conf: add an util to iterate on sequence

A YAML sequence of single key maps, such as `outputs`, stores its
entries at outputs.<n>.<name> so a direct lookup of outputs.<name>
never matches. Add SCConfNodeLookupInSequence() to walk such a
sequence and return the entries matching a given name.

Ticket: 8606

rust/sys/src/sys.rs

@@ -343,6 +343,11 @@ extern "C" {
         node: *const SCConfNode, key: *const ::std::os::raw::c_char,
     ) -> *const ::std::os::raw::c_char;
 }
+extern "C" {
+    pub fn SCConfNodeLookupInSequence(
+        seq: *const SCConfNode, key: *const ::std::os::raw::c_char, prev: *const SCConfNode,
+    ) -> *mut SCConfNode;
+}
 extern "C" {
     pub fn SCConfNodeRemove(arg1: *mut SCConfNode);
 }

src/conf.c

@@ -886,6 +886,48 @@ const char *SCConfNodeLookupChildValue(const SCConfNode *node, const char *name)
     return NULL;
 }
 
+/**
+ * \brief Find a named entry inside a sequence node.
+ *
+ * A YAML sequence of single key maps -- the shape used by "outputs" --
+ * stores each entry as an unnamed node holding one child, so an entry is
+ * found at seq.<n>.<key> and not at seq.<key>. This walks the sequence and
+ * returns the child named \a key.
+ *
+ * A sequence may hold several entries with the same name (several eve-log
+ * outputs for instance), so \a prev allows iterating over all of them:
+ * pass NULL to get the first match, then the previous result to get the
+ * next one.
+ *
+ * \param seq The sequence node, may be NULL.
+ * \param key The name of the entry to look for.
+ * \param prev NULL to start, or the previously returned node to continue.
+ *
+ * \retval The matching SCConfNode or NULL when there is no (further) match.
+ */
+SCConfNode *SCConfNodeLookupInSequence(
+        const SCConfNode *seq, const char *key, const SCConfNode *prev)
+{
+    if (seq == NULL || key == NULL)
+        return NULL;
+
+    bool seen = (prev == NULL);
+    SCConfNode *entry;
+    TAILQ_FOREACH (entry, &seq->head, next) {
+        SCConfNode *child = SCConfNodeLookupChild(entry, key);
+        if (child == NULL)
+            continue;
+        if (!seen) {
+            if (child == prev)
+                seen = true;
+            continue;
+        }
+        return child;
+    }
+
+    return NULL;
+}
+
 /**
  * \brief Lookup for a key value under a specific node
  *

src/conf.h

@@ -81,6 +81,8 @@ void SCConfCreateContextBackup(void);
 void SCConfRestoreContextBackup(void);
 SCConfNode *SCConfNodeLookupChild(const SCConfNode *node, const char *key);
 const char *SCConfNodeLookupChildValue(const SCConfNode *node, const char *key);
+SCConfNode *SCConfNodeLookupInSequence(
+        const SCConfNode *seq, const char *key, const SCConfNode *prev);
 void SCConfNodeRemove(SCConfNode *);
 void SCConfRegisterTests(void);
 int SCConfNodeChildValueIsTrue(const SCConfNode *node, const char *key);