https://blogs.damiendye.uk/en/tags/tcp/ Recent content in Tcp on Damien Dye's Blog Hugo en-GB Mon, 14 Sep 2026 15:00:00 +0100 https://blogs.damiendye.uk/en/networking/a-vpn-out-of-parts-and-what-egress-really-is/ Mon, 14 Sep 2026 15:00:00 +0100 https://blogs.damiendye.uk/en/networking/a-vpn-out-of-parts-and-what-egress-really-is/ A VPN is a virtual link plus a carrier, and Linux ships a program for each: pppd or a tap device, and netcat. Building it both ways — over TCP, UDP, TLS and DTLS, with zstd compression — shows what a VPN is made of, and what egress really is: once an attacker has root and outbound is open, the tunnel is already installed. https://blogs.damiendye.uk/en/networking/how-far-away-is-the-firewall/ Fri, 28 Aug 2026 09:00:00 +0100 https://blogs.damiendye.uk/en/networking/how-far-away-is-the-firewall/ A connection that times out tells you nothing about where it died. TTL does. Here is how to count the hops to whatever is eating your port, on Linux, macOS, the BSDs, Solaris and Redox, with a script that needs no root on Linux.