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// Copyright 2018-present the CoreDHCP Authors. All rights reserved
// This source code is licensed under the MIT license found in the
// LICENSE file in the root directory of this source tree.
package server
import (
"errors"
"fmt"
"net"
"sync"
"golang.org/x/net/ipv4"
"golang.org/x/net/ipv6"
"github.com/insomniacslk/dhcp/dhcpv4"
"github.com/insomniacslk/dhcp/dhcpv6"
)
// HandleMsg6 runs for every received DHCPv6 packet. It will run every
// registered handler in sequence, and reply with the resulting response.
// It will not reply if the resulting response is `nil`.
func (l *listener6) HandleMsg6(buf []byte, oob *ipv6.ControlMessage, peer *net.UDPAddr) {
d, err := dhcpv6.FromBytes(buf)
bufpool.Put(&buf)
if err != nil {
log.Printf("Error parsing DHCPv6 request: %v", err)
return
}
// decapsulate the relay message
msg, err := d.GetInnerMessage()
if err != nil {
log.Warningf("DHCPv6: cannot get inner message: %v", err)
return
}
// Create a suitable basic response packet
var resp dhcpv6.DHCPv6
switch msg.Type() {
case dhcpv6.MessageTypeSolicit:
if msg.GetOneOption(dhcpv6.OptionRapidCommit) != nil {
resp, err = dhcpv6.NewReplyFromMessage(msg)
} else {
resp, err = dhcpv6.NewAdvertiseFromSolicit(msg)
}
case dhcpv6.MessageTypeRequest, dhcpv6.MessageTypeConfirm, dhcpv6.MessageTypeRenew,
dhcpv6.MessageTypeRebind, dhcpv6.MessageTypeRelease, dhcpv6.MessageTypeInformationRequest:
resp, err = dhcpv6.NewReplyFromMessage(msg)
default:
err = fmt.Errorf("MainHandler6: message type %d not supported", msg.Type())
}
if err != nil {
log.Printf("MainHandler6: NewReplyFromDHCPv6Message failed: %v", err)
return
}
var stop bool
for _, handler := range l.handlers {
resp, stop = handler(d, resp)
if stop {
break
}
}
if resp == nil {
log.Print("MainHandler6: dropping request because response is nil")
return
}
// if the request was relayed, re-encapsulate the response
if d.IsRelay() {
if rmsg, ok := resp.(*dhcpv6.Message); !ok {
log.Warningf("DHCPv6: response is a relayed message, not reencapsulating")
} else {
tmp, err := dhcpv6.NewRelayReplFromRelayForw(d.(*dhcpv6.RelayMessage), rmsg)
if err != nil {
log.Warningf("DHCPv6: cannot create relay-repl from relay-forw: %v", err)
return
}
resp = tmp
}
}
var woob *ipv6.ControlMessage
if peer.IP.IsLinkLocalUnicast() {
// LL need to be directed to the correct interface. Globally reachable
// addresses should use the default route, in case of asymetric routing.
switch {
case l.Interface.Index != 0:
woob = &ipv6.ControlMessage{IfIndex: l.Interface.Index}
case oob != nil && oob.IfIndex != 0:
woob = &ipv6.ControlMessage{IfIndex: oob.IfIndex}
default:
log.Errorf("HandleMsg6: Did not receive interface information")
}
}
if _, err := l.WriteTo(resp.ToBytes(), woob, peer); err != nil {
log.Printf("MainHandler6: conn.Write to %v failed: %v", peer, err)
}
}
func (l *listener4) HandleMsg4(buf []byte, oob *ipv4.ControlMessage, _peer net.Addr) {
var (
resp, tmp *dhcpv4.DHCPv4
err error
stop bool
)
req, err := dhcpv4.FromBytes(buf)
bufpool.Put(&buf)
if err != nil {
log.Printf("Error parsing DHCPv4 request: %v", err)
return
}
if req.OpCode != dhcpv4.OpcodeBootRequest {
log.Printf("MainHandler4: unsupported opcode %d. Only BootRequest (%d) is supported", req.OpCode, dhcpv4.OpcodeBootRequest)
return
}
tmp, err = dhcpv4.NewReplyFromRequest(req)
if err != nil {
log.Printf("MainHandler4: failed to build reply: %v", err)
return
}
switch mt := req.MessageType(); mt {
case dhcpv4.MessageTypeDiscover:
tmp.UpdateOption(dhcpv4.OptMessageType(dhcpv4.MessageTypeOffer))
case dhcpv4.MessageTypeRequest:
tmp.UpdateOption(dhcpv4.OptMessageType(dhcpv4.MessageTypeAck))
default:
log.Printf("plugins/server: Unhandled message type: %v", mt)
return
}
resp = tmp
for _, handler := range l.handlers {
resp, stop = handler(req, resp)
if stop {
break
}
}
if resp != nil {
useEthernet := false
var peer *net.UDPAddr
if !req.GatewayIPAddr.IsUnspecified() {
// TODO: make RFC8357 compliant
peer = &net.UDPAddr{IP: req.GatewayIPAddr, Port: dhcpv4.ServerPort}
} else if resp.MessageType() == dhcpv4.MessageTypeNak {
peer = &net.UDPAddr{IP: net.IPv4bcast, Port: dhcpv4.ClientPort}
} else if !req.ClientIPAddr.IsUnspecified() {
peer = &net.UDPAddr{IP: req.ClientIPAddr, Port: dhcpv4.ClientPort}
} else if req.IsBroadcast() {
peer = &net.UDPAddr{IP: net.IPv4bcast, Port: dhcpv4.ClientPort}
} else {
//sends a layer2 frame so that we can define the destination MAC address
peer = &net.UDPAddr{IP: resp.YourIPAddr, Port: dhcpv4.ClientPort}
useEthernet = true
}
var woob *ipv4.ControlMessage
if peer.IP.Equal(net.IPv4bcast) || peer.IP.IsLinkLocalUnicast() || useEthernet {
// Direct broadcasts, link-local and layer2 unicasts to the interface the request was
// received on. Other packets should use the normal routing table in
// case of asymetric routing
switch {
case l.Interface.Index != 0:
woob = &ipv4.ControlMessage{IfIndex: l.Interface.Index}
case oob != nil && oob.IfIndex != 0:
woob = &ipv4.ControlMessage{IfIndex: oob.IfIndex}
default:
log.Errorf("HandleMsg4: Did not receive interface information")
}
}
if useEthernet {
intf, err := net.InterfaceByIndex(woob.IfIndex)
if err != nil {
log.Errorf("MainHandler4: Can not get Interface for index %d %v", woob.IfIndex, err)
return
}
err = sendEthernet(*intf, resp)
if err != nil {
log.Errorf("MainHandler4: Cannot send Ethernet packet: %v", err)
}
} else {
if _, err := l.WriteTo(resp.ToBytes(), woob, peer); err != nil {
log.Errorf("MainHandler4: conn.Write to %v failed: %v", peer, err)
}
}
} else {
log.Print("MainHandler4: dropping request because response is nil")
}
}
// XXX: performance-wise, Pool may or may not be good (see https://github.com/golang/go/issues/23199)
// Interface is good for what we want. Maybe "just" trust the GC and we'll be fine ?
var bufpool = sync.Pool{New: func() interface{} { r := make([]byte, MaxDatagram); return &r }}
// MaxDatagram is the maximum length of message that can be received.
const MaxDatagram = 1 << 16
// XXX: investigate using RecvMsgs to batch messages and reduce syscalls
// Serve6 handles datagrams received on conn and passes them to the pluginchain
func (l *listener6) Serve() error {
log.Printf("Listen %s", l.LocalAddr())
for {
b := *bufpool.Get().(*[]byte)
b = b[:MaxDatagram] //Reslice to max capacity in case the buffer in pool was resliced smaller
n, oob, peer, err := l.ReadFrom(b)
if errors.Is(err, net.ErrClosed) {
// Server is quitting
return nil
} else if err != nil {
log.Printf("Error reading from connection: %v", err)
return err
}
go l.HandleMsg6(b[:n], oob, peer.(*net.UDPAddr))
}
}
// Serve6 handles datagrams received on conn and passes them to the pluginchain
func (l *listener4) Serve() error {
log.Printf("Listen %s", l.LocalAddr())
for {
b := *bufpool.Get().(*[]byte)
b = b[:MaxDatagram] //Reslice to max capacity in case the buffer in pool was resliced smaller
n, oob, peer, err := l.ReadFrom(b)
if errors.Is(err, net.ErrClosed) {
// Server is quitting
return nil
} else if err != nil {
log.Printf("Error reading from connection: %v", err)
return err
}
go l.HandleMsg4(b[:n], oob, peer.(*net.UDPAddr))
}
}
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