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-rw-r--r--pkg/tcpip/header/ndp_router_advert.go75
-rw-r--r--pkg/tcpip/header/ndp_test.go91
2 files changed, 143 insertions, 23 deletions
diff --git a/pkg/tcpip/header/ndp_router_advert.go b/pkg/tcpip/header/ndp_router_advert.go
index bf7610863..7e2f0c797 100644
--- a/pkg/tcpip/header/ndp_router_advert.go
+++ b/pkg/tcpip/header/ndp_router_advert.go
@@ -19,12 +19,72 @@ import (
"time"
)
+// NDPRoutePreference is the preference values for default routers or
+// more-specific routes.
+//
+// As per RFC 4191 section 2.1,
+//
+// Default router preferences and preferences for more-specific routes
+// are encoded the same way.
+//
+// Preference values are encoded as a two-bit signed integer, as
+// follows:
+//
+// 01 High
+// 00 Medium (default)
+// 11 Low
+// 10 Reserved - MUST NOT be sent
+//
+// Note that implementations can treat the value as a two-bit signed
+// integer.
+//
+// Having just three values reinforces that they are not metrics and
+// more values do not appear to be necessary for reasonable scenarios.
+type NDPRoutePreference uint8
+
+const (
+ // HighRoutePreference indicates a high preference, as per
+ // RFC 4191 section 2.1.
+ HighRoutePreference NDPRoutePreference = 0b01
+
+ // MediumRoutePreference indicates a medium preference, as per
+ // RFC 4191 section 2.1.
+ //
+ // This is the default preference value.
+ MediumRoutePreference = 0b00
+
+ // LowRoutePreference indicates a low preference, as per
+ // RFC 4191 section 2.1.
+ LowRoutePreference = 0b11
+
+ // ReservedRoutePreference is a reserved preference value, as per
+ // RFC 4191 section 2.1.
+ //
+ // It MUST NOT be sent.
+ ReservedRoutePreference = 0b10
+)
+
// NDPRouterAdvert is an NDP Router Advertisement message. It will only contain
// the body of an ICMPv6 packet.
//
-// See RFC 4861 section 4.2 for more details.
+// See RFC 4861 section 4.2 and RFC 4191 section 2.2 for more details.
type NDPRouterAdvert []byte
+// As per RFC 4191 section 2.2,
+//
+// 0 1 2 3
+// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// | Type | Code | Checksum |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// | Cur Hop Limit |M|O|H|Prf|Resvd| Router Lifetime |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// | Reachable Time |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// | Retrans Timer |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// | Options ...
+// +-+-+-+-+-+-+-+-+-+-+-+-
const (
// NDPRAMinimumSize is the minimum size of a valid NDP Router
// Advertisement message (body of an ICMPv6 packet).
@@ -47,6 +107,14 @@ const (
// within the bit-field/flags byte of an NDPRouterAdvert.
ndpRAOtherConfFlagMask = (1 << 6)
+ // ndpDefaultRouterPreferenceShift is the shift of the Prf (Default Router
+ // Preference) field within the flags byte of an NDPRouterAdvert.
+ ndpDefaultRouterPreferenceShift = 3
+
+ // ndpDefaultRouterPreferenceMask is the mask of the Prf (Default Router
+ // Preference) field within the flags byte of an NDPRouterAdvert.
+ ndpDefaultRouterPreferenceMask = (0b11 << ndpDefaultRouterPreferenceShift)
+
// ndpRARouterLifetimeOffset is the start of the 2-byte Router Lifetime
// field within an NDPRouterAdvert.
ndpRARouterLifetimeOffset = 2
@@ -80,6 +148,11 @@ func (b NDPRouterAdvert) OtherConfFlag() bool {
return b[ndpRAFlagsOffset]&ndpRAOtherConfFlagMask != 0
}
+// DefaultRouterPreference returns the Default Router Preference field.
+func (b NDPRouterAdvert) DefaultRouterPreference() NDPRoutePreference {
+ return NDPRoutePreference((b[ndpRAFlagsOffset] & ndpDefaultRouterPreferenceMask) >> ndpDefaultRouterPreferenceShift)
+}
+
// RouterLifetime returns the lifetime associated with the default router. A
// value of 0 means the source of the Router Advertisement is not a default
// router and SHOULD NOT appear on the default router list. Note, a value of 0
diff --git a/pkg/tcpip/header/ndp_test.go b/pkg/tcpip/header/ndp_test.go
index 1b5093e58..8fd1f7d13 100644
--- a/pkg/tcpip/header/ndp_test.go
+++ b/pkg/tcpip/header/ndp_test.go
@@ -126,36 +126,83 @@ func TestNDPNeighborAdvert(t *testing.T) {
}
func TestNDPRouterAdvert(t *testing.T) {
- b := []byte{
- 64, 128, 1, 2,
- 3, 4, 5, 6,
- 7, 8, 9, 10,
+ tests := []struct {
+ hopLimit uint8
+ managedFlag, otherConfFlag bool
+ prf NDPRoutePreference
+ routerLifetimeS uint16
+ reachableTimeMS, retransTimerMS uint32
+ }{
+ {
+ hopLimit: 1,
+ managedFlag: false,
+ otherConfFlag: true,
+ prf: HighRoutePreference,
+ routerLifetimeS: 2,
+ reachableTimeMS: 3,
+ retransTimerMS: 4,
+ },
+ {
+ hopLimit: 64,
+ managedFlag: true,
+ otherConfFlag: false,
+ prf: LowRoutePreference,
+ routerLifetimeS: 258,
+ reachableTimeMS: 78492,
+ retransTimerMS: 13213,
+ },
}
- ra := NDPRouterAdvert(b)
+ for i, test := range tests {
+ t.Run(fmt.Sprintf("%d", i), func(t *testing.T) {
+ flags := uint8(0)
+ if test.managedFlag {
+ flags |= 1 << 7
+ }
+ if test.otherConfFlag {
+ flags |= 1 << 6
+ }
+ flags |= uint8(test.prf) << 3
- if got := ra.CurrHopLimit(); got != 64 {
- t.Errorf("got ra.CurrHopLimit = %d, want = 64", got)
- }
+ b := []byte{
+ test.hopLimit, flags, 1, 2,
+ 3, 4, 5, 6,
+ 7, 8, 9, 10,
+ }
+ binary.BigEndian.PutUint16(b[2:], test.routerLifetimeS)
+ binary.BigEndian.PutUint32(b[4:], test.reachableTimeMS)
+ binary.BigEndian.PutUint32(b[8:], test.retransTimerMS)
- if got := ra.ManagedAddrConfFlag(); !got {
- t.Errorf("got ManagedAddrConfFlag = false, want = true")
- }
+ ra := NDPRouterAdvert(b)
- if got := ra.OtherConfFlag(); got {
- t.Errorf("got OtherConfFlag = true, want = false")
- }
+ if got := ra.CurrHopLimit(); got != test.hopLimit {
+ t.Errorf("got ra.CurrHopLimit() = %d, want = %d", got, test.hopLimit)
+ }
- if got, want := ra.RouterLifetime(), time.Second*258; got != want {
- t.Errorf("got ra.RouterLifetime = %d, want = %d", got, want)
- }
+ if got := ra.ManagedAddrConfFlag(); got != test.managedFlag {
+ t.Errorf("got ManagedAddrConfFlag() = %t, want = %t", got, test.managedFlag)
+ }
- if got, want := ra.ReachableTime(), time.Millisecond*50595078; got != want {
- t.Errorf("got ra.ReachableTime = %d, want = %d", got, want)
- }
+ if got := ra.OtherConfFlag(); got != test.otherConfFlag {
+ t.Errorf("got OtherConfFlag() = %t, want = %t", got, test.otherConfFlag)
+ }
+
+ if got := ra.DefaultRouterPreference(); got != test.prf {
+ t.Errorf("got DefaultRouterPreference() = %d, want = %d", got, test.prf)
+ }
- if got, want := ra.RetransTimer(), time.Millisecond*117967114; got != want {
- t.Errorf("got ra.RetransTimer = %d, want = %d", got, want)
+ if got, want := ra.RouterLifetime(), time.Second*time.Duration(test.routerLifetimeS); got != want {
+ t.Errorf("got ra.RouterLifetime() = %d, want = %d", got, want)
+ }
+
+ if got, want := ra.ReachableTime(), time.Millisecond*time.Duration(test.reachableTimeMS); got != want {
+ t.Errorf("got ra.ReachableTime() = %d, want = %d", got, want)
+ }
+
+ if got, want := ra.RetransTimer(), time.Millisecond*time.Duration(test.retransTimerMS); got != want {
+ t.Errorf("got ra.RetransTimer() = %d, want = %d", got, want)
+ }
+ })
}
}
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-27 18:21:11 +0000