snmp plugin: Improve some comments.

[collectd.git] / src / snmp.c

diff --git a/src/snmp.c b/src/snmp.c
index 1c2828c1fb2469494e84aafebb6a77d01fadcde9..228ed8e246579053972002a1bb5bfb7d5b0cc455 100644 (file)
--- a/src/snmp.c
+++ b/src/snmp.c
@@ -302,7 +302,7 @@ static int csnmp_config_add_data_shift (data_definition_t *dd, oconfig_item_t *c
   if ((ci->values_num != 1)
       || (ci->values[0].type != OCONFIG_TYPE_NUMBER))
   {
-    WARNING ("snmp plugin: The `Scale' config option needs exactly one number argument.");
+    WARNING ("snmp plugin: The `Shift' config option needs exactly one number argument.");
     return (-1);
   }
 
@@ -727,7 +727,9 @@ static value_t csnmp_value_list_to_value (struct variable_list *vl, int type,
   value_t ret;
   uint64_t tmp_unsigned = 0;
   int64_t tmp_signed = 0;
-  int defined = 1;
+  _Bool defined = 1;
+  /* Set to true when the original SNMP type appears to have been signed. */
+  _Bool prefer_signed = 0;
 
   if ((vl->type == ASN_INTEGER)
       || (vl->type == ASN_UINTEGER)
@@ -739,7 +741,12 @@ static value_t csnmp_value_list_to_value (struct variable_list *vl, int type,
   {
     tmp_unsigned = (uint32_t) *vl->val.integer;
     tmp_signed = (int32_t) *vl->val.integer;
-    DEBUG ("snmp plugin: Parsed int32 value is %"PRIi64".", tmp_signed);
+
+    if ((vl->type == ASN_INTEGER)
+        || (vl->type == ASN_GAUGE))
+      prefer_signed = 1;
+
+    DEBUG ("snmp plugin: Parsed int32 value is %"PRIu64".", tmp_unsigned);
   }
   else if (vl->type == ASN_COUNTER64)
   {
@@ -828,14 +835,24 @@ static value_t csnmp_value_list_to_value (struct variable_list *vl, int type,
   }
   else if (type == DS_TYPE_GAUGE)
   {
-    ret.gauge = NAN;
-    if (defined != 0)
+    if (!defined)
+      ret.gauge = NAN;
+    else if (prefer_signed)
       ret.gauge = (scale * tmp_signed) + shift;
+    else
+      ret.gauge = (scale * tmp_unsigned) + shift;
   }
   else if (type == DS_TYPE_DERIVE)
-    ret.derive = (derive_t) tmp_signed;
+  {
+    if (prefer_signed)
+      ret.derive = (derive_t) tmp_signed;
+    else
+      ret.derive = (derive_t) tmp_unsigned;
+  }
   else if (type == DS_TYPE_ABSOLUTE)
+  {
     ret.absolute = (absolute_t) tmp_unsigned;
+  }
   else
   {
     ERROR ("snmp plugin: csnmp_value_list_to_value: Unknown data source "
@@ -869,10 +886,12 @@ static int csnmp_check_res_left_subtree (const host_definition_t *host,
       vb = vb->next_variable, i++)
   {
     num_checked++;
-    if (snmp_oid_ncompare (data->values[i].oid,
-         data->values[i].oid_len,
-         vb->name, vb->name_length,
-         data->values[i].oid_len) != 0)
+
+    if ((vb->type == SNMP_ENDOFMIBVIEW)
+       || (snmp_oid_ncompare (data->values[i].oid,
+           data->values[i].oid_len,
+           vb->name, vb->name_length,
+           data->values[i].oid_len) != 0))
       num_left_subtree++;
   }
 
@@ -990,12 +1009,13 @@ static int csnmp_instance_list_add (csnmp_list_instances_t **head,
   if (vb == NULL)
     return (-1);
 
-  il = (csnmp_list_instances_t *) malloc (sizeof (csnmp_list_instances_t));
+  il = malloc (sizeof (*il));
   if (il == NULL)
   {
     ERROR ("snmp plugin: malloc failed.");
     return (-1);
   }
+  /* XXX copy entire OID */
   il->subid = vb->name[vb->name_length - 1];
   il->next = NULL;
 
@@ -1299,7 +1319,8 @@ static int csnmp_read_table (host_definition_t *host, data_definition_t *data)
       break;
     }
 
-    /* if an instance-OID is configured.. */
+    /* Copy the OID of the value used as instance to oid_list, if an instance
+     * is configured. */
     if (data->instance.oid.oid_len > 0)
     {
       /* Allocate a new `csnmp_list_instances_t', insert the instance name and
@@ -1312,19 +1333,24 @@ static int csnmp_read_table (host_definition_t *host, data_definition_t *data)
        break;
       }
 
-      /* Set vb on the last variable */
+      /* The instance OID is added to the list of OIDs to GET from the
+       * snmp agent last, so set vb on the last variable returned and copy
+       * that OID. */
       for (vb = res->variables;
          (vb != NULL) && (vb->next_variable != NULL);
          vb = vb->next_variable)
        /* do nothing */;
       assert (vb != NULL);
 
-      /* Copy OID to oid_list[data->values_len] */
+      /* Copy the OID of the instance value to oid_list[data->values_len] */
       memcpy (oid_list[data->values_len].oid, vb->name,
          sizeof (oid) * vb->name_length);
       oid_list[data->values_len].oid_len = vb->name_length;
     }
 
+    /* Iterate over all the (non-instance) values returned by the agent. The
+     * (i < value_len) check will make sure we're not handling the instance OID
+     * twice. */
     for (vb = res->variables, i = 0;
        (vb != NULL) && (i < data->values_len);
        vb = vb->next_variable, i++)