feat(interfaces): Add support for interfaces file

This adds the ability for cloudinit to parse a debian interfaces
file and generate the coresponding networkd configs.

network/interface.go

@@ -0,0 +1,193 @@
+package network
+
+import (
+	"fmt"
+	"strconv"
+)
+
+type InterfaceGenerator interface {
+	Name() string
+	Netdev() string
+	Link() string
+	Network() string
+}
+
+type logicalInterface struct {
+	name     string
+	config   configMethod
+	children []InterfaceGenerator
+}
+
+func (i *logicalInterface) Network() string {
+	config := fmt.Sprintf("[Match]\nName=%s\n\n[Network]\n", i.name)
+
+	for _, child := range i.children {
+		switch iface := child.(type) {
+		case *vlanInterface:
+			config += fmt.Sprintf("VLAN=%s\n", iface.name)
+		case *bondInterface:
+			config += fmt.Sprintf("Bond=%s\n", iface.name)
+		}
+	}
+
+	switch conf := i.config.(type) {
+	case configMethodStatic:
+		for _, nameserver := range conf.nameservers {
+			config += fmt.Sprintf("DNS=%s\n", nameserver)
+		}
+		if conf.address.IP != nil {
+			config += fmt.Sprintf("\n[Address]\nAddress=%s\n", conf.address.String())
+		}
+		for _, route := range conf.routes {
+			config += fmt.Sprintf("\n[Route]\nDestination=%s\nGateway=%s\n", route.destination.String(), route.gateway)
+		}
+	case configMethodDHCP:
+		config += "DHCP=true\n"
+	}
+
+	return config
+}
+
+type physicalInterface struct {
+	logicalInterface
+}
+
+func (p *physicalInterface) Name() string {
+	return p.name
+}
+
+func (p *physicalInterface) Netdev() string {
+	return ""
+}
+
+func (p *physicalInterface) Link() string {
+	return ""
+}
+
+type bondInterface struct {
+	logicalInterface
+	slaves []string
+}
+
+func (b *bondInterface) Name() string {
+	return b.name
+}
+
+func (b *bondInterface) Netdev() string {
+	return fmt.Sprintf("[NetDev]\nKind=bond\nName=%s\n", b.name)
+}
+
+func (b *bondInterface) Link() string {
+	return ""
+}
+
+type vlanInterface struct {
+	logicalInterface
+	id        int
+	rawDevice string
+}
+
+func (v *vlanInterface) Name() string {
+	return v.name
+}
+
+func (v *vlanInterface) Netdev() string {
+	return fmt.Sprintf("[NetDev]\nKind=vlan\nName=%s\n\n[VLAN]\nId=%d\n", v.name, v.id)
+}
+
+func (v *vlanInterface) Link() string {
+	return ""
+}
+
+func buildInterfaces(stanzas []*stanzaInterface) []InterfaceGenerator {
+	bondStanzas := make(map[string]*stanzaInterface)
+	physicalStanzas := make(map[string]*stanzaInterface)
+	vlanStanzas := make(map[string]*stanzaInterface)
+	for _, iface := range stanzas {
+		switch iface.kind {
+		case interfaceBond:
+			bondStanzas[iface.name] = iface
+		case interfacePhysical:
+			physicalStanzas[iface.name] = iface
+		case interfaceVLAN:
+			vlanStanzas[iface.name] = iface
+		}
+	}
+
+	physicals := make(map[string]*physicalInterface)
+	for _, p := range physicalStanzas {
+		if _, ok := p.configMethod.(configMethodLoopback); ok {
+			continue
+		}
+		physicals[p.name] = &physicalInterface{
+			logicalInterface{
+				name:     p.name,
+				config:   p.configMethod,
+				children: []InterfaceGenerator{},
+			},
+		}
+	}
+
+	bonds := make(map[string]*bondInterface)
+	for _, b := range bondStanzas {
+		bonds[b.name] = &bondInterface{
+			logicalInterface{
+				name:     b.name,
+				config:   b.configMethod,
+				children: []InterfaceGenerator{},
+			},
+			b.options["slaves"],
+		}
+	}
+
+	vlans := make(map[string]*vlanInterface)
+	for _, v := range vlanStanzas {
+		var rawDevice string
+		id, _ := strconv.Atoi(v.options["id"][0])
+		if device := v.options["raw_device"]; len(device) == 1 {
+			rawDevice = device[0]
+		}
+		vlans[v.name] = &vlanInterface{
+			logicalInterface{
+				name:     v.name,
+				config:   v.configMethod,
+				children: []InterfaceGenerator{},
+			},
+			id,
+			rawDevice,
+		}
+	}
+
+	for _, vlan := range vlans {
+		if physical, ok := physicals[vlan.rawDevice]; ok {
+			physical.children = append(physical.children, vlan)
+		}
+		if bond, ok := bonds[vlan.rawDevice]; ok {
+			bond.children = append(bond.children, vlan)
+		}
+	}
+
+	for _, bond := range bonds {
+		for _, slave := range bond.slaves {
+			if physical, ok := physicals[slave]; ok {
+				physical.children = append(physical.children, bond)
+			}
+			if pBond, ok := bonds[slave]; ok {
+				pBond.children = append(pBond.children, bond)
+			}
+		}
+	}
+
+	interfaces := make([]InterfaceGenerator, 0, len(physicals)+len(bonds)+len(vlans))
+	for _, physical := range physicals {
+		interfaces = append(interfaces, physical)
+	}
+	for _, bond := range bonds {
+		interfaces = append(interfaces, bond)
+	}
+	for _, vlan := range vlans {
+		interfaces = append(interfaces, vlan)
+	}
+
+	return interfaces
+}