Pull request 2096: 4923 gopacket dhcp vol.5

Updates AdguardTeam#4923. Squashed commit of the following: commit 762a3f9 Merge: 2af65b4 34a34dc Author: Eugene Burkov <E.Burkov@AdGuard.COM> Date: Tue Dec 12 11:13:21 2023 +0300 Merge branch 'master' into 4923-gopacket-dhcp-vol.5 commit 2af65b4 Author: Eugene Burkov <E.Burkov@AdGuard.COM> Date: Fri Dec 8 16:22:51 2023 +0300 dhcpsvc: imp code commit 71233b9 Author: Eugene Burkov <E.Burkov@AdGuard.COM> Date: Fri Dec 8 15:26:25 2023 +0300 dhcpsvc: imp docs commit 2949544 Merge: 593e9ed 214175e Author: Eugene Burkov <E.Burkov@AdGuard.COM> Date: Thu Dec 7 16:48:18 2023 +0300 Merge branch 'master' into 4923-gopacket-dhcp-vol.5 commit 593e9ed Author: Eugene Burkov <E.Burkov@AdGuard.COM> Date: Thu Dec 7 16:45:10 2023 +0300 dhcpsvc: imp docs commit cdb1915 Author: Eugene Burkov <E.Burkov@AdGuard.COM> Date: Thu Dec 7 16:33:56 2023 +0300 dhcpsvc: imp code commit a0c423c Author: Eugene Burkov <E.Burkov@AdGuard.COM> Date: Tue Dec 5 20:56:43 2023 +0300 dnspsvc: add opts commit 050ab7f Author: Eugene Burkov <E.Burkov@AdGuard.COM> Date: Tue Dec 5 20:17:37 2023 +0300 WIP
annguyen0 · Dec 12, 2023 · 79d7a1e · 79d7a1e
1 parent 34a34dc
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Showing 3 changed files with 349 additions and 7 deletions.
diff --git a/internal/dhcpsvc/v4.go b/internal/dhcpsvc/v4.go
@@ -6,7 +6,10 @@ import (
 	"net/netip"
 	"time"
 
+	"github.com/AdguardTeam/golibs/log"
+	"github.com/AdguardTeam/golibs/netutil"
 	"github.com/google/gopacket/layers"
+	"golang.org/x/exp/slices"
 )
 
 // IPv4Config is the interface-specific configuration for DHCPv4.
@@ -26,7 +29,9 @@ type IPv4Config struct {
 	// RangeEnd is the last address in the range to assign to DHCP clients.
 	RangeEnd netip.Addr
 
-	// Options is the list of DHCP options to send to DHCP clients.
+	// Options is the list of DHCP options to send to DHCP clients.  The options
+	// having a zero value within the Length field are treated as deletions of
+	// the corresponding options, either implicit or explicit.
 	Options layers.DHCPOptions
 
 	// LeaseDuration is the TTL of a DHCP lease.
@@ -73,7 +78,14 @@ type iface4 struct {
 	// name is the name of the interface.
 	name string
 
-	// TODO(e.burkov):  Add options.
+	// implicitOpts are the options listed in Appendix A of RFC 2131 and
+	// initialized with default values.  It must not have intersections with
+	// explicitOpts.
+	implicitOpts layers.DHCPOptions
+
+	// explicitOpts are the user-configured options.  It must not have
+	// intersections with implicitOpts.
+	explicitOpts layers.DHCPOptions
 
 	// leaseTTL is the time-to-live of dynamic leases on this interface.
 	leaseTTL time.Duration
@@ -103,11 +115,206 @@ func newIface4(name string, conf *IPv4Config) (i *iface4, err error) {
 		return nil, fmt.Errorf("gateway ip %s in the ip range %s", conf.GatewayIP, addrSpace)
 	}
 
-	return &iface4{
+	i = &iface4{
 		name:      name,
 		gateway:   conf.GatewayIP,
 		subnet:    subnet,
 		addrSpace: addrSpace,
 		leaseTTL:  conf.LeaseDuration,
-	}, nil
+	}
+	i.implicitOpts, i.explicitOpts = conf.options()
+
+	return i, nil
+}
+
+// options returns the implicit and explicit options for the interface.  The two
+// lists are disjoint and the implicit options are initialized with default
+// values.
+//
+// TODO(e.burkov):  DRY with the IPv6 version.
+func (conf *IPv4Config) options() (implicit, explicit layers.DHCPOptions) {
+	// Set default values of host configuration parameters listed in Appendix A
+	// of RFC-2131.
+	implicit = layers.DHCPOptions{
+		// Values From Configuration
+
+		layers.NewDHCPOption(layers.DHCPOptSubnetMask, conf.SubnetMask.AsSlice()),
+		layers.NewDHCPOption(layers.DHCPOptRouter, conf.GatewayIP.AsSlice()),
+
+		// IP-Layer Per Host
+
+		// An Internet host that includes embedded gateway code MUST have a
+		// configuration switch to disable the gateway function, and this switch
+		// MUST default to the non-gateway mode.
+		//
+		// See https://datatracker.ietf.org/doc/html/rfc1122#section-3.3.5.
+		layers.NewDHCPOption(layers.DHCPOptIPForwarding, []byte{0x0}),
+
+		// A host that supports non-local source-routing MUST have a
+		// configurable switch to disable forwarding, and this switch MUST
+		// default to disabled.
+		//
+		// See https://datatracker.ietf.org/doc/html/rfc1122#section-3.3.5.
+		layers.NewDHCPOption(layers.DHCPOptSourceRouting, []byte{0x0}),
+
+		// Do not set the Policy Filter Option since it only makes sense when
+		// the non-local source routing is enabled.
+
+		// The minimum legal value is 576.
+		//
+		// See https://datatracker.ietf.org/doc/html/rfc2132#section-4.4.
+		layers.NewDHCPOption(layers.DHCPOptDatagramMTU, []byte{0x2, 0x40}),
+
+		// Set the current recommended default time to live for the Internet
+		// Protocol which is 64.
+		//
+		// See https://www.iana.org/assignments/ip-parameters/ip-parameters.xhtml#ip-parameters-2.
+		layers.NewDHCPOption(layers.DHCPOptDefaultTTL, []byte{0x40}),
+
+		// For example, after the PTMU estimate is decreased, the timeout should
+		// be set to 10 minutes; once this timer expires and a larger MTU is
+		// attempted, the timeout can be set to a much smaller value.
+		//
+		// See https://datatracker.ietf.org/doc/html/rfc1191#section-6.6.
+		layers.NewDHCPOption(layers.DHCPOptPathMTUAgingTimeout, []byte{0x0, 0x0, 0x2, 0x58}),
+
+		// There is a table describing the MTU values representing all major
+		// data-link technologies in use in the Internet so that each set of
+		// similar MTUs is associated with a plateau value equal to the lowest
+		// MTU in the group.
+		//
+		// See https://datatracker.ietf.org/doc/html/rfc1191#section-7.
+		layers.NewDHCPOption(layers.DHCPOptPathPlateuTableOption, []byte{
+			0x0, 0x44,
+			0x1, 0x28,
+			0x1, 0xFC,
+			0x3, 0xEE,
+			0x5, 0xD4,
+			0x7, 0xD2,
+			0x11, 0x0,
+			0x1F, 0xE6,
+			0x45, 0xFA,
+		}),
+
+		// IP-Layer Per Interface
+
+		// Don't set the Interface MTU because client may choose the value on
+		// their own since it's listed in the [Host Requirements RFC].  It also
+		// seems the values listed there sometimes appear obsolete, see
+		// https://github.com/AdguardTeam/AdGuardHome/issues/5281.
+		//
+		// [Host Requirements RFC]: https://datatracker.ietf.org/doc/html/rfc1122#section-3.3.3.
+
+		// Set the All Subnets Are Local Option to false since commonly the
+		// connected hosts aren't expected to be multihomed.
+		//
+		// See https://datatracker.ietf.org/doc/html/rfc1122#section-3.3.3.
+		layers.NewDHCPOption(layers.DHCPOptAllSubsLocal, []byte{0x0}),
+
+		// Set the Perform Mask Discovery Option to false to provide the subnet
+		// mask by options only.
+		//
+		// See https://datatracker.ietf.org/doc/html/rfc1122#section-3.2.2.9.
+		layers.NewDHCPOption(layers.DHCPOptMaskDiscovery, []byte{0x0}),
+
+		// A system MUST NOT send an Address Mask Reply unless it is an
+		// authoritative agent for address masks.  An authoritative agent may be
+		// a host or a gateway, but it MUST be explicitly configured as a
+		// address mask agent.
+		//
+		// See https://datatracker.ietf.org/doc/html/rfc1122#section-3.2.2.9.
+		layers.NewDHCPOption(layers.DHCPOptMaskSupplier, []byte{0x0}),
+
+		// Set the Perform Router Discovery Option to true as per Router
+		// Discovery Document.
+		//
+		// See https://datatracker.ietf.org/doc/html/rfc1256#section-5.1.
+		layers.NewDHCPOption(layers.DHCPOptRouterDiscovery, []byte{0x1}),
+
+		// The all-routers address is preferred wherever possible.
+		//
+		// See https://datatracker.ietf.org/doc/html/rfc1256#section-5.1.
+		layers.NewDHCPOption(layers.DHCPOptSolicitAddr, netutil.IPv4allrouter()),
+
+		// Don't set the Static Routes Option since it should be set up by
+		// system administrator.
+		//
+		// See https://datatracker.ietf.org/doc/html/rfc1122#section-3.3.1.2.
+
+		// A datagram with the destination address of limited broadcast will be
+		// received by every host on the connected physical network but will not
+		// be forwarded outside that network.
+		//
+		// See https://datatracker.ietf.org/doc/html/rfc1122#section-3.2.1.3.
+		layers.NewDHCPOption(layers.DHCPOptBroadcastAddr, netutil.IPv4bcast()),
+
+		// Link-Layer Per Interface
+
+		// If the system does not dynamically negotiate use of the trailer
+		// protocol on a per-destination basis, the default configuration MUST
+		// disable the protocol.
+		//
+		// See https://datatracker.ietf.org/doc/html/rfc1122#section-2.3.1.
+		layers.NewDHCPOption(layers.DHCPOptARPTrailers, []byte{0x0}),
+
+		// For proxy ARP situations, the timeout needs to be on the order of a
+		// minute.
+		//
+		// See https://datatracker.ietf.org/doc/html/rfc1122#section-2.3.2.1.
+		layers.NewDHCPOption(layers.DHCPOptARPTimeout, []byte{0x0, 0x0, 0x0, 0x3C}),
+
+		// An Internet host that implements sending both the RFC-894 and the
+		// RFC-1042 encapsulations MUST provide a configuration switch to select
+		// which is sent, and this switch MUST default to RFC-894.
+		//
+		// See https://datatracker.ietf.org/doc/html/rfc1122#section-2.3.3.
+		layers.NewDHCPOption(layers.DHCPOptEthernetEncap, []byte{0x0}),
+
+		// TCP Per Host
+
+		// A fixed value must be at least big enough for the Internet diameter,
+		// i.e., the longest possible path.  A reasonable value is about twice
+		// the diameter, to allow for continued Internet growth.
+		//
+		// See https://datatracker.ietf.org/doc/html/rfc1122#section-3.2.1.7.
+		layers.NewDHCPOption(layers.DHCPOptTCPTTL, []byte{0x0, 0x0, 0x0, 0x3C}),
+
+		// The interval MUST be configurable and MUST default to no less than
+		// two hours.
+		//
+		// See https://datatracker.ietf.org/doc/html/rfc1122#section-4.2.3.6.
+		layers.NewDHCPOption(layers.DHCPOptTCPKeepAliveInt, []byte{0x0, 0x0, 0x1C, 0x20}),
+
+		// Unfortunately, some misbehaved TCP implementations fail to respond to
+		// a probe segment unless it contains data.
+		//
+		// See https://datatracker.ietf.org/doc/html/rfc1122#section-4.2.3.6.
+		layers.NewDHCPOption(layers.DHCPOptTCPKeepAliveGarbage, []byte{0x1}),
+	}
+	slices.SortFunc(implicit, compareV4OptionCodes)
+
+	// Set values for explicitly configured options.
+	for _, exp := range conf.Options {
+		i, found := slices.BinarySearchFunc(implicit, exp, compareV4OptionCodes)
+		if found {
+			implicit = slices.Delete(implicit, i, i+1)
+		}
+
+		i, found = slices.BinarySearchFunc(explicit, exp, compareV4OptionCodes)
+		if exp.Length > 0 {
+			explicit = slices.Insert(explicit, i, exp)
+		} else if found {
+			explicit = slices.Delete(explicit, i, i+1)
+		}
+	}
+
+	log.Debug("dhcpsvc: v4: implicit options: %s", implicit)
+	log.Debug("dhcpsvc: v4: explicit options: %s", explicit)
+
+	return implicit, explicit
+}
+
+// compareV4OptionCodes compares option codes of a and b.
+func compareV4OptionCodes(a, b layers.DHCPOption) (res int) {
+	return int(a.Type) - int(b.Type)
 }
diff --git a/internal/dhcpsvc/v4_internal_test.go b/internal/dhcpsvc/v4_internal_test.go
@@ -0,0 +1,88 @@
+package dhcpsvc
+
+import (
+	"net/netip"
+	"testing"
+
+	"github.com/google/gopacket/layers"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestIPv4Config_Options(t *testing.T) {
+	oneIP, otherIP := netip.MustParseAddr("1.2.3.4"), netip.MustParseAddr("5.6.7.8")
+	subnetMask := netip.MustParseAddr("255.255.0.0")
+
+	opt1 := layers.NewDHCPOption(layers.DHCPOptSubnetMask, subnetMask.AsSlice())
+	opt6 := layers.NewDHCPOption(layers.DHCPOptDNS, append(oneIP.AsSlice(), otherIP.AsSlice()...))
+	opt28 := layers.NewDHCPOption(layers.DHCPOptBroadcastAddr, oneIP.AsSlice())
+	opt121 := layers.NewDHCPOption(layers.DHCPOptClasslessStaticRoute, []byte("cba"))
+
+	testCases := []struct {
+		name         string
+		conf         *IPv4Config
+		wantExplicit layers.DHCPOptions
+	}{{
+		name: "all_default",
+		conf: &IPv4Config{
+			Options: nil,
+		},
+		wantExplicit: nil,
+	}, {
+		name: "configured_ip",
+		conf: &IPv4Config{
+			Options: layers.DHCPOptions{opt28},
+		},
+		wantExplicit: layers.DHCPOptions{opt28},
+	}, {
+		name: "configured_ips",
+		conf: &IPv4Config{
+			Options: layers.DHCPOptions{opt6},
+		},
+		wantExplicit: layers.DHCPOptions{opt6},
+	}, {
+		name: "configured_del",
+		conf: &IPv4Config{
+			Options: layers.DHCPOptions{
+				layers.NewDHCPOption(layers.DHCPOptBroadcastAddr, nil),
+			},
+		},
+		wantExplicit: nil,
+	}, {
+		name: "rewritten_del",
+		conf: &IPv4Config{
+			Options: layers.DHCPOptions{
+				layers.NewDHCPOption(layers.DHCPOptBroadcastAddr, nil),
+				opt28,
+			},
+		},
+		wantExplicit: layers.DHCPOptions{opt28},
+	}, {
+		name: "configured_and_del",
+		conf: &IPv4Config{
+			Options: layers.DHCPOptions{
+				layers.NewDHCPOption(layers.DHCPOptClasslessStaticRoute, []byte("a")),
+				layers.NewDHCPOption(layers.DHCPOptClasslessStaticRoute, nil),
+				opt121,
+			},
+		},
+		wantExplicit: layers.DHCPOptions{opt121},
+	}, {
+		name: "replace_config_value",
+		conf: &IPv4Config{
+			SubnetMask: netip.MustParseAddr("255.255.255.0"),
+			Options:    layers.DHCPOptions{opt1},
+		},
+		wantExplicit: layers.DHCPOptions{opt1},
+	}}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			imp, exp := tc.conf.options()
+			assert.Equal(t, tc.wantExplicit, exp)
+
+			for c := range exp {
+				assert.NotContains(t, imp, c)
+			}
+		})
+	}
+}