xray: within one user batch the last entry for a user does not win #129

Found by code review and reproduced in a lab; never seen in production. This is a robustness fix: the upstream panel and bridge do not send such a batch today (see below).

Summary

When one batch lists the same email more than once, the Xray backend does not apply the last entry. UpdateUsers (reached through SyncUsersChunked, controller/users_chunk.go:37) compares every entry with the state from before the batch and applies all removals before any add, and Config.syncUsers (full sync and startup config) never takes off a user that an earlier entry added. The result follows an earlier entry.

Reproduction (real node, real Xray)

Real node built from dev 9ccd2638c7fe, REST, real Xray 26.3.27, macOS arm64; one trojan inbound; core state read with xray api inbounduser. Each step is one PUT /users/sync/chunked with one chunk:

All requests answered HTTP 200. The core keeps the wrong state until a later sync for that user (read from the code, not reproduced).

Not reachable from the upstream panel or bridge today

Found by reading, not run against a real panel. node_bridge_py c5632b65a10a queues one entry per email per node (PasarGuardNodeBridge/storage.py:159-166, pending[user.email] = ...) before it sends SyncUser / SyncUsersChunked, and panel dev f92acaf51cec sends users through the bridge (app/node/__init__.py:293,415,428). Any other client of the node's gRPC or REST API can send such a batch (read from the code; the lab used REST).

Config.updateUsers has the same ordering, but no RPC reaches it: its only caller is UpdateUsersAndRestart (backend/xray/user.go:439), and nothing outside the backends calls that (git grep at 9ccd2638).

Root cause (dev 9ccd2638)

• backend/xray/config.go:112 (buildInboundUpdates) handles every entry, so one email can be both in update.accounts and in removeEmailSet.
• backend/xray/user.go:387 changedAccounts compares each entry with the pre-batch state; user.go:392 applies every removal before the adds at user.go:407.
• backend/xray/config.go:66 Config.syncUsers -> Inbound.syncUsers (:143) only adds users that list the inbound.

Affected versions

dev 9ccd2638c7fe and main v0.5.7 739eab94a934.

Proposed fix

Keep only the last entry per email before building the per-inbound updates and before rebuilding an inbound's clients. PR #134.