Add DeviceRequests to HostConfig to support NVIDIA GPUs

This patch hard-codes support for NVIDIA GPUs.
In a future patch it should move out into its own Device Plugin.

Signed-off-by: Tibor Vass <tibor@docker.com>

pkg/capabilities/caps.go

@@ -0,0 +1,23 @@
+// Package capabilities allows to generically handle capabilities.
+package capabilities
+
+// Set represents a set of capabilities.
+type Set map[string]struct{}
+
+// Match tries to match set with caps, which is an OR list of AND lists of capabilities.
+// The matched AND list of capabilities is returned; or nil if none are matched.
+func (set Set) Match(caps [][]string) []string {
+	if set == nil {
+		return nil
+	}
+anyof:
+	for _, andList := range caps {
+		for _, cap := range andList {
+			if _, ok := set[cap]; !ok {
+				continue anyof
+			}
+		}
+		return andList
+	}
+	return nil
+}

pkg/capabilities/caps_test.go

@@ -0,0 +1,72 @@
+package capabilities
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestMatch(t *testing.T) {
+	set := Set{
+		"foo": struct{}{},
+		"bar": struct{}{},
+	}
+	type testcase struct {
+		caps     [][]string
+		expected []string
+	}
+	var testcases = []testcase{
+		// matches
+		{
+			caps:     [][]string{{}},
+			expected: []string{},
+		},
+		{
+			caps:     [][]string{{"foo"}},
+			expected: []string{"foo"},
+		},
+		{
+			caps:     [][]string{{"bar"}, {"foo"}},
+			expected: []string{"bar"},
+		},
+		{
+			caps:     [][]string{{"foo", "bar"}},
+			expected: []string{"foo", "bar"},
+		},
+		{
+			caps:     [][]string{{"qux"}, {"foo"}},
+			expected: []string{"foo"},
+		},
+		{
+			caps:     [][]string{{"foo", "bar"}, {"baz"}, {"bar"}},
+			expected: []string{"foo", "bar"},
+		},
+
+		// non matches
+		{caps: nil},
+		{caps: [][]string{}},
+		{caps: [][]string{{"qux"}}},
+		{caps: [][]string{{"foo", "bar", "qux"}}},
+		{caps: [][]string{{"qux"}, {"baz"}}},
+		{caps: [][]string{{"foo", "baz"}}},
+	}
+
+	for _, m := range testcases {
+		t.Run(fmt.Sprintf("%v", m.caps), func(t *testing.T) {
+			selected := set.Match(m.caps)
+			if m.expected == nil || selected == nil {
+				if m.expected == nil && selected == nil {
+					return
+				}
+				t.Fatalf("selected = %v, expected = %v", selected, m.expected)
+			}
+			if len(selected) != len(m.expected) {
+				t.Fatalf("len(selected) = %d, len(expected) = %d", len(selected), len(m.expected))
+			}
+			for i, s := range selected {
+				if m.expected[i] != s {
+					t.Fatalf("selected[%d] = %s, expected[%d] = %s", i, s, i, m.expected[i])
+				}
+			}
+		})
+	}
+}