[SNMP4J] Unusual Delay in sr.nextBytes()

[Frank Fock]

Hi,

This "problem" is caused by the Java Runtime and operating system 
combination.
If I rember it correctly, the OS computes a (very good) random seed 
based on some indeterministic
source (i.e. user's keyboard hits, etc.). If that source is not 
available, it could take a long time.

By setting the salt, you take over the responsability to provide the 
indeterministic seed.
That's why it has a predictable performance then.

Best regards,
Frank

Am 30.05.2013 16:13, schrieb Jim.Zenor at gdc4s.com:
> Hi,
> I've been using SNMP4J 2.1.0 (with JDK 1.7.0_05 on a VM with RHEL 2.6.32-279.2.1.el6.x86_64) for a month or so now and have noticed an unusual performance variation when running my trap-sender test program.  One time it will run in less than a second, the next time 10-30 seconds.
>
> I reproduced the delay with org.snmp4j.tools.console.SnmpRequest using the following command-line:
>
> java -classpath \
> $COMMON/lib/log4j.jar:\
> $SNMP4J/snmp4j-2.1.0/dist/lib/SNMP4J.jar:\
>   org.snmp4j.tools.console.SnmpRequest \
> -p TRAP \
> -a MD5 \
> -A myotherpassword \
> -u myuser \
> -v 3 \
> -x DES \
> -X mypassword \
> localhost/162 \
> "1.3.6.1.2.1.1.3.0={t}0" \
> "1.3.6.1.6.3.1.1.4.1.0={o}1.3.6.1.6.3.1.1.5.1" \
> "1.3.6.1.2.1.1.1.0={s}System XYZ, Version N.M"
>
> I loaded the SNMP4J 2.1.0 source into Eclipse and started adding debug trace statements.  The delay, when it happens, was occurring in the Salt constructor within the method call to sr.nextBytes(rnd).
>
> 		protected Salt() {
> 		    byte[] rnd = new byte[8];
> 		    try {
> 		      SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
> 		      sr.nextBytes(rnd);
> 		    }...
>
> I'm hacking here... but after reading the JDK Javadocs for SecureRandom, I added the method call "sr.setSeed(rnd);" before the call to sr.nextBytes(rnd).  It seems to have fixed the delay; however, I don't know why and I'm not sure if it causes other problems.
>
> Is this a known problem?  Is there a workaround or something I'm doing wrong?
> Thanks
>
> P.S. Here's the stdout.  It shows a 14.5 second delay which happened before the first line of debug trace:
>
> 0 [main] DEBUG org.snmp4j.security.Salt  - Entering Salt()
> 9 [main] DEBUG org.snmp4j.security.Salt  - calling sr.nextBytes(rnd)
> 14544 [main] DEBUG org.snmp4j.security.Salt  - Initialized Salt to 3aba6a14e42fcf0f.
> 14551 [main] DEBUG org.snmp4j.security.UsmUserTable  - Adding user myuser = UsmUser[secName=myuser,authProtocol=1.3.6.1.6.3.10.1.1.2,authPassphrase=myotherpassword,privProtocol=1.3.6.1.6.3.10.1.2.2,privPassphrase=mypassword,localizationEngineID=null]
> 14554 [DefaultUDPTransportMapping_10.248.169.158/0] DEBUG org.snmp4j.transport.DefaultUdpTransportMapping  - UDP receive buffer size for socket 10.248.169.158/0 is set to: 131072
> 14557 [main] DEBUG org.snmp4j.mp.MPv3  - Context engine ID of unconfirmed scoped PDU is empty! Setting it to local engine ID
> 14559 [main] DEBUG org.snmp4j.security.USM  - getUser(engineID=80:00:13:70:01:0a:f8:a9:9e, securityName=myuser)
> 14634 [main] DEBUG org.snmp4j.security.AuthGeneric  - MD5First digest: c4:8f:bc:c9:59:c4:73:23:9a:03:81:00:19:5d:c2:ad
> 14634 [main] DEBUG org.snmp4j.security.AuthGeneric  - MD5localized key: fe:5e:bc:fe:09:13:ba:f4:02:ac:52:2d:3c:f8:bf:37
> 14687 [main] DEBUG org.snmp4j.security.AuthGeneric  - MD5First digest: eb:3a:d6:ba:92:94:41:a0:ff:64:08:3d:02:1c:07:f1
> 14688 [main] DEBUG org.snmp4j.security.AuthGeneric  - MD5localized key: 8c:94:41:7b:6d:40:cb:d5:97:07:1a:31:76:eb:7d:96
> 14689 [main] DEBUG org.snmp4j.security.UsmUserTable  - Adding user myuser = UsmUser[secName=myuser,authProtocol=1.3.6.1.6.3.10.1.1.2,authPassphrase=fe:5e:bc:fe:09:13:ba:f4:02:ac:52:2d:3c:f8:bf:37,privProtocol=1.3.6.1.6.3.10.1.2.2,privPassphrase=8c:94:41:7b:6d:40:cb:d5:97:07:1a:31:76:eb:7d:96,localizationEngineID=80:00:13:70:01:0a:f8:a9:9e]
> 14690 [main] DEBUG org.snmp4j.security.USM  - RFC3414 §3.1.4.a Outgoing message needs to be encrypted
> 14690 [main] DEBUG org.snmp4j.security.PrivDES  - Preparing decrypt_params.
> 14690 [main] DEBUG org.snmp4j.security.PrivDES  - Preparing iv for encryption.
> 14871 [main] DEBUG org.snmp4j.security.PrivDES  - Using padding.
> 14871 [main] DEBUG org.snmp4j.security.PrivDES  - Encryption finished.
> 14872 [main] DEBUG org.snmp4j.mp.MPv3  - Adding cache entry: StateReference[msgID=803982166,pduHandle=PduHandle[2091434141],securityEngineID=80:00:13:70:01:0a:f8:a9:9e,securityModel=org.snmp4j.security.USM at 1b54a291,securityName=myuser,securityLevel=3,contextEngineID=80:00:13:70:01:0a:f8:a9:9e,contextName=,retryMsgIDs=null]
> 14873 [main] DEBUG org.snmp4j.transport.DefaultUdpTransportMapping  - Sending message to 127.0.0.1/162 with length 192: 30:81:bd:02:01:03:30:11:02:04:2f:eb:cb:56:02:03:00:ff:ff:04:01:03:02:01:03:04:33:30:31:04:09:80:00:13:70:01:0a:f8:a9:9e:02:01:00:02:01:00:04:06:6d:79:75:73:65:72:04:0c:05:50:9b:45:30:e5:99:85:fd:e8:91:24:04:08:00:00:00:00:e4:2f:cf:0f:04:70:6f:9e:d5:92:ae:bc:38:4f:d9:be:7e:7b:0e:0e:12:29:c6:44:8b:ed:90:cf:ec:82:8b:08:49:d5:9f:22:dc:eb:e7:31:17:86:5e:e8:16:d9:ff:ba:9d:48:1d:28:58:e7:eb:65:72:6f:a7:3e:13:a4:54:db:a4:30:6b:9b:46:8e:25:b6:3d:f4:6e:9f:95:a7:ac:31:62:6b:14:c4:ed:1c:42:e6:a2:43:70:12:87:88:7b:20:02:1a:af:ab:8e:2e:a5:7c:e7:5f:8d:3a:73:c7:30:71:40:f3:ce:35:8a:23
> 14873 [main] DEBUG org.snmp4j.transport.DefaultUdpTransportMapping  - Terminated worker task: org.snmp4j.transport.DefaultUdpTransportMapping$ListenThread
> 14873 [main] DEBUG org.snmp4j.transport.DefaultUdpTransportMapping  - Interrupting worker task: org.snmp4j.transport.DefaultUdpTransportMapping$ListenThread
> 14873 [DefaultUDPTransportMapping_10.248.169.158/0] DEBUG org.snmp4j.transport.DefaultUdpTransportMapping  - Worker task stopped:org.snmp4j.transport.DefaultUdpTransportMapping$ListenThread
> TRAP sent successfully
>
> _______________________________________________
> SNMP4J mailing list
> SNMP4J at agentpp.org
> http://lists.agentpp.org/mailman/listinfo/snmp4j

-- 
---
AGENT++
Maximilian-Kolbe-Str. 10
73257 Koengen, Germany
https://agentpp.com
Phone: +49 7024 8688230
Fax:   +49 7024 8688231