fix(dhcp): can not renew an ip address

The dhcp server is systemd-networkd, and the dhcp
plugin can request an ip but can not renew it.
The systemd-networkd just ignore the renew request.

```
2024/09/14 21:46:00 no DHCP packet received within 10s
2024/09/14 21:46:00 retrying in 31.529038 seconds
2024/09/14 21:46:42 no DHCP packet received within 10s
2024/09/14 21:46:42 retrying in 63.150490 seconds
2024/09/14 21:47:45 98184616c91f15419f5cacd012697f85afaa2daeb5d3233e28b0ec21589fb45a/iot/eth1: no more tries
2024/09/14 21:47:45 98184616c91f15419f5cacd012697f85afaa2daeb5d3233e28b0ec21589fb45a/iot/eth1: renewal time expired, rebinding
2024/09/14 21:47:45 Link "eth1" down. Attempting to set up
2024/09/14 21:47:45 98184616c91f15419f5cacd012697f85afaa2daeb5d3233e28b0ec21589fb45a/iot/eth1: lease rebound, expiration is 2024-09-14 22:47:45.309270751 +0800 CST m=+11730.048516519
```

Follow the https://datatracker.ietf.org/doc/html/rfc2131#section-4.3.6,
following options must not be sent in renew

- Requested IP Address
- Server Identifier

Since the upstream code has been inactive for 6 years,
we should switch to another dhcpv4 library.
The new selected one is https://github.com/insomniacslk/dhcp.

Signed-off-by: Songmin Li <lisongmin@protonmail.com>

vendor/github.com/mdlayher/socket/netns_linux.go

@@ -0,0 +1,150 @@
+//go:build linux
+// +build linux
+
+package socket
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"runtime"
+
+	"golang.org/x/sync/errgroup"
+	"golang.org/x/sys/unix"
+)
+
+// errNetNSDisabled is returned when network namespaces are unavailable on
+// a given system.
+var errNetNSDisabled = errors.New("socket: Linux network namespaces are not enabled on this system")
+
+// withNetNS invokes fn within the context of the network namespace specified by
+// fd, while also managing the logic required to safely do so by manipulating
+// thread-local state.
+func withNetNS(fd int, fn func() (*Conn, error)) (*Conn, error) {
+	var (
+		eg   errgroup.Group
+		conn *Conn
+	)
+
+	eg.Go(func() error {
+		// Retrieve and store the calling OS thread's network namespace so the
+		// thread can be reassigned to it after creating a socket in another network
+		// namespace.
+		runtime.LockOSThread()
+
+		ns, err := threadNetNS()
+		if err != nil {
+			// No thread-local manipulation, unlock.
+			runtime.UnlockOSThread()
+			return err
+		}
+		defer ns.Close()
+
+		// Beyond this point, the thread's network namespace is poisoned. Do not
+		// unlock the OS thread until all network namespace manipulation completes
+		// to avoid returning to the caller with altered thread-local state.
+
+		// Assign the current OS thread the goroutine is locked to to the given
+		// network namespace.
+		if err := ns.Set(fd); err != nil {
+			return err
+		}
+
+		// Attempt Conn creation and unconditionally restore the original namespace.
+		c, err := fn()
+		if nerr := ns.Restore(); nerr != nil {
+			// Failed to restore original namespace. Return an error and allow the
+			// runtime to terminate the thread.
+			if err == nil {
+				_ = c.Close()
+			}
+
+			return nerr
+		}
+
+		// No more thread-local state manipulation; return the new Conn.
+		runtime.UnlockOSThread()
+		conn = c
+		return nil
+	})
+
+	if err := eg.Wait(); err != nil {
+		return nil, err
+	}
+
+	return conn, nil
+}
+
+// A netNS is a handle that can manipulate network namespaces.
+//
+// Operations performed on a netNS must use runtime.LockOSThread before
+// manipulating any network namespaces.
+type netNS struct {
+	// The handle to a network namespace.
+	f *os.File
+
+	// Indicates if network namespaces are disabled on this system, and thus
+	// operations should become a no-op or return errors.
+	disabled bool
+}
+
+// threadNetNS constructs a netNS using the network namespace of the calling
+// thread. If the namespace is not the default namespace, runtime.LockOSThread
+// should be invoked first.
+func threadNetNS() (*netNS, error) {
+	return fileNetNS(fmt.Sprintf("/proc/self/task/%d/ns/net", unix.Gettid()))
+}
+
+// fileNetNS opens file and creates a netNS. fileNetNS should only be called
+// directly in tests.
+func fileNetNS(file string) (*netNS, error) {
+	f, err := os.Open(file)
+	switch {
+	case err == nil:
+		return &netNS{f: f}, nil
+	case os.IsNotExist(err):
+		// Network namespaces are not enabled on this system. Use this signal
+		// to return errors elsewhere if the caller explicitly asks for a
+		// network namespace to be set.
+		return &netNS{disabled: true}, nil
+	default:
+		return nil, err
+	}
+}
+
+// Close releases the handle to a network namespace.
+func (n *netNS) Close() error {
+	return n.do(func() error { return n.f.Close() })
+}
+
+// FD returns a file descriptor which represents the network namespace.
+func (n *netNS) FD() int {
+	if n.disabled {
+		// No reasonable file descriptor value in this case, so specify a
+		// non-existent one.
+		return -1
+	}
+
+	return int(n.f.Fd())
+}
+
+// Restore restores the original network namespace for the calling thread.
+func (n *netNS) Restore() error {
+	return n.do(func() error { return n.Set(n.FD()) })
+}
+
+// Set sets a new network namespace for the current thread using fd.
+func (n *netNS) Set(fd int) error {
+	return n.do(func() error {
+		return os.NewSyscallError("setns", unix.Setns(fd, unix.CLONE_NEWNET))
+	})
+}
+
+// do runs fn if network namespaces are enabled on this system.
+func (n *netNS) do(fn func() error) error {
+	if n.disabled {
+		return errNetNSDisabled
+	}
+
+	return fn()
+}