[review] Address comments and update XDE test infra

Includes:
   - geneve_verify: Add `assert_geneve_packet` helper and multi-packet parsing
   - geneve: Fix `packet_length()` for known options where body is consumed
     - Add `HeaderLen` supertrait bound to `OptionCast`
     - Implement `HeaderLen` for `Known<T>` delegating to T for known variants
     - `GeneveOptionParse::packet_length()` now uses `option.packet_length()`
       instead of relying solely on `body_remainder` which is empty for
       known options after parsing consumes the body
   - oxide-vpc geneve: Add `HeaderLen` impl for `ValidOxideOption`
   - overlay: Rewrite inner dest MAC to RFC-compliant multicast MAC for Tx
   - dhcpv6: Compute proper UDP checksum for IPv6
   - ip: Add `multicast_mac()` methods with RFC 1112/2464 citations
   - opteadm: Add `set-m2p`/`clear-m2p` commands for multicast-to-physical mappings
   - xde-tests: Use typed `Ipv4Addr`/`Ipv6Addr` instead of `String` in dualstack setup
   - xde-tests: Simplify topology helpers and naming conventions (tests run single-threaded)
   - test.sh: Exercise driver teardown with `rem_drv` after tests
    complete
   - xde: Normalize inner dst MAC on Rx
     - drop non‑multicast inner
     - add mcast_rx_bad_inner_dst stat
   - xde: Initialize `mcast_fwd` from token and add `RefreshScope` and
          use scoped refresh across create/delete/subscribe/unsubscribe

Author: zeeshanlakhani

.github/buildomat/jobs/test.sh

@@ -94,3 +94,7 @@ pfexec /input/xde/work/test/multicast_multi_sub --nocapture --test-threads=1
 
 pfexec chmod +x /input/xde/work/test/multicast_validation
 pfexec /input/xde/work/test/multicast_validation --nocapture --test-threads=1
+
+banner "teardown"
+# Ensure full driver teardown is exercised after tests complete
+pfexec rem_drv xde

bin/opteadm/src/bin/opteadm.rs

@@ -28,6 +28,7 @@ use oxide_vpc::api::AddFwRuleReq;
 use oxide_vpc::api::AddRouterEntryReq;
 use oxide_vpc::api::Address;
 use oxide_vpc::api::BOUNDARY_SERVICES_VNI;
+use oxide_vpc::api::ClearMcast2PhysReq;
 use oxide_vpc::api::ClearMcastForwardingReq;
 use oxide_vpc::api::ClearVirt2BoundaryReq;
 use oxide_vpc::api::ClearVirt2PhysReq;
@@ -59,6 +60,7 @@ use oxide_vpc::api::SNat4Cfg;
 use oxide_vpc::api::SNat6Cfg;
 use oxide_vpc::api::SetExternalIpsReq;
 use oxide_vpc::api::SetFwRulesReq;
+use oxide_vpc::api::SetMcast2PhysReq;
 use oxide_vpc::api::SetMcastForwardingReq;
 use oxide_vpc::api::SetVirt2BoundaryReq;
 use oxide_vpc::api::SetVirt2PhysReq;
@@ -236,6 +238,33 @@ enum Command {
     /// Clear a virtual-to-boundary mapping
     ClearV2B { prefix: IpCidr, tunnel_endpoint: Vec<Ipv6Addr> },
 
+    /// Set a multicast-to-physical (M2P) mapping
+    ///
+    /// Maps an overlay multicast group address to an underlay IPv6 multicast
+    /// address. This mapping is required before ports can subscribe to the
+    /// group. Subscriptions use overlay addresses while OPTE uses underlay
+    /// addresses for actual packet delivery.
+    ///
+    /// All multicast groups use the fleet-wide DEFAULT_MULTICAST_VNI (77).
+    SetM2P {
+        /// The overlay multicast group address (IPv4 or IPv6)
+        group: IpAddr,
+        /// The underlay IPv6 multicast address (admin-local scope ff04::/16)
+        underlay: MulticastUnderlay,
+    },
+
+    /// Clear a multicast-to-physical (M2P) mapping
+    ///
+    /// Removes the mapping from an overlay multicast group to its underlay
+    /// address. After clearing, ports can no longer subscribe to this group
+    /// (but existing subscriptions will succeed as no-ops on unsubscribe).
+    ClearM2P {
+        /// The overlay multicast group address (IPv4 or IPv6)
+        group: IpAddr,
+        /// The underlay IPv6 multicast address (admin-local scope ff04::/16)
+        underlay: MulticastUnderlay,
+    },
+
     /// Set a multicast forwarding entry
     ///
     /// Adds or updates a next hop for the specified underlay multicast address.
@@ -862,6 +891,16 @@ fn main() -> anyhow::Result<()> {
             hdl.clear_v2b(&req)?;
         }
 
+        Command::SetM2P { group, underlay } => {
+            let req = SetMcast2PhysReq { group, underlay };
+            hdl.set_m2p(&req)?;
+        }
+
+        Command::ClearM2P { group, underlay } => {
+            let req = ClearMcast2PhysReq { group, underlay };
+            hdl.clear_m2p(&req)?;
+        }
+
         Command::SetMcastFwd { underlay, next_hop, replication } => {
             // OPTE routes to the next hop's unicast address to determine which
             // underlay port to use via the illumos routing table and DDM.

crates/opte-api/src/ip.rs

@@ -314,6 +314,20 @@ impl IpAddr {
             IpAddr::Ip6(v6) => v6.is_multicast(),
         }
     }
+
+    /// Return the multicast MAC address associated with this multicast IP address.
+    /// If the IP address is not multicast, None will be returned.
+    ///
+    /// See [RFC 1112 §6.4] for IPv4 and [RFC 2464 §7] for IPv6.
+    ///
+    /// [RFC 1112 §6.4]: https://www.rfc-editor.org/rfc/rfc1112#section-6.4
+    /// [RFC 2464 §7]: https://www.rfc-editor.org/rfc/rfc2464
+    pub const fn multicast_mac(&self) -> Option<MacAddr> {
+        match self {
+            IpAddr::Ip4(v4) => v4.multicast_mac(),
+            IpAddr::Ip6(v6) => v6.multicast_mac(),
+        }
+    }
 }
 
 impl From<Ipv4Addr> for IpAddr {
@@ -444,6 +458,38 @@ impl Ipv4Addr {
     pub const fn is_multicast(&self) -> bool {
         matches!(self.inner[0], 224..240)
     }
+
+    /// Return the multicast MAC address associated with this multicast IPv4
+    /// address. If the IPv4 address is not multicast, None will be returned.
+    ///
+    /// See [RFC 1112 §6.4] for details.
+    ///
+    /// [RFC 1112 §6.4]: https://www.rfc-editor.org/rfc/rfc1112#section-6.4
+    pub const fn multicast_mac(&self) -> Option<MacAddr> {
+        if self.is_multicast() {
+            Some(self.unchecked_multicast_mac())
+        } else {
+            None
+        }
+    }
+
+    /// Return the multicast MAC address associated with this multicast IPv4
+    /// address, without checking if this IP address is a multicast address.
+    ///
+    /// See [RFC 1112 §6.4] for details.
+    ///
+    /// [RFC 1112 §6.4]: https://www.rfc-editor.org/rfc/rfc1112#section-6.4
+    pub const fn unchecked_multicast_mac(&self) -> MacAddr {
+        let bytes = &self.inner;
+        MacAddr::from_const([
+            0x01,
+            0x00,
+            0x5e,
+            bytes[1] & 0x7f, // Mask bit 24 to get lower 23 bits
+            bytes[2],
+            bytes[3],
+        ])
+    }
 }
 
 impl From<core::net::Ipv4Addr> for Ipv4Addr {
@@ -1601,6 +1647,19 @@ mod test {
         );
     }
 
+    fn to_ipv4(s: &str) -> Ipv4Addr {
+        s.parse().unwrap()
+    }
+
+    #[test]
+    fn test_ipv4_multicast_mac() {
+        assert!(to_ipv4("192.168.1.1").multicast_mac().is_none());
+        assert_eq!(
+            to_ipv4("224.0.0.251").multicast_mac().unwrap(),
+            MacAddr::from([0x01, 0x00, 0x5e, 0x00, 0x00, 0xfb]),
+        );
+    }
+
     #[test]
     fn test_ipv6_solicited_node_multicast() {
         let addr = to_ipv6("fd00:abcd:abcd:abcd:abcd:abcd:abcd:abcd");