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HTTP server example and DHCP Server rewrite (#38)
* improvements to dhcpv4 server * begin adding examples/httpserver * add better VLAN tagging methods * pcap: add error printing; fix bug in CRC * ipv4: ToS and Flags construction and flag manipulation improvements * add dhcp interception to httptap and improve httpserver example
This commit is contained in:
Pat Whittingslow
GitHub
@@ -0,0 +1,358 @@
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package dhcpv4
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import (
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"net/netip"
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"testing"
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)
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func testServerConfig(svAddr [4]byte) ServerConfig {
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return ServerConfig{
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ServerAddr: svAddr,
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Subnet: netip.PrefixFrom(netip.AddrFrom4(svAddr), 24),
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}
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}
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// TestServerMultipleClients verifies the server can handle multiple clients
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// going through the full DORA flow independently.
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func TestServerMultipleClients(t *testing.T) {
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svAddr := [4]byte{192, 168, 1, 1}
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var sv Server
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sv.Configure(testServerConfig(svAddr))
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const nClients = 3
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var clients [nClients]Client
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var bufs [nClients][1024]byte
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for i := range clients {
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err := clients[i].BeginRequest(uint32(100+i), RequestConfig{
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ClientHardwareAddr: [6]byte{0, 0, 0, 0, 0, byte(i + 1)},
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Hostname: "host",
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ClientID: string([]byte{byte(i + 1)}),
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})
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if err != nil {
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t.Fatalf("client %d BeginRequest: %v", i, err)
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}
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}
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// Phase 1: All clients send DISCOVER.
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for i := range clients {
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n, err := clients[i].Encapsulate(bufs[i][:], -1, 0)
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if err != nil {
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t.Fatalf("client %d discover encapsulate: %v", i, err)
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}
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err = sv.Demux(bufs[i][:n], 0)
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if err != nil {
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t.Fatalf("client %d discover demux: %v", i, err)
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}
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}
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// Route server responses to the correct client by XID (map iteration is non-deterministic).
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clientByXID := make(map[uint32]int)
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for i := range clients {
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clientByXID[uint32(100+i)] = i
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}
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// Phase 2: Server sends all OFFERs, clients receive.
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var assignedAddrs [nClients][4]byte
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for range clients {
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var buf [1024]byte
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n, err := sv.Encapsulate(buf[:], -1, 0)
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if err != nil {
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t.Fatalf("offer encapsulate: %v", err)
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} else if n == 0 {
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t.Fatal("no offer from server")
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}
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frm, _ := NewFrame(buf[:n])
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ci := clientByXID[frm.XID()]
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assignedAddrs[ci] = *frm.YIAddr()
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err = clients[ci].Demux(buf[:n], 0)
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if err != nil {
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t.Fatalf("client %d offer demux: %v", ci, err)
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}
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}
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// Phase 3: All clients send REQUEST.
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for i := range clients {
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n, err := clients[i].Encapsulate(bufs[i][:], -1, 0)
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if err != nil {
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t.Fatalf("client %d request encapsulate: %v", i, err)
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} else if n == 0 {
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t.Fatalf("client %d: no request data", i)
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}
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err = sv.Demux(bufs[i][:n], 0)
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if err != nil {
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t.Fatalf("client %d request demux: %v", i, err)
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}
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}
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// Phase 4: Server sends all ACKs, clients receive.
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for range clients {
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var buf [1024]byte
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n, err := sv.Encapsulate(buf[:], -1, 0)
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if err != nil {
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t.Fatalf("ack encapsulate: %v", err)
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} else if n == 0 {
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t.Fatal("no ack from server")
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}
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frm, _ := NewFrame(buf[:n])
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ci := clientByXID[frm.XID()]
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err = clients[ci].Demux(buf[:n], 0)
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if err != nil {
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t.Fatalf("client %d ack demux: %v", ci, err)
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}
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if clients[ci].State() != StateBound {
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t.Errorf("client %d: want StateBound, got %s", ci, clients[ci].State())
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}
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}
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// All assigned addresses must be unique.
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for i := 0; i < nClients; i++ {
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for j := i + 1; j < nClients; j++ {
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if assignedAddrs[i] == assignedAddrs[j] {
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t.Errorf("clients %d and %d got same address %v", i, j, assignedAddrs[i])
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}
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}
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}
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}
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// TestServerSequentialAddressAllocation verifies that the server allocates
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// addresses sequentially starting from serverAddr+1.
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func TestServerSequentialAddressAllocation(t *testing.T) {
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svAddr := [4]byte{192, 168, 1, 1}
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var sv Server
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sv.Configure(testServerConfig(svAddr))
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// Build raw DISCOVER frames for two clients.
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for i := byte(0); i < 2; i++ {
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var buf [512]byte
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frm, _ := NewFrame(buf[:])
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frm.ClearHeader()
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frm.SetOp(OpRequest)
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frm.SetHardware(1, 6, 0)
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frm.SetXID(uint32(200 + i))
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frm.SetSecs(1)
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copy(frm.CHAddrAs6()[:], []byte{0, 0, 0, 0, 0, 10 + i})
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frm.SetMagicCookie(MagicCookie)
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opts := buf[OptionsOffset:]
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n := writeOption(opts, OptMessageType, byte(MsgDiscover))
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n += writeOption(opts[n:], OptClientIdentifier, 10+i)
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opts[n] = byte(OptEnd)
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n++
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err := sv.Demux(buf[:OptionsOffset+n], 0)
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if err != nil {
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t.Fatalf("discover %d: %v", i, err)
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}
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}
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// Encapsulate both OFFERs and verify addresses are in expected range.
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var seen [2][4]byte
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for i := byte(0); i < 2; i++ {
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var buf [512]byte
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n, err := sv.Encapsulate(buf[:], -1, 0)
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if err != nil {
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t.Fatalf("offer %d encapsulate: %v", i, err)
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} else if n == 0 {
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t.Fatalf("offer %d: no data", i)
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}
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frm, _ := NewFrame(buf[:n])
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seen[i] = *frm.YIAddr()
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if seen[i][0] != 192 || seen[i][1] != 168 || seen[i][2] != 1 {
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t.Errorf("offer %d: unexpected subnet in %v", i, seen[i])
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}
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if seen[i][3] != 2 && seen[i][3] != 3 {
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t.Errorf("offer %d: expected .2 or .3, got .%d", i, seen[i][3])
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}
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}
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if seen[0] == seen[1] {
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t.Errorf("both offers got same address %v", seen[0])
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}
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}
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// TestServerOfferContainsOptions verifies that server OFFER responses
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// contain the expected DHCP options from the ServerConfig.
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func TestServerOfferContainsOptions(t *testing.T) {
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svAddr := [4]byte{192, 168, 1, 1}
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gwAddr := [4]byte{192, 168, 1, 254}
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dnsAddr := [4]byte{8, 8, 8, 8}
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var sv Server
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sv.Configure(ServerConfig{
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ServerAddr: svAddr,
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Gateway: gwAddr,
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DNS: dnsAddr,
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Subnet: netip.PrefixFrom(netip.AddrFrom4(svAddr), 24),
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LeaseSeconds: 7200,
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})
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var cl Client
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err := cl.BeginRequest(500, RequestConfig{
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ClientHardwareAddr: [6]byte{0xde, 0xad, 0xbe, 0xef, 0xca, 0xfe},
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})
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if err != nil {
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t.Fatal(err)
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}
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var buf [1024]byte
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n, err := cl.Encapsulate(buf[:], -1, 0)
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if err != nil {
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t.Fatal(err)
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}
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err = sv.Demux(buf[:n], 0)
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if err != nil {
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t.Fatal(err)
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}
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n, err = sv.Encapsulate(buf[:], -1, 0)
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if err != nil {
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t.Fatal(err)
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}
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frm, _ := NewFrame(buf[:n])
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var gotServerID, gotRouter, gotSubnet, gotDNS [4]byte
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var gotLease, gotRenew, gotRebind uint32
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var foundServerID, foundRouter, foundSubnet, foundDNS, foundLease bool
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frm.ForEachOption(func(_ int, opt OptNum, data []byte) error {
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switch opt {
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case OptServerIdentification:
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if len(data) == 4 {
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foundServerID = true
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copy(gotServerID[:], data)
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}
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case OptRouter:
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if len(data) == 4 {
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foundRouter = true
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copy(gotRouter[:], data)
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}
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case OptSubnetMask:
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if len(data) == 4 {
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foundSubnet = true
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copy(gotSubnet[:], data)
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}
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case OptDNSServers:
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if len(data) == 4 {
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foundDNS = true
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copy(gotDNS[:], data)
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}
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case OptIPAddressLeaseTime:
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if len(data) == 4 {
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foundLease = true
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gotLease = maybeU32(data)
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}
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case OptRenewTimeValue:
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gotRenew = maybeU32(data)
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case OptRebindingTimeValue:
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gotRebind = maybeU32(data)
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}
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return nil
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})
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if !foundServerID || gotServerID != svAddr {
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t.Errorf("server ID: found=%v got=%v want=%v", foundServerID, gotServerID, svAddr)
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}
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if !foundRouter || gotRouter != gwAddr {
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t.Errorf("router: found=%v got=%v want=%v", foundRouter, gotRouter, gwAddr)
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}
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if !foundSubnet || gotSubnet != [4]byte{255, 255, 255, 0} {
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t.Errorf("subnet: found=%v got=%v want=255.255.255.0", foundSubnet, gotSubnet)
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}
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if !foundDNS || gotDNS != dnsAddr {
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t.Errorf("DNS: found=%v got=%v want=%v", foundDNS, gotDNS, dnsAddr)
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}
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if !foundLease || gotLease != 7200 {
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t.Errorf("lease: found=%v got=%v want=7200", foundLease, gotLease)
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}
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if gotRenew != 3600 {
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t.Errorf("renew T1: got %d want 3600", gotRenew)
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}
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if gotRebind != 6300 {
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t.Errorf("rebind T2: got %d want 6300", gotRebind)
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}
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}
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// TestServerEncapsulateNoPending verifies Encapsulate returns 0 bytes
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// when there are no pending responses.
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func TestServerEncapsulateNoPending(t *testing.T) {
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var sv Server
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sv.Configure(testServerConfig([4]byte{192, 168, 1, 1}))
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var buf [512]byte
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n, err := sv.Encapsulate(buf[:], -1, 0)
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if err != nil {
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t.Fatal(err)
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}
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if n != 0 {
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t.Errorf("expected 0 bytes from empty server, got %d", n)
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}
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}
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// TestServerConfigValidation verifies that Configure rejects invalid configurations.
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func TestServerConfigValidation(t *testing.T) {
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var sv Server
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err := sv.Configure(ServerConfig{
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ServerAddr: [4]byte{192, 168, 1, 1},
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})
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if err == nil {
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t.Error("expected error for zero subnet")
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}
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err = sv.Configure(ServerConfig{
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ServerAddr: [4]byte{10, 0, 0, 1},
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Subnet: netip.PrefixFrom(netip.AddrFrom4([4]byte{192, 168, 1, 0}), 24),
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})
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if err == nil {
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t.Error("expected error for server address outside subnet")
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}
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}
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// TestServerRediscover verifies that a client that was previously bound
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// can send a fresh DISCOVER and get re-served.
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func TestServerRediscover(t *testing.T) {
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svAddr := [4]byte{192, 168, 1, 1}
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var sv Server
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sv.Configure(testServerConfig(svAddr))
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// First DORA cycle.
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var cl Client
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cl.BeginRequest(1, RequestConfig{
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ClientHardwareAddr: [6]byte{1, 2, 3, 4, 5, 6},
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ClientID: "rediscover-client",
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})
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var buf [1024]byte
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n, _ := cl.Encapsulate(buf[:], -1, 0)
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sv.Demux(buf[:n], 0)
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n, _ = sv.Encapsulate(buf[:], -1, 0)
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cl.Demux(buf[:n], 0)
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n, _ = cl.Encapsulate(buf[:], -1, 0)
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sv.Demux(buf[:n], 0)
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n, _ = sv.Encapsulate(buf[:], -1, 0)
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cl.Demux(buf[:n], 0)
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if cl.State() != StateBound {
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t.Fatalf("first DORA: want StateBound, got %s", cl.State())
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}
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// Client reboots and sends fresh DISCOVER.
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cl.Reset()
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cl.BeginRequest(2, RequestConfig{
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ClientHardwareAddr: [6]byte{1, 2, 3, 4, 5, 6},
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ClientID: "rediscover-client",
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})
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n, _ = cl.Encapsulate(buf[:], -1, 0)
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err := sv.Demux(buf[:n], 0)
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if err != nil {
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t.Fatalf("rediscover demux: %v", err)
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}
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n, _ = sv.Encapsulate(buf[:], -1, 0)
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if n == 0 {
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t.Fatal("no offer after rediscover")
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}
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err = cl.Demux(buf[:n], 0)
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if err != nil {
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t.Fatalf("rediscover offer demux: %v", err)
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}
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// Complete the second DORA.
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n, _ = cl.Encapsulate(buf[:], -1, 0)
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sv.Demux(buf[:n], 0)
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n, _ = sv.Encapsulate(buf[:], -1, 0)
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cl.Demux(buf[:n], 0)
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if cl.State() != StateBound {
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t.Errorf("second DORA: want StateBound, got %s", cl.State())
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}
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}
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