From 3aef1bc7fc54b5cd2f5575e3490e985d6d1561ad Mon Sep 17 00:00:00 2001
From: Ondrej Zajicek <santiago@crfreenet.org>
Date: Thu, 27 Apr 2023 17:09:00 +0200
Subject: [PATCH] Conf: Fix symbol lookup

The symbol table used just symbol name as a key, and used a trick with
active flag to find symbols in active scopes with one hash table lookup.

The disadvantage is that it can degenerate to O(n) for negative queries
in situations where are many symbols with the same name in different
scopes.

Thanks to Yanko Kaneti for the bugreport.
---
 conf/cf-lex.l | 22 ++++++++++++----------
 conf/conf.h   |  4 +++-
 lib/hash.h    |  2 +-
 3 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/conf/cf-lex.l b/conf/cf-lex.l
index ceedee8a..0a02dd73 100644
--- a/conf/cf-lex.l
+++ b/conf/cf-lex.l
@@ -73,10 +73,10 @@ static uint cf_hash(const byte *c);
 #define KW_FN(k)		cf_hash(k)
 #define KW_ORDER		8 /* Fixed */
 
-#define SYM_KEY(n)		n->name, n->scope->active
+#define SYM_KEY(n)		n->name, n->scope
 #define SYM_NEXT(n)		n->next
 #define SYM_EQ(a,s1,b,s2)	!strcmp(a,b) && s1 == s2
-#define SYM_FN(k,s)		cf_hash(k)
+#define SYM_FN(k,s)		cf_hash(k) ^ ptr_hash(s)
 #define SYM_ORDER		6 /* Initial */
 
 #define SYM_REHASH		sym_rehash
@@ -602,29 +602,31 @@ cf_new_symbol(const byte *c)
 }
 
 /**
- * cf_find_symbol - find a symbol by name
+ * cf_find_local_symbol - find a symbol by name
  * @cfg: specificed config
+ * @scope: specified symbol scope
  * @c: symbol name
  *
  * This functions searches the symbol table in the config @cfg for a symbol of
- * given name. First it examines the current scope, then the second recent one
+ * given name. First it examines the scope @scope, then the parent scope
  * and so on until it either finds the symbol and returns a pointer to its
  * &symbol structure or reaches the end of the scope chain and returns %NULL to
  * signify no match.
  */
 struct symbol *
-cf_find_symbol(const struct config *cfg, const byte *c)
+cf_find_local_symbol(const struct config *cfg, const struct sym_scope *scope, const byte *c)
 {
   struct symbol *s;
 
-  if (cfg->sym_hash.data &&
-      (s = HASH_FIND(cfg->sym_hash, SYM, c, 1)))
-    return s;
+  if (cfg->sym_hash.data)
+    for (; scope; scope = scope->next)
+      if (s = HASH_FIND(cfg->sym_hash, SYM, c, scope))
+	return s;
 
   /* In CLI command parsing, fallback points to the current config, otherwise it is NULL. */
   if (cfg->fallback &&
       cfg->fallback->sym_hash.data &&
-      (s = HASH_FIND(cfg->fallback->sym_hash, SYM, c, 1)))
+      (s = HASH_FIND(cfg->fallback->sym_hash, SYM, c, cfg->fallback->root_scope)))
     return s;
 
   return NULL;
@@ -642,7 +644,7 @@ cf_find_symbol(const struct config *cfg, const byte *c)
 struct symbol *
 cf_get_symbol(const byte *c)
 {
-  return cf_find_symbol(new_config, c) ?: cf_new_symbol(c);
+  return cf_find_local_symbol(new_config, conf_this_scope, c) ?: cf_new_symbol(c);
 }
 
 /**
diff --git a/conf/conf.h b/conf/conf.h
index b409750e..cb47e7d0 100644
--- a/conf/conf.h
+++ b/conf/conf.h
@@ -187,7 +187,9 @@ int cf_lex(void);
 void cf_lex_init(int is_cli, struct config *c);
 void cf_lex_unwind(void);
 
-struct symbol *cf_find_symbol(const struct config *cfg, const byte *c);
+struct symbol *cf_find_local_symbol(const struct config *cfg, const struct sym_scope *scope, const byte *c);
+static inline struct symbol *cf_find_symbol(const struct config *cfg, const byte *c)
+{ return cf_find_local_symbol(cfg, cfg->root_scope, c); }
 
 struct symbol *cf_get_symbol(const byte *c);
 struct symbol *cf_default_name(char *template, int *counter);
diff --git a/lib/hash.h b/lib/hash.h
index 8febb33f..b30f7830 100644
--- a/lib/hash.h
+++ b/lib/hash.h
@@ -237,7 +237,7 @@ mem_hash(const void *p, uint s)
 }
 
 static inline uint
-ptr_hash(void *ptr)
+ptr_hash(const void *ptr)
 {
   uintptr_t p = (uintptr_t) ptr;
   return p ^ (p << 8) ^ (p >> 16);