Uses both binded HostIP and HostPort when useBindPortIP=true

[geraldcroes]

What does this PR do?

Context: docker provider with usebindportip

Currently:

• Traefik doesn't find the port bindings when the API responds in lowercase.
• When the API responds in uppercase, Traefik uses the external IP only, and not the port
• When no IP is specified, Traefik creates a route using the IP 0.0.0.0
• When the label traefik.portis specified, it is used both for selecting the binding and in the route

This PR:

• ignores the case when looking for port bindings
• takes the external IP and port into account to create the routes
• excludes servers with no binding
• excludes servers with no IP specified in the binding (0.0.0.0)
• the label traefik.port is used to select the binding (which enables the use of segments)

To sum it up:

label	Binding	Routes to
traefik.port not set	IP_E1:P_E1:P_I1	IP_E1:P_E1
traefik.port not set	P_E1:P_I1	Warning & Ignored (cannot route to 0.0.0.0)
traefik.port not set	None	Warning & Ignored (Binding is missing)
traefik.port=P_I1	IP_E1:P_E1:P_I1	IP_E1:P_E1
traefik.port=P_I2	IP_E1:P_E1:P_I1	Warning & Ignored (cannot find binding for XX:XX:P_I2)
traefik.port=P_I2	IP_E1:P_E1:P_I1 & IP_E2:P_E2:P_I2	IP_E2:P_E2
traefik.port=P_I1	None	Warning & Ignored (Binding is missing)

Motivation

Fixes #3622

(kudos to @systemmonkey42 for the awesome description in the issue)

More

• Added/updated tests
• Added/updated documentation

Examples

docker-compose.yml

version: '3'

services:
  whoami-1:
    image: emilevauge/whoami
    ports:
      -  xx.xx.xx.xx:8082:80 # Routes to XX.XX.XX.XX:8082
    labels: 
      - traefik.enable=true
      - traefik.backend=whoami
      - "traefik.frontend.rule=PathPrefix:/whoami-1"

  whoami-2:
    image: emilevauge/whoami
    ports:
      -  8083:80 # Warning Cannot determine the IP address (got 0.0.0.0) for the container "/issue_3622_whoami-2_1": ignoring server 
    labels: 
      - traefik.enable=true
      - traefik.backend=whoami-2
      - "traefik.frontend.rule=PathPrefix:/whoami-2"

  whoami-3:
    image: emilevauge/whoami
    # Warning Unable to find a binding for the container "/issue_3622_whoami-3_1": ignoring server
    labels: 
      - traefik.enable=true
      - traefik.backend=whoami-3
      - "traefik.frontend.rule=PathPrefix:/whoami-3"
  
  whoami-4:
    image: emilevauge/whoami
    ports:
      -  xx.xx.xx.xx:8085:80 # routes to XX:XX:XX:XX:8085
    labels:
      - traefik.port=80
      - traefik.enable=true
      - traefik.backend=whoami-4
      - "traefik.frontend.rule=PathPrefix:/whoami-4"

  whoami-5:
    image: emilevauge/whoami
    ports:
      -  xx.xx.xx.xx:8086:80 # Warning Unable to find a binding for the container "/issue_3622_whoami-5_1": ignoring server
    labels:
      - traefik.port=81
      - traefik.enable=true
      - traefik.backend=whoami-5
      - "traefik.frontend.rule=PathPrefix:/whoami-5"

  whoami-6:
    image: emilevauge/whoami
    ports:
      -  xx.xx.xx.xx:8087:80
      -  xx.xx.xx.xx:8088:81 # routes to xx.xx.xx.xx:8088
    labels:
      - traefik.port=81
      - traefik.enable=true
      - traefik.backend=whoami-6
      - "traefik.frontend.rule=PathPrefix:/whoami-6"

  whoami-7:
    image: emilevauge/whoami
    # Warning Unable to find a binding for the container "/issue_3622_whoami-7_1": ignoring server
    labels:
      - traefik.port=81
      - traefik.enable=true
      - traefik.backend=whoami-7
      - "traefik.frontend.rule=PathPrefix:/whoami-7"

traefik/api

{
  "docker": {
    "backends": {
      "backend-whoami": {
        "servers": {
          "server-issue-3622-whoami-1-1-7c60b6958b968de9998659c11d7406a0": {
            "url": "http://xx.xx.xx.xx:8082",
            "weight": 1
          }
        },
      },
      "backend-whoami-4": {
        "servers": {
          "server-issue-3622-whoami-4-1-5dcf432359cd6ad04e1779a85d45314a": {
            "url": "http://xx.xx.xx.xx:8085",
            "weight": 1
          }
        },
      },
      "backend-whoami-6": {
        "servers": {
          "server-issue-3622-whoami-6-1-554f0078ab3c259e14fc03848f9f8ce4": {
            "url": "http://xx.xx.xx.xx:8088",
            "weight": 1
          }
        },
      }
    },
  }
}

[ldez]

could you return a pointer (*nat.PortBinding) instead of a struct?

[ldez]

return nil.

https://github.com/golang/go/wiki/CodeReviewComments#error-strings

fmt.Errorf("unable to find the external IP:Port for the container %q", container.Name)

[ldez]

could you create a function that returns an error to replace the continue

[ldez]

fail fast: could you invert the condition:

if portBinding.HostIP == "0.0.0.0" {
// ...
}
// ...

The else is not needed.

[ldez]

the map initialization must be done before.

[mmatur]

Should be "getIPAddress" instead of "getDeprecatedIPAddress"

[mmatur]

Should be "getIPAddress" instead of "getDeprecatedIPAddress"

[ldez]

LGTM

[mmatur]

LGTM

[nmengin]

LGTM 🐳 👏