resolv | An utility DNS library written in Go | DNS library
kandi X-RAY | resolv Summary
kandi X-RAY | resolv Summary
A context aware DNS library based on Miek's library. It's goal to offer a simple API to most common DNS operations while preserving access to low level data.
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Trending Discussions on DNS
QUESTION
My environment: hMailServer 5.6.8 on Windows Server 2022 Standard
Let's say I have two domains (I don't really own these domains, they're just examples), www.myblog.com
and www.mailserver.com
. They are both hosted on the same machine and have the same IP address 1.2.3.4
.
The blog site www.myblog.com
uses www.mailserver.com
to send emails. The site www.mailserver.com
only serves as a mail server; it is not accessible from a browser. I have set it up so that when www.myblog.com
sends an email to someone, the recipient's email server receives SENT: EHLO www.mailserver.com
, but sees SENT: MAIL FROM:
message, so the recipient sees that the email came from myblog.com
.
Everything is working fine so far. Recently I decided to check the "spam rating" of my setup at https://www.mail-tester.com. I sent an email to the spam tester using the setup described above, and I saw a warning under the SpamAssassin section that says
SPF_HELO_NONE SPF: HELO does not publish an SPF Record
My question is, how do I get rid of this warning? Are the DNS records as they should be? See below for the DNS records for each domain.
The DNS records for each domain are as follows (note the PTR record for 1.2.3.4):
...ANSWER
Answered 2022-Apr-10 at 22:48I was able to get rid of the warning by adding an extra TXT record with the name "www" to the www.mailserver.com
DNS:
QUESTION
I'm trying to parse a DNS response using java. I'm following RFC-1035 for guidelines on how to send requests and receieve responses, the format that is.
According to said RFC the answer section of a response should look like so:
...ANSWER
Answered 2022-Apr-04 at 15:33My problem is that I can't seem to parse the NAME in the answer section. It seems to start with a pointer which makes no sense.
I probably know at lot less about this than you but am wondering why you say that? firstByte
is telling you there's a pointer and the following value (0x0c) shows you the offset of the name for compression purposes (if I've got that right). None of the other bits in the same byte as firstByte
is set so that can be ignored from the point of view of the offset value
QUESTION
I have a k8 setup that looks like this
ingress -> headless service (k8 service with clusterIp: none) -> statefulsets ( 2pods)
Fqdn looks like this:
...ANSWER
Answered 2021-Aug-01 at 02:02example statefulset called foo
with image nginx
:
QUESTION
I am trying to create a custom DNS server for my domain on an AWS EC2 Instance. The instance is running Ubuntu 20.04 LTS and the DNS server is configured using bind 9. When I restart the bind server using
sudo service bind9 restart
The /var/log/syslog shows a successful start with no errors.
Now if I run a dig on the server itself like:
...ANSWER
Answered 2022-Feb-21 at 07:10From Modify the DNS attributes for your VPC - Amazon Virtual Private Cloud:
Amazon provides a DNS server (the Amazon Route 53 Resolver) for your VPC. To use your own DNS server instead, create a new set of DHCP options for your VPC.
See also: Add custom domain name resolution with DHCP options sets - Amazon Virtual Private Cloud
QUESTION
I'm looking to find a way to use a custom DNS resolver for a nodejs request using node-fetch. I think there is a star of explaining here : Node override request IP resolution but I can't manage to make it work for any request. My goal is to use an alternative DNS resolver, such as cloudflare (1.1.1.1) or Google public DNS (8.8.8.8) instead the OS / ISP default DNS resolution.
...ANSWER
Answered 2022-Feb-11 at 04:11Thanks to Martheen who answered in my first post I was able to achieve the result here :
QUESTION
I am requesting an API using the python requests library:
My python script is run once a day by the scheduler, Once the python script gets run, I am getting this error and the PID of the python script is getting killed showing OOM. I am not getting whether it's a DNS issue or an OOM (Out of memory) issue as the process is getting killed.
Previously script was running fine.
Any clues/help will be highly appreciable.
...ANSWER
Answered 2021-Sep-27 at 10:41I found the issue, in my case it was not DNS issue. The issue is related to the OOM(Out of memory) of the ec2 instance which is killing the process of a python script due to which the "Instance reachability check failed" and I was getting "Failed to establish a new connection: [Errno -3] Temporary failure in name resolution".
After upgrading ec2 instance, the instance reachability didn't fail and able to run python script containing api.
https://aws.amazon.com/premiumsupport/knowledge-center/system-reachability-check/
The instance status check failure indicates an issue with the reachability of the instance. This issue occurs due to operating system-level errors such as the following:
Failure to boot the operating system Failure to mount the volumes correctly Exhausted CPU and memory- This is happening in our case. Kernel panic
QUESTION
I want to create an instance in Google Cloud Engine with a custom (private) hostname. For that reason, when creating the instance from the Console (or from an SDK) I supply the hostname, or example instance0.custom.hostname
.
The instance is created and the search domain is set correctly in /etc/resolv.conf
For Ubuntu in particular I have to set the hostname with hostnamectl
but it is irrelevant to the question.
Forward DNS lookups work as normal for instance0.custom.hostname
. The problem comes when I do a reverse lookup for the private IP address of the instace. In that case the answer I get is the GCE "long" name instead of my custom hostname.
How can I make the reverse lookup reply with my custom name instead of the GCE?
I know in Azure you can use a Private DNS Zone with VM auto-registration to handle the "custom hostnames". I tried using a private zone with Google Cloud DNS (PTR records) but with no luck.
...ANSWER
Answered 2022-Feb-01 at 09:38After some serious digging I found a solution and tested it.
Reverse DNS works even without a "regular" DNS records for your custom.hostname
domain.
To get reverse dns working lets assume your VM's in 10.128.0.0/24
network.
Their IP's are 24,27,54,55 as in my example.
I created a private dns zone and named it "my-reverse-dns-zone" - the name is just for information and can be anything.
"DNS name" field however is very important. Since my network address starts with 10 I want all the instances that are created in that network segment to be subject to reverse dns. So the DNS name has to be 10.in-addr.arpa
in this case. If you're using 192.168....
or 172.16....
then adjust everything accordingly.
If you wanted just 10.128.0
then you can put 0.128.10.in-addr.arpa
. Then you select the VPC networks zone has to be visible in and voila:
Then you add the PTR records that will allow this to work. I'm setting all TTL's to 1 minute to shorten the wait :)
After accepting wait a minute (literally) and test it:
QUESTION
I have just set up a kubernetes cluster on bare metal using kubeadm, Flannel and MetalLB. Next step for me is to install ArgoCD.
I installed the ArgoCD yaml from the "Getting Started" page and logged in.
When adding my Git repositories ArgoCD gives me very weird error messages: The error message seems to suggest that ArgoCD for some reason is resolving github.com to my public IP address (I am not exposing SSH, therefore connection refused).
I can not find any reason why it would do this. When using https:// instead of SSH I get the same result, but on port 443.
I have put a dummy pod in the same namespace as ArgoCD and made some DNS queries. These queries resolved correctly.
What makes ArgoCD think that github.com resolves to my public IP address?
EDIT:
I have also checked for network policies in the argocd namespace and found no policy that was restricting egress.
I have had this working on clusters in the same network previously and have not changed my router firewall since then.
...ANSWER
Answered 2022-Jan-08 at 21:04That looks like argoproj/argo-cd issue 1510, where the initial diagnostic was that the cluster is blocking outbound connections to GitHub. And it suggested to check the egress configuration.
Yet, the issue was resolved with an ingress rule configuration:
need to define in
values.yaml
.
argo-cd
default provide subdomain but in our case it was/argocd
QUESTION
I purchased a custom domain name, I want now to modify my Github pages website which was accessible with : https://jeromevdev.github.io/santaclaus_nft/
to be accessible with https://santaclaus-nft.com
.
What I did :
- Added a file
CNAME
to my repository which containssantaclaus-nft.com
- Added a redirection on my hosting provider to redirect
https://santaclaus-nft.com
tohttps://jeromevdev.github.io/santaclaus_nft/
- In my project settings under pages I added
custom domain
and I setted it to : and here is the problem happening.
What am I missing ?
...ANSWER
Answered 2022-Jan-06 at 09:22Did you add the IPv4
addresses for the A
record to your DNS provider as explained on the Github Docs ? When you configure a custom domain with the Github Pages, you need to set a list of IPv4
addresses such as:
QUESTION
I am working on writing my own DNS server in .net core. I'm at the stage where I am encoding the response payload to send back, and the schema shows that most of the numbers are encoded as 16 bit numbers. C#'s ints are 32 bit numbers. Not a big deal, I'm just dropping off the remaining 16 bits from the front of the number I have no problem with that.
I was doing this by hand until I discovered the System.BitConverter class. I tried using it, however, and the results I came up with were reversed of what it came up with.
For example:
...ANSWER
Answered 2022-Jan-05 at 05:20As per the comments on the Question, the answer resides in Endianness.
Network byte order sent from the dig
command I am using to test with uses Big Endian order. However, my CPU architecture is Small Endian.
Dotnet behind the scenes in their UDPClient class reverses the bytes if your system is Small Endian when sending bytes, and vice verse when receiving bytes. But because I was creating the bytes by hand using bit shifting in the Big Endian format, they were then reversed to be in Non-Network Byte order while everything else was in Network Byte order.
The solution here is to either have conditional logic to test if your system is IsLittleEndian
According to the Microsoft dotnet docs, or let the System.BitConverter
class handle it for you.
For instance: in my above example I was trying to convert a 32 bit int into a 16 bit unsigned bit. I ended up replacing the above code with:
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