Posts

In this post, we want to understand how a DNS request in K8s pod gets resolved. Let’s create a mental model before we make a DNS request and see how packet moves through the cluster. Glossary Client Pod: This is going to be the pod which will make various kinds of DNS request. CoreDNS: This is the DNS server that we will use as DNS provider in our K8s cluster. Service: In K8s world, Service is a basically a ClusterIP backed by various Pods. Kube-Proxy: This component is responsible to configuring service routing on the Node. It configures the IPTable rules which translates the ServiceIP to PodIPs. Kubernetes DNS Architecture Before diving into the packet flow, let’s understand the basic DNS architecture in Kubernetes: ...

In this post, we will see how to communicate from gvisor user space network stack to Internet. We will be making a HTTP request to google.com from user space network stack. This post is building on top of my previous Gvisor related posts Gvisor - User space TCP Server and Client Gvisor - User space HTTP Server and Client Routing Using Linux Network Stack Lets briefly take a look at how a typical TCP request makes its way from the application to the target address. ...

This post is a follow-up from previous post Gvisor - User space TCP Server and Client. In this post, we are going to build user space HTTP server and client on top of TCP server and client that we created in previous post. To take a look at complete code for this, refer - https://github.com/viveksb007/gvisor-experiment/blob/main/cmd/userspace-http/main.go Creating a Http Server We are using GoLang standard net/http package to build the HTTP server. We can create the user space TCP listener and pass that to http.Serve() method. gvisor implementation adheres the GoLang std interfaces. ...

In this post, we will see how to create a simple TCP Server and TCP Client in user space network stack. Both server and client will be in the same network. To take a look at complete code for this, refer - https://github.com/viveksb007/gvisor-experiment/blob/main/cmd/userspace-tcpip/main.go Creating a Network stack In this section, we are creating a Network stack specifying which protocols it needs to support, assigning addresses to the network and adding default route table. ...

In this post, we are going to setup NodeLocalDNS in our EKS cluster. There is a clear guide on kubernetes.io on how to do so, I am writing this post for my reference with a bunch of k8s related commands to validate that its working as expected. I am assuming that you have a EKS cluster running. Before setting up NodeLocalDNS, lets make a DNS query from a pod and see where its getting answered from ...

Introduction I have been tracking my personal finances on an excel sheet on an ad-hoc basis. There was no specific system as such, I used to just dump my assets and their current value to calculate Net-Worth. I wanted more insights on how my investments in different asset classes are growing and see their performance over time (not point in time when I am checking it). Tools and Methods I recently found Paisa - Personal Finance Manager and decided to give it a try. Mainly because your data stays on your system, it’s not uploaded to any server. So this tool takes a privacy-first approach. This is a FOSS application, I didn’t look any further. ...

In this post, we are going to see how we can set up monitoring for AMM’s. This might be required for use-cases like Developing an API service which allows clients to query price of some asset in AMM Develop an arbitrage bot I am referring to AMM’s on the Solana blockchain. But the idea should be generally applicable to the AMMs of any blockchain. We are going to look into simple CFMM based AMM for example Orca. There are few AMMs whose liquidity is distributed into a pool and orderbook like Serum and Raydium. ...

I was always wondering how Flash loans actually work, how can we get uncollateralized loan on blockchain. I got better understanding of Flash loans while solving Free Rider problem. In this post, I tried to explain how Flash loans actually work using pseudo code. If you want to have a look at actual solidity code. See Reference section. What are Flash Loans? Flash loans are uncollateralized loans in DeFi. They enable users to borrow liquidity instantly without any collateral. There is a catch, the borrowed amount needs to be paid back in the same transaction, along with some fees which can vary for different protocols. It’s a bit difficult to understand how this actually happens, so we will look at some code examples to understand how this is achieved. ...

Recently, I came across bots doing arbitrage on Solana. Was reading about wormhole hack and how it created great opportunities for bots to make free money. Note that the wormhole hack was a long tail event. In general, arbitrage is a very competitive space and needs constant improvements in strategy. Misaka wrote a detailed analysis on bots which made money in the “Golden 30 mins” just after the hacker dumped stolen ETH into Solana AMM pools. Quoting from the post ...

I recently came across a post “How to become a Smart Contract Auditor” by cmichel. The post breaks down the skills required and points to good resources to get started with Smart Contract security. Before this, I was exploring development on Ethereum using Solidity. Solving these challenges has given me better insights to look at code from a security perspective and improved overall Solidity skills. Code solutions can be found on my fork of damn-vulnerable-defi repo. Feel free to suggest/comment some other ways to exploit the challenges or any gas optimizations (I didn’t tried to optimize for gas while writing exploits) ...