Validate --cpuset-cpus, --cpuset-mems

Before this patch libcontainer badly errored out with `invalid
argument` or `numerical result out of range` while trying to write
to cpuset.cpus or cpuset.mems with an invalid value provided.
This patch adds validation to --cpuset-cpus and --cpuset-mems flag along with
validation based on system's available cpus/mems before starting a container.

Signed-off-by: Antonio Murdaca <runcom@linux.com>

parsers/parsers.go

@@ -127,7 +127,7 @@ func PartParser(template, data string) (map[string]string, error) {
 		out           = make(map[string]string, len(templateParts))
 	)
 	if len(parts) != len(templateParts) {
-		return nil, fmt.Errorf("Invalid format to parse.  %s should match template %s", data, template)
+		return nil, fmt.Errorf("Invalid format to parse. %s should match template %s", data, template)
 	}
 
 	for i, t := range templateParts {
@@ -196,3 +196,53 @@ func ParseLink(val string) (string, string, error) {
 	}
 	return arr[0], arr[1], nil
 }
+
+// ParseUintList parses and validates the specified string as the value
+// found in some cgroup file (e.g. `cpuset.cpus`, `cpuset.mems`), which could be
+// one of the formats below. Note that duplicates are actually allowed in the
+// input string. It returns a `map[int]bool` with available elements from `val`
+// set to `true`.
+// Supported formats:
+//     7
+//     1-6
+//     0,3-4,7,8-10
+//     0-0,0,1-7
+//     03,1-3      <- this is gonna get parsed as [1,2,3]
+//     3,2,1
+//     0-2,3,1
+func ParseUintList(val string) (map[int]bool, error) {
+	if val == "" {
+		return map[int]bool{}, nil
+	}
+
+	availableInts := make(map[int]bool)
+	split := strings.Split(val, ",")
+	errInvalidFormat := fmt.Errorf("invalid format: %s", val)
+
+	for _, r := range split {
+		if !strings.Contains(r, "-") {
+			v, err := strconv.Atoi(r)
+			if err != nil {
+				return nil, errInvalidFormat
+			}
+			availableInts[v] = true
+		} else {
+			split := strings.SplitN(r, "-", 2)
+			min, err := strconv.Atoi(split[0])
+			if err != nil {
+				return nil, errInvalidFormat
+			}
+			max, err := strconv.Atoi(split[1])
+			if err != nil {
+				return nil, errInvalidFormat
+			}
+			if max < min {
+				return nil, errInvalidFormat
+			}
+			for i := min; i <= max; i++ {
+				availableInts[i] = true
+			}
+		}
+	}
+	return availableInts, nil
+}