i have a Ubuntu 16.04.5 server with Vesta CP.
I checked the server on https://dnsflagday.net, and I got this report:
domain.cl. #123.456.78.90 (ns1.domain.cl.): dns=ok edns=ok edns1=ok edns#512=ok ednsopt=ok edns1opt=ok do=ok ednsflags=ok docookie=ok edns512tcp=timeout optlist=ok
domain.cl. #123.456.78.90 (ns2.domain.cl.): dns=ok edns=ok edns1=ok edns#512=ok ednsopt=ok edns1opt=ok do=ok ednsflags=ok docookie=ok edns512tcp=timeout optlist=ok
I do not know what edns512tcp = timeout means and I have not had much luck looking for a solution on internet.
Can someone help me? thanks
For that tool, any kind of "timeout" error is a problem, it means some server did not reply or the message (either query or reply) was eaten by some active element on the path, so it needs to be fixed.
edns512tcp is when the testing software does an EDNS query with a buffer of 512 bytes and over TCP.
If you go to https://ednscomp.isc.org/ednscomp/ for your domain you will have the full test results.
For that specific error it is:
EDNS - over TCP Response (edns#512tcp)
dig +vc +nocookie +norec +noad +edns +dnssec +bufsize=512 dnskey zone #server
expect: NOERROR
expect: OPT record with version set to 0
See RFC5966 and See RFC6891
So you can see which DNS query was done with dig, that you can reproduce it (+vc is an old flag name that is an alias for +tcp). The test expects to get a NOERROR code back and an OPT record. Your servers did not reply at all, so the test failed.
It seems that your servers did not reply to that at all, which is wrong. Maybe they do not reply to TCP queries at all which is even more wrong. In all cases you will need to contact the entity responsible for maintaining those servers and point it to the test results so that they start to fix the problem.
thanks for your help.
I read more about it and I could detect that port 53 was being blocked by the firewall, I added the rule to the firewall to allow TCP connections on port 53.
Everything it's fine now
Related
I am using Fiddler 5.0 to capture https requests of mobile app. It works fine except one app. Below is logs of Fiddler.
21:31:59:7072 HTTPSLint> Warning: ClientHello record was 508 bytes long. Some servers have problems with ClientHello's greater than 255 bytes. https://github.com/ssllabs/research/wiki/Long-Handshake-Intolerance
21:31:59:7072 !SecureClientPipeDirect failed: System.Security.Authentication.AuthenticationException A call to SSPI failed, see inner exception. < 处理证书时，出现了一个未知错误。 for pipe (CN=ci.migudm.cn, O=DO_NOT_TRUST, OU=Created by http://www.fiddler2.com).
21:31:59:7412 !SecureClientPipeDirect failed: System.Security.Authentication.AuthenticationException A call to SSPI failed, see inner exception. < 处理证书时，出现了一个未知错误。 for pipe (CN=ci.migudm.cn, O=DO_NOT_TRUST, OU=Created by http://www.fiddler2.com).
21:31:59:7862 HTTPSLint> Warning: ClientHello record was 508 bytes long. Some servers have problems with ClientHello's greater than 255 bytes. https://github.com/ssllabs/research/wiki/Long-Handshake-Intolerance
Have you checked out the link provided by the logs? There's a bunch of very relevant information there that I think might help you get what you need:
Some web servers are unable to process Client Hello messages longer than 255 bytes, even though such messages are allowed by the protocol. Although most Client Hello messages are shorter than this limit, with the use of Server Name Indications (SNI), Elliptic Curve extensions, and the increase in the number of supported suites, the size can easily go over.
Browsers are thought not to be affected, but some other tools may be. In particular, OpenSSL 1.0.1+ is known to be affected. If you are using the s_client tool, try to reduce the size of the handshake by disabling some of the suites offered by OpenSSL (this can be done by specifying the desired suites using the -cipher switch).
OpenSSL Bug #2771: Openssl 1.0.1 times out when connecting to Outlook Exchange 2007; sign in with guest/guest.
F5 tracks this problem under bug #376483 and it is fixed in BIG-IP LTM 10.2.4 (see [SOL14758: SSL client connections may fail if the ClientHello message is greater than 255 bytes and uses TLS 1.1 or 1.2] (https://support.f5.com/kb/en-us/solutions/public/14000/700/sol14758.html) for more details).
Michael Tschannen says:
The issue is fixed according to F5 in 10.2.4, they are however not mentioned in any release notes (I have >just checked until 11.x)
To debug the issue on an F5, the log level of "SSH" needs to be at least "Informational".
Example:
Mar 22 09:44:21 local/tmm info tmm[4696]: 01260013:6: SSL Handshake failed for TCP from x.x.x.x:443 to x.x.x.x:49549
Source: https://github.com/ssllabs/research/wiki/Long-Handshake-Intolerance
If you've been through all of this information, could you please provide the F5 version, OpenSSL version, and log information from OpenSSL?
We're running a web API app on Kubernetes (1.9.3) in AWS (set with KOPS). The app is a Deployment and represented by a Service (type: LoadBalancer) which is actually an ELB (v1) on AWS.
This generally works - except that some packets (fragments of HTTP requests) are "delayed" somewhere between the client <-> app container. (In both HTTP and HTTPS which terminates on ELB).
From the node side:
( Note: Almost all packets on server-side arrive duplicated 3 times )
We use keep-alive so the tcp socket is open and requests arrive and return pretty fast. Then the problem happens:
first, a packet with only the headers arrives [PSH,ACK] (I see the headers in the payload with tcpdump).
an [ACK] is sent back by the container.
The tcp socket/stream is quiet for a very long time (up to 30s and more - but the interval is not consistent, we consider >1s as a problem ).
another [PSH, ACK] with the HTTP data arrives, and the request can finally be processed in the app.
From the client side:
I've run some traffic from my computer, recording it on the client side to see the other end of the problem, but not 100% sure it represents the real client side.
a [PSH,ASK] with the headers go out.
a couple of [ACK]s with parts of the payload start going out.
no response arrives for a few seconds (or more) and no more packets go out.
[ACK] marked as [TCP Window update] arrives.
a short pause again and [ACK]s start arriving and the session continues until the end of the payload.
This is only happening under load.
To my understanding, this is somewhere between the ELB and the Kube-Proxy, but I'm clueless and desperate for help.
This is the arguments Kube-Proxy runs with:
Commands: /bin/sh -c mkfifo /tmp/pipe; (tee -a /var/log/kube-proxy.log < /tmp/pipe & ) ; exec /usr/local/bin/kube-proxy --cluster-cidr=100.96.0.0/11 --conntrack-max-per-core=131072 --hostname-override=ip-10-176-111-91.ec2.internal --kubeconfig=/var/lib/kube-proxy/kubeconfig --master=https://api.internal.prd.k8s.local --oom-score-adj=-998 --resource-container="" --v=2 > /tmp/pipe 2>&1
And we use Calico as a CNI:
So far I've tried:
Using service.beta.kubernetes.io/aws-load-balancer-type: "nlb" - the issue remained.
(Playing around with ELB settings hoping something will do the trick ¯_(ツ)_/¯ )
Looking for errors in the Kube-Proxy, found rare occurrences of the following:
E0801 04:10:57.269475 1 reflector.go:205] k8s.io/kubernetes/pkg/client/informers/informers_generated/internalversion/factory.go:85: Failed to list *core.Endpoints: Get https://api.internal.prd.k8s.local/api/v1/endpoints?limit=500&resourceVersion=0: dial tcp: lookup api.internal.prd.k8s.local on 10.176.0.2:53: no such host
...and...
E0801 04:09:48.075452 1 proxier.go:1667] Failed to execute iptables-restore: exit status 1 (iptables-restore: line 7 failed
)
I0801 04:09:48.075496 1 proxier.go:1669] Closing local ports after iptables-restore failure
I couldn't find anything describing such issue and will appreciate any help. Ideas on how to continue and troubleshoot are welcome.
Best,
A
I have a Centos server with exim installed. I am trying to send en email from the command line like this:
exim -v account#gmail.com
From: email#mydomain.com
To: account#gmail.com
Subject: test email
this is a test
^D
I have also tried:
echo 'test message' | mail -s Test1 account#gmail.com
as well as sending from a PHP script.
The result is the email times out. The logs indicate exim is timing out:
H=alt2.gmail-smtp-in.l.google.com [173.194.219.26] Connection timed out
I believe iptables are correct. I have scanned the server from an external IP and ports 25, 265 and 587 are open. (Not sure 587 needs to be since this will be a send-only situation most likely.)
I have also telnet'd to port 25 successfully. (Most of the successful resolutions I have found involved port 25 being blocked. I don't think that is the case here. I have also called my provider and checked. They claim port 25 connections are not blocked.)
I would appreciate some ideas.
Thank you.
I'm troubleshooting an existing webservice. It previously worked just fine, but now SOAP-based requests to the postgreSQL database result in an "unknown error: Error Fetching http headers" error.
In looking up this problem, I come across the following tip:
When you get errors like: "Fatal error: Uncaught SoapFault exception:
[HTTP] Error Fetching http headers in" after a few (time intensive)
SOAP-Calls, check your webserver-config.
Sometimes the webservers "KeepAlive"-Setting tends to result in this
error. For SOAP-Environments I recommend you to disable KeepAlive.
Hint: It might be tricky to create a dedicated vhost for your
SOAP-Gateways and disable keepalive just for this vhost because for
normal webpages Keepalive is a nice speed-boost.
I haven't been able to figure out exactly how you disable KeepAlive or where this parameter would be set. I've tried grep -i "keepalive" /usr/share/tomcat5/conf/*, result negative.
Perhaps due to the variability of server environments this is a question for my sysadmin, but I do have root privileges.
Thanks for your help, stack!
In your Tomcat's server.xml file, set the maxKeepAliveRequests attribute to 1 on your HTTP connectors to effectively disable keep alive.
For more information:
http://tomcat.apache.org/tomcat-5.5-doc/config/http.html#Standard_Implementation
hi i am using smack.jar to connect to my gmail server. but xmppconnection.connet() is failing and it says that server is not responding . i am attaching the log. please help me out.
Exception in thread "main" Connection failed. No response from server.:
at org.jivesoftware.smack.PacketReader.startup(PacketReader.java:164)
at org.jivesoftware.smack.XMPPConnection.initConnection(XMPPConnection.java:945)
at org.jivesoftware.smack.XMPPConnection.connectUsingConfiguration(XMPPConnection.java:904)
at org.jivesoftware.smack.XMPPConnection.connect(XMPPConnection.java:1415)
at JabberSmackAPI.login(JabberSmackAPI.java:29)
at JabberSmackAPI.main(JabberSmackAPI.java:79)
To be clear, the server isn't returning this error, because you haven't connected to the server yet.
It might be a configuration problem. If your server doesn't have a client DNS SRV record (e.g. _xmpp-client._tcp.gmail.com), then you'll need to pass the XMPPConnection object a ConnectionConfiguration with the name of the machine to connect to for your domain.
It is also possible that this is a network problem (connectivity, routing, firewall, etc.). To test for this, try commands like this on the command line:
% dig +short _xmpp-client._tcp.gmail.com SRV
5 0 5222 talk.l.google.com.
20 0 5222 talk2.l.google.com.
20 0 5222 talk1.l.google.com.
20 0 5222 talk3.l.google.com.
20 0 5222 talk4.l.google.com.
% telnet talk.l.google.com 5222
Trying 74.125.155.125...
Connected to talk.l.google.com.
Escape character is '^]'.
>
Note that you type the greater-than character. Most XMPP servers will disconnect you immediately at this point, since you've sent them XML that is not well-formed.
If you've got a network problem, you'll see something like this:
Trying 74.125.155.125...
telnet: connect to address 74.125.155.125: Connection refused
telnet: Unable to connect to remote host