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package netboot
import (
"errors"
"fmt"
"log"
"time"
"github.com/insomniacslk/dhcp/dhcpv4"
"github.com/insomniacslk/dhcp/dhcpv4/client4"
"github.com/insomniacslk/dhcp/dhcpv6"
"github.com/insomniacslk/dhcp/dhcpv6/client6"
)
var sleeper = func(d time.Duration) {
time.Sleep(d)
}
// BootConf is a structure describes everything a host needs to know to boot over network
type BootConf struct {
// NetConf is the network configuration of the client
NetConf
// BootfileURL is "where is the image (kernel)".
// See RFC5970 section 3.1 for IPv6 and RFC2132 section 9.5 ("Bootfile name") for IPv4
BootfileURL string
// BootfileParam is "what arguments should we pass (cmdline)".
// See RFC5970 section 3.2 for IPv6.
BootfileParam []string
}
// 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
err error
)
modifiers = append(modifiers, dhcpv6.WithNetboot)
delay := 2 * time.Second
for i := 0; i <= retries; i++ {
log.Printf("sending request, attempt #%d", i+1)
client := client6.NewClient()
client.ReadTimeout = timeout
conversation, err = client.Exchange(ifname, modifiers...)
if err != nil {
log.Printf("Client.Exchange failed: %v", err)
if i >= retries {
// don't wait at the end of the last attempt
return nil, fmt.Errorf("netboot failed after %d attempts: %v", retries+1, err)
}
log.Printf("sleeping %v before retrying", delay)
sleeper(delay)
// TODO add random splay
delay = delay * 2
continue
}
break
}
return conversation, nil
}
// RequestNetbootv4 sends a netboot request via DHCPv4 and returns the exchanged packets. Additional modifiers
// can be passed to manipulate both the discover and offer packets.
func RequestNetbootv4(ifname string, timeout time.Duration, retries int, modifiers ...dhcpv4.Modifier) ([]*dhcpv4.DHCPv4, error) {
var (
conversation []*dhcpv4.DHCPv4
err error
)
delay := 2 * time.Second
modifiers = append(modifiers, dhcpv4.WithNetboot)
for i := 0; i <= retries; i++ {
log.Printf("sending request, attempt #%d", i+1)
client := client4.NewClient()
client.ReadTimeout = timeout
conversation, err = client.Exchange(ifname, 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
}
sleeper(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) (*BootConf, error) {
var advertise, reply, optionsSource *dhcpv6.Message
for _, m := range conversation {
switch m.Type() {
case dhcpv6.MessageTypeAdvertise:
advertise = m.(*dhcpv6.Message)
case dhcpv6.MessageTypeReply:
reply = m.(*dhcpv6.Message)
}
}
if reply == nil {
return nil, errors.New("no REPLY received")
}
bootconf := &BootConf{}
netconf, err := GetNetConfFromPacketv6(reply)
if err != nil {
return nil, fmt.Errorf("cannot get netconf from packet: %v", err)
}
bootconf.NetConf = *netconf
if u := reply.Options.BootFileURL(); len(u) > 0 {
bootconf.BootfileURL = u
optionsSource = reply
} else {
log.Printf("no bootfile URL option found in REPLY, fallback to ADVERTISE's value")
if u := advertise.Options.BootFileURL(); len(u) > 0 {
bootconf.BootfileURL = u
optionsSource = advertise
}
}
if len(bootconf.BootfileURL) == 0 {
return nil, errors.New("no bootfile URL option found")
}
if bootfileParamOption := optionsSource.GetOneOption(dhcpv6.OptionBootfileParam); bootfileParamOption != nil {
bootconf.BootfileParam = bootfileParamOption.(dhcpv6.OptBootFileParam)
}
return bootconf, nil
}
// ConversationToNetconfv4 extracts network configuration and boot file URL from a
// DHCPv4 4-way conversation and returns them, or an error if any.
func ConversationToNetconfv4(conversation []*dhcpv4.DHCPv4) (*BootConf, error) {
var reply *dhcpv4.DHCPv4
for _, m := range conversation {
// look for a BootReply packet of type Offer containing the bootfile URL.
// Normally both packets with Message Type OFFER or ACK do contain
// the bootfile URL.
if m.OpCode == dhcpv4.OpcodeBootReply && m.MessageType() == dhcpv4.MessageTypeOffer {
reply = m
break
}
}
if reply == nil {
return nil, errors.New("no OFFER with valid bootfile URL received")
}
bootconf := &BootConf{}
netconf, err := GetNetConfFromPacketv4(reply)
if err != nil {
return nil, fmt.Errorf("could not get netconf: %v", err)
}
bootconf.NetConf = *netconf
bootconf.BootfileURL = reply.BootFileName
// TODO: should we support bootfile parameters here somehow? (see netconf.BootfileParam)
return bootconf, nil
}
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