Avoid duplicate iptables NAT rule on container restart - #1024
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StaticNetwork.NetworkSetup() calls setNATRule() unconditionally on every setup, appending a MASQUERADE rule with -A regardless of whether it is already there. Since the network namespace survives a Kubernetes container restart (the same condition that used to leak TAP devices before CleanupAllUruncTaps() was added for urunc-dev#406), Kill() never removes this rule, so every restart appends another identical one to the same namespace. Check for the rule with iptables -C before appending it with -A, so setNATRule() becomes idempotent across restarts. Fixes urunc-dev#992 Signed-off-by: Akanksha Trehun <akankshatrehun@gmail.com>
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Description
StaticNetwork.NetworkSetup()always raniptables -t nat -A ...with no existence check, so restarting a container leaked a duplicate NAT rule each time. Adds an existence check (viaiptables -C, exit 0 = exists) before appending, matching the fix approach suggested in the issue.Related issues
How was this tested?
Cross-compiled and vetted clean (GOOS=linux GOARCH=amd64).
LLM usage
none
Checklist
make lint).make test_ctr,make test_nerdctl,make test_docker,make test_crictl).