26ef46bf81
When a Linux system acts as an exit node or subnet router with strict reverse path filtering (rp_filter=1), reply packets may be dropped because they fail the RPF check. Reply packets arrive on the WAN interface but the routing table indicates they should have arrived on the Tailscale interface, causing the kernel to drop them. This adds firewall rules in the mangle table to save outbound packet marks to conntrack and restore them on reply packets before the routing decision. When reply packets have their marks restored, the kernel uses the correct routing table (based on the mark) and the packets pass the rp_filter check. Implementation adds two rules per address family (IPv4/IPv6): - mangle/OUTPUT: Save packet marks to conntrack for NEW connections with non-zero marks in the Tailscale fwmark range (0xff0000) - mangle/PREROUTING: Restore marks from conntrack to packets for ESTABLISHED,RELATED connections before routing decision and rp_filter check The workaround is automatically enabled when UseConnmarkForRPFilter is set in the router configuration, which happens when subnet routes are advertised on Linux systems. Both iptables and nftables implementations are provided, with automatic backend detection. Fixes #3310 Fixes #14409 Fixes #12022 Fixes #15815 Fixes #9612 Signed-off-by: Mike O'Driscoll <mikeo@tailscale.com>
Tailscale
Private WireGuard® networks made easy
Overview
This repository contains the majority of Tailscale's open source code.
Notably, it includes the tailscaled daemon and
the tailscale CLI tool. The tailscaled daemon runs on Linux, Windows,
macOS, and to varying degrees
on FreeBSD and OpenBSD. The Tailscale iOS and Android apps use this repo's
code, but this repo doesn't contain the mobile GUI code.
Other Tailscale repos of note:
- the Android app is at https://github.com/tailscale/tailscale-android
- the Synology package is at https://github.com/tailscale/tailscale-synology
- the QNAP package is at https://github.com/tailscale/tailscale-qpkg
- the Chocolatey packaging is at https://github.com/tailscale/tailscale-chocolatey
For background on which parts of Tailscale are open source and why, see https://tailscale.com/opensource/.
Using
We serve packages for a variety of distros and platforms at https://pkgs.tailscale.com.
Other clients
The macOS, iOS, and Windows clients use the code in this repository but additionally include small GUI wrappers. The GUI wrappers on non-open source platforms are themselves not open source.
Building
We always require the latest Go release, currently Go 1.25. (While we build releases with our Go fork, its use is not required.)
go install tailscale.com/cmd/tailscale{,d}
If you're packaging Tailscale for distribution, use build_dist.sh
instead, to burn commit IDs and version info into the binaries:
./build_dist.sh tailscale.com/cmd/tailscale
./build_dist.sh tailscale.com/cmd/tailscaled
If your distro has conventions that preclude the use of
build_dist.sh, please do the equivalent of what it does in your
distro's way, so that bug reports contain useful version information.
Bugs
Please file any issues about this code or the hosted service on the issue tracker.
Contributing
PRs welcome! But please file bugs. Commit messages should reference bugs.
We require Developer Certificate of
Origin
Signed-off-by lines in commits.
See commit-messages.md (or skim git log) for our commit message style.
About Us
Tailscale is primarily developed by the people at https://github.com/orgs/tailscale/people. For other contributors, see:
- https://github.com/tailscale/tailscale/graphs/contributors
- https://github.com/tailscale/tailscale-android/graphs/contributors
Legal
WireGuard is a registered trademark of Jason A. Donenfeld.