checkpoint: add support to query for lazy page support

Before adding the actual lazy migration support, this adds the feature
check for lazy-pages. Right now lazy migration, which is based on
userfaultd is only available in the criu-dev branch and not yet in a
release. As the check does not dependent on a certain version but on
a CRIU feature which can be queried it can be part of runC without a new
version check depending on a feature from criu-dev.

Signed-off-by: Adrian Reber <[email protected]>

Author: adrianreber

libcontainer/container_linux.go

@@ -621,9 +621,24 @@ func (c *linuxContainer) checkCriuFeatures(criuOpts *CriuOpts, rpcOpts *criurpc.
 	logrus.Debugf("Feature check says: %s", criuFeatures)
 	missingFeatures := false
 
-	if *criuFeat.MemTrack && !*criuFeatures.MemTrack {
-		missingFeatures = true
-		logrus.Debugf("CRIU does not support MemTrack")
+	// The outer if checks if the fields actually exist
+	if (criuFeat.MemTrack != nil) &&
+		(criuFeatures.MemTrack != nil) {
+		// The inner if checks if they are set to true
+		if *criuFeat.MemTrack && !*criuFeatures.MemTrack {
+			missingFeatures = true
+			logrus.Debugf("CRIU does not support MemTrack")
+		}
+	}
+
+	// This needs to be repeated for every new feature check.
+	// Is there a way to put this in a function. Reflection?
+	if (criuFeat.LazyPages != nil) &&
+		(criuFeatures.LazyPages != nil) {
+		if *criuFeat.LazyPages && !*criuFeatures.LazyPages {
+			missingFeatures = true
+			logrus.Debugf("CRIU does not support LazyPages")
+		}
 	}
 
 	if missingFeatures {