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// +build darwin
package bsdp
// Implements Apple's netboot protocol BSDP (Boot Service Discovery Protocol).
// Canonical implementation is defined here:
// http://opensource.apple.com/source/bootp/bootp-198.1/Documentation/BSDP.doc
import (
"errors"
"fmt"
"net"
"syscall"
"github.com/insomniacslk/dhcp/dhcpv4"
)
// MaxDHCPMessageSize is the size set in DHCP option 57 (DHCP Maximum Message Size).
// BSDP includes its own sub-option (12) to indicate to NetBoot servers that the
// client can support larger message sizes, and modern NetBoot servers will
// prefer this BSDP-specific option over the DHCP standard option.
const MaxDHCPMessageSize = 1500
// makeVendorClassIdentifier calls the sysctl syscall on macOS to get the
// platform model.
func makeVendorClassIdentifier() (string, error) {
// Fetch hardware model for class ID.
hwModel, err := syscall.Sysctl("hw.model")
if err != nil {
return "", err
}
return fmt.Sprintf("AAPLBSDPC/i386/%s", hwModel), nil
}
// ParseBootImageListFromAck parses the list of boot images presented in the
// ACK[LIST] packet and returns them as a list of BootImages.
func ParseBootImageListFromAck(ack dhcpv4.DHCPv4) ([]BootImage, error) {
var bootImages []BootImage
o := ack.GetOption(dhcpv4.OptionVendorSpecificInformation)
vendorOpt := o.(*OptVendorSpecificInformation)
for _, o := range vendorOpt.GetOptions(OptionBootImageList) {
bootImages = append(bootImages, o.(*OptBootImageList).BootImages...)
}
return bootImages, nil
}
func needsReplyPort(replyPort uint16) bool {
return replyPort != 0 && replyPort != dhcpv4.ClientPort
}
// NewInformListForInterface creates a new INFORM packet for interface ifname
// with configuration options specified by config.
func NewInformListForInterface(iface string, replyPort uint16) (*dhcpv4.DHCPv4, error) {
d, err := dhcpv4.NewInformForInterface(iface /* needsBroadcast = */, false)
if err != nil {
return nil, err
}
// Validate replyPort first
if needsReplyPort(replyPort) && replyPort >= 1024 {
return nil, errors.New("replyPort must be a privileged port")
}
// These are vendor-specific options used to pass along BSDP information.
vendorOpts := []dhcpv4.Option{
&OptMessageType{MessageTypeList},
&OptVersion{Version1_1},
}
if needsReplyPort(replyPort) {
vendorOpts = append(vendorOpts, &OptReplyPort{replyPort})
}
d.AddOption(&OptVendorSpecificInformation{vendorOpts})
d.AddOption(&dhcpv4.OptParameterRequestList{
[]dhcpv4.OptionCode{
dhcpv4.OptionVendorSpecificInformation,
dhcpv4.OptionClassIdentifier,
},
})
d.AddOption(&dhcpv4.OptMaximumDHCPMessageSize{Size: MaxDHCPMessageSize})
vendorClassID, err := makeVendorClassIdentifier()
if err != nil {
return nil, err
}
d.AddOption(&dhcpv4.OptClassIdentifier{vendorClassID})
d.AddOption(&dhcpv4.OptionGeneric{OptionCode: dhcpv4.OptionEnd})
return d, nil
}
// InformSelectForAck constructs an INFORM[SELECT] packet given an ACK to the
// previously-sent INFORM[LIST] with Config config.
func InformSelectForAck(ack dhcpv4.DHCPv4, replyPort uint16, selectedImage BootImage) (*dhcpv4.DHCPv4, error) {
d, err := dhcpv4.New()
if err != nil {
return nil, err
}
if needsReplyPort(replyPort) && replyPort >= 1024 {
return nil, errors.New("replyPort must be a privilegded port")
}
d.SetOpcode(dhcpv4.OpcodeBootRequest)
d.SetHwType(ack.HwType())
d.SetHwAddrLen(ack.HwAddrLen())
clientHwAddr := ack.ClientHwAddr()
d.SetClientHwAddr(clientHwAddr[:])
d.SetTransactionID(ack.TransactionID())
if ack.IsBroadcast() {
d.SetBroadcast()
} else {
d.SetUnicast()
}
// Data for OptionSelectedBootImageID
vendorOpts := []dhcpv4.Option{
&OptMessageType{MessageTypeSelect},
&OptVersion{Version1_1},
&OptSelectedBootImageID{selectedImage.ID},
}
// Find server IP address
var serverIP net.IP
// TODO replace this loop with `ack.GetOneOption(OptionBootImageList)`
for _, opt := range ack.Options() {
if opt.Code() == dhcpv4.OptionServerIdentifier {
serverIP = net.IP(opt.(*dhcpv4.OptionGeneric).Data)
}
}
if serverIP.To4() == nil {
return nil, fmt.Errorf("could not parse server identifier from ACK")
}
vendorOpts = append(vendorOpts, &dhcpv4.OptServerIdentifier{serverIP})
// Validate replyPort if requested.
if needsReplyPort(replyPort) {
vendorOpts = append(vendorOpts, &OptReplyPort{replyPort})
}
vendorClassID, err := makeVendorClassIdentifier()
if err != nil {
return nil, err
}
d.AddOption(&dhcpv4.OptClassIdentifier{vendorClassID})
d.AddOption(&dhcpv4.OptParameterRequestList{
[]dhcpv4.OptionCode{
dhcpv4.OptionSubnetMask,
dhcpv4.OptionRouter,
dhcpv4.OptionBootfileName,
dhcpv4.OptionVendorSpecificInformation,
dhcpv4.OptionClassIdentifier,
},
})
d.AddOption(&dhcpv4.OptMessageType{dhcpv4.MessageTypeInform})
d.AddOption(&OptVendorSpecificInformation{vendorOpts})
d.AddOption(&dhcpv4.OptionGeneric{OptionCode: dhcpv4.OptionEnd})
return d, nil
}
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