From 1b004597c124110bcbddfc3b2b0bf202f70fb4c9 Mon Sep 17 00:00:00 2001
From: Michael Stapelberg <stapelberg@google.com>
Date: Mon, 4 Jun 2018 08:30:57 +0200
Subject: [PATCH] netconfig: implement spoof_hardware_addr for easier testing

---
 integrationnetconfig_test.go    |  9 +++++++++
 internal/netconfig/netconfig.go | 20 +++++++++++++++++---
 2 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/integrationnetconfig_test.go b/integrationnetconfig_test.go
index b06f325..b63d065 100644
--- a/integrationnetconfig_test.go
+++ b/integrationnetconfig_test.go
@@ -22,6 +22,7 @@ const goldenInterfaces = `
     },
     {
       "hardware_addr": "02:73:53:00:b0:0c",
+      "spoof_hardware_addr": "02:73:53:00:b0:aa",
       "name": "lan0",
       "addr": "192.168.42.1/24"
     }
@@ -124,6 +125,14 @@ func TestNetconfig(t *testing.T) {
 		t.Fatal(err)
 	}
 
+	link, err := exec.Command("ip", "netns", "exec", ns, "ip", "link", "show", "dev", "lan0").Output()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !strings.Contains(string(link), "link/ether 02:73:53:00:b0:aa") {
+		t.Errorf("lan0 MAC address is not 02:73:53:00:b0:aa")
+	}
+
 	addrs, err := exec.Command("ip", "netns", "exec", ns, "ip", "address", "show", "dev", "uplink0").Output()
 	if err != nil {
 		t.Fatal(err)
diff --git a/internal/netconfig/netconfig.go b/internal/netconfig/netconfig.go
index 9fc32c3..845a9d7 100644
--- a/internal/netconfig/netconfig.go
+++ b/internal/netconfig/netconfig.go
@@ -147,9 +147,10 @@ func applyDhcp6(dir string) error {
 }
 
 type InterfaceDetails struct {
-	HardwareAddr string `json:"hardware_addr"` // e.g. dc:9b:9c:ee:72:fd
-	Name         string `json:"name"`          // e.g. uplink0, or lan0
-	Addr         string `json:"addr"`          // e.g. 192.168.42.1/24
+	HardwareAddr      string `json:"hardware_addr"`       // e.g. dc:9b:9c:ee:72:fd
+	SpoofHardwareAddr string `json:"spoof_hardware_addr"` // e.g. dc:9b:9c:ee:72:fd
+	Name              string `json:"name"`                // e.g. uplink0, or lan0
+	Addr              string `json:"addr"`                // e.g. 192.168.42.1/24
 }
 
 type InterfaceConfig struct {
@@ -190,6 +191,9 @@ func applyInterfaces(dir, root string) error {
 	byHardwareAddr := make(map[string]InterfaceDetails)
 	for _, details := range cfg.Interfaces {
 		byHardwareAddr[details.HardwareAddr] = details
+		if spoof := details.SpoofHardwareAddr; spoof != "" {
+			byHardwareAddr[spoof] = details
+		}
 	}
 	links, err := netlink.LinkList()
 	for _, l := range links {
@@ -214,6 +218,16 @@ func applyInterfaces(dir, root string) error {
 			attr.Name = details.Name
 		}
 
+		if spoof := details.SpoofHardwareAddr; spoof != "" {
+			hwaddr, err := net.ParseMAC(spoof)
+			if err != nil {
+				return fmt.Errorf("ParseMAC(%q): %v", spoof, err)
+			}
+			if err := netlink.LinkSetHardwareAddr(l, hwaddr); err != nil {
+				return fmt.Errorf("LinkSetHardwareAddr(%v): %v", hwaddr, err)
+			}
+		}
+
 		if attr.OperState != netlink.OperUp {
 			// Set the interface to up, which is required by all other configuration.
 			if err := netlink.LinkSetUp(l); err != nil {