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added some dhcp4 packet functions and generic byte reading functions

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This commit is contained in:
hyung-hwan
2025-09-17 19:31:37 +09:00
parent 67b3e9727b
commit 90365bfdd4
8 changed files with 394 additions and 65 deletions
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8
Makefile
View File

@ -10,12 +10,14 @@ VERSION=1.0.0
SRCS=\
haza.go \
iface.go \
server.go
pkt.go \
server.go \
sock.go
CMD_SRCS=\
cmd/logger.go \
cmd/main.go
cmd/main.go \
cmd/signal.go
all: $(NAME)

15
cmd/main.go
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@ -12,6 +12,7 @@ func main() {
var logger *AppLogger
var addr *net.UDPAddr
var addr2 *net.UDPAddr
var addr3 *net.UDPAddr
var err error
// addr, err = net.ResolveUDPAddr("udp4", "0.0.0.0:10000")
@ -27,7 +28,13 @@ func main() {
os.Exit(-1)
}
logger = NewAppLogger("client", os.Stderr, haza.LOG_ALL)
addr3, err = net.ResolveUDPAddr("udp4", "192.168.1.189:10000")
if err != nil {
fmt.Printf("Failed to resolve address - %s\n", err.Error())
os.Exit(-1)
}
logger = NewAppLogger("server", os.Stderr, haza.LOG_ALL)
ds, err = haza.NewDhcpServer(context.Background(), "haza-dhcpd", logger)
if err != nil {
@ -49,8 +56,14 @@ if err != nil {
fmt.Printf("Failed to add listgener for %v - %s\n", addr2, err.Error())
goto oops
}
err = ds.AddListener4("enp1s0", addr3)
if err != nil {
fmt.Printf("Failed to add listgener for %v - %s\n", addr3, err.Error())
goto oops
}
ds.StartService(nil)
ds.StartExtService(&signal_handler{svc:ds}, nil)
ds.WaitForTermination()
os.Exit(0)

69
cmd/signal.go Normal file
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@ -0,0 +1,69 @@
package main
import "haza"
import "sync"
import "os"
import "os/signal"
import "syscall"
type signal_handler struct {
svc haza.Service
}
func (sh *signal_handler) RunTask(wg *sync.WaitGroup) {
var sighup_chan chan os.Signal
var sigterm_chan chan os.Signal
var sig os.Signal
if wg != nil {
defer wg.Done()
}
sighup_chan = make(chan os.Signal, 1)
sigterm_chan = make(chan os.Signal, 1)
signal.Notify(sighup_chan, syscall.SIGHUP)
signal.Notify(sigterm_chan, syscall.SIGTERM, os.Interrupt)
chan_loop:
for {
select {
case <-sighup_chan:
sh.svc.FixServices()
case sig = <-sigterm_chan:
sh.svc.StopServices()
sh.svc.WriteLog ("", haza.LOG_INFO, "Received %s signal", sig)
break chan_loop
}
}
//signal.Reset(syscall.SIGHUP)
//signal.Reset(syscall.SIGTERM)
signal.Stop(sighup_chan)
signal.Stop(sigterm_chan)
}
func (sh *signal_handler) StartService(data interface{}) {
// this isn't actually used standalone..
// if we are to implement it, it must use the wait group for signal handler itself
// however, this service is run through another service.
// sh.wg.Add(1)
// go sh.RunTask(&sh.wg)
}
func (sh *signal_handler) StopServices() {
syscall.Kill(syscall.Getpid(), syscall.SIGTERM) // TODO: find a better to terminate the signal handler...
}
func (sh *signal_handler) FixServices() {
}
func (sh *signal_handler) WaitForTermination() {
// not implemented. see the comment in StartServices()
// sh.wg.Wait()
}
func (sh *signal_handler) WriteLog(id string, level haza.LogLevel, fmt string, args ...interface{}) {
sh.svc.WriteLog(id, level, fmt, args...)
}

47
haza.go
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@ -1,5 +1,9 @@
package haza
import "bytes"
import "encoding/binary"
import "io"
import "net"
import "sync"
import "unsafe"
@ -75,3 +79,46 @@ func Ntoh32(v uint32) uint32 {
if _is_big_endian { return v }
return ((v >> 24) & 0xFF) | ((v >> 8) & 0xFF00) | ((v << 8) & 0xFF0000) | ((v << 24) & 0xFF000000)
}
// ---------------------------------------------------------
type ByteReader struct {
r *bytes.Reader
}
func NewByteReader(b []byte) *ByteReader {
return &ByteReader{ r: bytes.NewReader(b) }
}
func (br* ByteReader) ReadByte() (byte, error) {
return br.r.ReadByte()
}
func (br* ByteReader) ReadUint16() (uint16, error) {
var v uint16
var err error
err = binary.Read(br.r, binary.BigEndian, &v)
if err != nil { return 0, err }
return v, nil
}
func (br* ByteReader) ReadUint32() (uint32, error) {
var v uint32
var err error
err = binary.Read(br.r, binary.BigEndian, &v)
if err != nil { return 0, err }
return v, nil
}
func (br* ByteReader) ReadIp4() (net.IP, error) {
var buf [4]byte
var err error
_, err = io.ReadFull(br.r, buf[:])
if err != nil { return nil, err }
return net.IP(buf[:]), nil
}
func (br *ByteReader) ReadAllBytes(buf []byte) error {
var err error
_, err = io.ReadFull(br.r, buf)
return err
}

148
pkt.go Normal file
View File

@ -0,0 +1,148 @@
package haza
import "net"
type Dhcp4Op = uint8
type Dhcp4Htype = uint8
type Dhcp4Msg = uint8
const (
_ Dhcp4Op = iota
DHCP4_OP_BOOTREQUEST = 1
DHCP4_OP_BOOTREPLY = 2
)
const (
_ Dhcp4Htype = iota
DHCP4_HTYPE_ETHER = 1
DHCP4_HTYPE_IEEE802 = 6
DHCP4_HTYPE_ARCNET = 7
DHCP4_HTYPE_APPLETALK = 8
DHCP4_HTYPE_HDLC = 17
DHCP4_HTYPE_ATM = 19
DHCP4_HTYPE_ARPSEC = 30
DHCP4_HTYPE_IPSEC = 31
DHCP4_HTYPE_INFINIBAND = 32
DHCP4_HTYPE_PUREIP = 35
)
const (
_ Dhcp4Msg = iota
DHCP4_MSG_DISCOVER = 1
DHCP4_MSG_OFFER = 2
DHCP4_MSG_REQUEST = 3
DHCP4_MSG_DECLINE = 4
DHCP4_MSG_ACK = 5
DHCP4_MSG_NAK = 6
DHCP4_MSG_RELEASE = 7
DHCP4_MSG_INFORM = 8
DHCP4_MSG_FORCE_RENEW = 9
DHCP4_MSG_LEASE_QUERY = 10
DHCP4_MSG_LEASE_UNASSIGNED = 11
DHCP4_MSG_LEASE_UNKNOWN = 12
DHCP4_MSG_LEASE_ACTIVE = 13
DHCP4_MSG_BULK_LEASE_QUERY = 14
DHCP4_MSG_LEASE_QUERY_DONE = 15
DHCP4_MSG_ACTIVE_LEASE_QUERY = 16
DHCP4_MSG_LEASE_QUERY_STATUS = 17
DHCP4_MSG_TLS = 18
)
type Dhcp4Pkt struct {
Op Dhcp4Op
Htype Dhcp4Htype
Hlen uint8 // length of Chaddr
Hops uint8
Xid uint32
Secs uint16
Flags uint16
Ciaddr net.IP // uint32
Yiaddr net.IP // uint32
Siaddr net.IP // uint32
Gwaddr net.IP // uint32
Chaddr [16]byte
Sname [64]byte // server host name
File [128]byte // boot file name
// options are placed after the header.
// the first four bytes of the options compose a magic cookie
// 0x63 0x82 0x53 0x63
}
func (pkt *Dhcp4Pkt) Decode(b []byte) error {
// fill the packet with data from the bytes
var r *ByteReader
var u8 byte
var u16 uint16
var u32 uint32
var p Dhcp4Pkt
var err error
r = NewByteReader(b)
u8, err = r.ReadByte()
if err != nil { return err }
p.Op = Dhcp4Op(u8)
u8, err = r.ReadByte()
if err != nil { return err }
p.Htype = Dhcp4Htype(u8)
u8, err = r.ReadByte()
if err != nil { return err }
p.Hlen = u8
u8, err = r.ReadByte()
if err != nil { return err }
p.Hops = u8
u32, err = r.ReadUint32()
if err != nil { return err }
p.Xid = u32
u16, err = r.ReadUint16()
if err != nil { return err }
p.Secs = u16
u16, err = r.ReadUint16()
if err != nil { return err }
p.Flags = u16
p.Ciaddr, err = r.ReadIp4()
if err != nil { return err }
p.Yiaddr, err = r.ReadIp4()
if err != nil { return err }
p.Siaddr, err = r.ReadIp4()
if err != nil { return err }
p.Gwaddr, err = r.ReadIp4()
if err != nil { return err }
err = r.ReadAllBytes(p.Chaddr[:])
if err != nil { return err }
err = r.ReadAllBytes(p.Sname[:])
if err != nil { return err }
err = r.ReadAllBytes(p.File[:])
if err != nil { return err }
// magic
// options..
*pkt = p
return nil
}
func (pkt *Dhcp4Pkt) Encode() []byte {
return nil
}

141
server.go
View File

@ -17,22 +17,26 @@ type DhcpServer struct {
Ctx context.Context
CtxCancel context.CancelFunc
wg sync.WaitGroup
stop_req atomic.Bool
ext_mtx sync.Mutex
ext_svcs []Service
ext_closed bool
conns_mtx sync.Mutex
conns map[string]*Dhcp4Conn
conns_by_fd map[int]*Dhcp4Conn
conns map[string]DhcpConn
conns_by_fd map[int]DhcpConn
p int // epoll
efd int // eventfd
wg sync.WaitGroup
log Logger
}
func finalize_dhcp_server(s *DhcpServer) {
var dc *Dhcp4Conn
var dc DhcpConn
for _, dc = range s.conns_by_fd {
@ -42,9 +46,9 @@ func finalize_dhcp_server(s *DhcpServer) {
// unix.EpollCtl(s.p, unix.EPOLL_CTL_DEL, fd, nil)
//})
unix.EpollCtl(s.p, unix.EPOLL_CTL_DEL, dc.fd, nil)
delete(s.conns_by_fd, dc.fd)
delete(s.conns, dc.iface)
unix.EpollCtl(s.p, unix.EPOLL_CTL_DEL, dc.Fd(), nil)
delete(s.conns_by_fd, dc.Fd())
delete(s.conns, dc.Iface())
dc.Close()
}
@ -92,54 +96,50 @@ func NewDhcpServer(ctx context.Context, name string, logger Logger) (*DhcpServer
s = &DhcpServer{}
s.Ctx, s.CtxCancel = context.WithCancel(ctx)
s.name = name
s.log = logger
s.log = logger
s.stop_req.Store(false)
s.ext_svcs = make([]Service, 0, 1)
s.ext_closed = false
s.efd = efd
s.p = p
s.conns = make(map[string]*Dhcp4Conn, 0)
s.conns_by_fd = make(map[int]*Dhcp4Conn, 0)
s.conns = make(map[string]DhcpConn, 0)
s.conns_by_fd = make(map[int]DhcpConn, 0)
runtime.SetFinalizer(s, finalize_dhcp_server)
return s, nil
}
func (s *DhcpServer) AddListener4(iface string, addr *net.UDPAddr) error {
var conn *Dhcp4Conn
var conn DhcpConn
var ok bool
var err error
s.conns_mtx.Lock()
defer s.conns_mtx.Unlock()
conn, ok = s.conns[iface]
if ok {
err = conn.AddAddr(addr)
if err != nil {
s.conns_mtx.Unlock()
return err
}
if err != nil { return err }
} else {
conn, err = NewDhcp4Conn(iface, addr)
if err != nil {
fmt.Printf ("fAILED TO CRETEA %s\n", err.Error())
s.conns_mtx.Unlock()
return err
}
fmt.Printf ("ADDING dhcp4... %d\n", conn.fd)
err = unix.EpollCtl(s.p, unix.EPOLL_CTL_ADD, conn.fd,
if err != nil { return err }
fmt.Printf ("ADDING dhcp4... %d\n", conn.Fd())
err = unix.EpollCtl(s.p, unix.EPOLL_CTL_ADD, conn.Fd(),
&unix.EpollEvent{
Events: unix.EPOLLIN | unix.EPOLLERR | unix.EPOLLHUP,
Fd: int32(conn.fd),
Fd: int32(conn.Fd()),
},
)
if err != nil {
s.conns_mtx.Unlock()
conn.Close()
return err
}
s.conns[iface] = conn // this isn't needed??? or this must be a slice...
s.conns_by_fd[conn.Fd()] = conn
}
s.conns[iface] = conn // this isn't needed??? or this must be a slice...
s.conns_by_fd[conn.fd] = conn
s.conns_mtx.Unlock()
return nil
}
@ -176,15 +176,28 @@ func (s *DhcpServer) StartService(data interface{}) {
go s.RunTask(&s.wg)
}
func (s *DhcpServer) StartExtService(svc Service, data interface{}) {
s.ext_mtx.Lock()
if s.ext_closed {
// don't start it if it's already closed
s.ext_mtx.Unlock()
return
}
s.ext_svcs = append(s.ext_svcs, svc)
s.ext_mtx.Unlock()
s.wg.Add(1)
go svc.RunTask(&s.wg)
}
func (s *DhcpServer) StopServices() {
// var ext_svc Service
var ext_svc Service
s.ReqStop()
// s.ext_mtx.Lock()
// for _, ext_svc = range s.ext_svcs {
// ext_svc.StopServices()
// }
// s.ext_closed = true
// s.ext_mtx.Unlock()
s.ext_mtx.Lock()
for _, ext_svc = range s.ext_svcs {
ext_svc.StopServices()
}
s.ext_closed = true
s.ext_mtx.Unlock()
}
func (s *DhcpServer) FixServices() {
@ -200,45 +213,47 @@ func (s *DhcpServer) WriteLog(id string, level LogLevel, fmtstr string, args ...
s.log.Write(id, level, fmtstr, args...)
}
func get_offsets(frame []byte) (int, int, int, int, int, error) {
var eth_off int
var ip_off int
var ihl int
var udp_off int
var udp_len int
var dhcp_off int
var dhcp_end int
if len(frame) < 14 {
return 0, 0, 0, 0, 0, fmt.Errorf("frame too short for Ethernet header")
}
ethOff := 0
ipOff := ethOff + 14
eth_off = 0
ip_off = eth_off + 14
if len(frame) < ipOff+20 {
if len(frame) < ip_off + 20 {
return 0, 0, 0, 0, 0, fmt.Errorf("frame too short for IPv4 header")
}
// First byte of IPv4 header: 4 bits version, 4 bits IHL
ihl := int(frame[ipOff] & 0x0F) * 4
if len(frame) < ipOff+ihl {
return 0, 0, 0, 0, 0, fmt.Errorf("invalid IHL: %d", ihl)
ihl = int(frame[ip_off] & 0x0F) * 4 // the lower first 4 bits of the first bytes * 4
if len(frame) < ip_off + ihl {
return 0, 0, 0, 0, 0, fmt.Errorf("invalid IHL %d", ihl)
}
udpOff := ipOff + ihl
if len(frame) < udpOff+8 {
udp_off = ip_off + ihl
if len(frame) < udp_off + 8 {
return 0, 0, 0, 0, 0, fmt.Errorf("frame too short for UDP header")
}
// UDP length field (2 bytes at offset 4–5 of UDP header)
udpLen := int(frame[udpOff+4])<<8 | int(frame[udpOff+5])
if udpLen < 8 {
return 0, 0, 0, 0, 0, fmt.Errorf("invalid UDP length: %d", udpLen)
udp_len = int(frame[udp_off + 4]) << 8 | int(frame[udp_off + 5])
if udp_len < 8 {
return 0, 0, 0, 0, 0, fmt.Errorf("invalid UDP length %d", udp_len)
}
if len(frame) < udpOff+udpLen {
return 0, 0, 0, 0, 0, fmt.Errorf("frame too short for UDP length %d", udpLen)
if len(frame) < udp_off + udp_len {
return 0, 0, 0, 0, 0, fmt.Errorf("frame too short for UDP length %d", udp_len)
}
dhcpOff := udpOff + 8
dhcpEnd := udpOff + udpLen
dhcp_off = udp_off + 8
dhcp_end = udp_off + udp_len
return ethOff, ipOff, udpOff, dhcpOff, dhcpEnd, nil
return eth_off, ip_off, udp_off, dhcp_off, dhcp_end, nil
}
func (s *DhcpServer) run_recv_loop() error {
@ -253,13 +268,13 @@ epoll_loop:
nevts, err = unix.EpollWait(s.p, evts[:], -1)
if err != nil {
if errors.Is(err, unix.EINTR) { continue }
fmt.Printf ("epoll error - %s\n", err.Error())
break
s.log.Write("", LOG_ERROR, "event multiplexer error - %s", err.Error())
break epoll_loop
}
for i = 0; i < nevts ; i++ {
if (evts[i].Events & (unix.EPOLLHUP | unix.EPOLLERR)) != 0 {
fmt.Printf ("epoll something not right...\n")
s.log.Write("", LOG_ERROR, "event HUP or ERR detected on fd %d - %s", i)
break epoll_loop
}
@ -286,12 +301,16 @@ fmt.Printf ("epoll something not right...\n")
if string(buf[spos:epos]) == "quit\n" {
break epoll_loop
}
var pkt Dhcp4Pkt
pkt.Decode(buf[spos:epos])
fmt.Printf("%+v\n", pkt)
}
}
if err != nil {
// TODO: logging
fmt.Printf("ERROR... %s\n", err.Error())
s.log.Write("", LOG_ERROR, "Failed to read packet on fd %d - %s", i, err.Error())
break epoll_loop
}
}

31
iface.go → sock.go
View File

@ -8,6 +8,19 @@ import "sync"
import "golang.org/x/net/bpf"
import "golang.org/x/sys/unix"
type DhcpConn interface {
Version() int
Fd() int
Iface() string
Close()
AddAddr(addr *net.UDPAddr) error
//DelAddr(addr *net.UDPAddr) error
}
// TODO: add dhcp6 sockets
type Dhcp4UdpSock struct {
addr *net.UDPAddr
fd int
@ -131,6 +144,18 @@ func (d *Dhcp4Conn) Close() {
}
}
func (d *Dhcp4Conn) Version() int {
return 4
}
func (d *Dhcp4Conn) Fd() int {
return d.fd
}
func (d *Dhcp4Conn) Iface() string {
return d.iface
}
func (d *Dhcp4Conn) ForEachUdpSockFd(handler func (fd int)) {
var us *Dhcp4UdpSock
@ -388,6 +413,12 @@ func open_udp4_socket(addr *net.UDPAddr) (int, error) {
err = attach_discard_filter(fd)
if err != nil { goto oops }
err = unix.SetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_REUSEADDR, 1)
if err != nil { goto oops }
// i won't be setting unix.SO_REUSEPORT as i don't want multple programs
// to run on the same port.
err = unix.Bind(fd, &unix.SockaddrInet4{ Addr: [4]byte(ip[0:4]), Port: addr.Port})
if err != nil { goto oops }

0
iface_test.go → sock_test.go
View File