tue, 9 Mar 2004 03:59:05 -0800 (PST) From: ian j hart <ict@cardinalnewman.coventry.sch.uk> To: freebsd-gnats-submit@FreeBSD.org Subject: kern/63982: em0 hardware checksum offloading causes bogus errors in tcpdump Message-ID: <200403091159.i29Bx5Up091858@www.freebsd.org> Resent-Message-ID: <200403091200.i29C0Vbl008770@freefall.freebsd.org>
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>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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