RUST-BUG-078: avoid plaintext downgrade after obfuscated failure

Author: Threepwood-7

crates/emulebb-core/src/ed2k_sources.rs

@@ -29,8 +29,7 @@ use tokio_util::sync::CancellationToken;
 
 use crate::{
     ED2K_DOWNLOAD_KAD_SOURCE_CAP, ED2K_DOWNLOAD_KAD_SOURCE_QUIET_DELAY_MS,
-    ED2K_DOWNLOAD_KAD_SOURCE_RETRY_DELAY_MS, ED2K_HASH_ONLY_QUERY_PREFIX,
-    ED2K_SOURCE_OBFUSCATION_REQUIRES_CRYPT, Transfer,
+    ED2K_DOWNLOAD_KAD_SOURCE_RETRY_DELAY_MS, ED2K_HASH_ONLY_QUERY_PREFIX, Transfer,
 };
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -520,20 +519,6 @@ pub(crate) async fn collect_kad_ed2k_sources(
     sources
 }
 
-pub(crate) fn plaintext_fallback_for_obfuscated_source(
-    source: &Ed2kFoundSource,
-) -> Option<Ed2kFoundSource> {
-    let options = source.obfuscation_options?;
-    if options & ED2K_SOURCE_OBFUSCATION_REQUIRES_CRYPT != 0 {
-        return None;
-    }
-    let mut fallback = source.clone();
-    fallback.obfuscated = false;
-    fallback.obfuscation_options = None;
-    fallback.user_hash = None;
-    Some(fallback)
-}
-
 /// Identity used to recognize and drop our own client from a learned source set
 /// (eMule `CDownloadQueue::CheckAndAddSource`: a source whose user-hash equals
 /// ours, or whose IP/client-id + port equals ours, is never added as a source).

crates/emulebb-core/src/lib.rs

@@ -131,10 +131,10 @@ use ed2k_sources::{
     global_udp_source_batch_server_attempts, global_udp_source_search_excluded_endpoint,
     hash_only_ed2k_search_query, kad_source_result_to_ed2k_found_source, keyword_target,
     manifest_has_ed2k_transfer_progress, merge_download_sources, new_direct_ed2k_source_count,
-    plaintext_fallback_for_obfuscated_source, select_ed2k_keyword_metadata,
-    should_adopt_hash_only_metadata_name, should_query_kad_source_supplement,
-    should_query_server_udp_source_supplement, should_refresh_ed2k_server_sources,
-    should_skip_no_progress_source_requery, sort_download_sources, source_endpoint_key, source_key,
+    select_ed2k_keyword_metadata, should_adopt_hash_only_metadata_name,
+    should_query_kad_source_supplement, should_query_server_udp_source_supplement,
+    should_refresh_ed2k_server_sources, should_skip_no_progress_source_requery,
+    sort_download_sources, source_endpoint_key, source_key,
 };
 #[cfg(test)]
 use ed2k_sources::{
@@ -5389,16 +5389,6 @@ where
                         peer_addr
                     );
                     last_error = Some(error);
-                    if let Some(fallback_source) = plaintext_fallback_for_obfuscated_source(&source)
-                    {
-                        tracing::info!(
-                            "ED2K direct download scheduling plaintext fallback file_hash={} peer={}:{}",
-                            file_hash_hex,
-                            source.ip,
-                            source.tcp_port
-                        );
-                        pending_sources.push_front(fallback_source);
-                    }
                 }
             }
 
@@ -5551,8 +5541,6 @@ const ED2K_DOWNLOAD_KAD_SOURCE_QUIET_DELAY_MS: u64 = 750;
 const ED2K_DOWNLOAD_SOURCE_REQUERY_ROUNDS: usize = 2;
 const ED2K_DOWNLOAD_SOURCE_REQUERY_DELAY_SECS: u64 = 5;
 const ED2K_DOWNLOAD_BACKGROUND_RETRY_SECS: u64 = 5;
-const ED2K_SOURCE_OBFUSCATION_REQUIRES_CRYPT: u8 = 0x04;
-
 /// Parse a REST-surface IP string (the `Upload.address` / `TransferSource.ip`
 /// fields) into an `Ipv4Addr` for the ban store. Returns `None` when the value
 /// is empty or not a dialable IPv4 (e.g. a LowID client-id), so the ban falls
@@ -7724,9 +7712,9 @@ mod tests {
     }
 
     #[tokio::test]
-    async fn direct_download_scheduler_tries_plaintext_after_optional_obfuscated_failure() {
+    async fn direct_download_scheduler_does_not_downgrade_failed_obfuscated_peer() {
         let (transfer_runtime, secure_ident, file_hash_hex, file_name, file_size) =
-            completed_ed2k_transfer_runtime("emulebb-core-direct-download-plaintext-fallback")
+            completed_ed2k_transfer_runtime("emulebb-core-direct-download-no-plaintext-downgrade")
                 .await;
         let file_hash: Ed2kHash = file_hash_hex.parse().unwrap();
         let attempts = Arc::new(Mutex::new(Vec::new()));
@@ -7771,22 +7759,15 @@ mod tests {
         .await
         .unwrap();
 
-        assert!(outcome.completed);
         assert_eq!(
-            *attempts.lock().await,
-            vec![(41001, true, true), (41001, false, false)]
+            outcome
+                .last_error
+                .as_ref()
+                .map(ToString::to_string)
+                .as_deref(),
+            Some("simulated obfuscated peer close")
         );
-    }
-
-    #[test]
-    fn plaintext_fallback_preserves_crypt_required_sources() {
-        let file_hash = Ed2kHash::from_bytes([0x33; 16]);
-        let mut source = direct_test_source(file_hash, Ipv4Addr::new(192, 0, 2, 10), 41001);
-        source.obfuscated = true;
-        source.obfuscation_options = Some(0x07);
-        source.user_hash = Some([0x22; 16]);
-
-        assert!(plaintext_fallback_for_obfuscated_source(&source).is_none());
+        assert_eq!(*attempts.lock().await, vec![(41001, true, true)]);
     }
 
     #[test]

docs/active/INDEX.md

@@ -89,6 +89,7 @@ items.
 | [RUST-BUG-075](items/RUST-BUG-075.md) | Major | DONE | Preserve out-of-order requested ED2K blocks |
 | [RUST-BUG-076](items/RUST-BUG-076.md) | Major | DONE | Keep diag_event JSONL records line-atomic across shims |
 | [RUST-BUG-077](items/RUST-BUG-077.md) | Major | DONE | Persist accepted ED2K request blocks before bitmap recovery |
+| [RUST-BUG-078](items/RUST-BUG-078.md) | Major | DONE | Do not immediately downgrade failed obfuscated ED2K peers |
 
 ## Refactors (`REF`)
 

docs/active/items/RUST-BUG-078.md

@@ -0,0 +1,70 @@
+---
+id: RUST-BUG-078
+title: Do not immediately downgrade failed obfuscated ED2K peers
+status: done
+priority: Major
+category: bug
+workflow: local
+---
+
+# RUST-BUG-078: Do not immediately downgrade failed obfuscated ED2K peers
+
+## Problem
+
+The hide.me live-wire runs `rust-hideme-20260618T235505Z` and
+`rust-hideme-20260619T001217Z` stayed VPN-bound and completed transfers, but
+the obfuscation-enabled pass showed Rust immediately re-dialing the same ED2K
+peer in plaintext after an obfuscated direct-download connection failed.
+
+Comparing against eMuleBB MFC showed the parity rule:
+
+- `CUpDownClient::Connect` enables TCP obfuscation when the peer supports it,
+  local obfuscation is enabled, and either the peer requests it or local
+  preferences prefer it.
+- `CClientReqSocket::OnConnect` and `CClientReqSocket::Disconnect` tear down
+  failed sockets through `CUpDownClient::Disconnected`.
+- The client connection path does not immediately retry the same failed
+  obfuscated socket as plaintext. Normal source scheduling may later retry
+  sources through its ordinary timers and source records.
+
+Rust therefore must not synthesize an immediate plaintext source after a failed
+obfuscated attempt. A plaintext connection is still valid when an independent
+source record is actually plaintext.
+
+## Acceptance
+
+- [x] Failed obfuscated direct-download attempts do not enqueue an immediate
+      plaintext downgrade for the same endpoint.
+- [x] Independent plaintext source records remain eligible through the normal
+      source selection path.
+- [x] Existing direct-download retry behavior for other peers still works.
+- [x] Required-crypto peers are not downgraded.
+
+## Implementation Notes
+
+- Removed the direct scheduler's `plaintext_fallback_for_obfuscated_source`
+  downgrade path.
+- Removed the helper and the obsolete required-crypto guard constant that only
+  existed for that downgrade path.
+- Replaced the old fallback test with a regression test proving a failed
+  obfuscated source is attempted once and its error is retained.
+
+## Evidence
+
+- Live evidence source: `rust-hideme-20260618T235505Z`,
+  `rust-hideme-20260619T001217Z`.
+- Live log counts before the fix: 9 immediate plaintext fallbacks in
+  `rust-hideme-20260618T235505Z` obfuscation-on, 19 in
+  `rust-hideme-20260619T001217Z` obfuscation-on, and 1 in that run's
+  obfuscation-off pass due an obfuscated source record discovered while local
+  obfuscation was off.
+- Post-fix live proof: `rust-hideme-20260619T005416Z` passed, VPN-bound
+  (`10.55.68.38`), ED2K HighID, Kad connected, packet diagnostics captured, 20
+  downloads started, 1 completed, and `scheduling plaintext fallback` had zero
+  matches.
+- Post-fix transfer store: one `Verified` piece with 839,813 bytes, no completed
+  bitmap leftovers, and the completed transfer row marked completed.
+- `cargo test -p emulebb-core direct_download_scheduler_does_not_downgrade_failed_obfuscated_peer --locked`
+- `cargo test -p emulebb-core direct_download_scheduler --locked`
+- `python -m emule_workspace build clients --client emulebb-rust --diagnostics`
+- `python scripts/rust-live-wire-hideme.py --inputs live-wire-inputs.local.json --max-terms 3 --max-concurrent 20 --download-timeout 600 --require-packet-diagnostics --reask`