Added netboot package (#45)

Added netboot package

2 files changed, 224 insertions, 0 deletions

diff --git a/netboot/netboot.go b/netboot/netboot.go
new file mode 100644
index 0000000..6b10c3c
--- /dev/null
+++ b/netboot/netboot.go
@@ -0,0 +1,93 @@
+package netboot
+
+import (
+	"errors"
+	"fmt"
+	"log"
+	"time"
+
+	"github.com/insomniacslk/dhcp/dhcpv6"
+)
+
+// RequestNetbootv6 sends a netboot request via DHCPv6 and returns the exchanged packets. Additional modifiers
+// can be passed to manipulate both solicit and advertise packets.
+func RequestNetbootv6(ifname string, timeout time.Duration, retries int, modifiers ...dhcpv6.Modifier) ([]dhcpv6.DHCPv6, error) {
+	var (
+		conversation []dhcpv6.DHCPv6
+	)
+	modifiers = append(modifiers, dhcpv6.WithNetboot)
+	delay := 2 * time.Second
+	for i := 0; i <= retries; i++ {
+		log.Printf("sending request, attempt #%d", i+1)
+		solicit, err := dhcpv6.NewSolicitForInterface(ifname, modifiers...)
+		if err != nil {
+			return nil, fmt.Errorf("failed to create SOLICIT for interface %s: %v", ifname, err)
+		}
+
+		client := dhcpv6.NewClient()
+		client.ReadTimeout = timeout
+		conversation, err = client.Exchange(ifname, solicit, modifiers...)
+		if err != nil {
+			log.Printf("Client.Exchange failed: %v", err)
+			log.Printf("sleeping %v before retrying", delay)
+			if i >= retries {
+				// don't wait at the end of the last attempt
+				break
+			}
+			time.Sleep(delay)
+			// TODO add random splay
+			delay = delay * 2
+			continue
+		}
+		break
+	}
+	return conversation, nil
+}
+
+// ConversationToNetconf extracts network configuration and boot file URL from a
+// DHCPv6 4-way conversation and returns them, or an error if any.
+func ConversationToNetconf(conversation []dhcpv6.DHCPv6) (*NetConf, string, error) {
+	var reply dhcpv6.DHCPv6
+	for _, m := range conversation {
+		// look for a REPLY
+		if m.Type() == dhcpv6.REPLY {
+			reply = m
+			break
+		}
+	}
+	if reply == nil {
+		return nil, "", errors.New("no REPLY received")
+	}
+	netconf, err := GetNetConfFromPacketv6(reply.(*dhcpv6.DHCPv6Message))
+	if err != nil {
+		return nil, "", fmt.Errorf("cannot get netconf from packet: %v", err)
+	}
+	// look for boot file
+	var (
+		opt      dhcpv6.Option
+		bootfile string
+	)
+	opt = reply.GetOneOption(dhcpv6.OPT_BOOTFILE_URL)
+	if opt == nil {
+		log.Printf("no bootfile URL option found in REPLY, looking for it in ADVERTISE")
+		// as a fallback, look for bootfile URL in the advertise
+		var advertise dhcpv6.DHCPv6
+		for _, m := range conversation {
+			// look for an ADVERTISE
+			if m.Type() == dhcpv6.ADVERTISE {
+				advertise = m
+				break
+			}
+		}
+		if advertise == nil {
+			return nil, "", errors.New("no ADVERTISE found")
+		}
+		opt = advertise.GetOneOption(dhcpv6.OPT_BOOTFILE_URL)
+		if opt == nil {
+			return nil, "", errors.New("no bootfile URL option found in ADVERTISE")
+		}
+	}
+	obf := opt.(*dhcpv6.OptBootFileURL)
+	bootfile = string(obf.BootFileURL())
+	return netconf, bootfile, nil
+}
diff --git a/netboot/netconf.go b/netboot/netconf.go
new file mode 100644
index 0000000..4740b0f
--- /dev/null
+++ b/netboot/netconf.go
@@ -0,0 +1,131 @@
+package netboot
+
+import (
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"net"
+	"os"
+	"strings"
+	"time"
+
+	"github.com/insomniacslk/dhcp/dhcpv6"
+	"github.com/vishvananda/netlink"
+)
+
+// AddrConf holds a single IP address configuration for a NIC
+type AddrConf struct {
+	IPNet             net.IPNet
+	PreferredLifetime int
+	ValidLifetime     int
+}
+
+// NetConf holds multiple IP configuration for a NIC, and DNS configuration
+type NetConf struct {
+	Addresses     []AddrConf
+	DNSServers    []net.IP
+	DNSSearchList []string
+}
+
+// GetNetConfFromPacketv6 extracts network configuration information from a DHCPv6
+// Reply packet and returns a populated NetConf structure
+func GetNetConfFromPacketv6(d *dhcpv6.DHCPv6Message) (*NetConf, error) {
+	opt := d.GetOneOption(dhcpv6.OPTION_IA_NA)
+	if opt == nil {
+		return nil, errors.New("No option IA NA found")
+	}
+	netconf := NetConf{}
+	// get IP configuration
+	oiana := opt.(*dhcpv6.OptIANA)
+	iaaddrs := make([]*dhcpv6.OptIAAddress, 0)
+	for _, o := range oiana.Options() {
+		if o.Code() == dhcpv6.OPTION_IAADDR {
+			iaaddrs = append(iaaddrs, o.(*dhcpv6.OptIAAddress))
+		}
+	}
+	netmask := net.IPMask(net.ParseIP("ffff:ffff:ffff:ffff::"))
+	for _, iaaddr := range iaaddrs {
+		netconf.Addresses = append(netconf.Addresses, AddrConf{
+			IPNet: net.IPNet{
+				IP:   iaaddr.IPv6Addr(),
+				Mask: netmask,
+			},
+			PreferredLifetime: int(iaaddr.PreferredLifetime()),
+			ValidLifetime:     int(iaaddr.ValidLifetime()),
+		})
+	}
+	// get DNS configuration
+	opt = d.GetOneOption(dhcpv6.DNS_RECURSIVE_NAME_SERVER)
+	if opt == nil {
+		return nil, errors.New("No option DNS Recursive Name Servers found ")
+	}
+	odnsserv := opt.(*dhcpv6.OptDNSRecursiveNameServer)
+	// TODO should this be copied?
+	netconf.DNSServers = odnsserv.NameServers()
+
+	opt = d.GetOneOption(dhcpv6.DOMAIN_SEARCH_LIST)
+	if opt == nil {
+		return nil, errors.New("No option DNS Domain Search List found")
+	}
+	odomains := opt.(*dhcpv6.OptDomainSearchList)
+	// TODO should this be copied?
+	netconf.DNSSearchList = odomains.DomainSearchList()
+
+	return &netconf, nil
+}
+
+// IfUp brings up an interface by name, and waits for it to come up until a timeout expires
+func IfUp(ifname string, timeout time.Duration) (netlink.Link, error) {
+	start := time.Now()
+	for time.Since(start) < timeout {
+		iface, err := netlink.LinkByName(ifname)
+		if err != nil {
+			return nil, fmt.Errorf("cannot get interface %q by name: %v", ifname, err)
+		}
+
+		// if the interface is up, return
+		if iface.Attrs().OperState == netlink.OperUp {
+			// XXX despite the OperUp state, upon the first attempt I
+			// consistently get a "cannot assign requested address" error. This
+			// may be a bug in the netlink library. Need to investigate more.
+			time.Sleep(time.Second)
+			return iface, nil
+		}
+		// otherwise try to bring it up
+		if err := netlink.LinkSetUp(iface); err != nil {
+			return nil, fmt.Errorf("interface %q: %v can't make it up: %v", ifname, iface, err)
+		}
+	}
+
+	return nil, fmt.Errorf("timed out while waiting for %s to come up", ifname)
+
+}
+
+// ConfigureInterface configures a network interface with the configuration held by a
+// NetConf structure
+func ConfigureInterface(ifname string, netconf *NetConf) error {
+	iface, err := netlink.LinkByName(ifname)
+	if err != nil {
+		return fmt.Errorf("error getting interface information for %s: %v", ifname, err)
+	}
+	// configure interfaces
+	for _, addr := range netconf.Addresses {
+		dest := &netlink.Addr{
+			IPNet:       &addr.IPNet,
+			PreferedLft: addr.PreferredLifetime,
+			ValidLft:    addr.ValidLifetime,
+		}
+		if err := netlink.AddrReplace(iface, dest); err != nil {
+			if os.IsExist(err) {
+				return fmt.Errorf("cannot configure %s on %s,%d,%d: %v", ifname, addr.IPNet, addr.PreferredLifetime, addr.ValidLifetime, err)
+			}
+		}
+	}
+	// configure /etc/resolv.conf
+	resolvconf := ""
+	for _, ns := range netconf.DNSServers {
+		resolvconf += fmt.Sprintf("nameserver %s\n", ns)
+	}
+	resolvconf += fmt.Sprintf("search %s\n", strings.Join(netconf.DNSSearchList, " "))
+	return ioutil.WriteFile("/etc/resolv.conf", []byte(resolvconf), 0644)
+}