Hero Image
Dockertest: A Fast Way to Set Up Integration Test Environments

Dockertest: A Fast Way to Set Up Integration Test Environments dockertest

Thursday, May 12, 2022 Read
Hero Image
Tcpdump Usage Summary

Tcpdump Usage Summary Command usage tcpdump uses the command line. The command format is: tcpdump [ -AdDeflLnNOpqRStuUvxX ] [ -c count ] [ -C file_size ] [ -F file ] [ -i interface ] [ -m module ] [ -M secret ] [ -r file ] [ -s snaplen ] [ -T type ] [ -w file ] [ -W filecount ] [ -E spi@ipaddr algo:secret, ... ] [ -y datalinktype ] [ -Z user ] [ expression ] Simple option notes for tcpdump -E spi@ipaddr algo:secret , ... can decrypt IPsec ESP packets using spi@ipaddr algo:secret. The secret is the ESP key, expressed as an ASCII string. If it starts with 0x, the key is read as hex. In addition to the syntax above (spi@ipaddr algo:secret), you can append a syntax input filename for tcpdump to use (replace … in spi@ipaddr algo:secret, ... with a syntax filename). This file is opened when the first ESP packet arrives, so it is best to drop some privileges at that time (to reduce risk if the file is malicious). -T type forces tcpdump to analyze packets according to the protocol structure specified by type. Known type values include: aodv (Ad-hoc On-demand Distance Vector protocol, used in Ad hoc peer-to-peer networks) cnfp (Cisco NetFlow protocol) rpc (Remote Procedure Call) rtp (Real-Time Applications protocol) rtcp (Real-Time Applications control protocol) snmp (Simple Network Management Protocol) tftp (Trivial File Transfer Protocol) vat (Visual Audio Tool, an application-layer protocol used for video conferencing on the internet) wb (distributed White Board, an application-layer protocol for online meetings) Practical command examples Capture communication between host 210.27.48.1 and host 210.27.48.2 or 210.27.48.3

Thursday, May 5, 2022 Read
Hero Image
Go High-Performance Programming Handbook (Long Read)

Go High-Performance Programming Handbook (Long Read) Common data structures Reflection is nice, but don’t overuse it Prefer strconv over fmt A small amount of repetition is not worse than reflection Use binary.Read and binary.Write with caution binary.Read and binary.Write use reflection and are slow. If you need these two functions, implement the required logic manually instead of using them directly. Avoid repeated conversions from string to byte slice Specify container (slice/map) capacity

Friday, April 22, 2022 Read
Hero Image
How to Make an iPhone Ringtone: Turn an MP3 into a Ringtone or Alarm

How to Make an iPhone Ringtone: Turn an MP3 into a Ringtone or Alarm Video version of the iPhone ringtone steps Step 1: Prepare the MP3 you want to use as an iPhone ringtone First, prepare the music you want to use as a ringtone. MP3 is recommended. Save it in the Files app. Step 2: Make an iPhone ringtone with GarageBand Next, open the built-in GarageBand app on iPhone (re-download it if you deleted it), tap “Create Song”, and choose “Recorder”.

Sunday, April 10, 2022 Read
Hero Image
How to Choose a Go File Reading Approach

How to Choose a Go File Reading Approach Go provides one-shot methods for reading file content: os.ReadFile and ioutil.ReadFile. Starting from Go 1.16, ioutil.ReadFile is equivalent to os.ReadFile. The pros and cons of loading a file in one shot are obvious: it reduces IO operations, but it loads the entire file into memory. For large files, this risks running out of memory. Read line by line In Go, the bufio.Reader type provides ReadLine(), but in practice we more often use ReadBytes(’\n’) or ReadString(’\n’).

Tuesday, March 29, 2022 Read
Hero Image
Convert a List to a List of Dicts

Convert a List to a List of Dicts list my_users: - aaa - bbb - ccc dict my_users: - Name: aaa - Name: bbb - Name: ccc playbook - name: Transform data vars: orig_users: - aaa - bbb - ccc my_users: [] set_fact: my_users: "{{ my_users + [{} | combine({'Name': item})] }}" loop: "{{ orig_users }}" Explanation: Use the combine filter to build a dict Use loop to iterate orig_users Use my_users + [{} | combine({‘Name’: item})] to append to the list```

Wednesday, March 9, 2022 Read
Hero Image
Misspelling, missing collection, or incorrect module path for fortios_system_config_backup_restore

Misspelling, missing collection, or incorrect module path for fortios_system_config_backup_restore issue Hi, I’m trying to retrieve the configuration from a Fortigate using the module fortios_system_config_backup_restore and basing on your playbook example. I have ansible 2.10.6. When I use the collection fortinet.fortios:1.1.8, I got the following error: missing 1 required positional argument: 'mod' The full traceback is: Traceback (most recent call last): File "/home/ansible/.ansible/tmp/ansible-local-8668osvgufxk/ansible-tmp-1615481963.0092971-8768-3877705280026/AnsiballZ_fortios_system_config_backup_restore.py", line 102, in <module> _ansiballz_main() File "/home/ansible/.ansible/tmp/ansible-local-8668osvgufxk/ansible-tmp-1615481963.0092971-8768-3877705280026/AnsiballZ_fortios_system_config_backup_restore.py", line 94, in _ansiballz_main invoke_module(zipped_mod, temp_path, ANSIBALLZ_PARAMS) File "/home/ansible/.ansible/tmp/ansible-local-8668osvgufxk/ansible-tmp-1615481963.0092971-8768-3877705280026/AnsiballZ_fortios_system_config_backup_restore.py", line 40, in invoke_module runpy.run_module(mod_name='ansible_collections.fortinet.fortios.plugins.modules.fortios_system_config_backup_restore', init_globals=None, run_name='__main__', alter_sys=True) File "/usr/lib/python3.8/runpy.py", line 207, in run_module return _run_module_code(code, init_globals, run_name, mod_spec) File "/usr/lib/python3.8/runpy.py", line 97, in _run_module_code _run_code(code, mod_globals, init_globals, File "/usr/lib/python3.8/runpy.py", line 87, in _run_code exec(code, run_globals) File "/tmp/ansible_fortinet.fortios.fortios_system_config_backup_restore_payload_mplamrs7/ansible_fortinet.fortios.fortios_system_config_backup_restore_payload.zip/ansible_collections/fortinet/fortios/plugins/modules/fortios_system_config_backup_restore.py", line 472, in <module> File "/tmp/ansible_fortinet.fortios.fortios_system_config_backup_restore_payload_mplamrs7/ansible_fortinet.fortios.fortios_system_config_backup_restore_payload.zip/ansible_collections/fortinet/fortios/plugins/modules/fortios_system_config_backup_restore.py", line 436, in main TypeError: __init__() missing 1 required positional argument: 'mod' fatal: [fortigate-01]: FAILED! => { "changed": false, "module_stderr": "Traceback (most recent call last):\n File \"/home/ansible/.ansible/tmp/ansible-local-8668osvgufxk/ansible-tmp-1615481963.0092971-8768-3877705280026/AnsiballZ_fortios_system_config_backup_restore.py\", line 102, in <module>\n _ansiballz_main()\n File \"/home/ansible/.ansible/tmp/ansible-local-8668osvgufxk/ansible-tmp-1615481963.0092971-8768-3877705280026/AnsiballZ_fortios_system_config_backup_restore.py\", line 94, in _ansiballz_main\n invoke_module(zipped_mod, temp_path, ANSIBALLZ_PARAMS)\n File \"/home/ansible/.ansible/tmp/ansible-local-8668osvgufxk/ansible-tmp-1615481963.0092971-8768-3877705280026/AnsiballZ_fortios_system_config_backup_restore.py\", line 40, in invoke_module\n runpy.run_module(mod_name='ansible_collections.fortinet.fortios.plugins.modules.fortios_system_config_backup_restore', init_globals=None, run_name='__main__', alter_sys=True)\n File \"/usr/lib/python3.8/runpy.py\", line 207, in run_module\n return _run_module_code(code, init_globals, run_name, mod_spec)\n File \"/usr/lib/python3.8/runpy.py\", line 97, in _run_module_code\n _run_code(code, mod_globals, init_globals,\n File \"/usr/lib/python3.8/runpy.py\", line 87, in _run_code\n exec(code, run_globals)\n File \"/tmp/ansible_fortinet.fortios.fortios_system_config_backup_restore_payload_mplamrs7/ansible_fortinet.fortios.fortios_system_config_backup_restore_payload.zip/ansible_collections/fortinet/fortios/plugins/modules/fortios_system_config_backup_restore.py\", line 472, in <module>\n File \"/tmp/ansible_fortinet.fortios.fortios_system_config_backup_restore_payload_mplamrs7/ansible_fortinet.fortios.fortios_system_config_backup_restore_payload.zip/ansible_collections/fortinet/fortios/plugins/modules/fortios_system_config_backup_restore.py\", line 436, in main\nTypeError: __init__() missing 1 required positional argument: 'mod'\n", "module_stdout": "", "msg": "MODULE FAILURE\nSee stdout/stderr for the exact error", "rc": 1 } Using the recent pre release fortinet.fortios:2.0.0 , I got:

Thursday, January 6, 2022 Read
Hero Image
Struct Tricks Every Gopher Should Know

Struct Tricks Every Gopher Should Know NoCopy $ go vet aaa.go # command-line-arguments ./aaa.go:7:14: test passes lock by value: sync.WaitGroup contains sync.noCopy ./aaa.go:15:10: call of test copies lock value: sync.WaitGroup contains sync.noCopy type noCopy struct{} type WaitGroup struct { noCopy noCopy // 64-bit value: high 32 bits are counter, low 32 bits are waiter count. // 64-bit atomic operations require 64-bit alignment, but 32-bit // compilers only guarantee that 64-bit fields are 32-bit aligned. // For this reason on 32 bit architectures we need to check in state() // if state1 is aligned or not, and dynamically "swap" the field order if // needed. state1 uint64 state2 uint32 } noCopy is very simple: an empty struct. It has zero size and takes no space (as long as it is not the last field of a struct; otherwise there is still an 8-byte space overhead).

Monday, January 3, 2022 Read
Hero Image
How Nginx Hides Upstream Errors

How Nginx Hides Upstream Errors Nginx allows enabling next upstream for the following seven retryable error codes 403 Forbidden 404 Not Found 429 Too Many Requests 500 Internal Server Error 502 Bad Gateway 503 Server Unavailable 504 Gateway Timeout When upstream returns 404, return a 200 response with a not-found image You can use proxy_intercept_errors to achieve this.\n> When proxy_intercept_errors is enabled, requests with upstream response codes >= 300 can be further handled via the error_page directive.

Monday, December 27, 2021 Read
Hero Image
Argo CD ApplicationSet Controller: The World Turns for Me!

Argo CD ApplicationSet Controller: The World Turns for Me! Argo CD # Install kind; see the official docs for other platforms # Run a lightweight k8s cluster locally ~$ brew install kind # Install kubectx; see the official docs for other platforms # Use it to switch between k8s contexts ~$ brew install kubectx # Install helm; see the official docs for other platforms # K8s package manager ~$ brew install helm # Install kubectl; see the official docs for other platforms # Communicate with the k8s cluster API server ~$ brew install kubectl # Install argocd cli; see the official docs for other platforms # Communicate with Argo CD ~$ brew install argocd

Monday, December 27, 2021 Read
Hero Image
Go AES Encryption and Decryption in Three Modes (CBC/ECB/CFB)

Go AES Encryption and Decryption in Three Modes (CBC/ECB/CFB) How to encrypt a file using Go

Wednesday, December 22, 2021 Read
Hero Image
Understanding Cilium Series (1): Introduction to Cilium

Understanding Cilium Series (1): Introduction to Cilium Current status of k8s Service load balancing implementations Before Cilium, Services were implemented by kube-proxy in three modes: userspace, iptables, and ipvs. Userspace In this mode, kube-proxy acts as a reverse proxy and listens on random ports. It redirects traffic to the proxy port via iptables rules, and kube-proxy forwards the traffic to backend pods. Service requests go from user space into kernel iptables and then back to user space, which is costly and has poor performance.

Tuesday, December 21, 2021 Read