From 3ca1aa9cb1ce4b02738028712a7dcf7d2129c7bc Mon Sep 17 00:00:00 2001
From: James Shubin <james@shubin.ca>
Date: Wed, 12 Mar 2025 03:16:08 -0400
Subject: [PATCH] engine: resources: Fix backwards docker ports

This wasn't setup properly, now it's fixed. Woops.
---
 docs/resources.md                    |  2 +-
 engine/resources/docker_container.go | 30 ++++++++++++++++++++--------
 examples/lang/docker0.mcl            |  2 +-
 examples/lang/docker_container0.mcl  |  2 +-
 4 files changed, 25 insertions(+), 11 deletions(-)

diff --git a/docs/resources.md b/docs/resources.md
index 6c2bdf11..fefaa923 100644
--- a/docs/resources.md
+++ b/docs/resources.md
@@ -56,7 +56,7 @@ It has the following properties:
 * `image`: docker `image` or `image:tag`
 * `cmd`: a command or list of commands to run on the container
 * `env`: a list of environment variables, e.g. `["VAR=val",],`
-* `ports`: a map of portmappings, e.g. `{"tcp" => {80 => 8080, 443 => 8443,},},`
+* `ports`: a map of portmappings, e.g. `{"tcp" => {8080 => 80, 8443 => 443,},},`
 * `apiversion:` override the host's default docker version, e.g. `"v1.35"`
 * `force`: destroy and rebuild the container instead of erroring on wrong image
 
diff --git a/engine/resources/docker_container.go b/engine/resources/docker_container.go
index 0e3d0299..385a6cb6 100644
--- a/engine/resources/docker_container.go
+++ b/engine/resources/docker_container.go
@@ -81,7 +81,9 @@ type DockerContainerRes struct {
 	// Env is a list of environment variables. E.g. ["VAR=val",].
 	Env []string `lang:"env" yaml:"env"`
 
-	// Ports is a map of port bindings. E.g. {"tcp" => {80 => 8080},}.
+	// Ports is a map of port bindings. E.g. {"tcp" => {8080 => 80},}. The
+	// key is the host port, and the val is the inner service port to
+	// forward to.
 	Ports map[string]map[int64]int64 `lang:"ports" yaml:"ports"`
 
 	// APIVersion allows you to override the host's default client API
@@ -261,6 +263,8 @@ func (obj *DockerContainerRes) CheckApply(ctx context.Context, apply bool) (bool
 		}
 	}
 
+	// XXX: Check if defined ports matches what we expect.
+
 	if !apply {
 		return false, nil
 	}
@@ -309,15 +313,25 @@ func (obj *DockerContainerRes) CheckApply(ctx context.Context, apply bool) (bool
 			PortBindings: make(map[nat.Port][]nat.PortBinding),
 		}
 
-		for k, v := range obj.Ports {
+		for proto, v := range obj.Ports {
+			// On the outside, on the host, we'd see 8080 which is p
+			// and on the inside, the container would have something
+			// running on 80, which is q.
 			for p, q := range v {
-				containerConfig.ExposedPorts[nat.Port(k)] = struct{}{}
-				hostConfig.PortBindings[nat.Port(fmt.Sprintf("%d/%s", p, k))] = []nat.PortBinding{
-					{
-						HostIP:   "0.0.0.0",
-						HostPort: fmt.Sprintf("%d", q),
-					},
+				// Port is a string containing port number and
+				// protocol in the format "80/tcp".
+				port := fmt.Sprintf("%d/%s", q, proto)
+				n := nat.Port(port)
+				containerConfig.ExposedPorts[n] = struct{}{} // PortSet
+
+				pb := nat.PortBinding{
+					HostIP:   "0.0.0.0",
+					HostPort: fmt.Sprintf("%d", p), // eg: 8080
 				}
+				if _, exists := hostConfig.PortBindings[n]; !exists {
+					hostConfig.PortBindings[n] = []nat.PortBinding{}
+				}
+				hostConfig.PortBindings[n] = append(hostConfig.PortBindings[n], pb)
 			}
 		}
 
diff --git a/examples/lang/docker0.mcl b/examples/lang/docker0.mcl
index e6bf7ae7..a9264906 100644
--- a/examples/lang/docker0.mcl
+++ b/examples/lang/docker0.mcl
@@ -2,7 +2,7 @@ docker:container "mgmt-nginx" {
 	state => "running",
 	image => "nginx",
 	cmd => ["nginx", "-g", "daemon off;",],
-	ports => {"tcp" => {80 => 8080,},},
+	ports => {"tcp" => {8080 => 80,},},
 }
 
 docker:image "nginx" {
diff --git a/examples/lang/docker_container0.mcl b/examples/lang/docker_container0.mcl
index 93eed38f..b8ec993b 100644
--- a/examples/lang/docker_container0.mcl
+++ b/examples/lang/docker_container0.mcl
@@ -2,5 +2,5 @@ docker:container "mgmt-nginx" {
 	state => "running",
 	image => "nginx",
 	cmd => ["nginx", "-g", "daemon off;",],
-	ports => {"tcp" => {80 => 8080,},},
+	ports => {"tcp" => {8080 => 80,},},
 }