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### Description We are plotting the call success rate on each of our proxies. Using the Kamailio snmpstats module, we try to obtain three counters in order to plot them on a graph: - Total Calls - Active Calls - Error Calls

Most of the time, everything works well and we obtain sensible values: `snmpwalk -c mycommunity -v 2c W.X.Y.Z 1.3.6.1.4.1.34352.3.1.3.1.3.2 -O n`

.1.3.6.1.4.1.34352.3.1.3.1.3.2.1.0 = Gauge32: 309 -> Total Calls

.1.3.6.1.4.1.34352.3.1.3.1.3.2.2.0 = Gauge32: 95 -> Active Calls .1.3.6.1.4.1.34352.3.1.3.1.3.2.3.0 = Gauge32: 214 -> Error calls

However, **when our proxies are facing intense peaks of failed calls in a short timespan**, sometimes, the **"Error Calls"** counter returns a value **higher than "Total Calls"**. As a result, **"Active Calls"** suddenly reaches a value close to the **maximum of a _Gauge32_** (because ${TotalCalls} - {ErrorCalls} < 0$).

`snmpwalk -c mycommunity -v 2c W.X.Y.Z 1.3.6.1.4.1.34352.3.1.3.1.3.2 -O n`

.1.3.6.1.4.1.34352.3.1.3.1.3.2.1.0 = Gauge32: 153 -> Total Calls

.1.3.6.1.4.1.34352.3.1.3.1.3.2.2.0 = Gauge32: 4294967226 -> Active Calls .1.3.6.1.4.1.34352.3.1.3.1.3.2.3.0 = Gauge32: 223 -> Error calls

As a result, our graphs make no more sense.

### Troubleshooting There seems to be a bug causing Total calls to be lower than Error calls when a high number of failed calls are received in a short time window. Moreover, there is an integer overflow resulting to the negative result of the substraction being converted to a _Gauge32_. Maybe setting it to 0 in case of a negative result would be safer ?

#### Reproduction Using the following configuration for the snmpstats module of your Kamailio proxy:

``` # -------- snmpstats params ------- modparam("snmpstats", "snmpgetPath", "/usr/bin/") modparam("snmpstats", "snmpCommunity", "mycommunity") modparam("snmpstats", "sipEntityType", "proxyServer") ``` On intense peaks of failed calls, get the call success metrics using `snmpwalk` :

`snmpwalk -c mycommunity -v 2c W.X.Y.Z 1.3.6.1.4.1.34352.3.1.3.1.3.2 -O n`

.1.3.6.1.4.1.34352.3.1.3.1.3.2.1.0 = Gauge32: 153 -> Total Calls

.1.3.6.1.4.1.34352.3.1.3.1.3.2.2.0 = Gauge32: 4294967226 -> Active Calls .1.3.6.1.4.1.34352.3.1.3.1.3.2.3.0 = Gauge32: 223-> Error calls

### Additional Information

**Kamailio Version**: `kamailio -v`

version: kamailio 5.6.4 (x86_64/linux) a004cf

flags: USE_TCP, USE_TLS, USE_SCTP, TLS_HOOKS, USE_RAW_SOCKS, DISABLE_NAGLE, USE_ MCAST, DNS_IP_HACK, SHM_MMAP, PKG_MALLOC, Q_MALLOC, F_MALLOC, TLSF_MALLOC, DBG_S R_MEMORY, USE_FUTEX, FAST_LOCK-ADAPTIVE_WAIT, USE_DNS_CACHE, USE_DNS_FAILOVER, U SE_NAPTR, USE_DST_BLOCKLIST, HAVE_RESOLV_RES ADAPTIVE_WAIT_LOOPS 1024, MAX_RECV_BUFFER_SIZE 262144, MAX_URI_SIZE 1024, BUF_SI ZE 65535, DEFAULT PKG_SIZE 64MB poll method support: poll, epoll_lt, epoll_et, sigio_rt, select. id: a004cf compiled on 16:10:41 May 22 2023 with gcc 4.4.7

* **Operating System**:

`uname -r`

2.6.32-279.el6.x86_64

`lsb_release -a`

LSB Version: :core-4.0-amd64:core-4.0-noarch:graphics-4.0-amd64:graphics-4.0-noarch:printing-4.0-amd64:printing-4.0-noarch

Distributor ID: RedHatEnterpriseServer Description: Red Hat Enterprise Linux Server release 6.3 (Santiago) Release: 6.3 Codename: Santiago