Hello list,
when playing around with bitstrings, I found a small bug in
net-snmp-5.7.1/snmplib/mib.c
in function sprint_realloc_bitstring:
---------8<----------
for (; enums; enums = enums->next) {
if (enums->value == (len * 8) + bit) {
enum_string = enums->label;
break;
}
}
---------8<----------
The snippet above assumes that all bits are enumerated in an ascending
order. But, Cisco
has a mib (CISCO-QOS-PIB-MIB) that enumerates
QosInterfaceTypeCapabilities in a random
order:
---------8<----------
QosInterfaceTypeCapabilities ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"An enumeration of interface capabilities. Used by the PDP to
select policies and configuration to push to the PEP."
SYNTAX BITS {
unspecified (0),
-- Classification support
inputL2Classification (1), inputIpClassification (2),
outputL2Classification (3), outputIpClassification (4),
inputPortClassification (19), outputPortClassification (20),
-- Policing support
inputUflowPolicing (5), inputAggregatePolicing (6),
outputUflowPolicing (7), outputAggregatePolicing (8),
policeByMarkingDown (9), policeByDropping (10),
inputUflowShaping (21), inputAggregateShaping (22),
outputUflowShaping (23), outputAggregateShaping (24),
-- Supported scheduling mechanisms
fifo (11), wrr (12), wfq (13), cq (14), pq (15), cbwfq (16),
pqWrr (25), pqCbwfq (26),
-- Supported congestion control mechanisms
tailDrop (17), wred (18)
}
---------8<----------
When I run my little program that prints out all bits using
snmp_varlist_add_variable
and snprint_variable:
---------8<----------
/* val is a pointer to an u_char string */
snmp_varlist_add_variable (&vars, name, name_length,
ASN_BIT_STR, (u_char *)val, val_size);
snprint_variable (n, sizeof (n), name, name_length,
vars);
printf ("test vars: %s\n", n);
snmp_free_varbind(vars);
---------8<----------
It outputs:
$ ./snmpt
test vars: CISCO-QOS-PIB-MIB::qosInterfaceTypeCapabilities = BITS: FF
FF FF E0 00 unspecified(0) inputL2Classification(1)
inputIpClassification(2) outputL2Classification(3)
outputIpClassification(4) inputUflowPolicing(5)
inputAggregatePolicing(6) outputUflowPolicing(7)
outputAggregatePolicing(8) policeByMarkingDown(9) policeByDropping(10)
fifo(11) wrr(12) wfq(13) cq(14) pq(15) cbwfq(16) tailDrop(17) wred(18)
19 20 21 22 23 24 25 26
When I put these bits in ascending order in the MIB, it outputs the
following:
$ ./snmpt
test vars: CISCO-QOS-PIB-MIB::qosInterfaceTypeCapabilities = BITS: FF
FF FF E0 00 unspecified(0) inputL2Classification(1)
inputIpClassification(2) outputL2Classification(3)
outputIpClassification(4) inputUflowPolicing(5)
inputAggregatePolicing(6) outputUflowPolicing(7)
outputAggregatePolicing(8) policeByMarkingDown(9) policeByDropping(10)
fifo(11) wrr(12) wfq(13) cq(14) pq(15) cbwfq(16) tailDrop(17) wred(18)
inputPortClassification(19) outputPortClassification(20)
inputUflowShaping(21) inputAggregateShaping(22) outputUflowShaping(23)
outputAggregateShaping(24) pqWrr(25) pqCbwfq(26)
Which is correct and should be the output for both situations of
course...
T
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