feat: server-side loopback overrides and Hub diagnostic fixes

- Add modules/core/local-domain-loopback.nix: systemd service and
  activation script that write configured service domains to a
  Sovran-managed block in /etc/hosts (127.0.0.1 / ::1) so requests
  originating on this computer reach Caddy without NAT loopback.

- Import local-domain-loopback.nix in modules/modules.nix.

- server.py: add _validate_domain_value, _is_loopback_address,
  _resolve_all_addresses, _trigger_hosts_update helpers.

- server.py: update _check_domain_reachable to use --resolve so
  reachability is checked locally via Caddy, not via NAT loopback.

- server.py: update _evaluate_domain_checklist, api_services inline DNS
  check, and api_domains_check to recognise loopback resolution as an
  intentional local override rather than a DNS mismatch.

- server.py: call _trigger_hosts_update from api_domains_set after
  saving a service domain so the /etc/hosts entry is applied immediately.

- Add app/tests/test_loopback_diagnostics.py with 47 tests covering
  domain validation, loopback detection, diagnostic checklist logic,
  composite health, and api_domains_check."
This commit is contained in:
copilot-swe-agent[bot]
2026-07-15 15:24:16 +00:00
committed by GitHub
parent 6f908513e3
commit 2cb0c734d8
4 changed files with 705 additions and 64 deletions
+143
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@@ -0,0 +1,143 @@
{ config, pkgs, lib, ... }:
# ── Server-local domain loopback overrides ────────────────────────────────────
#
# Some routers (especially newer ISP-provided devices) do not support NAT
# loopback (hairpin NAT). When a request originates on this computer and
# targets a public domain name that resolves to the router's WAN address, the
# router may refuse to loop the connection back in — causing Nextcloud, WordPress
# background jobs, and other server-side callbacks to fail even when the service
# is fully operational from the internet.
#
# This module installs a one-shot systemd service,
# ``sovran-hosts-update.service``, that reads the configured service domains
# from ``/var/lib/domains/`` at boot (and whenever triggered by the Hub after a
# domain is saved) and writes ``127.0.0.1`` entries for them into a dedicated
# Sovran-managed block in ``/etc/hosts``.
#
# With those entries in place:
# • Requests originating on this computer resolve the public domain name to
# 127.0.0.1, reach Caddy directly, and never touch the router.
# • Caddy still receives the correct public hostname via TLS SNI so virtual-
# host routing and certificate validation continue to work.
# • The Sovran Hub can verify Caddy reachability locally without needing NAT
# loopback.
#
# Limitation: this does not help other devices on your home network (phones,
# laptops). Those devices resolve domains via the router's DNS and still depend
# on NAT loopback (or require manual router DNS overrides). For now, only
# server-originated requests benefit from this override.
#
# On NixOS, /etc/hosts is normally a symlink into the Nix store and is
# regenerated by the system activation script. The ``system.activationScripts``
# hook below converts it to a writable file each time the system is activated
# (i.e. after every ``nixos-rebuild switch``) and then injects the Sovran block.
# The same script is also run by the ``sovran-hosts-update.service`` unit so
# that the Hub can trigger it immediately after saving a domain without
# requiring a full rebuild.
{
# ── Helper script (stored in the Nix store, never reads /var/lib at eval) ──
environment.systemPackages = [ pkgs.coreutils ];
environment.etc."sovran-hosts-update.sh" = {
mode = "0755";
text = ''
#!/bin/sh
# Regenerate the Sovran-managed loopback block in /etc/hosts.
# Safe to run multiple times idempotent.
set -euf
DOMAINS_DIR="/var/lib/domains"
HOSTS_FILE="/etc/hosts"
BEGIN_MARKER="# Sovran managed begin server-local loopback overrides"
END_MARKER="# Sovran managed end"
# Step 1: ensure /etc/hosts is a regular writable file
# On NixOS /etc/hosts starts as a symlink to the Nix store. We replace
# it with a copy so we can append our block without touching the store.
if [ -L "$HOSTS_FILE" ]; then
TARGET=$(readlink -f "$HOSTS_FILE")
cp --no-preserve=all "$TARGET" "$HOSTS_FILE.sovran-tmp"
mv "$HOSTS_FILE.sovran-tmp" "$HOSTS_FILE"
chmod 644 "$HOSTS_FILE"
fi
# Step 2: remove any existing Sovran block
# Use a temp file so the operation is atomic.
TMP=$(mktemp "$HOSTS_FILE.XXXXXX")
trap 'rm -f "$TMP"' EXIT
awk "
/^$BEGIN_MARKER\$/ { skip=1; next }
/^$END_MARKER\$/ { skip=0; next }
!skip
" "$HOSTS_FILE" > "$TMP"
# Step 3: collect valid configured service domains
ENTRIES=""
for KEY in matrix wordpress nextcloud btcpayserver vaultwarden haven element-calling; do
FILE="$DOMAINS_DIR/$KEY"
[ -f "$FILE" ] || continue
# Read the domain value (strip all whitespace, limit to 253 chars)
DOMAIN=$(tr -d '[:space:]' < "$FILE" | head -c 253)
[ -z "$DOMAIN" ] && continue
# Validate: must match a reasonable hostname pattern
if ! printf '%s' "$DOMAIN" | grep -qE \
'^[a-zA-Z0-9]([a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(\.[a-zA-Z0-9]([a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)+$'; then
echo "sovran-hosts-update: skipping invalid domain value for $KEY: $DOMAIN" >&2
continue
fi
ENTRIES="$ENTRIES
127.0.0.1 $DOMAIN
::1 $DOMAIN"
done
# Step 4: append the Sovran block if there are any entries
if [ -n "$ENTRIES" ]; then
printf '\n%s\n' "$BEGIN_MARKER" >> "$TMP"
printf '%s\n' "# These entries route configured service domains to local Caddy." >> "$TMP"
printf '%s\n' "# They are managed automatically do not edit this block." >> "$TMP"
printf '%s\n' "$ENTRIES" >> "$TMP"
printf '%s\n' "$END_MARKER" >> "$TMP"
fi
# Step 5: atomically replace /etc/hosts
mv "$TMP" "$HOSTS_FILE"
chmod 644 "$HOSTS_FILE"
'';
};
# ── Systemd service ────────────────────────────────────────────────────────
systemd.services.sovran-hosts-update = {
description = "Update /etc/hosts with Sovran server-local loopback overrides";
documentation = [ "https://github.com/naturallaw777/sovran-systems" ];
# Run before Caddy so loopback entries are ready when it starts.
before = [
"caddy.service"
"network-online.target"
];
wantedBy = [ "multi-user.target" ];
serviceConfig = {
Type = "oneshot";
RemainAfterExit = true;
ExecStart = "/etc/sovran-hosts-update.sh";
};
};
# ── Activation script (runs after every nixos-rebuild switch) ─────────────
# This ensures the loopback block survives rebuilds that restore the /etc/hosts
# symlink. The "users" and "etc" scripts must complete first.
system.activationScripts.sovranDomainLoopback = {
text = ''
if [ -x /etc/sovran-hosts-update.sh ] && [ -d /var/lib/domains ]; then
/etc/sovran-hosts-update.sh || true
fi
'';
deps = [ "etc" "users" ];
};
}
+1
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@@ -16,6 +16,7 @@
./core/remote-deploy.nix
./core/no-sleep.nix
./core/cpu-performance.nix
./core/local-domain-loopback.nix
# ── Always on (no flag) ───────────────────────────────────
./php.nix