Mellanox "hw csum failure" error and other upcoming changes

[qbarnes]

We encountered a "hw csum failure" for the latest Mellanox driver which turned up a long latent bug in the xt_DADDR.c code. I'm making the patch available now on the hw_csum_failure branch for those that run across the issue before I can get some other fixes into master.

Some of the other upcoming changes that are pending for master are:

• Change default table from "mangle" to "raw" to resolve problems with conntrack (issue #5)
• Deprecate iptables 1.2 (RHEL 4) and iptables 1.3 (RHEL 5) support
• Add dsrtools which deprecates yvipagent
• Add rpm package building support for RHEL 8
• Add support for suppressing kmod side of the build
• Some general bookkeeping and clean up

If you'd like any of these changes before I can publish them on github, let me know and I'll see if I can send you an isolated patch for it.