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pxe.go
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pxe.go
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// Copyright 2016 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package pixiecore
import (
"errors"
"fmt"
"net"
"go.universe.tf/netboot/dhcp4"
"golang.org/x/net/ipv4"
)
// TODO: this may actually be the BINL protocol, a
// Microsoft-proprietary fork of PXE that is more universally
// supported in UEFI than PXE itself. Need to comb through the
// TianoCore EDK2 source code to figure out if what this is doing is
// actually BINL, and if so rename everything.
func (s *Server) servePXE(conn net.PacketConn) error {
buf := make([]byte, 1024)
l := ipv4.NewPacketConn(conn)
if err := l.SetControlMessage(ipv4.FlagInterface, true); err != nil {
return fmt.Errorf("Couldn't get interface metadata on PXE port: %s", err)
}
for {
n, msg, addr, err := l.ReadFrom(buf)
if err != nil {
return fmt.Errorf("Receiving packet: %s", err)
}
pkt, err := dhcp4.Unmarshal(buf[:n])
if err != nil {
s.debug("PXE", "Packet from %s is not a DHCP packet: %s", addr, err)
continue
}
if err = s.isBootDHCP(pkt); err != nil {
s.debug("PXE", "Ignoring packet from %s (%s): %s", pkt.HardwareAddr, addr, err)
}
fwtype, err := s.validatePXE(pkt)
if err != nil {
s.log("PXE", "Unusable packet from %s (%s): %s", pkt.HardwareAddr, addr, err)
continue
}
intf, err := net.InterfaceByIndex(msg.IfIndex)
if err != nil {
s.log("PXE", "Couldn't get information about local network interface %d: %s", msg.IfIndex, err)
continue
}
serverIP, err := interfaceIP(intf)
if err != nil {
s.log("PXE", "Want to boot %s (%s) on %s, but couldn't get a source address: %s", pkt.HardwareAddr, addr, intf.Name, err)
continue
}
s.machineEvent(pkt.HardwareAddr, machineStatePXE, "Sent PXE configuration")
resp, err := s.offerPXE(pkt, serverIP, fwtype)
if err != nil {
s.log("PXE", "Failed to construct PXE offer for %s (%s): %s", pkt.HardwareAddr, addr, err)
continue
}
bs, err := resp.Marshal()
if err != nil {
s.log("PXE", "Failed to marshal PXE offer for %s (%s): %s", pkt.HardwareAddr, addr, err)
continue
}
if _, err := l.WriteTo(bs, &ipv4.ControlMessage{
IfIndex: msg.IfIndex,
}, addr); err != nil {
s.log("PXE", "Failed to send PXE response to %s (%s): %s", pkt.HardwareAddr, addr, err)
}
}
}
func (s *Server) validatePXE(pkt *dhcp4.Packet) (fwtype Firmware, err error) {
fwt, err := pkt.Options.Uint16(93)
if err != nil {
return 0, fmt.Errorf("malformed DHCP option 93 (required for PXE): %s", err)
}
switch fwt {
case 6:
fwtype = FirmwareEFI32
case 7:
fwtype = FirmwareEFI64
case 9:
fwtype = FirmwareEFIBC
default:
return 0, fmt.Errorf("unsupported client firmware type '%d'", fwt)
}
if s.Ipxe[fwtype] == nil {
return 0, fmt.Errorf("unsupported client firmware type '%d'", fwt)
}
guid := pkt.Options[97]
switch len(guid) {
case 0:
// Accept missing GUIDs even though it's a spec violation,
// same as in dhcp.go.
case 17:
if guid[0] != 0 {
return 0, errors.New("malformed client GUID (option 97), leading byte must be zero")
}
default:
return 0, errors.New("malformed client GUID (option 97), wrong size")
}
return fwtype, nil
}
func (s *Server) offerPXE(pkt *dhcp4.Packet, serverIP net.IP, fwtype Firmware) (resp *dhcp4.Packet, err error) {
resp = &dhcp4.Packet{
Type: dhcp4.MsgAck,
TransactionID: pkt.TransactionID,
HardwareAddr: pkt.HardwareAddr,
ClientAddr: pkt.ClientAddr,
RelayAddr: pkt.RelayAddr,
ServerAddr: serverIP,
BootServerName: serverIP.String(),
BootFilename: fmt.Sprintf("%s/%d", pkt.HardwareAddr, fwtype),
Options: dhcp4.Options{
dhcp4.OptServerIdentifier: serverIP,
dhcp4.OptVendorIdentifier: []byte("PXEClient"),
},
}
if pkt.Options[97] != nil {
resp.Options[97] = pkt.Options[97]
}
return resp, nil
}