fix(hermit): pass the gateway as part of ip=

.github/contributors.yaml

@@ -161,3 +161,6 @@ users:
   Inuth0603:
     name: Divyam Agarwal
     email: iitdivyamagarwal@gmail.com
+  martijnhoekstra:
+    name: Martijn
+    email: martijnhoekstra@gmail.com

pkg/unikontainers/unikernels/hermit_rs.go

@@ -39,11 +39,13 @@ type HermitNet struct {
 func (h *Hermit) CommandString() (string, error) {
 	var args []string
 
+	// Hermit takes the gateway as part of ip=<ip>/<prefix>:<gateway>.
 	if h.Net.Address != "" {
-		args = append(args, fmt.Sprintf("ip=%s/%d", h.Net.Address, h.Net.Mask))
-	}
-	if h.Net.Gateway != "" {
-		args = append(args, fmt.Sprintf("gateway=%s", h.Net.Gateway))
+		ip := fmt.Sprintf("%s/%d", h.Net.Address, h.Net.Mask)
+		if h.Net.Gateway != "" {
+			ip += ":" + h.Net.Gateway
+		}
+		args = append(args, "ip="+ip)
 	}
 
 	// Add separator ONLY if we have net args AND a command

pkg/unikontainers/unikernels/hermit_rs_test.go

@@ -0,0 +1,87 @@
+// Copyright (c) 2023-2026, Nubificus LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package unikernels
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestHermitCommandString(t *testing.T) {
+	t.Parallel()
+
+	testCases := []struct {
+		name     string
+		hermit   *Hermit
+		expected string
+	}{
+		{
+			name:     "no network configured",
+			hermit:   &Hermit{},
+			expected: "",
+		},
+		{
+			name: "address and gateway",
+			hermit: &Hermit{
+				Net: HermitNet{
+					Address: "10.0.0.2",
+					Mask:    24,
+					Gateway: "10.0.0.1",
+				},
+			},
+			expected: "ip=10.0.0.2/24:10.0.0.1",
+		},
+		{
+			name: "address without gateway",
+			hermit: &Hermit{
+				Net: HermitNet{
+					Address: "10.0.0.2",
+					Mask:    24,
+				},
+			},
+			expected: "ip=10.0.0.2/24",
+		},
+		{
+			name: "network and application arguments",
+			hermit: &Hermit{
+				Command: "/app --port 8080",
+				Net: HermitNet{
+					Address: "10.0.0.2",
+					Mask:    24,
+					Gateway: "10.0.0.1",
+				},
+			},
+			expected: "ip=10.0.0.2/24:10.0.0.1 -- /app --port 8080",
+		},
+		{
+			name: "application arguments without network",
+			hermit: &Hermit{
+				Command: "/app --port 8080",
+			},
+			expected: "/app --port 8080",
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			result, err := tc.hermit.CommandString()
+			require.NoError(t, err)
+			assert.Equal(t, tc.expected, result)
+		})
+	}
+}