Avamar: Säkerhetskopieringen misslyckas på grund av att DNS-frågan tar för lång tid – avtar FATAL <8941>: Allvarligt serveranslutningsproblem, initieringen avbryts. Verifiera korrekt serveradress och inloggningsuppgifter.

Summary: Syftet med den här KB-artikeln är att förklara det särskilda scenariot där avtar-handskakningen misslyckas men pingen fungerar och de nödvändiga TCP-portnumren också är öppna.

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Symptoms



I det här scenariot fann vi att vissa kunder påverkades medan andra inte påverkades.
För den berörda klienten uppstår problemet med både Win FS-säkerhetskopior och VSS-säkerhetskopieringar.

Från avtar-loggarna kan vi se följande felmeddelande: 
avtar FATAL <8941>: Fatal server connection problem, aborting initialization. Verify correct server address and login credentials.
avtar Info <5694>: - Failed initial handshake, trying again
avtar Info <5562>: - - Connect: Trying 10.xx.xx.xx:29000
Adding log debugging we can see the extra bit of information in the log:


[avtar]  sslcertificate::verify_certificate_ip CN Name='Avamar Server RSA TLS'
    [avtar]  sslcertificate::verify_cnname Performing CN Name validation for Avamar Server RSA TLS
    [avtar]  uwrapper::gethostbyaddr DnsQuery(dns)  returned (9002) for 10.xx.xx.xx
    [avtar]  sslcertificate::verify_certificate_ip CN Name='<avamar-server-fqdn>'
    [avtar]  sslcertificate::verify_cnname Performing CN Name validation for <avamar-server-fqdn>
    [avtar]  uwrapper::gethostbyaddr DnsQuery(dns)  returned (9002) for 10.xx.xx.xx
    [avtar]  sslcertificate::verify_certificate_ip CN Name field did not match Hostname - Checking SA Names
    [avtar]  sslcertificate::verify_certificate_ip rawIPAddrLen = 4
    [avtar]  sslcertificate::verify_certificate_ip Comparing 10.xx.xx.xx with 10.xx.xx.xx
    [avtar]  sslcertificate::verify_certificate_ip Certificate successfully verified
    [avtar]  <-- SSL
    [avtar]  <-- TLS 1.2 Handshake, ServerHelloDone
    [avtar]  --> SSL
    [avtar]  --> TLS 1.2 Handshake, ClientKeyExchange
    [avtar]  --> SSL
    [avtar]  --> TLS 1.2 ChangeCipherSpec
    [avtar]  --> SSL
    [avtar]  --> TLS 1.2 Handshake, Finished
>[avtar]  sslsockimpl::open  connect failure  (setrslt 1)  (conrslt 0)
>[avtar]  Printing ssl error stack
    [avtar]  certlock::~certlock() success to remove SSL cert lock 'C:\Program Files\avs\etc\.tmp\.certlock'
    [avtar]  sslsockimpl::save_server_cert saving cert='C:\Program Files\avs\etc\servercert.pem'
    [avtar]  sslsockimpl::save_server_cert cipher='AES256-SHA'
>[avtar]  sslsockimpl::open  failure
> avtar Info <5694>: - Failed initial handshake, trying again
For the troubleshooting purpose we checked and confirmed that the TCP ports 28001, 28002, 27000 and 29000 were all open and within the correct TCP directions as per Avamar security guide, ping and DNS resolution were also working fine.



 

Cause

Det här problemet beror på den långa svarstiden i DNS-frågorna, i själva verket kan vi se att "DnsQuery(dns) returnerade" tog mer än 10 sekunder varje gång, observera att handskakningsprocessen kör ett antal frågeförsök innan den misslyckas helt.

Se till exempel: 
2019/03/05-10:22:41.39299 [avtar]  sslcertificate::verify_cnname Performing CN Name validation for Avamar Server RSA TLS
2019/03/05-10:22:53.30100 [avtar]  uwrapper::gethostbyaddr DnsQuery(dns)  returned (9002) for 10.xx.xx.xx
And the entire handshake process would require about 50 seconds to complete and fail:


2019/03/05-10:22:14.89800 [avtar]  sslsockimpl::open  initclient success
....
2019/03/05-10:23:05.41599 [avtar]  sslsockimpl::open  failure

For comparison here is an example from a working client where we see that the the "DnsQuery" is returned in less than 1 second:

2019/03/05-11:56:06.97600 [avtar]  sslcertificate::verify_cnname Performing CN Name validation for <avamar-server-fqdn>
2019/03/05-11:56:07.79600 [avtar]  uwrapper::gethostbyaddr DnsQuery(dns)  returned (9002) for 10.xx.xx.xx
And the entire handshake process would complete in about 13 seconds:


2019/03/05-11:55:54.12400 [avtar]  sslsockimpl::open  initclient success
...
2019/03/05-11:56:07.82899 [avtar]  sslsockimpl::open  initclient success, cipher: AES256-SHA
In a summary, the root cause is identified as DnsQuery spent too much time on the affected client machines.

Resolution

För att åtgärda den här typen av problem måste systemadministratören vidta åtgärder på DNS-servern för att lösa fördröjningen.

Eftersom problemet ligger utanför Avamar-säkerhetskopieringsproduktens omfattning måste sys-administratören engageras.

Additional Information

Om du upplever samma fel men i ditt fall DNS-återställningen på mindre än en sekund kan du uppleva en annan typ av problem.
Kontrollera först i Dell EMC:s kunskapsdatabas om någon annan kunskapsbasartikel kan hjälpa dig att lösa problemet. Kontakta annars Avamars supportteam.

Affected Products

Avamar

Products

Avamar, Avamar Client for Windows
Article Properties
Article Number: 000055434
Article Type: Solution
Last Modified: 11 Oct 2024
Version:  3
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