+ install: check static ip

* move code to network_utils

+ add tests

'dhcp' package has its own network_utils for now

+ doc: add static ip configuration algorithm on Ubuntu

home/network_utils_test.go

@@ -0,0 +1,61 @@
+package home
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestHasStaticIPDhcpcdConf(t *testing.T) {
+	dhcpdConf := `#comment
+# comment
+
+interface eth0
+static ip_address=192.168.0.1/24
+
+# interface wlan0
+static ip_address=192.168.1.1/24
+
+# comment
+`
+	assert.True(t, !hasStaticIPDhcpcdConf(dhcpdConf, "wlan0"))
+
+	dhcpdConf = `#comment
+# comment
+
+interface eth0
+static ip_address=192.168.0.1/24
+
+# interface wlan0
+static ip_address=192.168.1.1/24
+
+# comment
+
+interface wlan0
+# comment
+static ip_address=192.168.2.1/24
+`
+	assert.True(t, hasStaticIPDhcpcdConf(dhcpdConf, "wlan0"))
+}
+
+func TestSetStaticIPDhcpcdConf(t *testing.T) {
+	dhcpcdConf := `
+interface wlan0
+static ip_address=192.168.0.2/24
+static routers=192.168.0.1
+static domain_name_servers=192.168.0.2
+
+`
+	s := setStaticIPDhcpcdConf("wlan0", "192.168.0.2/24", "192.168.0.1", "192.168.0.2")
+	assert.Equal(t, dhcpcdConf, s)
+
+	// without gateway
+	dhcpcdConf = `
+interface wlan0
+static ip_address=192.168.0.2/24
+static domain_name_servers=192.168.0.2
+
+`
+	s = setStaticIPDhcpcdConf("wlan0", "192.168.0.2/24", "", "192.168.0.2")
+	assert.Equal(t, dhcpcdConf, s)
+}