Can you try the V5-7-patches branch and see what you experience? I think
this is fixed by:
commit 56c30b11f3616ea4f0c38a21e08e78f050096020
Author: Bill Fenner <fen...@gmail.com>
Date: Wed Dec 20 21:52:10 2017 +0000
NEWS: snmplib: PATCH: 1349: Fix perl/other crash against bad SNMPv3
agent
With the patch in 1214, the snmp_api code assumed that if magic was
set, it was the "struct synch-state" from snmp_client. Of course,
magic belongs to the caller, and the perl library uses it differently,
so reaching into it is verboten. Introduce a new callback (that
was already introduced in 5.8) to report this "retries exceeded"
state, and use it in snmp_client.
Thanks,
Bill
On Sat, Jan 13, 2018 at 1:36 AM, Hao Chen <earthlovepyt...@outlook.com>
wrote:
> Hi All:
>
>
>
> 1.
>
> My program need to use "callback" function and pass something back.
>
> So, I use "callback_magic" to store an C++ object address.
>
> So, I can get my C++ object and use it my callback function.
>
>
>
> My code looks like:
>
> ================================
>
> bool CERSnmpSession::open()
>
> {
>
> .....
>
> m_sessionData.callback = callBack;
>
> m_sessionData.callback_magic = this;
>
> .....
>
> }
>
>
>
> int SNMPSession::callBack(
>
> int operation,
>
> struct snmp_session *ses,
>
> int reqid,
>
> struct snmp_pdu *pdu,
>
> void* magic)
>
> {
>
> SNMPSession* ss = static_cast<SNMPSession*>(magic);
>
> .....
>
> }
>
>
>
>
>
> 2.
>
> The above code works well with net-snmp 5.4.4.
>
> But it coredump with net-snmp 5.7.3 while I set correct username & wrong
> password to do negative test.
>
>
>
> (1).
>
> The reason is that "_sess_process_packet()" (in snmp_api.c in 5.7.3) does:
>
> if (callback == NULL
>
> || callback(NETSNMP_CALLBACK_OP_RECEIVED_MESSAGE, sp,
>
> pdu->reqid, pdu, magic) == 1) {
>
> if (pdu->command == SNMP_MSG_REPORT) {
>
> if (sp->s_snmp_errno == SNMPERR_NOT_IN_TIME_WINDOW ||
>
> snmpv3_get_report_type(pdu) ==
>
> SNMPERR_NOT_IN_TIME_WINDOW) {
>
> /*
>
> * trigger immediate retry on recoverable Reports
>
> * * (notInTimeWindow), incr_retries == TRUE to prevent
>
> * * inifinite resend
>
> */
>
> if (rp->retries <= sp->retries) {
>
> snmp_resend_request(slp, rp, TRUE);
>
> break;
>
> } else {
>
> /* We're done with retries, so no longer waiting for
> a response */
>
> if (magic) {
>
> ((struct synch_state*)magic)->waiting = 0;
>
> }
>
> }
>
> } else {
>
> if (SNMPV3_IGNORE_UNAUTH_REPORTS) {
>
> break;
>
> } else { /* Set the state to no longer be waiting,
> since we're done with retries */
>
> if (magic) {
>
> ((struct synch_state*)magic)->waiting = 0;
> ====>
> culprit
>
> }
>
>
>
>
>
> (2).
>
> I compared the same code in 5.4.4, it is:
>
> if (callback == NULL
>
> || callback(NETSNMP_CALLBACK_OP_RECEIVED_MESSAGE, sp,
>
> pdu->reqid, pdu, magic) == 1) {
>
> if (pdu->command == SNMP_MSG_REPORT) {
>
> if (sp->s_snmp_errno == SNMPERR_NOT_IN_TIME_WINDOW ||
>
> snmpv3_get_report_type(pdu) ==
>
> SNMPERR_NOT_IN_TIME_WINDOW) {
>
> /*
>
> * trigger immediate retry on recoverable Reports
>
> * * (notInTimeWindow), incr_retries == TRUE to prevent
>
> * * inifinite resend
>
> */
>
> if (rp->retries <= sp->retries) {
>
> snmp_resend_request(slp, rp, TRUE);
>
> break;
>
> }
>
> } else {
>
> if (SNMPV3_IGNORE_UNAUTH_REPORTS) {
>
> break;
>
> }
>
> }
>
>
>
>
>
> (3).
>
> We can see 5.7.3 has extra "((struct synch_state*)magic)->waiting = 0;"
> than 5.4.4
>
>
>
> 3.
>
> Can you please help me:
>
> 1). If I want to pass private stuff, shall I use "callback_magic" or
> "myvoid in struct snmp_session" to contain it?
>
> I tested by using "myvoid" instead of "callback_magic" to contain my
> private call back data. It works fine.
>
>
>
> 2). Since "callback_magic" was changed since net-snmp 5.6.x, will net-snmp
> change "myvoid" in future release?
>
>
>
>
>
>
>
> Thanks and regards
>
>
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