From 854c1b52238af9922f73f8decfededc81efba8de Mon Sep 17 00:00:00 2001
From: Luke Cyca <me@lukecyca.com>
Date: Thu, 8 Oct 2020 15:45:58 -0700
Subject: [PATCH] Created IPv6 (markdown)

---
 docs/content/advanced/ipv6.md | 42 +++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)
 create mode 100644 docs/content/advanced/ipv6.md

diff --git a/docs/content/advanced/ipv6.md b/docs/content/advanced/ipv6.md
new file mode 100644
index 00000000..4a00485e
--- /dev/null
+++ b/docs/content/advanced/ipv6.md
@@ -0,0 +1,42 @@
+## Background
+
+If your container host supports IPv6, then `docker-mailserver` will automatically accept IPv6 connections by way of the docker host's IPv6. However, incoming mail will fail SPF checks because they will appear to come from the IPv4 gateway that docker is using to proxy the IPv6 connection (172.20.0.1 is the gateway).
+
+This can be solved by supporting IPv6 connections all the way to the `docker-mailserver` container.
+
+## Setup steps
+
+```diff
++++ b/serv/docker-compose.yml
+@@ -1,4 +1,4 @@
+-version: '2'
++version: '2.1'
+ 
+@@ -32,6 +32,16 @@ services:
+ 
++  ipv6nat:
++    image: robbertkl/ipv6nat
++    restart: always
++    network_mode: "host"
++    cap_add:
++      - NET_ADMIN
++      - SYS_MODULE
++    volumes:
++      - /var/run/docker.sock:/var/run/docker.sock:ro
++      - /lib/modules:/lib/modules:ro
+
+@@ -306,4 +316,13 @@ networks:
+
++  default:
++    driver: bridge
++    enable_ipv6: true
++    ipam:
++      driver: default
++      config:
++        - subnet: fd00:0123:4567::/48
++          gateway: fd00:0123:4567::1
+```
+
+## Further discussion
+
+See [issue #1438](https://github.com/tomav/docker-mailserver/issues/1438)
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