diff options
Diffstat (limited to 'pkg')
| -rw-r--r-- | pkg/tcpip/header/ndp_router_advert.go | 75 |
1 files changed, 74 insertions, 1 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 |