Fixed: [SNMP: snmpwalk is slow and can timeout #404 ](https://github.com/clicon/clixon/issues/404)

Optimized yang_extension_value

CHANGELOG.md

@@ -105,6 +105,7 @@ Developers may need to change their code
 
 ### Corrected Bugs
 
+* Fixed: [SNMP: snmpwalk is slow and can timeout #404 ](https://github.com/clicon/clixon/issues/404)
 * Fixed: [SNMP accepts only u32 & u64 #405](https://github.com/clicon/clixon/issues/405)
 * Fixed: [Yang leaves without smiv2:oid directive are not shown well in snmpwalk #398](https://github.com/clicon/clixon/issues/398)
 * Fixed: [Netconf commit confirm session-id mismatch #407](https://github.com/clicon/clixon/issues/407)

apps/snmp/snmp_handler.c

@@ -149,7 +149,7 @@ snmp_scalar_return(cxobj                      *xs,
 
     /* SMI default value, How is this different from yang defaults?
      */
-    if (yang_extension_value(ys, "defval", IETF_YANG_SMIV2_NS, NULL, &defaultval) < 0)
+    if (yang_extension_value_opt(ys, "smiv2:defval", NULL, &defaultval) < 0)
         goto done;
     if (xs != NULL && (body = xml_body(xs)) != NULL){
         if ((ret = type_xml2snmp_pre(body, ys, &xmlstr)) < 0) // XXX <---
@@ -887,7 +887,7 @@ snmp_table_get(clicon_handle               h,
     }
     /* SMI default value, How is this different from yang defaults?
      */
-    if (yang_extension_value(ys, "defval", IETF_YANG_SMIV2_NS, NULL, &defaultval) < 0)
+    if (yang_extension_value_opt(ys, "smiv2:defval", NULL, &defaultval) < 0)
         goto done;
     
     /* Create xpath with right keys from later part of OID 
@@ -1033,7 +1033,7 @@ snmp_table_set(clicon_handle               h,
         char *modes_str = NULL;
         int   modes;
 
-        if (yang_extension_value(ys, "max-access", IETF_YANG_SMIV2_NS, NULL, &modes_str) < 0)
+        if (yang_extension_value_opt(ys, "smiv2:max-access", NULL, &modes_str) < 0)
             goto done;
         if (modes_str){
             modes = snmp_access_str2int(modes_str);

apps/snmp/snmp_lib.c

@@ -335,6 +335,56 @@ snmp_yang_type_get(yang_stmt  *ys,
     return retval;
 }
 
+/*! Specialized and optimized variant of yang_extension_value
+ * 
+ * In this optimized version, "id" on the form "<prefix>:<name>" is hardcoded
+ * and not derived from "name" and "namespace" in the original version.
+
+ * @param[in]  ys     Yang statement where unknown statement may occur referencing to extension
+ * @param[out] exist  The extension exists.
+ * @param[out] value  clispec operator (hide/none) - direct pointer into yang, dont free
+ * @retval     0      OK: Look in exist and value for return value
+ * @retval     -1     Error
+ *
+ * @note This optimizatoin may not work if the unknown statements are augmented in ys.
+ * @see yang_extension_value for the generic function
+ */
+int
+yang_extension_value_opt(yang_stmt *ys,
+                         char      *id,
+                         int       *exist,
+                         char     **value)
+{
+    int        retval = -1;
+    yang_stmt *yext;
+    cg_var    *cv;
+
+    if (ys == NULL){
+        clicon_err(OE_YANG, EINVAL, "ys is NULL");
+        goto done;
+    }
+    if (exist)
+        *exist = 0;
+    yext = NULL; /* This loop gets complicated in the case the extension is augmented */
+    while ((yext = yn_each(ys, yext)) != NULL) {
+        if (yang_keyword_get(yext) != Y_UNKNOWN)
+            continue;
+        if (strcmp(yang_argument_get(yext), id) != 0)
+            continue;
+        break;
+    }
+    if (yext != NULL){ /* Found */
+        if (exist)
+            *exist = 1;
+        if (value &&
+            (cv = yang_cv_get(yext)) != NULL)
+            *value = cv_string_get(cv);
+    }
+    retval = 0;
+ done:
+    return retval;
+}
+
 /*! Given a YANG node, return SMIv2 oid extension as OID 
  * @param[in]  yn        Yang node
  * @param[out] objid     OID vector, assume allocated with MAX_OID_LEN > oidlen
@@ -361,8 +411,8 @@ yangext_oid_get(yang_stmt *yn,
     }
     else
         yref = yn;
-    /* Get OID from table /list  */
-    if (yang_extension_value(yref, "oid", IETF_YANG_SMIV2_NS, &exist, &oidstr) < 0)
+    /* Get OID from table /list */
+    if (yang_extension_value_opt(yref, "smiv2:oid", &exist, &oidstr) < 0)
         goto done;
     if (exist == 0 || oidstr == NULL){
         clicon_debug(1, "OID not found as SMIv2 yang extension of %s", yang_argument_get(yref));
@@ -382,20 +432,19 @@ yangext_oid_get(yang_stmt *yn,
     goto done;
 }
 
-
-
 /*! Given a YANG node, return 1 if leaf has oid directive in it, otherwise 0
  * @param[in]  yn        Yang node
  * @retval     1         found
  * @retval     0         not found
  */
-int  yangext_is_oid_exist(yang_stmt *yn) {
+int
+yangext_is_oid_exist(yang_stmt *yn) {
  
     int        exist = 0;
     char      *oidstr = NULL;
  
     if ((yang_keyword_get(yn) != Y_LEAF) ||
-       (yang_extension_value(yn, "oid", IETF_YANG_SMIV2_NS, &exist, &oidstr) < 0) ||
+       (yang_extension_value_opt(yn, "smiv2:oid", &exist, &oidstr) < 0) ||
        (exist == 0) ||
        (oidstr == NULL)) {
         return 0;
@@ -495,8 +544,9 @@ type_yang2asn1(yang_stmt    *ys,
         yang_stmt *yrp;
         char *display_hint = NULL;
         yrp = yang_parent_get(yrestype);
-        if (yang_extension_value(yrp, "display-hint", IETF_YANG_SMIV2_NS, NULL, &display_hint) < 0)
+        if (yang_extension_value_opt(yrp, "smiv2:display-hint", NULL, &display_hint) < 0)
             goto done;  
+
         /* RFC2578/2579 but maybe all strings with display-hint should use this, eg exist>0? */
         if (display_hint &&
             (strcmp(display_hint, "255a")==0 ||

apps/snmp/snmp_lib.h

@@ -86,6 +86,7 @@ int    oid_append(const oid *objid0, size_t *objid0len, const oid *objid1, size_
 int    oid_cbuf(cbuf *cb, const oid *objid, size_t objidlen);
 int    oid_print(FILE *f, const oid *objid, size_t objidlen);
 int    snmp_yang_type_get(yang_stmt *ys, yang_stmt **yrefp, char **origtypep, yang_stmt **yrestypep, char **restypep);
+int    yang_extension_value_opt(yang_stmt *ys, char *id, int *exist, char **value);
 int    yangext_oid_get(yang_stmt *yn, oid *objid, size_t *objidlen, char **objidstr);
 int    yangext_is_oid_exist(yang_stmt *yn);
 int    snmp_access_str2int(char *modes_str);

apps/snmp/snmp_register.c

@@ -127,7 +127,7 @@ mibyang_leaf_register(clicon_handle h,
     /* Check if already registered */
     if (clixon_snmp_api_oid_find(oid1, oid1len) == 1)
         goto ok;
-    if (yang_extension_value(ys, "max-access", IETF_YANG_SMIV2_NS, NULL, &modes_str) < 0)
+    if (yang_extension_value_opt(ys, "smiv2:max-access", NULL, &modes_str) < 0)
         goto done;
     /* Only for sanity check of types initially to fail early */
     if (type_yang2asn1(ys, NULL, 0) < 0)
@@ -141,9 +141,8 @@ mibyang_leaf_register(clicon_handle h,
 
     /* SMI default value, How is this different from yang defaults?
      */
-    if (yang_extension_value(ys, "defval", IETF_YANG_SMIV2_NS, NULL, &default_str) < 0)
+    if (yang_extension_value_opt(ys, "smiv2:defval", NULL, &default_str) < 0)
         goto done;
-
     name = yang_argument_get(ys);
     /* Stateless function, just returns ptr */ 
     if ((handler = netsnmp_create_handler(name, clixon_snmp_scalar_handler)) == NULL){

lib/src/clixon_yang.c

@@ -3734,6 +3734,7 @@ yang_anydata_add(yang_stmt *yp,
  *     }
  * @endcode
  * @see ys_populate_unknown  Called when parsing YANG
+ * XXX consider optimizing, the call to yang_find_prefix_by_namespace may be slow
  */
 int
 yang_extension_value(yang_stmt *ys,
@@ -3766,6 +3767,7 @@ yang_extension_value(yang_stmt *ys,
             continue;
         if ((ymod = ys_module(yext)) == NULL)
             continue;
+        /* XXX this is slow */
         if ((ret = yang_find_prefix_by_namespace(ymod, ns, &prefix)) < 0)
             goto done;
         if (ret == 0) /* not found (this may happen in augment and maybe should be treated otherwise) */