>Number:         34799
>Category:       kern
>Synopsis:       IP Filter does not work correctly with gem(4) when hardware checksumming is enabled
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Oct 12 17:45:00 +0000 2006
>Originator:     David H. Gutteridge
>Release:        3.0 series on macppc and i386
>Organization:
>Environment:
>Description:
When hardware checksumming is enabled for gem(4), IP Filter does not work correctly with outbound connections.  ipfstat(8) does not report any checksum failures, but ipmon(8) logs the affected outbound packets, marking them "bad".

I cannot duplicate this problem on another machine running the same NetBSD release with an ex(4) card with hardware checksumming enabled.  The latter machine has no problems with outbound packets through IP Filter.

I also cannot duplicate this problem on the machine with gem(4) when using OpenBSD's pf, only with IP Filter, so it appears not to be an issue with the driver.

Another user reported the same problem back in April.  (http://mail-index.netbsd.org/port-macppc/2006/04/02/0000.html)  I thought this had already been PRed, but apparently not.
>How-To-Repeat:
Enable TCP and UDP checksumming with gem(4) and use IP Filter.
>Fix: