[Net-snmp-patches] [ net-snmp-Patches-2941811 ] snmpd logs a non-error when sending response with req-id=0

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Patches item #2941811, was opened at 2010-01-28 20:22
Message generated for change (Comment added) made by dts12
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Category: None
Group: None
>Status: Closed
>Resolution: Accepted
Priority: 5
Private: No
Submitted By: Bill Fenner (fenner)
Assigned to: Nobody/Anonymous (nobody)
Summary: snmpd logs a non-error when sending response with req-id=0

Initial Comment:
In net-snmp 5.5, the return value of snmp_send() says it's:

 * Return on success:
 *   The request id of the pdu is returned, and the pdu is freed.
 * Return on failure:
 *   Zero (0) is returned.
 *   The caller must call snmp_free_pdu if 0 is returned.

So, zero means failure.  But zero is a valid request id:

   PDU ::= SEQUENCE {
           request-id INTEGER (-214783648..214783647),

so when a caller (like snmp_agent.c::netsnmp_wrap_up_request() calls snmp_send(), it seems that it must not only check that snmp_send returned zero but also that netsnmp_errno != SUCCESS (and snmp_send should make sure to set netsnmp_errno to success before trying, to enable this type of oob error reporting).

It may be simpler to change snmp_send's return value to simply return 1 if it succeeds or zero if it fails, and if needed find another way to return the request-id.  I didn't see any code in agent/ that uses the request-id return value, only success/failure.  Or, change the return value to only be the request-id, and make the error indication completely out of band with netsnmp_errno.

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>Comment By: Dave Shield (dts12)
Date: 2011-01-06 12:46

Message:
SVN revision 19806

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Comment By: Dave Shield (dts12)
Date: 2011-01-06 12:46

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

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Comment By: Thomas Anders (tanders)
Date: 2010-12-02 00:34

Message:
moving to patches

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Comment By: Bill Fenner (fenner)
Date: 2010-12-01 14:05

Message:
I've uploaded a patch that leaves snmp_send alone, and just checks for
s_snmp_errno != SNMP_SUCCESS in netsnmp_wrap_up_request().  snmp_send()
already sets s_snmp_errno to 0 before doing much of anything, so if it is
still zero at return it is fairly safe to assume success.

(I am using the patch with 5.6.)


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