mirror of
https://github.com/AdguardTeam/AdGuardHome.git
synced 2024-11-25 14:35:48 +03:00
242 lines
6.9 KiB
Go
242 lines
6.9 KiB
Go
//go:build darwin || freebsd || linux || openbsd
|
|
|
|
package dhcpd
|
|
|
|
import (
|
|
"fmt"
|
|
"net"
|
|
"os"
|
|
"time"
|
|
|
|
"github.com/AdguardTeam/golibs/errors"
|
|
"github.com/AdguardTeam/golibs/netutil"
|
|
"github.com/google/gopacket"
|
|
"github.com/google/gopacket/layers"
|
|
"github.com/insomniacslk/dhcp/dhcpv4"
|
|
"github.com/insomniacslk/dhcp/dhcpv4/server4"
|
|
"github.com/mdlayher/ethernet"
|
|
|
|
//lint:ignore SA1019 See the TODO in go.mod.
|
|
"github.com/mdlayher/raw"
|
|
)
|
|
|
|
// dhcpUnicastAddr is the combination of MAC and IP addresses for responding to
|
|
// the unconfigured host.
|
|
type dhcpUnicastAddr struct {
|
|
// raw.Addr is embedded here to make *dhcpUcastAddr a net.Addr without
|
|
// actually implementing all methods. It also contains the client's
|
|
// hardware address.
|
|
raw.Addr
|
|
|
|
// yiaddr is an IP address just allocated by server for the host.
|
|
yiaddr net.IP
|
|
}
|
|
|
|
// dhcpConn is the net.PacketConn capable of handling both net.UDPAddr and
|
|
// net.HardwareAddr.
|
|
type dhcpConn struct {
|
|
// udpConn is the connection for UDP addresses.
|
|
udpConn net.PacketConn
|
|
// bcastIP is the broadcast address specific for the configured
|
|
// interface's subnet.
|
|
bcastIP net.IP
|
|
|
|
// rawConn is the connection for MAC addresses.
|
|
rawConn net.PacketConn
|
|
// srcMAC is the hardware address of the configured network interface.
|
|
srcMAC net.HardwareAddr
|
|
// srcIP is the IP address of the configured network interface.
|
|
srcIP net.IP
|
|
}
|
|
|
|
// newDHCPConn creates the special connection for DHCP server.
|
|
func (s *v4Server) newDHCPConn(iface *net.Interface) (c net.PacketConn, err error) {
|
|
var ucast net.PacketConn
|
|
if ucast, err = raw.ListenPacket(iface, uint16(ethernet.EtherTypeIPv4), nil); err != nil {
|
|
return nil, fmt.Errorf("creating raw udp connection: %w", err)
|
|
}
|
|
|
|
// Create the UDP connection.
|
|
var bcast net.PacketConn
|
|
bcast, err = server4.NewIPv4UDPConn(iface.Name, &net.UDPAddr{
|
|
// TODO(e.burkov): Listening on zeroes makes the server handle
|
|
// requests from all the interfaces. Inspect the ways to
|
|
// specify the interface-specific listening addresses.
|
|
//
|
|
// See https://github.com/AdguardTeam/AdGuardHome/issues/3539.
|
|
IP: net.IP{0, 0, 0, 0},
|
|
Port: dhcpv4.ServerPort,
|
|
})
|
|
if err != nil {
|
|
return nil, fmt.Errorf("creating ipv4 udp connection: %w", err)
|
|
}
|
|
|
|
return &dhcpConn{
|
|
udpConn: bcast,
|
|
bcastIP: s.conf.broadcastIP.AsSlice(),
|
|
rawConn: ucast,
|
|
srcMAC: iface.HardwareAddr,
|
|
srcIP: s.conf.dnsIPAddrs[0].AsSlice(),
|
|
}, nil
|
|
}
|
|
|
|
// wrapErrs is a helper to wrap the errors from two independent underlying
|
|
// connections.
|
|
func (*dhcpConn) wrapErrs(action string, udpConnErr, rawConnErr error) (err error) {
|
|
switch {
|
|
case udpConnErr != nil && rawConnErr != nil:
|
|
return errors.List(fmt.Sprintf("%s both connections", action), udpConnErr, rawConnErr)
|
|
case udpConnErr != nil:
|
|
return fmt.Errorf("%s udp connection: %w", action, udpConnErr)
|
|
case rawConnErr != nil:
|
|
return fmt.Errorf("%s raw connection: %w", action, rawConnErr)
|
|
default:
|
|
return nil
|
|
}
|
|
}
|
|
|
|
// WriteTo implements net.PacketConn for *dhcpConn. It selects the underlying
|
|
// connection to write to based on the type of addr.
|
|
func (c *dhcpConn) WriteTo(p []byte, addr net.Addr) (n int, err error) {
|
|
switch addr := addr.(type) {
|
|
case *dhcpUnicastAddr:
|
|
// Unicast the message to the client's MAC address. Use the raw
|
|
// connection.
|
|
//
|
|
// Note: unicasting is performed on the only network interface
|
|
// that is configured. For now it may be not what users expect
|
|
// so additionally broadcast the message via UDP connection.
|
|
//
|
|
// See https://github.com/AdguardTeam/AdGuardHome/issues/3539.
|
|
var rerr error
|
|
n, rerr = c.unicast(p, addr)
|
|
|
|
_, uerr := c.broadcast(p, &net.UDPAddr{
|
|
IP: netutil.IPv4bcast(),
|
|
Port: dhcpv4.ClientPort,
|
|
})
|
|
|
|
return n, c.wrapErrs("writing to", uerr, rerr)
|
|
case *net.UDPAddr:
|
|
if addr.IP.Equal(net.IPv4bcast) {
|
|
// Broadcast the message for the client which supports
|
|
// it. Use the UDP connection.
|
|
return c.broadcast(p, addr)
|
|
}
|
|
|
|
// Unicast the message to the client's IP address. Use the UDP
|
|
// connection.
|
|
return c.udpConn.WriteTo(p, addr)
|
|
default:
|
|
return 0, fmt.Errorf("addr has an unexpected type %T", addr)
|
|
}
|
|
}
|
|
|
|
// ReadFrom implements net.PacketConn for *dhcpConn.
|
|
func (c *dhcpConn) ReadFrom(p []byte) (n int, addr net.Addr, err error) {
|
|
return c.udpConn.ReadFrom(p)
|
|
}
|
|
|
|
// unicast wraps respData with required frames and writes it to the peer.
|
|
func (c *dhcpConn) unicast(respData []byte, peer *dhcpUnicastAddr) (n int, err error) {
|
|
var data []byte
|
|
data, err = c.buildEtherPkt(respData, peer)
|
|
if err != nil {
|
|
return 0, err
|
|
}
|
|
|
|
return c.rawConn.WriteTo(data, &peer.Addr)
|
|
}
|
|
|
|
// Close implements net.PacketConn for *dhcpConn.
|
|
func (c *dhcpConn) Close() (err error) {
|
|
rerr := c.rawConn.Close()
|
|
if errors.Is(rerr, os.ErrClosed) {
|
|
// Ignore the error since the actual file is closed already.
|
|
rerr = nil
|
|
}
|
|
|
|
return c.wrapErrs("closing", c.udpConn.Close(), rerr)
|
|
}
|
|
|
|
// LocalAddr implements net.PacketConn for *dhcpConn.
|
|
func (c *dhcpConn) LocalAddr() (a net.Addr) {
|
|
return c.udpConn.LocalAddr()
|
|
}
|
|
|
|
// SetDeadline implements net.PacketConn for *dhcpConn.
|
|
func (c *dhcpConn) SetDeadline(t time.Time) (err error) {
|
|
return c.wrapErrs("setting deadline on", c.udpConn.SetDeadline(t), c.rawConn.SetDeadline(t))
|
|
}
|
|
|
|
// SetReadDeadline implements net.PacketConn for *dhcpConn.
|
|
func (c *dhcpConn) SetReadDeadline(t time.Time) error {
|
|
return c.wrapErrs(
|
|
"setting reading deadline on",
|
|
c.udpConn.SetReadDeadline(t),
|
|
c.rawConn.SetReadDeadline(t),
|
|
)
|
|
}
|
|
|
|
// SetWriteDeadline implements net.PacketConn for *dhcpConn.
|
|
func (c *dhcpConn) SetWriteDeadline(t time.Time) error {
|
|
return c.wrapErrs(
|
|
"setting writing deadline on",
|
|
c.udpConn.SetWriteDeadline(t),
|
|
c.rawConn.SetWriteDeadline(t),
|
|
)
|
|
}
|
|
|
|
// ipv4DefaultTTL is the default Time to Live value in seconds as recommended by
|
|
// RFC-1700.
|
|
//
|
|
// See https://datatracker.ietf.org/doc/html/rfc1700.
|
|
const ipv4DefaultTTL = 64
|
|
|
|
// buildEtherPkt wraps the payload with IPv4, UDP and Ethernet frames.
|
|
// Validation of the payload is a caller's responsibility.
|
|
func (c *dhcpConn) buildEtherPkt(payload []byte, peer *dhcpUnicastAddr) (pkt []byte, err error) {
|
|
udpLayer := &layers.UDP{
|
|
SrcPort: dhcpv4.ServerPort,
|
|
DstPort: dhcpv4.ClientPort,
|
|
}
|
|
|
|
ipv4Layer := &layers.IPv4{
|
|
Version: uint8(layers.IPProtocolIPv4),
|
|
Flags: layers.IPv4DontFragment,
|
|
TTL: ipv4DefaultTTL,
|
|
Protocol: layers.IPProtocolUDP,
|
|
SrcIP: c.srcIP,
|
|
DstIP: peer.yiaddr,
|
|
}
|
|
|
|
// Ignore the error since it's only returned for invalid network layer's
|
|
// type.
|
|
_ = udpLayer.SetNetworkLayerForChecksum(ipv4Layer)
|
|
|
|
ethLayer := &layers.Ethernet{
|
|
SrcMAC: c.srcMAC,
|
|
DstMAC: peer.HardwareAddr,
|
|
EthernetType: layers.EthernetTypeIPv4,
|
|
}
|
|
|
|
buf := gopacket.NewSerializeBuffer()
|
|
setts := gopacket.SerializeOptions{
|
|
FixLengths: true,
|
|
ComputeChecksums: true,
|
|
}
|
|
|
|
err = gopacket.SerializeLayers(
|
|
buf,
|
|
setts,
|
|
ethLayer,
|
|
ipv4Layer,
|
|
udpLayer,
|
|
gopacket.Payload(payload),
|
|
)
|
|
if err != nil {
|
|
return nil, fmt.Errorf("serializing layers: %w", err)
|
|
}
|
|
|
|
return buf.Bytes(), nil
|
|
}
|