Core now owns the question -- "should this socket be denied?" -- and none of the
answers. The firewall was the last implementation left in core, and the reasons
to keep it did not survive scrutiny: it is not extended downstream, and a shard
running bare core has no way to populate it anyway, since the admin gump and
the commands that mutate it are both content. Larger shards front the server
with an upstream proxy or edge scrubbing and never use it; it survives as the
fallback an admin reaches for over a single player, which is squarely content's
concern.
Nothing about the firewall changes for operators: same Server.Network namespace,
same Configuration/firewall.json, same gump and commands, same legacy .cfg
migration. It reaches the accept path through ConnectionFilters like any other
filter, and registers itself first because an empty set is the cheapest gate.
Untangling core from the firewall entry types first:
- NetworkUtilities built its reserved-network tables out of CidrFirewallEntry,
which made core depend on the firewall for something with nothing to do with
banning. Those are constant CIDR blocks answering "is this address in one of
these ranges?", so they are now a SortedRangeIndex<UInt128> -- the same
primitive the firewall and blocklist already share. Same semantics, same
public API, one linear scan replaced by a binary search.
- The CIDR -> normalized range parse those tables needed is now
IPAddressUtility.TryParseCidrRange, and CidrFirewallEntry drops its private
copy of that logic in favor of it.
Core no longer references IFirewallEntry or Firewall anywhere. 1344 tests pass.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Writes up IConnectionFilter for content authors: the accept-path contract
(allocation-free, non-blocking, side effects owned by the filter), registration
order and short-circuiting, the unregister-on-throw policy, and why this must
not be routed through EventSink.InvokeSocketConnect.
Also records the IPAddress <-> UInt128 normalization quirk. Addresses are
normalized to IPv6 form, so a v4 address round-tripped through UInt128 can come
back as InterNetworkV6 with IsIPv4MappedToIPv6 set. That is what the seemingly
redundant clause in ToUInt128 is defending, not a stray condition. Noted as a
follow-up rather than churned mid-feature: the normalization would read better
as an explicit "to canonical v6 bits" step that never needs the family check.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
## Summary
Captures the durable learnings from the message-interpolation work (PRs #2434, #2436, #2437, #2438, #2440) as reference documentation. **Doc-only PR — no code changes.**
The original Phase 2 audit (PR #2435) was development scaffolding and was closed unmerged once Phase 3 consumed it. This PR replaces it with proper reference docs that future authors can consult.
## What's added
### `dev-docs/string-handling.md`
- Promote `RawInterpolatedStringHandler` from a one-line note to a proper section listing all APIs that accept it (messages, OPL, gumps, packets).
- Document the `:L` lowercase format specifier.
- New comprehensive **"Interpolation Anti-Patterns"** section covering 8 patterns with before/after examples — applies to any handler-aware API:
1. Ternary with interpolated branches
2. Switch expression with interpolated arms
3. Pre-built local typed as `string`
4. `.ToString()` (or any string-returning method) inside a hole
5. String concatenation inside a hole
6. `string.Format` feeding a handler-aware API
7. LINQ-built strings inside a hole
8. Pre-built concat var
### `dev-docs/networking-packets.md`
- Add **"Player-Facing Message APIs"** section listing `Mobile` / `Item` / `NetState` message methods with their handler overloads.
- Note the `IBroadcastFilter` pattern for new spatial-broadcast helpers.
### `dev-docs/property-lists.md`, `dev-docs/gump-system.md`
- Cross-reference the new anti-patterns section.
- Add explicit `.ToString()` inside holes warning to property-lists (it had no such guidance before).
### `dev-docs/claude-skills/`
- Mirror the same content (condensed) in `modernuo-string-handling.md`, `modernuo-networking.md`, `modernuo-property-lists.md`, `modernuo-gump-system.md`.
- Add audit rule #17 to `modernuo-code-audit.md` covering all 8 anti-patterns with severity WARNING, plus the `:L` format spec.
### `CLAUDE.md`
- Add audit rule #18 summarizing the interpolation anti-patterns + `:L`, pointing to `dev-docs/string-handling.md` for details.
## Why this matters
Before this PR there was no documentation explaining when an interpolated string call site silently allocates a string despite the receiving API providing a handler overload. The Phase 3 cleanup (PRs #2436/#2437/#2438) discovered ~28 such sites in the codebase; without these docs the same patterns would re-emerge. The new audit rule + CLAUDE.md entry will catch them at write time.
Summary
- Adds CLAUDE.md at repo root with 14 terse code audit rules (always loaded, low token cost)
- Adds pointer files for other AI tools: AGENTS.md (Codex), GEMINI.md, .github/COPILOT-INSTRUCTIONS.md (Copilot), .cursorrules (Cursor) — all redirect to CLAUDE.md as single source of truth
- Gitignores /.claude so personal AI config isn't distributed
- Moves Claude skills to dev-docs/claude-skills/ (opt-in, not auto-loaded)
- Adds 14 dev-docs covering codebase conventions
Code Audit Rules (in CLAUDE.md)
1. LINQ tiered rules (Tier 1 free, Tier 2 warm, Tier 3 forbidden)
2. No Console.WriteLine — use LogFactory.GetLogger()
3. No concurrency primitives in game code
4. No World.Mobiles/World.Items iteration
5. Clean up refs in OnDelete()/OnAfterDelete()
6. Cancel timers in OnDelete()/OnAfterDelete()
7. STArrayPool<T>.Shared not ArrayPool<T>.Shared
8. PooledRefList<T> not new List<T>() on hot paths
9. Serialization: partial class, [Constructible], no serialized TimerExecutionToken
10. No Task.Run/new Thread() in game code
11. Never assume era — ask which expansion
12. _camelCase fields, PascalCase properties/methods
13. No empty gumps — use DisplayTo() pattern
14. PropertyList string literals must be {} holes, cliloc-as-argument uses :#
