[Bug 227502] Unable to add pfsense as monitored target in ntopng

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=227502

--- Comment #3 from Eugene Grosbein <eugen at freebsd.org> ---
(In reply to Florin Samareanu from comment #2)

The problem is more complex. Indeed, "In SNMP some fields are encoded with TLV
(Type Length Value), where the length specifies how many bytes to read on the
next field" - that's true. But ASN.1/DER encoding standard states that if
integer value is small enought to be fit in single byte, it MUST be encoded
with single byte and using 4 bytes is not allowed for such case by this
standard.

snmpwalk can send small or large integers and it encodes them just right using
noted "minimal integer" encoding: 1 or more bytes correspongingly. bsnmpd
parses both of small and large TLV fileds just fine.

On the other hand, ejrh/snmp library used by ntopng ALWAYS encodes integers
using 4 bytes, even for small values (R=1 in the test above). That is standard
violation that does not pass bsnmpd's strict validation, but pass relaxed
validation of net-snmpd.

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