linux-networking

linux-networking is a skill for Claude Code, Codex from RightNow-AI/openfang. It costs 21 tokens per session (734 once invoked), scanned A, original, Apache-2.0.

A guide to networking on Linux servers, including firewalls, routing, DNS, and tools for inspecting network connections. DNS is the system that translates names such as example.com into network addresses.

In plain words
What is it for?
Use it to configure iptables or nftables firewalls, inspect packet handling, manage routing rules, diagnose DNS, and examine active connections.
Why use it?
It helps explain and fix blocked traffic, incorrect routes, failed name lookups, and other network problems that can be difficult to trace later.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/rightnow-ai/openfang/linux-networking
Any agent
npx skills add RightNow-AI/openfang --skill linux-networking
Clone the repo
git clone --depth 1 https://github.com/RightNow-AI/openfang

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for linux-networking

README.md
[![agentmods](https://agentmods.dev/badge/skills/rightnow-ai/openfang/linux-networking.svg)](https://agentmods.dev/skills/rightnow-ai/openfang/linux-networking)
Your own site
<a href="https://agentmods.dev/skills/rightnow-ai/openfang/linux-networking"><img src="https://agentmods.dev/badge/skills/rightnow-ai/openfang/linux-networking.svg" alt="Measured on agentmods" height="20"></a>
Per session 21 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 734 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00021 $0.00734
Opus 5 $0.00010 $0.00367
Sonnet 5 $0.00004 $0.00147
Haiku 4.5 $0.00002 $0.00073

Measured 4d ago against content hash bc44d96b83ca, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

linux-networking scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 4d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

Copies of this mod

2 near-identical copies found in the catalogue:

crates/openfang-skills/bundled/linux-networking/SKILL.md · 41 lines

How it starts

The opening of the file, as written. The whole thing — 41 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Linux Networking Expert

A senior systems engineer with extensive expertise in Linux networking internals, firewall configuration, routing policy, DNS resolution, and network diagnostics. This skill provides practical, production-grade guidance for configuring, securing, and troubleshooting Linux network stacks across bare-metal, virtualized, and containerized environments.

Key Principles

  • Understand the packet flow through the kernel: ingress, prerouting, input, forward, output, postrouting chains determine where filtering and NAT decisions occur
  • Use nftables as the modern replacement for iptables; it offers a unified syntax for IPv4, IPv6, ARP, and bridge filtering in a single framework
  • Apply the principle of least privilege to firewall rules: default-deny with explicit allow rules for required traffic
  • Monitor with ss (socket statistics) rather than the deprecated netstat for faster, more detailed connection information
  • Document every routing rule and firewall change; network misconfigurations are among the hardest issues to diagnose retroactively

Techniques

  • Use iptables -L -n -v --line-numbers to inspect rules with packet counters; use -t nat or -t mangle to inspect specific tables
  • Write nftables rulesets in /etc/nftables.conf with named tables and chains; use nft list ruleset to verify and nft -f to reload atomically
  • Configure policy-based routing with ip rule add and ip route add table to route traffic based on source address, mark, or interface
  • Capture traffic with tcpdump -i eth0 -nn -w capture.pcap for offline analysis; filter with host, port, and protocol expressions
  • Diagnose DNS with dig +trace for full delegation chain, and check systemd-resolved status with resolvectl status
  • Create network namespaces with ip netns add for isolated testing; connect them with veth pairs and bridges
  • Tune TCP performance with sysctl parameters: net.core.rmem_max, net.ipv4.tcp_window_scaling, net.ipv4.tcp_congestion_control
  • Configure WireGuard interfaces with wg-quick using [Interface] and [Peer] sections for encrypted point-to-point or hub-spoke VPN topologies

Read the full file on GitHub · 41 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 4d ago First seen · 41 lines · 21 tokens per session scan A bc44d96b83ca

Subscribe to this mod's changes

linux-networking is a skill published in the GitHub repository RightNow-AI/openfang (18,162 stars, last pushed 2mo ago), licensed Apache-2.0. It adds 21 tokens to every session and 734 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.