#825 5.4 agent crashes on duplicate exec names

[Jan Safranek]

Net-SNMP 5.4 uses different implementation of 'exec' statements in snmpd.conf. Following part of snmpd.conf causes snmpd 5.4 to crash on snmpwalk (snmpd 5.3 works):

exec shelltest /usr/local/bin/tempstat VRM2
exec shelltest /usr/local/bin/tempstat CPU1
exec shelltest /usr/local/bin/tempstat CPU2
exec shelltest /usr/local/bin/tempstat VRM1

-> snmpd prints "duplicate table data attempted to be entered. row exists"

snmpwalk -v 2c -c public localhost .1.3.6.1.4.1.2021.8
-> snmpd crashes

It does not matter what is in the tempstat script, simple "echo hello world" is enough.

It's easy to fix the crash (see patch attached), but why it is not allowed to have multiple 'shelltest' entries in snmpd.conf? It was working OK in net-snmp 5.3.

[Jan Safranek]

patch for the crash

[Dave Shield]

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SVN revisions 16662/3

I've tweaked the error message slightly, since the triggering
condition is somewhat more general (though duplicate names
is certainly the most likely cause).

The reason for not allowing duplicate names is that the
new "extend" mechanism uses it as used as an index into
the various nsExtend* tables. Since it's an index, it
clearly has to be unique.
And starting with 5.4, the "exec" directive is now
handled as a special-case of "extend" (at least by default,
though it is possible to revert to the previous code).

I think that we've always assumed that the NAME token would
be unique anyway - if only to identify which "exec" directive
was being activated. It's just that nothing has relied on
this before.

[Dave Shield]

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Thanks for the patch! It has been applied to the 5.2.x, 5.3.x and 5.4.x code branches and the main development tree, and will appear in future releases of the Net-SNMP package.