You haven't used my latest branch! My fix on ARP should address the ARP duplicate problem.
In your local repo, run git log to check if commit hash. Another way to check is to see if file BasiliskII/src/Unix/Linux/NetDriver/README.md exists or not.
If it does, you are on the right track and commit. Rebuild the sheep_net module by runing
sh build.sh [your account]
You ** must ** rebuild and reload sheep_net module. One way to check it is to run dmesg after you ping from guest OS.
dmesg | grep sheep_net
Show what IP packet is dropped/kept by sheep_net module.
BTW, I also arp duplicate issues last night. It is because sheep_net broadcast its ARP back to host. It should be eliminated, otherwise it spoof ARP.