Arduino_SNMP
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0neblock
getBulk appears to have the worng 'next' behaviour - which breaks SNMP Tables
Tables appear to not be quite working; given a trivial 1 entry EntityMIB table with one entry:
snmp.addReadOnlyIntegerHandler(oidEntPhysicalIndex, 1);
snmp.addReadOnlyIntegerHandler(entPhysicalContainedIn,0 /* top level item/container */);
snmp.addReadOnlyIntegerHandler(oidEntPhysicalClass, 1 /* (other) */);
snmp.addReadOnlyStaticStringHandler(oidEntPhysicalDesc, "a desc");
snmp.addReadOnlyStaticStringHandler(oidEntPhysicalName, "a name");
snprintf(buff, sizeof(buff), "ESP32-%016llx", ESP.getEfuseMac());
snmp.addReadOnlyStaticStringHandler(oidEntPhysicalSerialNum, std::string(buff));
Will give the right results on an snmpwalk
$ snmpwalk 10.11.0.181 entPhysicalTable
ENTITY-MIB::entPhysicalIndex.1 = INTEGER: 1
ENTITY-MIB::entPhysicalDescr.1 = STRING: a desc
ENTITY-MIB::entPhysicalContainedIn.1 = INTEGER: 0
ENTITY-MIB::entPhysicalClass.1 = INTEGER: other(1)
ENTITY-MIB::entPhysicalName.1 = STRING: a name
ENTITY-MIB::entPhysicalSerialNum.1 = STRING: ESP32-00004045651b5ae0
$
But will give an empty/no table on an
$ snmptable 10.11.0.181 entPhysicalTable
ENTITY-MIB::entPhysicalTable: No entries
$
The reason for this appears a wrong GetBulk response:
00:00:00.000000 IP (tos 0x0, ttl 64, id 21691, offset 0, flags [none], proto UDP (17), length 74, bad cksum 0 (->102e)!)
10.11.0.240.57576 > 10.11.0.181.161: { SNMPv2c { GetBulk(31) R=1397163026 N=0 M=10 .1.3.6.1.2.1.47.1.1.1.1.0 } }
00:00:00.002582 IP (tos 0x0, ttl 255, id 27, offset 0, flags [none], proto UDP (17), length 83)
10.11.0.181.161 > 10.11.0.240.57576: { SNMPv2c { GetResponse(37) R=1397163026 .1.3.6.1.2.1.47.1.1.1.1.0=[endOfMibView] } }
i.e. the ENTITY-MIB::entPhysicalEntry.0 does not give the right reply. If we add, as dirty workaround/hack:
snmp.addReadOnlyIntegerHandler(oidEntPhysicalTable, 0);
to the above code; things do work:
$ snmptable 10.11.0.181 entPhysicalTable
SNMP table: ENTITY-MIB::entPhysicalTable
entPhysicalDescr entPhysicalVendor ...
a desc ? .....
$
With TCPDUMP showing the expected:
10.11.0.240.60651 > 10.11.0.181.161: { SNMPv2c { GetBulk(31) R=343496280 N=0 M=10 .1.3.6.1.2.1.47.1.1.1.1.0 } }
00:00:00.005414 IP (tos 0x0, ttl 255, id 18, offset 0, flags [none], proto UDP (17), length 417)
10.11.0.181.161 > 10.11.0.240.60651: { SNMPv2c { GetResponse(367) R=343496280 .1.3.6.1.2.1.47.1.1.1.1.1.1=1 .1.3.6.1.2.1.47.1.1.1.1.2.1="Valve controller" .1.3.6.1.2.1.47.1.1.1.1.4.1=0 .1.3.6.1.2.1.47.1.1.1.1.5.1=1 .1.3.6.1.2.1.47.1.1.1.1.7.1="XXX" .1.3.6.1.2.1.47.1.1.1.1.8.1="XX" .1.3.6.1.2.1.47.1.1.1.1.9.1="XXX" .1.3.6.1.2.1.47.1.1.1.1.10.1="XXX" .1.3.6.1.2.1.47.1.1.1.1.11.1="ESP32-00004045651b5ae0" .1.3.6.1.2.1.47.1.1.1.1.12.1="XXX" } }
However - this breaks various SNMP tools - as now
% snmpget 10.11.0.181 entPhysicalEntry.0
ENTITY-MIB::entPhysicalEntry.0 = INTEGER: 0
instead of the expected
ENTITY-MIB::entPhysicalEntry.0 = No Such Object available on this agent at this OID
i.e. it returns a value (0) - confusing most tools, crashing some or causing an empty table entry. So this work around is not ideal. It seems that the getBulk() handler does not do a 'getNext' enough of a search.
I suspect that ValueCallback::findCallback() is too much subtree focused; and somehow misses, on a getNext / walk=True that, for example, a get next on a nonexistent .1.3.6.1.2.1.1.9.1.0 should return, for example, .1.3.6.1.2.1.1.9.1.2.1 (i.e. the first SNMPv2-MIB::sysORID.1 of the fist SNMPv2-MIB::sysORTable).
Complete/functional example that will reliably crash most SNMP tooling due to the 'fake' entry that is needed to make getBulk do the right getNext thing.
/* Wire any DS18B20 sensor up to the Sensor SNMP mib. Will generally get auto discovered
* by most SNMP tools and shown as a temperature v.s. time graph.
*/
#include <WiFi.h>
#include <vector>
#define ONE_WIRE_PIN (5)
#define FAKE_DS
#ifndef FAKE_DS
#include <DS18B20.h>
DS18B20 ds(ONE_WIRE_PIN);
#endif
#include <WiFiUdp.h>
#include <SNMP_Agent.h>
#include <SNMPTrap.h>
// Uncomment and set as needed.
//
// #define WIFI_NETWORK "My Network"
// #define WIFI_PASSWD "Password"
#if !defined(WIFI_NETWORK) || !defined(WIFI_PASSWD)
#error "Set Wifi network name and password !"
#endif
WiFiUDP udp;
SNMPAgent snmp = SNMPAgent("public");
const char* oidSysContact = ".1.3.6.1.2.1.1.4.0";
const char* oidSysName = ".1.3.6.1.2.1.1.5.0";
const char* oidSysLocation = ".1.3.6.1.2.1.1.6.0";
#define ENTITY_SENSOR_TABLE ".1.3.6.1.2.1.99.1.1.1"
#define ENTITY_SENSOR_TYPE ENTITY_SENSOR_TABLE ".1.%d" // This object identifies the type of data units associated with the sensor value.
#define ENTITY_SENSOR_SCALE ENTITY_SENSOR_TABLE ".2.%d" // This object identifies the (power of 10) scaling factor associated with the sensor value.
#define ENTITY_SENSOR_VALUE ENTITY_SENSOR_TABLE ".4.%d" // Actual value
#define ENTITY_SENSOR_UNITS_DISPLAY ENTITY_SENSOR_TABLE ".6.%d" // Unit - e.g. Celcius in this case.
int *cachedValuesInMillis;
void setup() {
Serial.begin(115200);
Serial.println("\n\n\n" __FILE__ " " __DATE__ " " __TIME__);
WiFi.begin(WIFI_NETWORK, WIFI_PASSWD);
while (WiFi.status() != WL_CONNECTED) delay(50);
snmp.setUDP(&udp);
snmp.begin();
// add some standard entries in system.
snmp.addReadOnlyStaticStringHandler(oidSysContact, "your local admin");
snmp.addReadOnlyStaticStringHandler(oidSysName, "this ESP32");
snmp.addReadOnlyStaticStringHandler(oidSysLocation, "On an ESP32 near you");
Serial.print("snmpwalk -v2c -c public ");
Serial.print(WiFi.localIP());
Serial.println(" system");
// Add a (temperature) sensor table; one table entry for each sensor.
//
#ifdef FAKE_DS
size_t n = 5;
#else
size_t n = ds.getNumberOfDevices();
#endif
cachedValuesInMillis = (int *)malloc( n * sizeof(int));
for (int i = 1; i <= n; i++) {
cachedValuesInMillis[ i - 1 ] = 0;
char oid[128];
snprintf(oid, sizeof(oid), ENTITY_SENSOR_TYPE, i);
snmp.addReadOnlyIntegerHandler(oid, 8 /* temperature */);
snprintf(oid, sizeof(oid), ENTITY_SENSOR_SCALE, i);
snmp.addReadOnlyIntegerHandler(oid, 8 /* milli */); // x 0.001; to allow for deci-degrees
snprintf(oid, sizeof(oid), ENTITY_SENSOR_VALUE, i);
snmp.addIntegerHandler(oid, &(cachedValuesInMillis[i - 1]));
snprintf(oid, sizeof(oid), ENTITY_SENSOR_UNITS_DISPLAY, i);
snmp.addReadOnlyStaticStringHandler(oid, "C");
};
// fool walk mechanish - not overly clear why we need this & crashes librenms.
// or a bug in SNMP where it does not respont right to getbulk on this endpoint.
//
// The issue is that a get GetBulk(31) for 1.3.6.1.2.1.99.1.1.1.0
// gets a endOfMibView reply if this is not in place.
//
// https://github.com/0neblock/Arduino_SNMP/issues/53
//
snmp.addReadOnlyIntegerHandler(ENTITY_SENSOR_TABLE ".0", 0);
snmp.sortHandlers();
Serial.print("snmpwalk -v2c -c public ");
Serial.print(WiFi.localIP());
Serial.println(" .1.3.6.1.2.1.99");
Serial.print("snmptable -m +ENTITY-SENSOR-MIB -v2c -c public ");
Serial.print(WiFi.localIP());
Serial.println(" entPhySensorTable");
}
void loop() {
snmp.loop();
// update the temperature cache every 5 seconds.
static unsigned long lst = 0;
if (millis() - lst > 5000) {
#ifdef FAKE_DS
for (int i = 0; i< 5; i++)
cachedValuesInMillis[i] = 2000 + i * 50;
#else
ds.startConversion();
for (int i = 0; ds.selectNext(); i++)
cachedValuesInMillis[i] = 0.5 + ds.getTempC(false) * 1000;
#endif
lst = millis();
};
};