Systems running SunOS 4.1.x , HP-UX 9.0.x , or UnixWare 2.1.x do not enable UDP checksums by default for NFS traffic. This may put data under ClearCase control at risk, as ClearCase can use NFS to read and write container files for sources in views and VOBs. We recommend that you enable UDP checksums on all SunOS 4.1. x , HP-UX 9.0.x , and UnixWare 2.1.x systems running ClearCase.
In addition, we recommend that you enable UDP checksums on any system that is on an NFS network, if that NFS network might be accessed by a system running ClearCase, or if that system might ever be used to write data to a ClearCase data structure, for example through non-ClearCase access. Note that all other platforms supported by ClearCase enable UDP checksums by default. If you are running platforms not supported by ClearCase on your NFS network, check with the platform OS vendor to learn whether UDP checksums are enabled, and how to enable them if they are not.
To enable UDP checksums on SunOS 4.1.x , HP-UX 9.0.x , and UnixWare 2.1.x systems, follow the directions below.
Edit the file /usr/sys/netinet/in_proto.c (you may need root
or administrator privileges to do
this). In this file, change the
line
int udp_cksum = 0; /* turn on to check & generate udp checksums */
to
int udp_cksum = 1; /* turn on to check & generate udp checksums */
After editing the file, rebuild the kernel, install it and
reboot your system. UDP checksums must
be enabled on both the NFS
client and NFS server for them to protect your data.
As root, patch the kernel image file and the running kernel with the adb utility:
# adb -k -w /hp-ux /dev/mem kudp_checksumming/W 2 kudp_checksumming?W 2 $q
NOTE: You must repeat this procedure whenever you rebuild the kernel, for example when you install a new version of ClearCase. Please see the description in the HP-UX section of the chapter "ClearCase Platform-Specific Information" in the ClearCase and MultiSite Release Notes for more information.
Asroot, set the UDPCKSUM parameter with the idtune utility:
# /etc/conf/bin/idtune -f UDPCKSUM 1 # /etc/conf/bin/idbuild
After setting the parameter, reboot your system so that the change will take effect.
Please contact Rational Support
Technical Bulletin number 26 - 20 May 1998