Discover IP address of the network cards attached to a LAN

When a network card is attached to a LAN the `domain.ListAllInterfaceAddresses`
API cannot be used to get the IP address associated with the interfaces.

The only solution to this problem is to use the [Qemu guest agent](http://wiki.libvirt.org/page/Qemu_guest_agent)
to fetch this information.

This PR will take advantage of the qemu guest ageint (when installed
inside of the domain) to workaround the limitations of the
`domain.ListAllInterfaceAddresses`.

In theory this PR could also allow to relax the required version of
libvirt.

Signed-off-by: Flavio Castelli <fcastelli@suse.com>

3 files changed, 128 insertions, 1 deletions

diff --git a/docs/providers/libvirt/r/domain.html.markdown b/docs/providers/libvirt/r/domain.html.markdown
index 752d55bd..b4a3624e 100644
--- a/docs/providers/libvirt/r/domain.html.markdown
+++ b/docs/providers/libvirt/r/domain.html.markdown
@@ -120,3 +120,7 @@ resource "libvirt_domain" "my-domain" {
   }
 }
 ```
+
+**Warning:** the [Qemu guest agent](http://wiki.libvirt.org/page/Qemu_guest_agent)
+must be installed and running inside of the domain in order to discover the IP
+addresses of all the network interfaces attached to a LAN.
diff --git a/libvirt/qemu_agent.go b/libvirt/qemu_agent.go
new file mode 100644
index 00000000..10bf45cc
--- /dev/null
+++ b/libvirt/qemu_agent.go
@@ -0,0 +1,90 @@
+package libvirt
+
+import (
+	"encoding/json"
+	"log"
+	"strings"
+
+	libvirt "github.com/dmacvicar/libvirt-go"
+)
+
+type QemuAgentInterfacesResponse struct {
+	Interfaces []QemuAgentInterface `json:"return"`
+}
+
+type QemuAgentInterface struct {
+	Name        string `json:"name"`
+	Hwaddr      string `json:"hardware-address"`
+	IpAddresses []struct {
+		Type    string `json:"ip-address-type"`
+		Address string `json:"ip-address"`
+		Prefix  uint   `json:"prefix"`
+	} `json:"ip-addresses"`
+}
+
+// Retrieve all the interfaces attached to a domain and their addresses. Only
+// the interfaces with at least an IP address are returned.
+// When wait4ipv4 is turned on the code will not report interfaces that don't
+// have a ipv4 address set. This is useful when a domain gets the ipv6 address
+// before the ipv4 one.
+func getDomainInterfacesViaQemuAgent(domain *libvirt.VirDomain, wait4ipv4 bool) []libvirt.VirDomainInterface {
+	log.Print("[DEBUG] get network interfaces using qemu agent")
+
+	var interfaces []libvirt.VirDomainInterface
+
+	result := domain.QemuAgentCommand(
+		"{\"execute\":\"guest-network-get-interfaces\"}",
+		libvirt.VIR_DOMAIN_QEMU_AGENT_COMMAND_DEFAULT,
+		0)
+
+	log.Printf("[DEBUG] qemu-agent response: %s", result)
+
+	response := QemuAgentInterfacesResponse{}
+	if err := json.Unmarshal([]byte(result), &response); err != nil {
+		log.Printf("[DEBUG] Error converting Qemu agent response about domain interfaces: %s", err)
+		log.Printf("[DEBUG] Original message: %s", response)
+		log.Print("[DEBUG] Returning an empty list of interfaces")
+		return interfaces
+	}
+	log.Printf("[DEBUG] Parsed response %+v", response)
+
+	for _, iface := range response.Interfaces {
+		if iface.Name == "lo" {
+			// ignore loopback interface
+			continue
+		}
+
+		libVirtIface := libvirt.VirDomainInterface{}
+		libVirtIface.Name = iface.Name
+		libVirtIface.Hwaddr = iface.Hwaddr
+
+		ipv4Assigned := false
+		for _, addr := range iface.IpAddresses {
+			if addr.Address == "" {
+				// ignore interfaces without an address (eg. waiting for dhcp lease)
+				continue
+			}
+
+			libVirtAddr := libvirt.VirDomainIPAddress{}
+			libVirtAddr.Addr = addr.Address
+			libVirtAddr.Prefix = addr.Prefix
+			switch strings.ToLower(addr.Type) {
+			case "ipv4":
+				libVirtAddr.Type = libvirt.VIR_IP_ADDR_TYPE_IPV4
+				ipv4Assigned = true
+			case "ipv6":
+				libVirtAddr.Type = libvirt.VIR_IP_ADDR_TYPE_IPV6
+			default:
+				log.Printf("[ERROR] Cannot handle unknown address type %s", addr.Type)
+			}
+			libVirtIface.Addrs = append(libVirtIface.Addrs, libVirtAddr)
+		}
+		if len(libVirtIface.Addrs) > 0 && (ipv4Assigned || !wait4ipv4) {
+			interfaces = append(interfaces, libVirtIface)
+		}
+	}
+
+	log.Printf("[DEBUG] Interfaces obtained via qemu Agent: %+v", interfaces)
+
+	return interfaces
+}
diff --git a/libvirt/resource_libvirt_domain.go b/libvirt/resource_libvirt_domain.go
index e1fc7dc6..bbf0a110 100644
--- a/libvirt/resource_libvirt_domain.go
+++ b/libvirt/resource_libvirt_domain.go
@@ -692,7 +692,7 @@ func waitForNetworkAddresses(ifaces []defNetworkInterface, domain libvirt.VirDom
 	waitLoop:
 		for {
 			log.Printf("[DEBUG] waiting for network address for interface with hwaddr: '%s'\n", iface.Mac.Address)
-			ifacesWithAddr, err := domain.ListAllInterfaceAddresses(libvirt.VIR_DOMAIN_INTERFACE_ADDRESSES_SRC_LEASE)
+			ifacesWithAddr, err := getDomainInterfaces(&domain)
 			if err != nil {
 				return fmt.Errorf("Error retrieving interface addresses: %s", err)
 			}
@@ -749,3 +749,36 @@ func newDiskForCloudInit(virConn *libvirt.VirConnection, volumeKey string) (defD
 
 	return disk, nil
 }
+
+func getDomainInterfaces(domain *libvirt.VirDomain) ([]libvirt.VirDomainInterface, error) {
+
+	// get all the interfaces using the qemu-agent, this includes also
+	// interfaces that are not attached to networks managed by libvirt
+	// (eg. bridges, macvtap,...)
+	interfaces := getDomainInterfacesViaQemuAgent(domain, true)
+	if len(interfaces) > 0 {
+		// the agent will always return all the interfaces, both the
+		// ones managed by libvirt and the ones attached to bridge interfaces
+		// or macvtap. Hence it has the highest priority
+		return interfaces, nil
+	}
+
+	log.Print("[DEBUG] fetching networking interfaces using libvirt API")
+
+	// get all the interfaces attached to libvirt networks
+	interfaces, err := domain.ListAllInterfaceAddresses(libvirt.VIR_DOMAIN_INTERFACE_ADDRESSES_SRC_LEASE)
+	if err != nil {
+		switch err.(type) {
+		default:
+			return interfaces, fmt.Errorf("Error retrieving interface addresses: %s", err)
+		case libvirt.VirError:
+			virErr := err.(libvirt.VirError)
+			if virErr.Code != libvirt.VIR_ERR_OPERATION_INVALID || virErr.Domain != libvirt.VIR_FROM_QEMU {
+				return interfaces, fmt.Errorf("Error retrieving interface addresses: %s", err)
+			}
+		}
+	}
+	log.Printf("[DEBUG] Interfaces %+v", interfaces)
+
+	return interfaces, nil
+}