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nixos/modules/tailscale/ts-dns-forwarder.nix
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beatzaplentyandClaude Sonnet 4.6 3123565011 fix(tailscale-router): scope ts.net forwarder to tailnet subdomain
IPA refuses to create a forward zone for ts.net because it's a real
public TLD with DNSimple nameservers. The forward zone must use the
tailnet-specific subdomain (vars.tailnetDomain, e.g. tail13f623.ts.net)
instead. Update dnsmasq server selector and comments to match.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ULXzafSDwGhmFGnn3LtDSQ
2026-07-27 19:23:46 +10:00

53 lines
2.3 KiB
Nix

{ vars, ... }:
{
# Run dnsmasq on the LAN interface as a forwarding-only resolver for
# *.ts.net (Tailscale MagicDNS names). FreeIPA's bind-dyndb-ldap
# cannot reach 100.100.100.100 (Tailscale's internal resolver) directly
# because the DC is not a Tailscale node. This host IS a Tailscale node
# and can reach 100.100.100.100 via its tailscale0 interface, so it
# acts as an intermediary: FreeIPA has a conditional forward zone for
# ts.net pointing here (vars.tailscaleRouterIp), and this dnsmasq
# instance forwards those queries onward to Tailscale's resolver.
#
# Configure FreeIPA once after deploying this host:
# kinit admin
# ipa dnsforwardzone-add ${vars.tailnetDomain} \
# --forwarder=${vars.tailscaleRouterIp} \
# --forward-policy=only
# Note: IPA refuses to shadow ts.net (a real public TLD); use the
# tailnet-specific subdomain (vars.tailnetDomain) instead.
services.dnsmasq = {
enable = true;
settings = {
# Listen only on the LAN interface — not tailscale0 or loopback.
# bind-interfaces prevents dnsmasq from binding to 0.0.0.0 and
# then filtering by interface later; combined with `interface` this
# ensures it genuinely listens only on eth0.
bind-interfaces = true;
interface = [ vars.lxcLanInterface ];
# Forward-only: no local /etc/hosts or /etc/resolv.conf reading,
# no negative caching of NXDOMAIN for names this instance doesn't
# serve. All ts.net queries come from FreeIPA's conditional forwarder
# and must be answered by Tailscale's resolver.
no-hosts = true;
no-resolv = true;
# Tailscale's internal "Quad100" resolver — reachable from any
# Tailscale node via the tailscale0 interface. Scoped to the
# specific tailnet subdomain (vars.tailnetDomain) rather than
# all of ts.net: FreeIPA refuses to shadow ts.net (a real public
# TLD with DNSimple nameservers) so the conditional forward zone
# in FreeIPA must use the tailnet-specific subdomain instead:
# ipa dnsforwardzone-add ${vars.tailnetDomain} \
# --forwarder=${vars.tailscaleRouterIp} \
# --forward-policy=only
server = [ "/${vars.tailnetDomain}/100.100.100.100" ];
};
};
networking.firewall.allowedUDPPorts = [ 53 ];
networking.firewall.allowedTCPPorts = [ 53 ];
}