fix(firewall): iptables detection improved

1. Try setting a dummy output rule
2. Remove the dummy output rule
3. Get the INPUT table policy
4. Set the INPUT table policy to its existing policy

internal/firewall/runner_mock_test.go

@@ -0,0 +1,50 @@
+// Code generated by MockGen. DO NOT EDIT.
+// Source: github.com/qdm12/golibs/command (interfaces: Runner)
+
+// Package firewall is a generated GoMock package.
+package firewall
+
+import (
+	reflect "reflect"
+
+	gomock "github.com/golang/mock/gomock"
+	command "github.com/qdm12/golibs/command"
+)
+
+// MockRunner is a mock of Runner interface.
+type MockRunner struct {
+	ctrl     *gomock.Controller
+	recorder *MockRunnerMockRecorder
+}
+
+// MockRunnerMockRecorder is the mock recorder for MockRunner.
+type MockRunnerMockRecorder struct {
+	mock *MockRunner
+}
+
+// NewMockRunner creates a new mock instance.
+func NewMockRunner(ctrl *gomock.Controller) *MockRunner {
+	mock := &MockRunner{ctrl: ctrl}
+	mock.recorder = &MockRunnerMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use.
+func (m *MockRunner) EXPECT() *MockRunnerMockRecorder {
+	return m.recorder
+}
+
+// Run mocks base method.
+func (m *MockRunner) Run(arg0 command.ExecCmd) (string, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "Run", arg0)
+	ret0, _ := ret[0].(string)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// Run indicates an expected call of Run.
+func (mr *MockRunnerMockRecorder) Run(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Run", reflect.TypeOf((*MockRunner)(nil).Run), arg0)
+}