From cbd7aef7637a4ca647380118a2d3e9146121d5d2 Mon Sep 17 00:00:00 2001 From: =?utf8?q?=C5=81ukasz=20Stelmach?= Date: Thu, 21 Aug 2025 12:38:40 +0200 Subject: [PATCH] doc: Add a note about route_localnet sysctl MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit See ip_route_input_slow() in net/ipv4/route.c in the Linux kernel sources. Signed-off-by: Łukasz Stelmach Signed-off-by: Florian Westphal --- doc/statements.txt | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/doc/statements.txt b/doc/statements.txt index 4aeb0a73..6226713b 100644 --- a/doc/statements.txt +++ b/doc/statements.txt @@ -459,6 +459,11 @@ netfilter and therefore no reverse translation will take place. The optional *prefix* keyword allows to map *n* source addresses to *n* destination addresses. See 'Advanced NAT examples' below. +If the 'address' for *dnat* is an IPv4 loopback address +(i.e. 127.0.0.0/8) the "net.ipv4.conf.*.route_localnet" sysctl for the +input interface needs to be set to 1. Otherwise packets will be +dropped by the routing code as "martians". + .NAT statement values [options="header"] |================== -- 2.47.2