@@ -3904,6 +3904,19 @@ definitions:

           such as number of nodes, and expiration are included.

         type: "string"

         example: "Community Engine"

+      Warnings:

+        description: |

+          List of warnings / informational messages about missing features, or

+          issues related to the daemon configuration.

+

+          These messages can be printed by the client as information to the user.

+        type: "array"

+        items:

+          type: "string"

+        example:

+          - "WARNING: No memory limit support"

+          - "WARNING: bridge-nf-call-iptables is disabled"

+          - "WARNING: bridge-nf-call-ip6tables is disabled"

   # PluginsInfo is a temp struct holding Plugins name

@@ -206,6 +206,7 @@ type Info struct {

 	InitCommit         Commit

 	SecurityOptions    []string

 	ProductLicense     string `json:",omitempty"`

+	Warnings           []string

 }

 // KeyValue holds a key/value pair

@@ -134,6 +134,8 @@ func (daemon *Daemon) fillDriverInfo(v *types.Info) {

 	v.Driver = drivers

 	v.DriverStatus = ds

+

+	fillDriverWarnings(v)

 }

 func (daemon *Daemon) fillPluginsInfo(v *types.Info) {

@@ -4,6 +4,7 @@ package daemon // import "github.com/docker/docker/daemon"

 import (

 	"context"

+	"fmt"

 	"os/exec"

 	"strings"

@@ -68,6 +69,80 @@ func (daemon *Daemon) fillPlatformInfo(v *types.Info, sysInfo *sysinfo.SysInfo)

 		logrus.Warnf("failed to retrieve %s version: %s", defaultInitBinary, err)

 		v.InitCommit.ID = "N/A"

 	}

+

+	if !v.MemoryLimit {

+		v.Warnings = append(v.Warnings, "WARNING: No memory limit support")

+	}

+	if !v.SwapLimit {

+		v.Warnings = append(v.Warnings, "WARNING: No swap limit support")

+	}

+	if !v.KernelMemory {

+		v.Warnings = append(v.Warnings, "WARNING: No kernel memory limit support")

+	}

+	if !v.OomKillDisable {

+		v.Warnings = append(v.Warnings, "WARNING: No oom kill disable support")

+	}

+	if !v.CPUCfsQuota {

+		v.Warnings = append(v.Warnings, "WARNING: No cpu cfs quota support")

+	}

+	if !v.CPUCfsPeriod {

+		v.Warnings = append(v.Warnings, "WARNING: No cpu cfs period support")

+	}

+	if !v.CPUShares {

+		v.Warnings = append(v.Warnings, "WARNING: No cpu shares support")

+	}

+	if !v.CPUSet {

+		v.Warnings = append(v.Warnings, "WARNING: No cpuset support")

+	}

+	if !v.IPv4Forwarding {

+		v.Warnings = append(v.Warnings, "WARNING: IPv4 forwarding is disabled")

+	}

+	if !v.BridgeNfIptables {

+		v.Warnings = append(v.Warnings, "WARNING: bridge-nf-call-iptables is disabled")

+	}

+	if !v.BridgeNfIP6tables {

+		v.Warnings = append(v.Warnings, "WARNING: bridge-nf-call-ip6tables is disabled")

+	}

+}

+

+func fillDriverWarnings(v *types.Info) {

+	if v.DriverStatus == nil {

+		return

+	}

+	for _, pair := range v.DriverStatus {

+		if pair[0] == "Data loop file" {

+			msg := fmt.Sprintf("WARNING: %s: usage of loopback devices is "+

+				"strongly discouraged for production use.\n         "+

+				"Use `--storage-opt dm.thinpooldev` to specify a custom block storage device.", v.Driver)

+

+			v.Warnings = append(v.Warnings, msg)

+			continue

+		}

+		if pair[0] == "Supports d_type" && pair[1] == "false" {

+			backingFs := getBackingFs(v)

+

+			msg := fmt.Sprintf("WARNING: %s: the backing %s filesystem is formatted without d_type support, which leads to incorrect behavior.\n", v.Driver, backingFs)

+			if backingFs == "xfs" {

+				msg += "         Reformat the filesystem with ftype=1 to enable d_type support.\n"

+			}

+			msg += "         Running without d_type support will not be supported in future releases."

+

+			v.Warnings = append(v.Warnings, msg)

+			continue

+		}

+	}

+}

+

+func getBackingFs(v *types.Info) string {

+	if v.DriverStatus == nil {

+		return ""

+	}

+	for _, pair := range v.DriverStatus {

+		if pair[0] == "Backing Filesystem" {

+			return pair[1]

+		}

+	}

+	return ""

 }

 // parseInitVersion parses a Tini version string, and extracts the version.

@@ -8,3 +8,6 @@ import (

 // fillPlatformInfo fills the platform related info.

 func (daemon *Daemon) fillPlatformInfo(v *types.Info, sysInfo *sysinfo.SysInfo) {

 }

+

+func fillDriverWarnings(v *types.Info) {

+}

@@ -21,6 +21,8 @@ keywords: "API, Docker, rcli, REST, documentation"

   and `OperatingSystem` if the daemon was unable to obtain this information.

 * `GET /info` now returns information about the product license, if a license

   has been applied to the daemon.

+* `GET /info` now returns a `Warnings` field, containing warnings and informational

+  messages about missing features, or issues related to the daemon configuration.

 * `POST /swarm/init` now accepts a `DefaultAddrPool` property to set global scope default address pool

 * `POST /swarm/init` now accepts a `SubnetSize` property to set global scope networks by giving the

   length of the subnet masks for every such network