docs: warn about firehol_level1 RFC1918 gotcha in default blocklist#467
Merged
9seconds merged 2 commits into9seconds:masterfrom Apr 14, 2026
Merged
docs: warn about firehol_level1 RFC1918 gotcha in default blocklist#4679seconds merged 2 commits into9seconds:masterfrom
9seconds merged 2 commits into9seconds:masterfrom
Conversation
The default [defense.blocklist] uses firehol_level1.netset, which includes bogon networks and therefore all RFC1918 ranges. Clients connecting from a LAN address (e.g. a phone on the home Wi-Fi when mtg runs at home) are silently rejected with "ip was blacklisted" and routed to the fronting domain. This is a recurring source of confusion (see issue 9seconds#466 for the latest example). Add a warning next to the urls list in example.config.toml and a Troubleshooting section in README.md covering the symptom, the cause, and three resolution paths (disable blocklist, swap for a narrower list, or use hairpin NAT). Docs only, no code changes.
The previous wording ("silently routed to the fronting domain")
is inaccurate. In mtglib/proxy.go the blocklist path calls
conn.Close() immediately with no further handshake or fronting;
domain fronting only happens on FakeTLS failures for non-blocked
IPs. Reword to "TCP connection is closed with no response" so
users searching the docs get the same symptom they actually see.
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Summary
Follow-up to #466. The default
[defense.blocklist]usesfirehol_level1.netset, which includes bogon networks and therefore all RFC1918 ranges. Clients connecting from the same LAN as mtg (typical home setup: phone on Wi-Fi, mtg on a home server) are silently rejected withip was blacklistedand routed to the fronting domain. This keeps tripping people up.This PR is docs-only and does not change the default behavior:
example.config.toml: a shortNOTEblock next to[defense.blocklist].urlsdescribing the gotcha and pointing to the README.README.md: a new## Troubleshootingsection before## Metricswith the symptom (including the exact log line), the cause, and three resolution paths (disable the blocklist, swap for a narrower list likefirehol_abusers_1d, or use hairpin NAT).No defaults are changed — that is a separate discussion and I didn't want to couple it with a doc fix. Happy to open a follow-up issue/PR if you'd like to revisit the default list choice.
Refs #466.
Test plan
example.config.tomlstill parses as TOML (only comment lines added).