CIRCLE WITH A DOT

🫀 SO_KEEPALIVE — How your server detects dead connections before the client knowsA client connects to your server. Then their laptop lid closes. WiFi drops. Router reboots.The TCP connection is dead — but your server has no idea. It just sits there. Holding a socket. Waiting forever. This is called a half-open connection — one of TCP’s most silent failure modes. The fix — one line: setsockopt(fd, SOL_SOCKET, SO_KEEPALIVE, &flag, sizeof(flag));The kernel now sends small probe packets on idle connections. No response after a few tries? Connection gets cleaned up automatically.️ Three knobs you control:→ tcp_keepalive_time — idle time before first probe (default: 2h )→ tcp_keepalive_intvl — time between probes (default: 75s)→ tcp_keepalive_probes — failures before giving up (default: 9)The defaults are hilariously conservative. For a real server you want minutes, not hours. Without it you risk:→ File descriptor leaks→ Thread pool exhaustion→ Memory piling up for connections that died hours ago Who needs it most:→ WebSockets & long-lived connections→ Servers behind NAT — routers silently drop idle mappings→ Any server where clients disappear without sending FIN Your server shouldn’t mourn connections that are already gone.#Linux #Networking #SystemsProgramming #ServerDevelopment

🪧 HTTP/2 From Scratch: Part 4: More HPACK and using http.Request and http.Responsehttps://kmcd.dev/posts/http2-from-scratch-part-4/#Go #Http2 #Protocols #Networking

#NetMCR (https://www.netmcr.uk/) is on again this Thursday (12th) in #Manchester.The talk will be by Mark Tearle, titled:‘It is a disaster! Reacting to the Unexpected’*Mark has flown across the world, avoiding flight disruptions, to present an interactive talk about disasters that befall networks, data centres and telecommunications infrastructure across the globe. A curated set of incidents will be discussed and the question posed - how would you or your organisation respond?Go and chat with some nice people, have some weird , and if you're hungry, and !#Networking #MeetUp

@stepech @tux I don't use SLAAC. It's all statically assigned adresses. (Multiple /80s)

@ammarfaizi2@gnuweeb.org @Suiseiseki@freesoftwareextremist.com @marcelschmall@infosec.exchange the retval from poll can help optimize the traversal as it indicates the number of ready file descriptors. I know it is still not as efficient as epoll, but if you find all ready fds earlier, you can break the iteration earlier too: ready_fds = poll(fds, 10000, -1); if (ready_fds < 0) { handle_error(ready_fds); return; } for (i = 0; i < 10000; i++) { if (ready_fds == 0) { // All ready fds have been handled. // Break out of the loop early to // avoid unnecessary iterations. break; } if (fds[i].revents & (POLLIN|POLLOUT)) { handle_events(i, fds[i]); ready_fds--; } } If you are lucky: that one client is not in the last index, you can break earlier.

RE: https://mastodon.social/@pitrh/116182418029757504Again for the Monday morning (CET) crowd - There's a new book out for your #networking, #openbsd, #freebsd cravings:

@Larvitz OT: Patches accepted for IPv6 "longer loopback": https://datatracker.ietf.org/doc/draft-kumari-ipv6-loopback/

I know that #network equipment makers has a tendency of shipping buggy software to routers, but I don't know whether this is a significant risk for Rj45 - USB adapters.#fedihelp #networking #router

@Aaron Although its unfortunately centralisation of the internet, Cloudflare has done wonders for ipv6 in the last few years as more and systems and sites have thrown themselves behind the cloudflare tunnel and proxy network.A small win, even if it comes with a loss

The Prefork server model gets dismissed as “old school”. I think that’s wrong – especially on Linux.With SO_REUSEPORT, the kernel distributes incoming connections across multiple pre-forked worker processes natively. No thread contention. No shared memory complexity. Each worker is an isolated process – a crash stays contained.What you get:– True process isolation per connection– Kernel-level load balancing, no userspace overhead– Predictable memory footprint– Simpler security boundaries between workersIn a world obsessed with async event loops, we forget that prefork scales surprisingly well for workloads with high per-connection compute and where isolation actually matters – think security-sensitive services.SO_REUSEPORT didn’t just fix the thundering herd problem. It quietly gave prefork a second life.More on this soon.#linux #infosec #networking #serversecurity #prefork

The Book of PF, 4th Edition Spotted in the Wild https://undeadly.org/cgi?action=article;sid=20260306131150 #openbsd #freebsd #pf #packetfilter #networking #security #networktrickery #freesoftware #libresoftware

@subnetspider Yep, classic jails. I mentioned them briefly and in the comparisson table of the article

New Blog Post!https://blog.transitory.social/posts/2026-02-05-protonvpn-exit-via-egress-gateway-policy(No AIs were inconvenienced in the writing of this post. @homelab@fedigroups.social #Homelab #SelfHosted #Kubernetes #Networking

@drixter Good hint Thank you. I'll definitely do that.

#Wireshark 4.6.4 Is Out to Update Protocol and Capture File Support, Fix More Bugs https://9to5linux.com/wireshark-4-6-4-updates-protocol-and-capture-file-support-fixes-more-bugs#OpenSource #Linux #networking

@goetz Ach, du bist auch ein Mainzer?

@madamada Two address spaces on the same protocol always gets finicky. But on FreeBSD with two sperate fib's (basically routing tables) and reply-to in the PF rules, it's possible to do.