chore: improve freeport usage

router-tests/freeport/ephemeral_darwin.go

@@ -0,0 +1,40 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
+//go:build darwin
+
+package freeport
+
+import (
+	"fmt"
+	"os/exec"
+	"regexp"
+	"strconv"
+)
+
+const ephemeralPortRangeSysctlFirst = "net.inet.ip.portrange.first"
+const ephemeralPortRangeSysctlLast = "net.inet.ip.portrange.last"
+
+var ephemeralPortRangePatt = regexp.MustCompile(`^\s*(\d+)\s+(\d+)\s*$`)
+
+func getEphemeralPortRange() (int, int, error) {
+	cmd := exec.Command("/usr/sbin/sysctl", "-n", ephemeralPortRangeSysctlFirst, ephemeralPortRangeSysctlLast)
+	out, err := cmd.Output()
+	if err != nil {
+		return 0, 0, err
+	}
+
+	val := string(out)
+
+	m := ephemeralPortRangePatt.FindStringSubmatch(val)
+	if m != nil {
+		min, err1 := strconv.Atoi(m[1])
+		max, err2 := strconv.Atoi(m[2])
+
+		if err1 == nil && err2 == nil {
+			return min, max, nil
+		}
+	}
+
+	return 0, 0, fmt.Errorf("unexpected sysctl value %q for keys %q, %q", val, ephemeralPortRangeSysctlFirst, ephemeralPortRangeSysctlLast)
+}

router-tests/freeport/ephemeral_darwin_test.go

@@ -0,0 +1,21 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
+//go:build darwin
+
+package freeport
+
+import (
+	"testing"
+)
+
+func TestGetEphemeralPortRange(t *testing.T) {
+	min, max, err := getEphemeralPortRange()
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+	if min <= 0 || max <= 0 || min > max {
+		t.Fatalf("unexpected values: min=%d, max=%d", min, max)
+	}
+	t.Logf("min=%d, max=%d", min, max)
+}

router-tests/freeport/ephemeral_fallback.go

@@ -0,0 +1,10 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
+//go:build !linux && !darwin
+
+package freeport
+
+func getEphemeralPortRange() (int, int, error) {
+	return 0, 0, nil
+}

router-tests/freeport/ephemeral_linux.go

@@ -0,0 +1,38 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
+//go:build linux
+
+package freeport
+
+import (
+	"fmt"
+	"os"
+	"regexp"
+	"strconv"
+)
+
+const ephemeralPortRangeProcFile = "/proc/sys/net/ipv4/ip_local_port_range"
+
+var ephemeralPortRangePatt = regexp.MustCompile(`^\s*(\d+)\s+(\d+)\s*$`)
+
+func getEphemeralPortRange() (int, int, error) {
+	out, err := os.ReadFile(ephemeralPortRangeProcFile)
+	if err != nil {
+		return 0, 0, err
+	}
+
+	val := string(out)
+
+	m := ephemeralPortRangePatt.FindStringSubmatch(val)
+	if m != nil {
+		min, err1 := strconv.Atoi(m[1])
+		max, err2 := strconv.Atoi(m[2])
+
+		if err1 == nil && err2 == nil {
+			return min, max, nil
+		}
+	}
+
+	return 0, 0, fmt.Errorf("unexpected sysctl value %q for key %q", val, ephemeralPortRangeProcFile)
+}

router-tests/freeport/ephemeral_linux_test.go

@@ -0,0 +1,21 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
+//go:build linux
+
+package freeport
+
+import (
+	"testing"
+)
+
+func TestGetEphemeralPortRange(t *testing.T) {
+	min, max, err := getEphemeralPortRange()
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+	if min <= 0 || max <= 0 || min > max {
+		t.Fatalf("unexpected values: min=%d, max=%d", min, max)
+	}
+	t.Logf("min=%d, max=%d", min, max)
+}