Cache helper problems with cross-compiled net-snmp-5.7.2.1

[pota...@gmail.com]

Hi All,

I built the last version of the net-snmp-5.7.2.1 using the arm-linux-gcc compiler with the following flags:
CC=arm-linux-gcc ./configure --target=arm-linux --host=arm-linux --build=x86 \.
--program-prefix=/usr --prefix=/usr --exec-prefix=/usr --with-endianness=big \.
--enable-privacy --enable-des --enable-md5 --without-rpm --enable-shared \
--with-cflags="-O2 -fsigned-char -I$WORKSPACE/Build/target/usr/include" \
--with-persistent-directory=/var/net-snmp --with-copy-persistent-files="no" \
--with-out-mib-modules="ucd_snmp notification notification-log-mib target utilities disman/event disman/schedule host" \.
--sysconfdir=/conf --with-openssl=internal --disable-embedded-perl \.
--disable-perl-cc-checks --with-perl-modules=no --with-sys-contact=root@localhost \
--disable-manuals --disable-scripts --disable-applications --disable-mibs --disable-mib-loading \
--disable-deprecated --enable-ipv6 --with-default-snmp-version="3" \.
--with-sys-location="Unknown" --with-logfile=/var/log/snmpd.log --with-security-modules="usm tsm"

The cross-compiled net-snmp libraries I use in my sub-agent implementation.
And it seems that the cache helper doesn't work in my case.
Before I decided to use the net-snmp-5.7.2 I use the net-snmp-5.4.3 and everything works fine.

My sub-agent uses the cache mechanism to update the particular MIB table before the GET/GETNEXT request comes.
In my case the first calling of the cache load works fine but after the cache timeout expires the sub-agents crashes with segmentation fault and the snmpwalk command gets the message: "Error in packet. Reason: (genError) A general failure occured Failed object: iso.3.6.1.4.1.231.2.10.2.2.10.3.1."

I analyzed the core dump of my application with gdb and it shows, that sub-agent crashes in the _cache_load () when it tries to call the _cache_free().

Maybe somebody can help me and explain what is wrong?

I have the following code:

struct ManagementNodeTable_entry {
long mnUnitId;
long mnNodeNr;
...
};


#define MANAGEMENTNODETABLE_TIMEOUT 10


initialize_table_ManagementNodeTable(void)
{
oid ManagementNodeTable_oid[] = { 1, 3, 6, 1, 4, 1, 231, 2, 10, 2, 2, 10, 3, 1 };
size_t ManagementNodeTable_oid_len = OID_LENGTH(ManagementNodeTable_oid);
netsnmp_tdata *table_data = NULL;
netsnmp_handler_registration *reg;
netsnmp_table_registration_info *table_info;
netsnmp_cache *cache;
reg = netsnmp_create_handler_registration("ManagementNodeTable",
ManagementNodeTable_handler,
ManagementNodeTable_oid,
ManagementNodeTable_oid_len,
HANDLER_CAN_RONLY);
table_data = netsnmp_tdata_create_table("ManagementNodeTable", 0);
if (NULL == table_data) {
snmp_log(LOG_ERR,
"error creating tdata table for ManagementNodeTable\n");
return;
}

cache = netsnmp_cache_create(MANAGEMENTNODETABLE_TIMEOUT,
ManagementNodeTable_load,
ManagementNodeTable_free,
ManagementNodeTable_oid,
ManagementNodeTable_oid_len);
if (NULL == cache) {
snmp_log(LOG_ERR,
"error creating cache for ManagementNodeTable\n");
return;
}
else {
cache->magic = (void *) table_data;
cache->flags |= (NETSNMP_CACHE_DONT_FREE_BEFORE_LOAD | NETSNMP_CACHE_DONT_FREE_EXPIRED | NETSNMP_CACHE_DONT_AUTO_RELEASE);
}

table_info = SNMP_MALLOC_TYPEDEF(netsnmp_table_registration_info);
if (NULL == table_info) {
snmp_log(LOG_ERR,
"error creating table info for ManagementNodeTable\n");
return;
}
netsnmp_table_helper_add_indexes(table_info,
ASN_INTEGER, /* index: mnUnitId */
ASN_INTEGER, /* index: mnNodeNr */
0);

table_info->min_column = COLUMN_MNUNITID;
table_info->max_column = COLUMN_UNITNODECONTROLLERFWVERSION;
netsnmp_tdata_register(reg, table_data, table_info);

if (cache) {
netsnmp_inject_handler (reg,
netsnmp_cache_handler_get(cache)
);
}
}


/** Create a new row in the table */
netsnmp_tdata_row *
ManagementNodeTable_createEntry (netsnmp_tdata *table_data,
struct ManagementNodeTable_entry *srcEntry)
{
struct ManagementNodeTable_entry *destEntry;
netsnmp_tdata_row *row;

destEntry = SNMP_MALLOC_TYPEDEF (struct ManagementNodeTable_entry);
if (!destEntry)
return NULL;
row = netsnmp_tdata_create_row();
if (!row) {
SNMP_FREE (destEntry);
return NULL;
}

memcpy (destEntry, srcEntry, sizeof (struct ManagementNodeTable_entry));
row->data = destEntry;

netsnmp_tdata_row_add_index (row, ASN_INTEGER,
&(destEntry->mnUnitId),
sizeof(destEntry->mnUnitId));
netsnmp_tdata_row_add_index (row, ASN_INTEGER,
&(destEntry->mnNodeNr),
sizeof(destEntry->mnNodeNr));
if (table_data) {
netsnmp_tdata_add_row( table_data, row );
}

return row;
}


/** Cache handling */
int
ManagementNodeTable_load(netsnmp_cache * cache, void *vmagic)
{
//don't work!!!
//netsnmp_tdata *table = (netsnmp_tdata *) vmagic;
netsnmp_tdata *table = (netsnmp_tdata *) cache->magic;
struct ManagementNodeTable_entry mnNodeEntry;
if (table != NULL) {
netsnmp_tdata_row *row;
// Update ManagementNodeTable table
....
row = ManagementNodeTable_createEntry (table, &mnNodeEntry);
}
return 0;
}


void
ManagementNodeTable_free(netsnmp_cache * cache, void *vmagic)
{
netsnmp_tdata *table = (netsnmp_tdata *) cache->magic;
netsnmp_tdata_row *row;

// remove all existing rows
while ( netsnmp_tdata_row_count(table) > 0 )
{
struct ManagementNodeTable_entry *entry;
row = netsnmp_tdata_row_first( table );
entry = (struct ManagementNodeTable_entry *) row->data;
SNMP_FREE(entry);
netsnmp_tdata_remove_and_delete_row( table, row );
}
}


/** Handles requests for the ManagementNodeTable table */
int
ManagementNodeTable_handler(netsnmp_mib_handler *handler,
netsnmp_handler_registration *reginfo,
netsnmp_agent_request_info *reqinfo,
netsnmp_request_info *requests)
{
netsnmp_request_info *request;
netsnmp_table_request_info *table_info;
struct ManagementNodeTable_entry *table_entry;
DEBUGMSGTL(("ManagementNodeTable:handler",
"Processing request (%d)\n", reqinfo->mode));

switch (reqinfo->mode) {
/* Read-support (also covers GetNext requests) */
case MODE_GET:
for (request = requests; request; request = request->next) {
if (request->processed)
continue;
table_entry = (struct ManagementNodeTable_entry *) netsnmp_tdata_extract_entry(request);
table_info = netsnmp_extract_table_info(request);

switch (table_info->colnum) {
case COLUMN_MNUNITID:
if (!table_entry) {
netsnmp_set_request_error(reqinfo, request,
SNMP_NOSUCHINSTANCE);
continue;
}
snmp_set_var_typed_integer(request->requestvb, ASN_INTEGER,
table_entry->mnUnitId);
break;
case COLUMN_MNNODENR:
if (!table_entry) {
netsnmp_set_request_error(reqinfo, request,
SNMP_NOSUCHINSTANCE);
continue;
}
snmp_set_var_typed_integer(request->requestvb, ASN_INTEGER,
table_entry->mnNodeNr);
break;

....

default:
netsnmp_set_request_error(reqinfo, request,
SNMP_NOSUCHOBJECT);
break;
}
}
break;

}
return SNMP_ERR_NOERROR;
}


Thanks,
Ekaterina

[roa5...@gmail.com]

Did you resolve this problem? I have a similar situation...