Support add/remove IPv6 multicast group sock opt

IPv4 was always supported but UDP never supported joining/leaving IPv6
multicast groups via socket options.

Add: IPPROTO_IPV6, IPV6_JOIN_GROUP/IPV6_ADD_MEMBERSHIP
Remove: IPPROTO_IPV6, IPV6_LEAVE_GROUP/IPV6_DROP_MEMBERSHIP

Test: integration_test.TestUDPAddRemoveMembershipSocketOption
PiperOrigin-RevId: 350396072

1 files changed, 34 insertions, 3 deletions

diff --git a/pkg/sentry/socket/netstack/netstack.go b/pkg/sentry/socket/netstack/netstack.go
index 3f587638f..fe11fca9c 100644
--- a/pkg/sentry/socket/netstack/netstack.go
+++ b/pkg/sentry/socket/netstack/netstack.go
@@ -2091,9 +2091,29 @@ func setSockOptIPv6(t *kernel.Task, s socket.SocketOps, ep commonEndpoint, name
 		ep.SocketOptions().SetV6Only(v != 0)
 		return nil
 
-	case linux.IPV6_ADD_MEMBERSHIP,
-		linux.IPV6_DROP_MEMBERSHIP,
-		linux.IPV6_IPSEC_POLICY,
+	case linux.IPV6_ADD_MEMBERSHIP:
+		req, err := copyInMulticastV6Request(optVal)
+		if err != nil {
+			return err
+		}
+
+		return syserr.TranslateNetstackError(ep.SetSockOpt(&tcpip.AddMembershipOption{
+			NIC:           tcpip.NICID(req.InterfaceIndex),
+			MulticastAddr: tcpip.Address(req.MulticastAddr[:]),
+		}))
+
+	case linux.IPV6_DROP_MEMBERSHIP:
+		req, err := copyInMulticastV6Request(optVal)
+		if err != nil {
+			return err
+		}
+
+		return syserr.TranslateNetstackError(ep.SetSockOpt(&tcpip.RemoveMembershipOption{
+			NIC:           tcpip.NICID(req.InterfaceIndex),
+			MulticastAddr: tcpip.Address(req.MulticastAddr[:]),
+		}))
+
+	case linux.IPV6_IPSEC_POLICY,
 		linux.IPV6_JOIN_ANYCAST,
 		linux.IPV6_LEAVE_ANYCAST,
 		// TODO(b/148887420): Add support for IPV6_PKTINFO.
@@ -2181,6 +2201,7 @@ func setSockOptIPv6(t *kernel.Task, s socket.SocketOps, ep commonEndpoint, name
 var (
 	inetMulticastRequestSize        = int(binary.Size(linux.InetMulticastRequest{}))
 	inetMulticastRequestWithNICSize = int(binary.Size(linux.InetMulticastRequestWithNIC{}))
+	inet6MulticastRequestSize       = int(binary.Size(linux.Inet6MulticastRequest{}))
 )
 
 // copyInMulticastRequest copies in a variable-size multicast request. The
@@ -2214,6 +2235,16 @@ func copyInMulticastRequest(optVal []byte, allowAddr bool) (linux.InetMulticastR
 	return req, nil
 }
 
+func copyInMulticastV6Request(optVal []byte) (linux.Inet6MulticastRequest, *syserr.Error) {
+	if len(optVal) < inet6MulticastRequestSize {
+		return linux.Inet6MulticastRequest{}, syserr.ErrInvalidArgument
+	}
+
+	var req linux.Inet6MulticastRequest
+	binary.Unmarshal(optVal[:inet6MulticastRequestSize], usermem.ByteOrder, &req)
+	return req, nil
+}
+
 // parseIntOrChar copies either a 32-bit int or an 8-bit uint out of buf.
 //
 // net/ipv4/ip_sockglue.c:do_ip_setsockopt does this for its socket options.