From 4b633b4e90d3b84abdd9f4bcd133d7948042b24a Mon Sep 17 00:00:00 2001
From: David Karlsson <35727626+dvdksn@users.noreply.github.com>
Date: Fri, 3 Nov 2023 14:20:54 +0100
Subject: [PATCH] docs: add default-network-opt daemon option

Signed-off-by: David Karlsson <35727626+dvdksn@users.noreply.github.com>
---
 docs/reference/commandline/dockerd.md | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/docs/reference/commandline/dockerd.md b/docs/reference/commandline/dockerd.md
index 2549d5d95dc6..f1a248c466a7 100644
--- a/docs/reference/commandline/dockerd.md
+++ b/docs/reference/commandline/dockerd.md
@@ -46,6 +46,7 @@ Options:
       --default-gateway ip                    Container default gateway IPv4 address
       --default-gateway-v6 ip                 Container default gateway IPv6 address
       --default-ipc-mode string               Default mode for containers ipc ("shareable" | "private") (default "private")
+      --default-network-opt mapmap            Default network options (default map[])
       --default-runtime string                Default OCI runtime for containers (default "runc")
       --default-shm-size bytes                Default shm size for containers (default 64MiB)
       --default-ulimit ulimit                 Default ulimits for containers (default [])
@@ -1017,6 +1018,7 @@ This is a full example of the allowed configuration options on Linux:
   "default-cgroupns-mode": "private",
   "default-gateway": "",
   "default-gateway-v6": "",
+  "default-network-opts": "",
   "default-runtime": "runc",
   "default-shm-size": "64M",
   "default-ulimits": {
@@ -1134,6 +1136,7 @@ This is a full example of the allowed configuration options on Windows:
   "containerd-plugin-namespace": "docker-plugins",
   "data-root": "",
   "debug": true,
+  "default-network-opts": "",
   "default-runtime": "",
   "default-ulimits": {},
   "dns": [],
@@ -1279,3 +1282,25 @@ $ sudo dockerd \
         --data-root=/var/lib/docker-bootstrap \
         --exec-root=/var/run/docker-bootstrap
 ```
+
+### Default network options
+
+The `--default-network-opt` flag, and the equivalent `default-network-opts` key
+in the configuratio file, lets you specify custom default options for custom
+networks.
+
+This option accepts a value with the format `driver=opt=value`, for example:
+
+```console
+$ sudo dockerd \
+  --default-network-opt bridge=com.docker.network.bridge.host_binding_ipv4=127.0.0.1 \
+  --default-network-opt bridge=com.docker.network.bridge.mtu=1234
+```
+
+New networks that you create inherit the specified options by default.
+
+```console
+$ docker network create mynet
+$ docker network inspect mynet --format "{{json .Options}}"
+{"com.docker.network.bridge.host_binding_ipv4":"127.0.0.1","com.docker.network.bridge.mtu":"1234"}
+```