Split advertised address from listen address

There are currently problems with "swarm init" and "swarm join" when an
explicit --listen-addr flag is not provided. swarmkit defaults to
finding the IP address associated with the default route, and in cloud
setups this is often the wrong choice.

Introduce a notion of "advertised address", with the client flag
--advertise-addr, and the daemon flag --swarm-default-advertise-addr to
provide a default. The default listening address is now 0.0.0.0, but a
valid advertised address must be detected or specified.

If no explicit advertised address is specified, error out if there is
more than one usable candidate IP address on the system. This requires a
user to explicitly choose instead of letting swarmkit make the wrong
choice. For the purposes of this autodetection, we ignore certain
interfaces that are unlikely to be relevant (currently docker*).

The user is also required to choose a listen address on swarm init if
they specify an explicit advertise address that is a hostname or an IP
address that's not local to the system. This is a requirement for
overlay networking.

Also support specifying interface names to --listen-addr,
--advertise-addr, and the daemon flag --swarm-default-advertise-addr.
This will fail if the interface has multiple IP addresses (unless it has
a single IPv4 address and a single IPv6 address - then we resolve the
tie in favor of IPv4).

This change also exposes the node's externally-reachable address in
docker info, as requested by #24017.

Make corresponding API and CLI docs changes.

Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>

contrib/completion/bash/docker

@@ -1839,11 +1839,17 @@ _docker_swarm_init() {
 			fi
 			return
 			;;
+		--advertise-addr)
+			if [[ $cur == *: ]] ; then
+				COMPREPLY=( $( compgen -W "2377" -- "${cur##*:}" ) )
+			fi
+			return
+			;;
 	esac
 
 	case "$cur" in
 		-*)
-			COMPREPLY=( $( compgen -W "--force-new-cluster --help --listen-addr" -- "$cur" ) )
+			COMPREPLY=( $( compgen -W "--advertise-addr --force-new-cluster --help --listen-addr" -- "$cur" ) )
 			;;
 	esac
 }
@@ -1873,11 +1879,17 @@ _docker_swarm_join() {
 			fi
 			return
 			;;
+		--advertise-addr)
+			if [[ $cur == *: ]] ; then
+				COMPREPLY=( $( compgen -W "2377" -- "${cur##*:}" ) )
+			fi
+			return
+			;;
 	esac
 
 	case "$cur" in
 		-*)
-			COMPREPLY=( $( compgen -W "--help --listen-addr --token" -- "$cur" ) )
+			COMPREPLY=( $( compgen -W "--adveritse-addr --help --listen-addr --token" -- "$cur" ) )
 			;;
 		*:)
 			COMPREPLY=( $( compgen -W "2377" -- "${cur##*:}" ) )

contrib/completion/zsh/_docker

@@ -1203,6 +1203,7 @@ __docker_swarm_subcommand() {
         (init)
             _arguments $(__docker_arguments) \
                 $opts_help \
+                "($help)--advertise-addr[Advertised address]:ip\:port: " \
                 "($help)*--external-ca=[Specifications of one or more certificate signing endpoints]:endpoint: " \
                 "($help)--force-new-cluster[Force create a new cluster from current state]" \
                 "($help)--listen-addr=[Listen address]:ip\:port: " && ret=0
@@ -1215,6 +1216,7 @@ __docker_swarm_subcommand() {
         (join)
             _arguments $(__docker_arguments) \
                 $opts_help \
+                "($help)--advertise-addr[Advertised address]:ip\:port: " \
                 "($help)--listen-addr=[Listen address]:ip\:port: " \
                 "($help)--token=[Token for entry into the swarm]:secret: " \
                 "($help -):host\:port: " && ret=0

docs/reference/commandline/dockerd.md

@@ -69,6 +69,7 @@ Options:
       -s, --storage-driver                   Storage driver to use
       --selinux-enabled                      Enable selinux support
       --storage-opt=[]                       Storage driver options
+      --swarm-default-advertise-addr         Set default address or interface for swarm advertised address
       --tls                                  Use TLS; implied by --tlsverify
       --tlscacert=~/.docker/ca.pem           Trust certs signed only by this CA
       --tlscert=~/.docker/cert.pem           Path to TLS certificate file
@@ -1042,6 +1043,7 @@ This is a full example of the allowed configuration options on Linux:
 	"tlscacert": "",
 	"tlscert": "",
 	"tlskey": "",
+	"swarm-default-advertise-addr": "",
 	"api-cors-header": "",
 	"selinux-enabled": false,
 	"userns-remap": "",
@@ -1112,6 +1114,7 @@ This is a full example of the allowed configuration options on Windows:
     "tlscacert": "",
     "tlscert": "",
     "tlskey": "",
+    "swarm-default-advertise-addr": "",
     "group": "",
     "default-ulimits": {},
     "bridge": "",

docs/reference/commandline/swarm_init.md

@@ -17,12 +17,13 @@ Usage:  docker swarm init [OPTIONS]
 Initialize a swarm
 
 Options:
+      --advertise-addr value            Advertised address (format: <ip|hostname|interface>[:port])
       --cert-expiry duration            Validity period for node certificates (default 2160h0m0s)
       --dispatcher-heartbeat duration   Dispatcher heartbeat period (default 5s)
       --external-ca value               Specifications of one or more certificate signing endpoints
       --force-new-cluster               Force create a new cluster from current state.
       --help                            Print usage
-      --listen-addr value               Listen address (default 0.0.0.0:2377)
+      --listen-addr value               Listen address (format: <ip|hostname|interface>[:port])
       --task-history-limit int          Task history retention limit (default 5)
 ```
 
@@ -31,7 +32,7 @@ in the newly created one node swarm cluster.
 
 
 ```bash
-$ docker swarm init --listen-addr 192.168.99.121:2377
+$ docker swarm init --advertise-addr 192.168.99.121
 Swarm initialized: current node (bvz81updecsj6wjz393c09vti) is now a manager.
 
 To add a worker to this swarm, run the following command:
@@ -70,11 +71,31 @@ The URL specifies the endpoint where signing requests should be submitted.
 
 ### `--force-new-cluster`
 
-This flag forces an existing node that was part of a quorum that was lost to restart as a single node Manager without losing its data
+This flag forces an existing node that was part of a quorum that was lost to restart as a single node Manager without losing its data.
 
 ### `--listen-addr value`
 
-The node listens for inbound swarm manager traffic on this IP:PORT
+The node listens for inbound Swarm manager traffic on this address. The default is to listen on
+0.0.0.0:2377. It is also possible to specify a network interface to listen on that interface's
+address; for example `--listen-addr eth0:2377`.
+
+Specifying a port is optional. If the value is a bare IP address, hostname, or interface
+name, the default port 2377 will be used.
+
+### `--advertise-addr value`
+
+This flag specifies the address that will be advertised to other members of the
+swarm for API access and overlay networking. If unspecified, Docker will check
+if the system has a single IP address, and use that IP address with with the
+listening port (see `--listen-addr`). If the system has multiple IP addresses,
+`--advertise-addr` must be specified so that the correct address is chosen for
+inter-manager communication and overlay networking.
+
+It is also possible to specify a network interface to advertise that interface's address;
+for example `--advertise-addr eth0:2377`.
+
+Specifying a port is optional. If the value is a bare IP address, hostname, or interface
+name, the default port 2377 will be used.
 
 ### `--task-history-limit`
 

docs/reference/commandline/swarm_join.md

@@ -17,9 +17,10 @@ Usage:  docker swarm join [OPTIONS] HOST:PORT
 Join a swarm as a node and/or manager
 
 Options:
-      --help                Print usage
-      --listen-addr value   Listen address (default 0.0.0.0:2377)
-      --token string        Token for entry into the swarm
+      --advertise-addr value   Advertised address (format: <ip|hostname|interface>[:port])
+      --help                   Print usage
+      --listen-addr value      Listen address
+      --token string           Token for entry into the swarm
 ```
 
 Join a node to a swarm. The node joins as a manager node or worker node based upon the token you
@@ -31,7 +32,7 @@ pass a worker token, the node joins as a worker.
 The example below demonstrates joining a manager node using a manager token.
 
 ```bash
-$ docker swarm join --token SWMTKN-1-3pu6hszjas19xyp7ghgosyx9k8atbfcr8p2is99znpy26u2lkl-7p73s1dx5in4tatdymyhg9hu2 --listen-addr 192.168.99.122:2377 192.168.99.121:2377
+$ docker swarm join --token SWMTKN-1-3pu6hszjas19xyp7ghgosyx9k8atbfcr8p2is99znpy26u2lkl-7p73s1dx5in4tatdymyhg9hu2 192.168.99.121:2377
 This node joined a swarm as a manager.
 $ docker node ls
 ID                           HOSTNAME  STATUS  AVAILABILITY  MANAGER STATUS
@@ -48,7 +49,7 @@ should join as workers instead. Managers should be stable hosts that have static
 The example below demonstrates joining a worker node using a worker token.
 
 ```bash
-$ docker swarm join --token SWMTKN-1-3pu6hszjas19xyp7ghgosyx9k8atbfcr8p2is99znpy26u2lkl-1awxwuwd3z9j1z3puu7rcgdbx --listen-addr 192.168.99.123:2377 192.168.99.121:2377
+$ docker swarm join --token SWMTKN-1-3pu6hszjas19xyp7ghgosyx9k8atbfcr8p2is99znpy26u2lkl-1awxwuwd3z9j1z3puu7rcgdbx 192.168.99.121:2377
 This node joined a swarm as a worker.
 $ docker node ls
 ID                           HOSTNAME  STATUS  AVAILABILITY  MANAGER STATUS
@@ -59,7 +60,36 @@ dvfxp4zseq4s0rih1selh0d20 *  manager1  Ready   Active        Leader
 
 ### `--listen-addr value`
 
-The node listens for inbound swarm manager traffic on this IP:PORT
+If the node is a manager, it will listen for inbound Swarm manager traffic on this
+address. The default is to listen on 0.0.0.0:2377. It is also possible to specify a
+network interface to listen on that interface's address; for example `--listen-addr eth0:2377`.
+
+Specifying a port is optional. If the value is a bare IP address, hostname, or interface
+name, the default port 2377 will be used.
+
+This flag is generally not necessary when joining an existing swarm.
+
+### `--advertise-addr value`
+
+This flag specifies the address that will be advertised to other members of the
+swarm for API access. If unspecified, Docker will check if the system has a
+single IP address, and use that IP address with with the listening port (see
+`--listen-addr`). If the system has multiple IP addresses, `--advertise-addr`
+must be specified so that the correct address is chosen for inter-manager
+communication and overlay networking.
+
+It is also possible to specify a network interface to advertise that interface's address;
+for example `--advertise-addr eth0:2377`.
+
+Specifying a port is optional. If the value is a bare IP address, hostname, or interface
+name, the default port 2377 will be used.
+
+This flag is generally not necessary when joining an existing swarm.
+
+### `--manager`
+
+Joins the node as a manager
+>>>>>>> 22565e1... Split advertised address from listen address
 
 ### `--token string`
 

man/dockerd.8.md

@@ -55,6 +55,7 @@ dockerd - Enable daemon mode
 [**-s**|**--storage-driver**[=*STORAGE-DRIVER*]]
 [**--selinux-enabled**]
 [**--storage-opt**[=*[]*]]
+[**--swarm-default-advertise-addr**[=*IP|HOSTNAME|INTERFACE*]]
 [**--tls**]
 [**--tlscacert**[=*~/.docker/ca.pem*]]
 [**--tlscert**[=*~/.docker/cert.pem*]]
@@ -239,6 +240,11 @@ output otherwise.
 **--storage-opt**=[]
   Set storage driver options. See STORAGE DRIVER OPTIONS.
 
+**--swarm-default-advertise-addr**=*IP|HOSTNAME|INTERFACE*
+  Set default address or interface for swarm to advertise as its externally-reachable address to other cluster
+  members. This can be a hostname, an IP address, or an interface such as `eth0`. A port cannot be specified with
+  this option.
+
 **--tls**=*true*|*false*
   Use TLS; implied by --tlsverify. Default is false.