[multicast] Narrow underlay scope to ff04::/64 and add ASM source filtering (#189)

Underlay changes:
- Restrict internal multicast from admin/site/org scoped (ff04, ff05, ff08)
  to just Omicron's reserved subnet (ff04::/64). These underlay addresses are
  made unique in Omicron.
- Rename `AdminScopedIpv6` to `UnderlayMulticastIpv6`.
- Simplify P4 to only match ff04::/64.
- Use omicron-common multicast constants for validation.

Source filtering changes:
- Replace IpSrc::Subnet with IpSrc::Any for any-source matching.
- Change IPv6 source filter from exact to LPM match.
- Allow source filters on ASM groups (previously SSM-only).

API changes:
- API v5 adds IpSrc::Any for ASM source filtering.
- API v6 enforces strict underlay subnet validation.

Author: zeeshanlakhani

Cargo.lock

@@ -51,7 +51,7 @@ omicron-common = { git = "https://github.com/oxidecomputer/omicron", branch= "ma
 oximeter = { git = "https://github.com/oxidecomputer/omicron", branch = "main" }
 oximeter-producer = { git = "https://github.com/oxidecomputer/omicron", branch = "main" }
 oximeter-instruments = { git = "https://github.com/oxidecomputer/omicron", branch = "main", default-features = false, features = ["kstat"] }
-oxnet = { version = "0.1.3", default-features = false, features = ["schemars", "serde"] }
+oxnet = { version = "0.1.4", default-features = false, features = ["schemars", "serde"] }
 propolis = { git = "https://github.com/oxidecomputer/propolis" }
 smf = { git = "https://github.com/illumos/smf-rs" }
 softnpu-lib = { git = "https://github.com/oxidecomputer/softnpu" , package = "softnpu" , branch = "main"}
@@ -69,7 +69,7 @@ colored = "3"
 csv = "1.3"
 curl = "0.4"
 display-error-chain = "0.2"
-dropshot = "0.16.4"
+dropshot = "0.16.6"
 dropshot-api-manager = "0.2.2"
 dropshot-api-manager-types = "0.2.2"
 expectorate = "1"

Cargo.toml

@@ -341,5 +341,14 @@ proxy_arp:
 3. run `SDE=/opt/oxide/tofino_sde cargo test --features=<feature>` to execute
    the tests.
 
-If regenerating the openapi specifications, set `EXPECTORATE=overwrite` when
-runnning the tests with the `tofino_asic` feature.
+### OpenAPI Generation
+
+`dpd-api/src/lib.rs` contains endpoint [dropshot][dropshot-gh] definitions and
+controls API versioning for the `dpd` OpenAPI interface. If you add/remove or
+edit API points and/or documentation, you can update the API version and
+regenerate the latest OpenAPI specification bindings by running
+`cargo xtask openapi generate`. Use `cargo xtask openapi check` to verify
+specs are up-to-date.
+
+
+[dropshot-gh]: https://github.com/oxidecomputer/dropshot