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fix: Fix connection interface binding, JSON lease DB

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This commit is contained in:
Adrian Rumpold
2024-01-09 12:23:41 +01:00
parent cb8b6c03b6
commit ac7185bfb5
8 changed files with 277 additions and 75 deletions
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70
cmd/conn_unix.go Normal file
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@@ -0,0 +1,70 @@
// Copied with modifications from https://github.com/insomniacslk/dhcp/blob/master/dhcpv4/server4/conn_unix.go (under BSD-3-Clause license)
//go:build !windows
package cmd
import (
"errors"
"fmt"
"net"
"os"
"github.com/adrianokf/go-dhcp/pkg/types"
"golang.org/x/sys/unix"
)
// NewIPv4UDPConn returns a UDP connection bound to both the interface and port
// given based on a IPv4 DGRAM socket. The UDP connection allows broadcasting.
//
// The interface must already be configured.
func NewIPv4UDPConn(iface string, addr *net.UDPAddr) (*net.UDPConn, error) {
fd, err := unix.Socket(unix.AF_INET, unix.SOCK_DGRAM, unix.IPPROTO_UDP)
if err != nil {
return nil, fmt.Errorf("cannot get a UDP socket: %v", err)
}
f := os.NewFile(uintptr(fd), "")
// net.FilePacketConn dups the FD, so we have to close this in any case.
defer f.Close()
// Allow broadcasting.
if err := unix.SetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_BROADCAST, 1); err != nil {
return nil, fmt.Errorf("cannot set broadcasting on socket: %v", err)
}
// Allow reusing the addr to aid debugging.
if err := unix.SetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_REUSEADDR, 1); err != nil {
return nil, fmt.Errorf("cannot set reuseaddr on socket: %v", err)
}
// Allow reusing the port to aid debugging and testing.
if err := unix.SetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_REUSEPORT, 1); err != nil {
return nil, fmt.Errorf("cannot set reuseport on socket: %v", err)
}
if len(iface) != 0 {
// Bind directly to the interface.
if err := unix.BindToDevice(fd, iface); err != nil {
return nil, fmt.Errorf("cannot bind to interface %s: %v", iface, err)
}
}
if addr == nil {
addr = &net.UDPAddr{Port: types.ServerPort}
}
// Bind to the port.
saddr := unix.SockaddrInet4{Port: addr.Port}
if addr.IP != nil && addr.IP.To4() == nil {
return nil, fmt.Errorf("wrong address family (expected v4) for %s", addr.IP)
}
copy(saddr.Addr[:], addr.IP.To4())
if err := unix.Bind(fd, &saddr); err != nil {
return nil, fmt.Errorf("cannot bind to port %d: %v", addr.Port, err)
}
conn, err := net.FilePacketConn(f)
if err != nil {
return nil, err
}
udpconn, ok := conn.(*net.UDPConn)
if !ok {
return nil, errors.New("BUG: incorrect socket type, expected UDP")
}
return udpconn, nil
}

101
cmd/root.go
View File

@@ -11,20 +11,22 @@ import (
"github.com/adrianokf/go-dhcp/pkg/leases"
"github.com/adrianokf/go-dhcp/pkg/messages"
"github.com/adrianokf/go-dhcp/pkg/types"
"github.com/adrianokf/go-dhcp/pkg/util"
"github.com/spf13/cobra"
"go.uber.org/zap"
)
var listenInterface string
var manager = leases.NewLeaseManager()
type Handler struct {
conn *net.UDPConn
leaseManager leases.LeaseManager
}
var magic = [4]byte{0x63, 0x82, 0x53, 0x63}
func parseOptions(data []byte) messages.Options {
s := zap.S()
i := 0
options := make(messages.Options)
out:
@@ -32,11 +34,11 @@ out:
code := messages.OptionCode(data[i])
switch code {
case messages.OptionEnd:
s.Debug("Found END option at offset ", i)
zap.S().Debug("Found END option at offset ", i)
break out
case messages.OptionPad:
s.Debug("Found padding option at offset ", i)
zap.S().Debug("Found padding option at offset ", i)
i += 1
continue
}
@@ -44,12 +46,12 @@ out:
size := int(data[i+1])
payload := data[i+2 : i+2+size]
s.Debugf("code=%d, size=%d, payload=%x", code, size, payload)
zap.S().Debugf("code=%d, size=%d, payload=%x", code, size, payload)
options[code] = messages.Option{Code: code, Data: data[i+1 : i+2+size]}
i += size + 2
}
s.Debugf("Parsed options: ", options)
zap.S().Debugf("Parsed options: ", options)
return options
}
@@ -108,7 +110,18 @@ func prepareAck(request messages.DhcpMessage, lease leases.Lease) messages.DhcpM
// sendMessage transmits a DHCP message with options via a UDP connection
// The end option (code 255) is automatically appended and does not need to
// be passed explicitly.
func sendMessage(conn *net.UDPConn, message messages.DhcpMessage, options []messages.Option) error {
func (h Handler) sendMessage(remote *net.UDPAddr, message messages.DhcpMessage, options []messages.Option) error {
// Send packets for 0.0.0.0 to broadcast address (255.255.255.255) instead
var destination *net.UDPAddr
if remote.IP.IsUnspecified() {
destination = &net.UDPAddr{
IP: net.ParseIP("255.255.255.255"),
Port: types.ClientPort,
}
} else {
destination = remote
}
buf := make([]byte, 0)
w := bytes.NewBuffer(buf)
err := binary.Write(w, binary.BigEndian, message)
@@ -127,16 +140,16 @@ func sendMessage(conn *net.UDPConn, message messages.DhcpMessage, options []mess
}
}
// Automatically add END option, so the caller doesn't
// need to specificy it for every invocation.
// Automatically add END option, so the caller doesn't need to specify it for every invocation.
err = w.WriteByte(byte(messages.OptionEnd))
if err != nil {
return err
}
msg := w.Bytes()
zap.S().Debug("Msg", msg)
_, err = conn.Write(msg)
zap.S().Debugf("Local addr: %s, remote addr: %s ", h.conn.LocalAddr(), destination)
zap.S().Debug("Msg data: ", msg)
_, err = h.conn.WriteToUDP(msg, destination)
if err != nil {
return err
}
@@ -144,21 +157,14 @@ func sendMessage(conn *net.UDPConn, message messages.DhcpMessage, options []mess
return nil
}
func handleOffer(dhcp messages.DhcpMessage, remote *net.UDPAddr) error {
func (h Handler) sendOffer(dhcp messages.DhcpMessage, remote *net.UDPAddr) error {
s := zap.S()
lease, err := manager.Request(dhcp.Xid, dhcp.Chaddr)
lease, err := h.leaseManager.Request(dhcp.Xid, dhcp.Chaddr)
if err != nil {
panic(err)
}
offer := prepareOffer(dhcp, *lease)
localAddr, _ := net.ResolveUDPAddr("udp", "172.17.0.1:68")
clientAddr, _ := net.ResolveUDPAddr("udp", "255.255.255.255:68")
conn, err := net.DialUDP("udp", localAddr, clientAddr)
if err != nil {
panic(err)
}
defer conn.Close()
s.Info("Sending DHCPOFFER...")
options := []messages.Option{
@@ -167,14 +173,14 @@ func handleOffer(dhcp messages.DhcpMessage, remote *net.UDPAddr) error {
Data: []byte{1, byte(messages.MessageTypeOffer)},
},
}
sendMessage(conn, offer, options)
h.sendMessage(remote, offer, options)
return nil
}
func handleAck(dhcp messages.DhcpMessage, remote *net.UDPAddr) error {
func (h Handler) sendAck(dhcp messages.DhcpMessage, remote *net.UDPAddr) error {
s := zap.S()
lease, err := manager.Lookup(dhcp.Xid)
lease, err := h.leaseManager.Lookup(dhcp.Xid)
if err != nil {
panic(err)
}
@@ -188,31 +194,23 @@ func handleAck(dhcp messages.DhcpMessage, remote *net.UDPAddr) error {
},
{
Code: messages.OptionIPAddressLeaseTime,
Data: append([]byte{4}, u32tob(3600)...),
Data: append([]byte{4}, util.U32ToByte(3600)...),
},
}
s.Debug("Options: ", options)
localAddr, _ := net.ResolveUDPAddr("udp", "172.17.0.1:68")
clientAddr, _ := net.ResolveUDPAddr("udp", "255.255.255.255:68")
conn, err := net.DialUDP("udp", localAddr, clientAddr)
if err != nil {
panic(err)
}
defer conn.Close()
s.Info("Sending DHCPACK")
sendMessage(conn, ack, options)
h.sendMessage(remote, ack, options)
lease, err = manager.Request(dhcp.Xid, dhcp.Chaddr)
lease, err = h.leaseManager.Request(dhcp.Xid, dhcp.Chaddr)
if err != nil {
return err
}
s.Debug("Found lease", lease)
s.Debug("Found lease: ", lease)
return nil
}
func handleMsg(data []byte, remote *net.UDPAddr) {
func (h Handler) handleMsg(data []byte, remote *net.UDPAddr) {
s := zap.S()
s.Debugf("Connection from client %v", remote.IP)
@@ -222,7 +220,7 @@ func handleMsg(data []byte, remote *net.UDPAddr) {
binary.Read(reader, binary.BigEndian, &dhcp)
dhcp.Debug(s)
if dhcp.Magic != [4]byte{0x63, 0x82, 0x53, 0x63} {
if dhcp.Magic != magic {
panic("Invalid DHCP magic field")
}
@@ -236,10 +234,10 @@ func handleMsg(data []byte, remote *net.UDPAddr) {
switch messages.MessageType(dhcpMsgType.Data[1]) {
case messages.MessageTypeDiscover:
go handleOffer(dhcp, remote)
go h.sendOffer(dhcp, remote)
case messages.MessageTypeRequest:
go handleAck(dhcp, remote)
go h.sendAck(dhcp, remote)
}
}
@@ -249,7 +247,7 @@ func runServer(interfaceName string) {
zap.L().Debug("Listening on all interfaces")
addr, _ = net.ResolveUDPAddr("udp4", ":67")
} else {
zap.S().Debugf("Listening on interface %s", interfaceName)
zap.S().Debug("Listening on interface ", interfaceName)
iface, err := net.InterfaceByName(interfaceName)
if err != nil {
panic(err)
@@ -275,17 +273,28 @@ func runServer(interfaceName string) {
}
}
if ip == nil {
zap.S().Panicf("No IPv4 address associated with interface %s", interfaceName)
zap.S().Panic("No IPv4 address associated with interface ", interfaceName)
}
fmt.Printf("%+v\n", ip)
addr, _ = net.ResolveUDPAddr("udp4", ip.String()+":67")
addr, _ = net.ResolveUDPAddr("udp4", ":67")
}
var conn *net.UDPConn
var err error
if interfaceName != "all" {
conn, err = NewIPv4UDPConn(interfaceName, addr)
} else {
conn, err = net.ListenUDP("udp4", addr)
}
conn, err := net.ListenUDP("udp4", addr)
if err != nil {
panic(err)
}
defer conn.Close()
handler := Handler{
conn: conn,
leaseManager: *leases.NewLeaseManager(),
}
zap.S().Infof("Listening for incoming connections on %s", addr.String())
for {
@@ -301,7 +310,7 @@ func runServer(interfaceName string) {
zap.S().Warn("Not a valid remote IP address: ", remote)
continue
}
go handleMsg(buf[0:rlen], remoteAddr)
go handler.handleMsg(buf[0:rlen], remoteAddr)
}
}

11
cmd/util.go
View File

@@ -1,11 +0,0 @@
package cmd
import (
"encoding/binary"
)
func u32tob(u uint32) []byte {
buf := make([]byte, 4)
binary.BigEndian.PutUint32(buf, u)
return buf
}