LS,
when playing around with bitstrings, I found a small bug in
net-snmp-5.7.1/snmplib/mib.c
in sprint_realloc_bitstring:
--------8<-----------
for (; enums; enums = enums->next) {
if (enums->value == (len * 8) + bit) {
enum_string = enums->label;
break;
}
}
--------8<-----------
The above snippet 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 a small tool that print out all bits using
snmp_varlist_add_variable and
snprint_variable:
--------8<-----------
/* val is a pointer to a 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 the bits in ascending order in the MIB, 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)
inputPortClassification(19) outputPortClassification(20)
inputUflowShaping(21) inputAggregateShaping(22) outputUflowShaping(23)
outputAggregateShaping(24) pqWrr(25) pqCbwfq(26)
Which is correct and should be the output in both situations.
The correct way should be to start the loop in the snippet above at the
start of the
list.
Kind regards, Edgar Matzinger.
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