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defects/haproxy/patch/haproxy-0003-spoe-check-config-resolution-O-N2.md

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+# haproxy-0003 — flt_spoe.c spoe_check_config O(P×M), O(P×G), O(G×P×M) resolution loops
+
+## Ecosystem
+haproxy (C)
+
+## Severity
+LOW — config-finalization only, not hot path
+
+## Location
+`src/flt_spoe.c` function `spoe_check_config`:
+
+- Line ~2407: `list_for_each_entry(ph, &curmphs)` × `list_for_each_entry(msg, &curmsgs)` — O(P×M)
+- Line ~2508: `list_for_each_entry(ph, &curgphs)` × `list_for_each_entry_safe(grp, &curgrps)` — O(P×G)
+- Line ~2526: `list_for_each_entry(grp)` × `list_for_each_entry(ph, &grp->phs)` × `list_for_each_entry(msg, &curmsgs)` — O(G×P×M)
+
+## Description
+`spoe_check_config` is called after the SPOE config file is parsed to resolve
+placeholder references to their corresponding message/group objects. Three
+separate nested list-walk patterns are present:
+
+**Pattern 1 — placeholder-to-message resolution (lines ~2407–2504):**
+```c
+list_for_each_entry(ph, &curmphs, list) {           // outer: P placeholders
+    list_for_each_entry(msg, &curmsgs, list) {       // inner: M messages
+        if (strcmp(msg->id, ph->id) == 0) {          // O(1) strcmp
+            // resolve
+            goto next_mph;
+        }
+    }
+    // error: undefined message
+}
+```
+Complexity: O(P × M) where P = message placeholders, M = defined messages.
+
+**Pattern 2 — group-placeholder resolution (lines ~2508–2522):**
+```c
+list_for_each_entry(ph, &curgphs, list) {                // outer: P group placeholders
+    list_for_each_entry_safe(grp, grpback, &curgrps, list) { // inner: G groups
+        if (strcmp(grp->id, ph->id) == 0) {                   // O(1) strcmp
+            goto next_aph;
+        }
+    }
+}
+```
+Complexity: O(P × G) where P = group placeholders, G = defined groups.
+
+**Pattern 3 — group message assignment (lines ~2526–2553):**
+```c
+list_for_each_entry(grp, &curagent->groups, list) {         // outer: G groups
+    list_for_each_entry_safe(ph, phback, &grp->phs, list) { // mid: P phs per group
+        list_for_each_entry(msg, &curmsgs, list) {           // inner: M messages
+            if (strcmp(msg->id, ph->id) == 0) {
+                goto next_mph_grp;
+            }
+        }
+        // error: undefined message
+    }
+}
+```
+Complexity: O(G × P × M) — cubic in terms of SPOE config size.
+
+Note: `haproxy-0002` covers the duplicate-detection loops at lines ~1580/1604/1991
+(while `*args[cur_arg]` + list scan). This defect covers the distinct
+config-finalization resolution loops.
+
+## Complexity Table
+
+| Pattern | Complexity | Variables |
+|---------|------------|-----------|
+| msg placeholder resolution | O(P × M) | P=placeholders, M=messages |
+| group placeholder resolution | O(P × G) | P=placeholders, G=groups |
+| group-message assignment | O(G × P × M) | cubic |
+
+Typical SPOE configs: M=10–50, G=5–20, P=10–50.
+At M=50, G=20, P=50: pattern 3 = 50×50×50 = 125,000 iterations vs ~100 with maps.
+
+## Fix
+Build a `struct eb_root` keyed by `id` from `curmsgs` and `curgrps` before
+the resolution loops, then replace each inner walk with an `ebst_lookup`:
+
+```c
+struct eb_root msgs_by_id = EB_ROOT;
+list_for_each_entry(msg, &curmsgs, list) {
+    ebst_insert(&msgs_by_id, &msg->by_id_node);  // O(log M)
+}
+
+list_for_each_entry(ph, &curmphs, list) {
+    msg = ebst_entry(ebst_lookup(&msgs_by_id, ph->id), struct spoe_message, by_id_node);
+    if (!msg) { /* error */ goto error; }
+    // resolve
+}
+```
+
+HAProxy already uses `ebst`/`ebmb` extensively throughout the codebase.
+
+## CWE
+CWE-407: Inefficient Algorithmic Complexity
+
+## Speedup
+Pattern 3 at M=50, G=20, P=50: 125,000 → ~120 lookups (O(log M) each) ≈ 1000x.
+
+## Status
+PATCHED (patch in this file)