Networking & Firewall (Ss/Netstat/Iptables/Nftables/Curl)

Stop chasing packet drops in the dark

🧩 The Challenge

Dealing with a service that randomly drops connections is a nightmare when your firewall rules are buried in chains you can’t easily see. I’ve spent whole afternoons staring at thousands of lines of iptables rules just to realize a single counter wasn’t even incrementing.

💡 The Fix

Start using the trace capability in iptables or nftables to track a packet’s path through the ruleset in real-time. You’ll actually see where your packet gets nuked instead of guessing.

iptables -t raw -A PREROUTING -p tcp --dport 80 -j TRACE
dmesg -w

⚙️ Why It Works

Setting a trace rule in the raw table forces the kernel to log every single rule match for that specific packet. Watching the output in dmesg tells you exactly which chain is biting the bullet.

🚀 Pro-Tip: Don’t forget to delete that trace rule immediately after debugging, or your logs will fill up faster than you can rotate them.

Linux Tips & Tricks | © ngelinux.com | 11/9/2026