Pull request: all: fix lint and naming issues vol. 2

Merge in DNS/adguard-home from 2276-fix-lint-2 to master

Updates #2276.

Squashed commit of the following:

commit 24760b9586bb31be134ef9518dbece485560b1a0
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Mon Dec 7 14:39:50 2020 +0300

    all: fix lint and naming issues vol. 2

internal/dhcpd/netutil_test.go

@@ -0,0 +1,63 @@
+// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris
+
+package dhcpd
+
+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 := updateStaticIPDhcpcdConf("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 = updateStaticIPDhcpcdConf("wlan0", "192.168.0.2/24", "", "192.168.0.2")
+	assert.Equal(t, dhcpcdConf, s)
+}