api/types: fix KernelMemory deprecation comment, and omitempty

This fixes the "deprecated" comment to have the correct format to be picked
up by editors, and adds `omitempty` labels for KernelMemory and KernelMemoryTCP.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

api/swagger.yaml

@@ -578,7 +578,12 @@ definitions:
         items:
           $ref: "#/definitions/DeviceRequest"
       KernelMemoryTCP:
-        description: "Hard limit for kernel TCP buffer memory (in bytes)."
+        description: |
+          Hard limit for kernel TCP buffer memory (in bytes). Depending on the
+          OCI runtime in use, this option may be ignored. It is no longer supported
+          by the default (runc) runtime.
+
+          This field is omitted when empty.
         type: "integer"
         format: "int64"
       MemoryReservation:

api/types/container/host_config.go

@@ -376,14 +376,17 @@ type Resources struct {
 	Devices              []DeviceMapping // List of devices to map inside the container
 	DeviceCgroupRules    []string        // List of rule to be added to the device cgroup
 	DeviceRequests       []DeviceRequest // List of device requests for device drivers
-	KernelMemory         int64           // Kernel memory limit (in bytes), Deprecated: kernel 5.4 deprecated kmem.limit_in_bytes
-	KernelMemoryTCP      int64           // Hard limit for kernel TCP buffer memory (in bytes)
-	MemoryReservation    int64           // Memory soft limit (in bytes)
-	MemorySwap           int64           // Total memory usage (memory + swap); set `-1` to enable unlimited swap
-	MemorySwappiness     *int64          // Tuning container memory swappiness behaviour
-	OomKillDisable       *bool           // Whether to disable OOM Killer or not
-	PidsLimit            *int64          // Setting PIDs limit for a container; Set `0` or `-1` for unlimited, or `null` to not change.
-	Ulimits              []*units.Ulimit // List of ulimits to be set in the container
+
+	// KernelMemory specifies the kernel memory limit (in bytes) for the container.
+	// Deprecated: kernel 5.4 deprecated kmem.limit_in_bytes.
+	KernelMemory      int64           `json:",omitempty"`
+	KernelMemoryTCP   int64           `json:",omitempty"` // Hard limit for kernel TCP buffer memory (in bytes)
+	MemoryReservation int64           // Memory soft limit (in bytes)
+	MemorySwap        int64           // Total memory usage (memory + swap); set `-1` to enable unlimited swap
+	MemorySwappiness  *int64          // Tuning container memory swappiness behaviour
+	OomKillDisable    *bool           // Whether to disable OOM Killer or not
+	PidsLimit         *int64          // Setting PIDs limit for a container; Set `0` or `-1` for unlimited, or `null` to not change.
+	Ulimits           []*units.Ulimit // List of ulimits to be set in the container
 
 	// Applicable to Windows
 	CPUCount           int64  `json:"CpuCount"`   // CPU count

docs/api/version-history.md

@@ -46,6 +46,8 @@ keywords: "API, Docker, rcli, REST, documentation"
   `POST /containers/{id}/update` endpoints, any value it is set to will be ignored
   on API version `v1.42` and up. Older API versions still accept this field, but
   may take no effect, depending on the kernel version and OCI runtime in use.
+* `GET /containers/{id}/json` now omits the `KernelMemory` and `KernelMemoryTCP`
+  if they are not set.
 * `GET /info` now omits the `KernelMemory` and `KernelMemoryTCP` if they are not
   supported by the host or host's configuration (if cgroups v2 are in use).