added network config

.gitignore

@@ -1 +1,2 @@
 .idea/
+test_*

go.mod

@@ -0,0 +1,5 @@
+module gitlab.com/bboehmke/raspi-alpine-builder
+
+go 1.13
+
+require github.com/stretchr/testify v1.4.0

go.sum

@@ -0,0 +1,13 @@
+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/iris-contrib/go.uuid v2.0.0+incompatible/go.mod h1:iz2lgM/1UnEf1kP0L/+fafWORmlnuysV2EMP8MW+qe0=
+github.com/kataras/iris v11.1.1+incompatible/go.mod h1:ki9XPua5SyAJbIxDdsssxevgGrbpBmmvoQmo/A0IodY=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0 h1:4G4v2dO3VZwixGIRoQ5Lfboy6nUhCyYzaqnIAPPhYs4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.4.0 h1:2E4SXV/wtOkTonXsotYi4li6zVWxYlZuYNCXe9XRJyk=
+github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v2 v2.2.2 h1:ZCJp+EgiOT7lHqUV2J862kp8Qj64Jo6az82+3Td9dZw=
+gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=

network.go

@@ -0,0 +1,171 @@
+package alpine_builder
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"regexp"
+	"strings"
+)
+
+// network configuration
+var networkConfig = "/data/etc/network/interfaces"
+var networkInterface = "eth0"
+
+// regular expressions
+var reSectionStart = regexp.MustCompile("^(iface|mapping|auto|allow-|source)")
+var reIface = regexp.MustCompile("^iface (\\w+) inet (\\w+)")
+var reStaticAddress = regexp.MustCompile("^(\\s*)address ([0-9.]+)")
+var reStaticNetmask = regexp.MustCompile("^(\\s*)netmask ([0-9.]+)")
+var reStaticGateway = regexp.MustCompile("^(\\s*)gateway ([0-9.]+)")
+
+// NetworkInfo represents the actual network configuration
+type NetworkInfo struct {
+	IsStatic bool
+	Address  string
+	Netmask  string
+	Gateway  string
+}
+
+// GetNetworkInfo from config file
+func GetNetworkInfo() (*NetworkInfo, error) {
+	// load config file
+	file, err := os.Open(networkConfig)
+	if err != nil {
+		return nil, fmt.Errorf("failed to open network config: %w", err)
+	}
+	defer file.Close()
+
+	var info *NetworkInfo
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		line := strings.TrimSpace(scanner.Text())
+
+		// check for section start
+		if reSectionStart.MatchString(line) {
+			infLine := reIface.FindStringSubmatch(line)
+			if infLine != nil {
+				// interface found
+				if infLine[1] == networkInterface {
+					info = &NetworkInfo{
+						IsStatic: infLine[2] == "static",
+					}
+				}
+			} else {
+				// info set -> stop here
+				if info != nil {
+					break
+				}
+			}
+
+		} else if info != nil {
+			// interface config
+			address := reStaticAddress.FindStringSubmatch(line)
+			if address != nil {
+				info.Address = address[2]
+			}
+			netmask := reStaticNetmask.FindStringSubmatch(line)
+			if netmask != nil {
+				info.Netmask = netmask[2]
+			}
+			gateway := reStaticGateway.FindStringSubmatch(line)
+			if gateway != nil {
+				info.Gateway = gateway[2]
+			}
+		}
+	}
+	if info != nil {
+		return info, nil
+	}
+	return nil, errors.New("invalid network config")
+}
+
+// NetworkEnableDHCP configures the network to use DHCP client
+func NetworkEnableDHCP() error {
+	// load config file
+	file, err := os.Open(networkConfig)
+	if err != nil {
+		return fmt.Errorf("failed to open network config: %w", err)
+	}
+	defer file.Close()
+
+	var buffer bytes.Buffer
+	var infFound bool
+
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		line := strings.TrimSpace(scanner.Text())
+
+		// check for section start
+		if reSectionStart.MatchString(line) {
+			infLine := reIface.FindStringSubmatch(line)
+			if infLine != nil {
+				// interface found
+				if infLine[1] == networkInterface {
+					infFound = true
+					buffer.WriteString(fmt.Sprintf("iface %s inet dhcp\n", networkInterface))
+					continue
+				}
+			} else {
+				if infFound {
+					infFound = false
+				}
+			}
+			buffer.WriteString(line + "\n")
+
+		} else if !infFound {
+			buffer.WriteString(line + "\n")
+		}
+	}
+
+	// write config file
+	return ioutil.WriteFile(networkConfig, buffer.Bytes(), os.ModePerm)
+}
+
+// NetworkSetStatic IP configuration
+func NetworkSetStatic(address, netmask, gateway string) error {
+	// load config file
+	file, err := os.Open(networkConfig)
+	if err != nil {
+		return fmt.Errorf("failed to open network config: %w", err)
+	}
+	defer file.Close()
+
+	var buffer bytes.Buffer
+	var infFound bool
+
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		line := strings.TrimSpace(scanner.Text())
+
+		// check for section start
+		if reSectionStart.MatchString(line) {
+			infLine := reIface.FindStringSubmatch(line)
+			if infLine != nil {
+				// interface found
+				if infLine[1] == networkInterface {
+					infFound = true
+					buffer.WriteString(fmt.Sprintf("iface %s inet static\n", networkInterface))
+					buffer.WriteString(fmt.Sprintf("  address %s\n", address))
+					buffer.WriteString(fmt.Sprintf("  netmask %s\n", netmask))
+					buffer.WriteString(fmt.Sprintf("  gateway %s\n", gateway))
+					continue
+				}
+			} else {
+				if infFound {
+					infFound = false
+				}
+			}
+			buffer.WriteString(line + "\n")
+
+		} else if !infFound {
+			buffer.WriteString(line + "\n")
+		}
+	}
+
+	// write config file
+	return ioutil.WriteFile(networkConfig, buffer.Bytes(), os.ModePerm)
+}

network_test.go

@@ -0,0 +1,116 @@
+package alpine_builder
+
+import (
+	"io/ioutil"
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func init() {
+	networkConfig = "test_interfaces"
+}
+
+func TestGetNetworkInfo(t *testing.T) {
+	ass := assert.New(t)
+
+	// file does not exist
+	_, err := GetNetworkInfo()
+	ass.EqualError(err, "failed to open network config: open test_interfaces: no such file or directory")
+
+	// invalid config file
+	ass.NoError(ioutil.WriteFile(networkConfig, []byte(""), os.ModePerm))
+	_, err = GetNetworkInfo()
+	ass.EqualError(err, "invalid network config")
+
+	// dynamic config
+	ass.NoError(ioutil.WriteFile(networkConfig, []byte(`auto lo
+iface lo inet loopback
+
+auto eth0
+iface eth0 inet dhcp`), os.ModePerm))
+	info, err := GetNetworkInfo()
+	ass.NoError(err)
+	ass.False(info.IsStatic)
+
+	// static config
+	ass.NoError(ioutil.WriteFile(networkConfig, []byte(`auto lo
+iface lo inet loopback
+
+auto eth0
+iface eth0 inet static
+  address 1.2.3.4
+  netmask 255.255.255.0
+  gateway 4.3.2.1`), os.ModePerm))
+	info, err = GetNetworkInfo()
+	ass.NoError(err)
+	ass.True(info.IsStatic)
+	ass.Equal("1.2.3.4", info.Address)
+	ass.Equal("255.255.255.0", info.Netmask)
+	ass.Equal("4.3.2.1", info.Gateway)
+
+	_ = os.Remove(networkConfig)
+}
+
+func TestNetworkEnableDHCP(t *testing.T) {
+	ass := assert.New(t)
+
+	// file does not exist
+	_, err := GetNetworkInfo()
+	ass.EqualError(err, "failed to open network config: open test_interfaces: no such file or directory")
+
+	ass.NoError(ioutil.WriteFile(networkConfig, []byte(`auto lo
+iface lo inet loopback
+
+auto eth0
+iface eth0 inet static
+  address 1.2.3.4
+  netmask 255.255.255.0
+  gateway 4.3.2.1`), os.ModePerm))
+
+	ass.NoError(NetworkEnableDHCP())
+
+	data, err := ioutil.ReadFile(networkConfig)
+	ass.NoError(err)
+
+	ass.Equal(`auto lo
+iface lo inet loopback
+
+auto eth0
+iface eth0 inet dhcp
+`, string(data))
+
+	_ = os.Remove(networkConfig)
+}
+
+func TestNetworkSetStatic(t *testing.T) {
+	ass := assert.New(t)
+
+	// file does not exist
+	_, err := GetNetworkInfo()
+	ass.EqualError(err, "failed to open network config: open test_interfaces: no such file or directory")
+
+	ass.NoError(ioutil.WriteFile(networkConfig, []byte(`auto lo
+iface lo inet loopback
+
+auto eth0
+iface eth0 inet dhcp`), os.ModePerm))
+
+	ass.NoError(NetworkSetStatic("1.2.3.4", "255.255.255.0", "4.3.2.1"))
+
+	data, err := ioutil.ReadFile(networkConfig)
+	ass.NoError(err)
+
+	ass.Equal(`auto lo
+iface lo inet loopback
+
+auto eth0
+iface eth0 inet static
+  address 1.2.3.4
+  netmask 255.255.255.0
+  gateway 4.3.2.1
+`, string(data))
+
+	_ = os.Remove(networkConfig)
+}

resources/build.sh

@@ -99,7 +99,7 @@ EOF
 
 # prepare network
 chroot_exec rc-update add networking default
-ln -fs /data/etc/interfaces ${ROOTFS_PATH}/etc/network/interfaces
+ln -fs /data/etc/network/interfaces ${ROOTFS_PATH}/etc/network/interfaces
 
 # run local before network -> local brings up the interface
 sed -i '/^\tneed/ s/$/ local/' ${ROOTFS_PATH}/etc/init.d/networking
@@ -200,8 +200,8 @@ root_pw=\$(mkpasswd -m sha-512 -s "${DEFAULT_ROOT_PASSWORD}")
 echo "root:\${root_pw}:0:0:::::" > /data/etc/shadow
 
 # interface
-if [ ! -f /data/etc/interfaces ]; then
+if [ ! -f /data/etc/network/interfaces ]; then
-cat > /data/etc/interfaces <<EOF2
+cat > /data/etc/network/interfaces <<EOF2
 auto lo
 iface lo inet loopback