yoursunny blog
computer, Internet, and life

May I Borrow your IPv4?

Junxiao Shi

With the rise of IPv4 costs, IPv6-only servers are becoming more popular in low end hosting world. In one occasion, I acquired an IPv6-only server, but wanted to have IPv4 on it. Somewhere else, I have a dual-stack IPv4+IPv6 server, idling away. Can I "borrow" the IPv4 of that dual-stack server, to use on the IPv6-only server? I tried several methods, and found a way to make this work.

Situation / Assumption / Requirement

In this case, both servers have KVM virtualization and are running Debian 12 operating system. Server A is a dual-stack server, with IPv4 address 192.0.2.158 and IPv6 address 2001:db8:aefc::2. Server B is an IPv6-only server, with IPv6 address 2001:db8:eec0::2. At server A, both IPv4 and IPv6 service are delivered on the same network interface.

My goal is to somehow "move" the IPv4 address from server A to server B. In particular, I want all IPv4 traffic to the 192.0.2.158 destination address to reach server B, and allow server B to send any IPv4 traffic with 192.0.2.158 source address. This shall include all TCP and UDP ports, as well as other IPv4 traffic such as ICMP ping. A "port forwarding" solution would be insufficient, as it cannot deliver non-TCP/UDP traffic.

Tunnel + Ethernet Bridge (does not work)

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Domain Transfer, WHOIS Privacy, DNSSEC, and the Absence of Push-ups

Junxiao Shi
last updated

Annual Domain Transfer for Profit

Since my first domain name in 2006, I have purchased several domain names for my various websites. A few years ago, I discovered a secret in the domain registration business: many registrars offer a cheaper price for domain transfer than domain renewal, as a means to attract new customers. Therefore, if I transfer my domain every year to a different registrar, I would pay less than renewing the domain at the same registrar.

DNS services for a domain used to be associated with the registrar. When I transfer a domain away, the DNS server of the old registrar would stop responding to queries regarding my domain, and the DNS server of the new registrar does not yet have any records about the IP addresses of my web server. Therefore, a domain transfer would usually cause the website to become inaccessible for a day or two. Typically, I post a tweet when a domain transfer is about to happen, so that my readers could know why my website is down.

Nowadays, I'm using Cloudflare DNS for most of my domains. Cloudflare DNS server is independent from the domain registrar, so that my website continues to resolve correctly throughout a domain transfer, as long as neither registrars modify the name server delegation records. In case the new registrar automatically updates the delegation records to their DNS servers, I have to quickly login to the control panel and change it back to Cloudflare, which would then cause a brief downtime of the website. Having done so for many years, I am accustomed to this process.

Transfer of ndn.today

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Intel iGPU VAAPI in Unprivileged LXC 4.0 Container

Junxiao Shi

Background

I recently bought a DELL OptiPlex 7040 Micro (paid link) desktop computer and wanted to operate it as a dedicated server. I installed Debian 11 on the computer, and placed it into the closet to be accessed over SSH only. To keep the host machine stable, I decide to run most workloads in LXC containers, which are said to be Fast-as-Metal. Since I operate my own video streaming website, I have an LXC container for encoding the videos.

The computer comes with an Intel Core i5-6500T processor. It has 4 hardware cores running at 2.50GHz frequency, and belongs to the Skylake family. FFmpeg is happily encoding my videos on this CPU.

As I read through the processor specification, I noticed this section:

  • Processor Graphics: Intel® HD Graphics 530
    • Processor Graphics indicates graphics processing circuitry integrated into the processor, providing the graphics, compute, media, and display capabilities.
  • Intel® Quick Sync Video: Yes
    • Intel® Quick Sync Video delivers fast conversion of video for portable media players, online sharing, and video editing and authoring.
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Install Ubuntu from ISO on IPv6-only KVM Server in SolusIO

Junxiao Shi

I recently obtained a KVM virtual server on SolusIO platform, and I want to install Ubuntu 20.04 Server from the official ISO image. This is not as easy as I hoped, but I figured it out.

Note: if you are in a hurry, skip the "Background" and start from "Part 1" section.

Background: SolusIO cannot Mount ISO Image

SolusIO is a virtual infrastructure management solution published by Plesk International Gmbh, the same company behind the popular SolusVM software. They describe SolusIO to be the successor of SolusVM, with more focus on the self-service approach for end users.

SolusIO inherits the same clean user interface from SolusVM, and is easy to use. However, as a power user, I notice several features are missing in SolusIO. One of these features is the ability to install the operating system from an ISO image.

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Disabling VNC in Virtualizor ⇒ Lost Connectivity?

Junxiao Shi

The KVM server hosting my website went offline last month. Thinking the server might have crashed, I went to Virtualizor, the VPS control panel, to reboot the VPS. It did not solve the problem, so I proceeded with my disaster recovery plan.

The hosting provider, Spartan Host, explained that it was a router bug. They fixed the router after 4 hours, but my server did not come online.

Symptom

To investigate what went wrong with my VPS, I came back to Virtualizor to enable VNC access. Having VNC access is like attaching a monitor and a keyboard to the server. It would allow me to see any error messages printed on the screen and login to check whether there are configuration errors.

I didn't see any error through VNC connection. Thinking it might be a routing problem, I logged in with username and password, and ran a traceroute. To my surprise, the traceroute was able to reach Internet destination. Moreover, I can SSH into this server again.

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IPv6 Neighbor Discovery Responder for KVM VPS

Junxiao Shi

I Want IPv6 for Docker

I'm playing with Docker these days, and I want IPv6 in my Docker containers. The best guide for enabling IPv6 in Docker is how to enable IPv6 for Docker containers on Ubuntu 18.04. The first method in that article assigns private IPv6 addresses to containers, and uses IPv6 NAT similar to how Docker handles IPv4 NAT. I quickly got it working, but I noticed an undesirable behavior: Network Address Translation (NAT) changes the source port number of outgoing UDP datagrams, even if there's a port forwarding rule for inbound traffic; consequently, a UDP flow with the same source and destination ports is being recognized as two separate flows.

$ docker exec nfd nfdc face show 262
    faceid=262
    remote=udp6://[2001:db8:f440:2:eb26:f0a9:4dc3:1]:6363
     local=udp6://[fd00:2001:db8:4d55:0:242:ac11:4]:6363
congestion={base-marking-interval=100ms default-threshold=65536B}
       mtu=1337
  counters={in={25i 4603d 2n 1179907B} out={11921i 14d 0n 1506905B}}
     flags={non-local permanent point-to-point congestion-marking}
$ docker exec nfd nfdc face show 270
    faceid=270
    remote=udp6://[2001:db8:f440:2:eb26:f0a9:4dc3:1]:1024
     local=udp6://[fd00:2001:db8:4d55:0:242:ac11:4]:6363
   expires=0s
congestion={base-marking-interval=100ms default-threshold=65536B}
       mtu=1337
  counters={in={11880i 0d 0n 1498032B} out={0i 4594d 0n 1175786B}}
     flags={non-local on-demand point-to-point congestion-marking}

The second method in that article allows every container to have a public IPv6 address. It avoids NAT and the problems that come with it, but requires the host to have a routed IPv6 subnet. However, routed IPv6 is hard to come by on KVM servers, because virtualization platform such as Virtualizor does not support routed IPv6 subnets, but can only provide on-link IPv6.

On-Link IPv6 vs Routed IPv6

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yoursunny.com Disaster Recovery Plan: 104 Minutes Downtime, No Tears

Junxiao Shi

The OVH fire taught us the importance of having a disaster recovery plan for your website and online services. In 2017, I rebuilt yoursunny.com and moved everything from configuration to content into git repositories. One of the reasons was that, the git repository could serve as a backup of the website, so that I can recover the site from a data loss.

uptime last 24 hours, vps4 server, yoursunny.com website

Today, I was forced to execute (part of) my disaster recovery plan. The result was: website is successfully recovered after 1 hour and 44 minutes of downtime.

🟥 Down

When I waked up this morning, there were several alert emails from UptimeRobot telling me that my website was down, up, down, and up again. At the same time, I also received alerts that the VPS hosting the website was not responding to ping. I ignored those alerts, thinking that they would resolve itself in a few minutes.

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OVH Strasbourg: Halt and Catch Fire, Data Uploaded to the Cloud

Junxiao Shi

2021-03-10, an OVH Cloud data center in Strasbourg, France caught on fire. Thousands of servers have been destroyed by fire. Thousands more are currently unavailable due to power cut, and will remain offline for several more days.

Data stored in those servers have been uploaded to the cloud via black smoke.

a building is burning with black smoke rising to the sky

According to Hacker News, a Dev mistakenly invoked the Halt and Catch Fire instruction on an Uninterrupted Power Supply unit, causing this incident.

Chairman of OVH cloud advised clients to activate their disaster recovery plans, such as restoring off-site backups to a new cloud server. Some clients are crying because they did not have backups, or they stored their backups on another machine in the same data center. Other clients experienced no downtime because they designed their systems for datacenter scale redundancy.

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yoursunny.com is Served by Caddy

Junxiao Shi

The last rebuild of yoursunny.com was in Spring 2017, when I moved the whole website into git repositories. It's been more than 3 years, and I think I should share an update on a few changes in the stack that serves this website.

History of HTTP Servers Behind yoursunny.com

Since 2011, my HTTP server of choice was lighttpd. Then, I have PHP running in FastCGI mode to serve the dynamic pages. It works, but I don't really like the lighttpd's script-like configuration structure. Moreover, there were suspected memory leaks in my setup, so that I had to use a cron job to restart the HTTP server weekly.

I keep hearing good words about nginx, as well as the benefits of running PHP in FPM mode. In 2013, I made the switch to nginx and PHP-FPM. The declarative configuration of nginx is easy to understand and makes sense to me.

HTTPS came to yoursunny.com at the end of 2015. Like many other websites, the TLS certificates were issued by Let's Encrypt, and requested through certbot command line client. One problem is that, my VPS at the time had only 64MB memory, and certbot would not work in such a small amount of memory. I had to request the TLS certificate on my laptop, and then upload it to the VPS.

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How to Host a Website in Oracle Cloud Free Tier

Junxiao Shi
last updated

Oracle Cloud is a cloud computing service offered by Oracle Corporation. Oracle Cloud has a generous free tier that offers two "always free" Micro instances with the following specification:

  • KVM virtualization
  • 1/8 CPU cores (AMD EPYC 7551)
  • 1GB memory
  • 47GB disk storage
  • 1 IPv4 address
  • up to 32 IPv6 addresses
  • 50Mbps Internet bandwidth

I signed up for Oracle Cloud, so that I can have some more free computing resources to play with. The sign-up procedure requires a credit card for identity confirmation purpose, but the credit card will not be charged. During sign-up, there's a choice of home region, which determines the location of VM instances; once selected, it cannot be changed in the future.

A common use case for a virtual machine is to host a website. Due to the firewalls, hosting a website on Oracle Cloud needs a few more steps. Here's exactly how to deploy a website in a Oracle Cloud Free Tier VM instance.

UPDATED 2022-01-27: Oracle Cloud now supports IPv6. Instructions are updated to enable IPv6 on the web server.

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