caaf8469e0
REDIRECT in the OUTPUT chain rewrites the destination to 127.0.0.1, then ip_route_me_harder() reroutes with the socket's bound interface constraint (flowi4_oif). Since 127.0.0.1 is only reachable via lo, the routing lookup fails and the packet is silently dropped. Add a fallback routing table with `local 127.0.0.1` entries for each non-loopback interface. When the local table lookup fails due to OIF mismatch, the fallback table provides a matching RTN_LOCAL route. The kernel then overrides dev_out to loopback (route.c:2857), so the packet is delivered locally to the redirect server as intended. This fixes NetworkManager connectivity checks and other tools that use SO_BINDTODEVICE (e.g. curl --interface).
sing-tun
Simple transparent proxy library.
For Linux, Windows, macOS and iOS.
License
Copyright (C) 2022 by nekohasekai <contact-sagernet@sekai.icu>
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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(at your option) any later version.
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