fix: Missing nil checks

Fixes #3095

npc/rule.go

@@ -30,13 +30,19 @@ func newRuleSpec(proto *string, srcHost *selectorSpec, dstHost *selectorSpec, ds
 		args = append(args, "--dport", *dstPort)
 	}
 	args = append(args, "-j", "ACCEPT")
-	srcComment := ""
-	if srcHost.nsName != "" {
-		srcComment = fmt.Sprintf("pods: namespace: %s, selector: %s", srcHost.nsName, srcHost.key)
-	} else {
-		srcComment = fmt.Sprintf("namespaces: selector: %s", srcHost.key)
+	srcComment := "anywhere"
+	if srcHost != nil {
+		if srcHost.nsName != "" {
+			srcComment = fmt.Sprintf("pods: namespace: %s, selector: %s", srcHost.nsName, srcHost.key)
+		} else {
+			srcComment = fmt.Sprintf("namespaces: selector: %s", srcHost.key)
+		}
 	}
-	args = append(args, "-m", "comment", "--comment", fmt.Sprintf("%s -> namespace: %s, key: %s", srcComment, dstHost.nsName, dstHost.key))
+	dstComment := "anywhere"
+	if dstHost != nil {
+		dstComment = fmt.Sprintf("pods: namespace: %s, selector: %s", dstHost.nsName, dstHost.key)
+	}
+	args = append(args, "-m", "comment", "--comment", fmt.Sprintf("%s -> %s", srcComment, dstComment))
 	key := strings.Join(args, " ")
 
 	return &ruleSpec{key, args}

npc/rule_test.go

@@ -0,0 +1,16 @@
+package npc
+
+import (
+	"github.com/stretchr/testify/require"
+	"testing"
+)
+
+func TestRegressionHandleNil3095(t *testing.T) {
+	// Test for handling nil values
+	// https://github.com/weaveworks/weave/issues/3095
+
+	rs := newRuleSpec(nil, nil, nil, nil)
+
+	require.NotEqual(t, rs.key, "")
+
+}