From d18bb4f38a7a89456dad1f3a0e8ff13a0b65ba7f Mon Sep 17 00:00:00 2001 From: Chris Kuiper Date: Wed, 5 Jun 2019 16:07:18 -0700 Subject: Adjust route when looping multicast packets Multicast packets are special in that their destination address does not identify a specific interface. When sending out such a packet the multicast address is the remote address, but for incoming packets it is the local address. Hence, when looping a multicast packet, the route needs to be tweaked to reflect this. PiperOrigin-RevId: 251739298 --- pkg/tcpip/stack/route.go | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'pkg/tcpip/stack') diff --git a/pkg/tcpip/stack/route.go b/pkg/tcpip/stack/route.go index 3d4c282a9..55ed02479 100644 --- a/pkg/tcpip/stack/route.go +++ b/pkg/tcpip/stack/route.go @@ -187,3 +187,13 @@ func (r *Route) Clone() Route { r.ref.incRef() return *r } + +// MakeLoopedRoute duplicates the given route and tweaks it in case of multicast. +func (r *Route) MakeLoopedRoute() Route { + l := r.Clone() + if header.IsV4MulticastAddress(r.RemoteAddress) || header.IsV6MulticastAddress(r.RemoteAddress) { + l.RemoteAddress, l.LocalAddress = l.LocalAddress, l.RemoteAddress + l.RemoteLinkAddress = l.LocalLinkAddress + } + return l +} -- cgit v1.2.3