Nanik Tolaram

Software Development with Go

Cloud-Native Programming using Golang with Linux and Docker

Nanik Tolaram
Sydney, NSW, Australia
ISBN 978-1-4842-8730-9e-ISBN 978-1-4842-8731-6
https://doi.org/10.1007/978-1-4842-8731-6
© Nanik Tolaram 2023
This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed.
The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use.
The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

This Apress imprint is published by the registered company APress Media, LLC, part of Springer Nature.

The registered company address is: 1 New York Plaza, New York, NY 10004, U.S.A.

I would like to dedicate this book to my late Dad who stood by me and encouraged me to write my very first book when I was 17 years old. To my dearest Mum who always supported me in pursuing my dreams and encouraged me to keep on going no matter what life brings. To my beautiful wife and best friend for allowing me the time to write the book and supporting me in every step of our life. To both my sons, Rahul and Manav, for allowing me to spend time in front of the computer on weekends to chase my dream and passion. Last but not least, to God for giving me this life and opportunity to be where I am in this world.

Introduction

Go has been out for more than 10 years, and open source projects were developed using Go. The aim of this book is to show you the way to use Go to write a variety of applications that are useful in cloud-based systems.

Deploying applications into the cloud is a normal process that developers do every day. There are many questions that developers ask themselves about the cloud, like

  • How do containers work in a cloud environment?

  • How do cloud monitoring applications knows how much memory is left for my virtual machines?

  • How can I build a high performance networking server in Linux environment?

  • How do I scan code before deploying to the cloud to stop code deployment if it contains related information?

and many other cloud-relevant questions.

The book talk about different topics that are relevant in today’s cloud environment. The approach is to explain each topic at a high level and then help you understand it by going through the details with the code. The book uses combination of open source projects hosted in GitHub and sample code. The open source projects chosen are relevant to the topic. You will get a good grasp about the tool and also how the code works internally.

Acknowledgments

Thanks to everyone on the Apress team who helped and guided me so much. Special thanks to James Robinson-Prior who guided me through the writing process and to Nirmal Selvaraj who made sure everything was done correctly and things were on track.

Thanks to the technical reviewers for taking time from their busy schedules to review my book and provide great feedback.

Finally, thanks to you, the reader, for spending time reading this book and spreading the love of Go.

Table of Contents
Part I: System Programming1
Chapter 1:​ System Calls 3
Source Code 3
What Is a System Call?​ 4
C System Call 5
sys/​unix Package 8
System Call in Go 10
Summary 14
Chapter 2:​ System Calls Using Go 15
Source Code 15
Syscall Package 16
syscall Application 16
Checking Disk Space 18
Webserver with syscall 20
ELF Package 22
High-Level ELF Format 23
Dump Example 24
/​sys Filesystem 28
Reading AppArmor 29
Summary 31
Chapter 3:​ Accessing proc File System 33
Source Code 33
Peeking Inside procfs 34
Reading Memory Information 38
Peeking Network Information 41
Using the procfs Library 44
Code Sample 44
Inside the procfs Library 46
Summary 48
Part II: Containers49
Chapter 4:​ Simple Containers 51
Linux Namespace 51
cgroups 55
rootfs 58
Gontainer Project 63
Summary 70
Chapter 5:​ Containers with Networking 71
Source Code 71
Network Namespace 72
Setting Up with the ip Tool 74
Containers with Networks 79
Summary 88
Chapter 6:​ Docker Security 89
Source Code 89
seccomp Profiles 89
libseccomp 91
Docker seccomp 95
Docker Proxy 98
Container Attack Surface 105
Summary 106
Part III: Application Security109
Chapter 7:​ Gosec and AST 111
Source Code 111
Abstract Syntax Tree 111
Modules 115
Sample Code 116
gosec 122
Inside gosec 123
Rules 128
Summary 130
Chapter 8:​ Scorecard 131
Source Code 131
What Is Scorecard?​ 131
Setting Up Scorecard 133
Running Scorecard 137
High-Level Flow 139
GitHub 145
GitHub API 145
GitHub Explorer 156
Summary 159
Part IV: Networking161
Chapter 9:​ Simple Networking 163
Source Code 163
TCP Networking 163
TCP Client 164
TCP Server 166
UDP Networking 168
UDP Client 169
UDP Server 172
Concurrent Servers 174
Load Testing 175
Summary 179
Chapter 10:​ System Networking 181
Source Code 181
Ping Utility 181
Code Walkthrough 182
DNS Server 188
Running a DNS Server 188
DNS Forwarder 189
Pack and Unpack 193
Summary 196
Chapter 11:​ Google gopacket 199
Source Code 199
gopacket 200
Layer 200
Packet 204
Using gopacket 205
pcap 205
Networking Sniffer 206
Capturing With BPF 217
Summary 222
Chapter 12:​ Epoll Library 223
Source Code 224
Understanding epoll 224
epoll in Golang 226
Epoll Registration 227
Epoll Wait 229
Epoll Library 232
Summary 235
Part V: Securing Linux239
Chapter 13:​ Vulnerability Scanner 239
Source Code 239
Vulnerability Scanners 240
Using Vuls 241
Checking Out the Code 241
Running Scan 243
Learning From Vuls 248
Port Scan 248
Exec 255
SQLite 257
Summary 263
Chapter 14:​ CrowdSec 265
Source Code 265
CrowdSec Project 266
Using CrowdSec 266
crowdsec.​db 270
Learning From CrowdSec 273
System Signal Handling 274
Handling Service Dependencies 280
GeoIP Database 285
Summary 290
Part VI: Terminal User Interface293
Chapter 15:​ ANSI and UI 293
Source Code 293
ANSI Escape Code 294
ANSI-Based UI 296
Color Table 296
Styling Text 299
Open Source Library 300
Gookit 300
Spinner 303
Summary 306
Chapter 16:​ TUI Framework 307
uiprogress 307
Code Flow 309
Updating Progress 310
Bubbletea 313
Init 315
Update 318
View 319
Summary 321
Part VII: Linux System325
Chapter 17:​ systemd 325
Source Code 325
systemd 325
systemctl 329
Hello Server systemd 332
go-systemd Library 334
Summary 345
Chapter 18:​ cadvisor 347
Source Code 347
Running cAdvisor 347
Web User Interface 352
Architecture 355
Initialization 357
Manager 361
Monitoring Filesystem 368
Information from /​sys and /​proc 371
Client Library 375
Summary 375
Index 377
About the Author
Nanik Tolaram

is a big proponent of open source software with over 20 years of industry experience. He has dabbled in different programming languages like Java, JavaScript, C, and C++. He has developed different products from the ground up while working in start-up companies. He is a software engineer at heart, but he loves to write technical articles and share his knowledge with others. He learned to program with Go during the COVID-19 pandemic and hasn’t looked back.

 
About the Technical Reviewer
Fabio Claudio Ferracchiati

is a senior consultant and a senior analyst/developer using Microsoft technologies. He works for BluArancio ( www.bluarancio.com ). He is a Microsoft Certified Solution Developer for .NET, a Microsoft Certified Application Developer for .NET, a Microsoft Certified Professional, and a prolific author and technical reviewer. Over the past ten years, he’s written articles for Italian and international magazines and coauthored more than ten books on a variety of computer topics.

 
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