add dhcp.ClientState and it's tests

eth/dhcp/dhcp.go

@@ -23,6 +23,35 @@ const (
 	DefaultServerPort = 67
 )
 
+// ClientState represents the state of a DHCP client.
+// Below is a state diagram of a DHCP client.
+type ClientState uint8
+
+// IsValid returns true if the state is within the valid range.
+func (s ClientState) IsValid() bool {
+	return s > 0 || s < ClientState(s)
+}
+
+// install stringer with `go install golang.org/x/tools/cmd/stringer@latest`
+//
+//go:generate stringer -type=ClientState -trimprefix=State
+const (
+	_ ClientState = iota
+	// On clean slate boot, abort, NAK or decline enter the INIT state.
+	StateInit
+	// After sending out a Discover enter SELECTING.
+	StateSelecting
+	// After receiving a worthy offer enter REQUESTING.
+	StateRequesting
+	// On reboot enter INIT-REBOOT state.
+	// StateInitReboot
+	// On sending out a Request enter REBOOTING.
+	// StateRebooting
+	// On ACK to Request enter BOUND.
+	StateBound
+	numStates uint8 = iota
+)
+
 type Option struct {
 	Num  OptNum
 	Data []byte

eth/dns/types.go

@@ -62,7 +62,7 @@ const (
 // An RCode is a DNS response status code.
 type RCode uint16
 
-//go:generate stringer -type=RCode -trimprefix=RCode -output=rcode_string.go
+// /go:generate stringer -type=RCode -trimprefix=RCode -output=rcode_string.go
 const (
 	RCodeSuccess        RCode = 0 // No error condition.
 	RCodeFormatError    RCode = 1 // Format error - The name server was unable to interpret the query.

stacks/dhcp_client.go

@@ -120,10 +120,30 @@ func (d *DHCPClient) BeginRequest(cfg DHCPRequestConfig) error {
 	return d.stack.FlagPendingUDP(d.port)
 }
 
+// IsDone
+//
+// Deprecated: Use d.State()==dhcp.StateBound instead.
 func (d *DHCPClient) IsDone() bool {
 	return d.state == dhcpStateDone || d.state == dhcpStateNaked
 }
 
+// State returns the current state of the DHCP client.
+func (d *DHCPClient) State() dhcp.ClientState {
+	switch d.state {
+	case dhcpStateNone:
+		return dhcp.StateInit
+	case dhcpStateWaitOffer, dhcpStateGotOffer:
+		return dhcp.StateSelecting
+	case dhcpStateWaitAck:
+		return dhcp.StateRequesting
+	case dhcpStateDone:
+		return dhcp.StateBound
+	case dhcpStateNaked:
+		return dhcp.StateInit
+	}
+	return 0
+}
+
 // DHCPServer IP address field of the DHCP packet. Is the siaddr field of the DHCP packet, which can be overriden with the Server IP option.
 func (d *DHCPClient) DHCPServer() netip.Addr {
 	return ipv4orInvalid(d.svip)

stacks/stacks_test.go

@@ -14,6 +14,7 @@ import (
 
 	"github.com/soypat/seqs"
 	"github.com/soypat/seqs/eth"
+	"github.com/soypat/seqs/eth/dhcp"
 	"github.com/soypat/seqs/eth/dns"
 	"github.com/soypat/seqs/stacks"
 )
@@ -89,6 +90,13 @@ func TestDHCP(t *testing.T) {
 }
 
 func testDHCP(t *testing.T, cl *stacks.DHCPClient, sv *stacks.DHCPServer) {
+	checkClientState := func(t *testing.T, want dhcp.ClientState) {
+		t.Helper()
+		if cl.State() != want {
+			t.Fatalf("client state=%s want=%s", cl.State().String(), want.String())
+		}
+	}
+	checkClientState(t, dhcp.StateInit)
 	var requestedIP = netip.AddrFrom4([4]byte{192, 168, 1, 69})
 	cstack := cl.PortStack()
 	sstack := sv.PortStack()
@@ -103,6 +111,7 @@ func testDHCP(t *testing.T, cl *stacks.DHCPClient, sv *stacks.DHCPServer) {
 	if err != nil {
 		t.Fatal(err)
 	}
+
 	checkClientNotDone := func(msg string) {
 		t.Helper()
 		if cl.IsDone() {
@@ -116,6 +125,7 @@ func testDHCP(t *testing.T, cl *stacks.DHCPClient, sv *stacks.DHCPServer) {
 	if n < minDHCPSize {
 		t.Errorf("ex[%d] sent=%d want>=%d", ex, n, minDHCPSize)
 	}
+	checkClientState(t, dhcp.StateSelecting)
 	checkNoMoreDataSent(t, "after cl DISCOVER send", egr)
 	checkClientNotDone("after DISCOVER send")
 	egr.HandleRx(t)
@@ -125,6 +135,7 @@ func testDHCP(t *testing.T, cl *stacks.DHCPClient, sv *stacks.DHCPServer) {
 	if n < minDHCPSize {
 		t.Errorf("ex[%d] sent=%d want>=%d", ex, n, minDHCPSize)
 	}
+	checkClientState(t, dhcp.StateSelecting)
 	checkNoMoreDataSent(t, "after sv OFFER send", egr)
 	egr.HandleRx(t) // Client receives OFFER.
 	checkClientNotDone("after OFFER recv")
@@ -134,6 +145,7 @@ func testDHCP(t *testing.T, cl *stacks.DHCPClient, sv *stacks.DHCPServer) {
 	if n < minDHCPSize {
 		t.Errorf("ex[%d] sent=%d want>=%d", ex, n, minDHCPSize)
 	}
+	checkClientState(t, dhcp.StateRequesting)
 	checkNoMoreDataSent(t, "after client REQUEST send", egr)
 	checkClientNotDone("after REQUEST send")
 	egr.HandleRx(t) // Server receives REQUEST.
@@ -148,6 +160,7 @@ func testDHCP(t *testing.T, cl *stacks.DHCPClient, sv *stacks.DHCPServer) {
 	if !cl.IsDone() {
 		t.Fatal("client not processed ACK yet")
 	}
+	checkClientState(t, dhcp.StateBound)
 }
 
 func TestARP(t *testing.T) {