#2810 Logical error in agent/helpers/table.c when --enable-read-only is used during configuring

[Minzhuan Gong]

When configuring net-snmp version 5.7.3 from the source, --enable-read-only will cause NETSNMP_NO_WRITE_SUPPORT to be #defined. Reviewing the source agent/helpers/table.c, I noticed the following segment of code will behave differently depneds on --enable-read-only is used or not:
line #478:

#ifndef NETSNMP_NO_WRITE_SUPPORT
                if (reqinfo->mode == MODE_SET_RESERVE1)
                    table_helper_cleanup(reqinfo, request,
                                         SNMP_ERR_NOTWRITABLE);
                else if (reqinfo->mode == MODE_GET)
#endif /* NETSNMP_NO_WRITE_SUPPORT */
                    table_helper_cleanup(reqinfo, request,
                                         SNMP_NOSUCHOBJECT);

In the above segment, if NETSNMP_NO_WRITE_SUPPORT is defined, function "table_helper_cleanup" is called without checking (reqinfo->mode == MODE_GET). I think the correct logic should be:

#ifndef NETSNMP_NO_WRITE_SUPPORT
                if (reqinfo->mode == MODE_SET_RESERVE1)
                    table_helper_cleanup(reqinfo, request,
                                         SNMP_ERR_NOTWRITABLE);
                else 
#endif /* NETSNMP_NO_WRITE_SUPPORT */
                 if (reqinfo->mode == MODE_GET)
                    table_helper_cleanup(reqinfo, request,
                                         SNMP_NOSUCHOBJECT);

I do not have a specific example to demonstrate the problem. I believe if you create an agentX subagent for a MIB with tables defined, you could see different behavior with get operation on table objects when net-snmp package is built with or without "--enable-read-only" configuration option,

[Bill Fenner]

Just reformatted the report to be more readable.

[Bill Fenner]

I've committed a patch to the V5-7-patches and master git branches. Could you please test?