VM log filled with error 55 / VM packet loss

Scenarios

The [~]/Library/Logs/Anka/{UUID}.log or ankanetd.log is filled with 22: failed to write packet, error 55 and failed to send # packets: error 55
Sudden packet loss inside of the VM or to the VM.

Solution

This is very common when the VMs have heavy CPU usage. Normally it shouldn’t be a critical error – packet loss is being handled by the TCP stack of guest. But if the error rate is very high, it definitely could cause applications or downloads to fail inside of the VM or even communication to the VM to be severed. If the occurrence of these errors is more than just a few log entries, you can increase the value of net.local.dgram.recvspace and net.local.dgram.maxdgram with sysctl ON THE HOST.

You may need to keep increasing the value until the errors are no longer visible.

$ sudo sysctl -a | grep "local.dgram"
net.local.dgram.maxdgram: 2048
net.local.dgram.recvspace: 4096

sudo sysctl net.local.dgram.recvspace=65536
sudo sysctl net.local.dgram.maxdgram=16384

Manually executed sysctl changes do not persist across reboots. You can setup a plist under /Library/LaunchDaemons to have it set on each boot.

echo -n '
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
        <key>Label</key>
        <string>custom.net.local.dgram.recvspace</string>
        <key>ProgramArguments</key>
        <array>
        <string>/usr/sbin/sysctl</string>
        <string>net.local.dgram.recvspace=65536</string>
        </array>
        <key>RunAtLoad</key>
        <true/>
</dict>
</plist>' | sudo tee /Library/LaunchDaemons/custom.net.local.dgram.recvspace.plist
sudo launchctl load -w /Library/LaunchDaemons/custom.net.local.dgram.recvspace.plist
echo -n '
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
        <key>Label</key>
        <string>custom.net.local.dgram.maxdgram</string>
        <key>ProgramArguments</key>
        <array>
        <string>/usr/sbin/sysctl</string>
        <string>net.local.dgram.maxdgram=16384</string>
        </array>
        <key>RunAtLoad</key>
        <true/>
</dict>
</plist>' | sudo tee /Library/LaunchDaemons/custom.net.local.dgram.maxdgram.plist
sudo launchctl load -w /Library/LaunchDaemons/custom.net.local.dgram.maxdgram.plist

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