Add support for missing Cache-Control directives (#8619)

no-cache, only-if-cached and no-store directives are
being enforced in this PR.

cmd/disk-cache-utils.go

@@ -29,11 +29,14 @@ import (
 )
 
 type cacheControl struct {
-	expiry   time.Time
-	maxAge   int
-	sMaxAge  int
-	minFresh int
-	maxStale int
+	expiry       time.Time
+	maxAge       int
+	sMaxAge      int
+	minFresh     int
+	maxStale     int
+	noStore      bool
+	onlyIfCached bool
+	noCache      bool
 }
 
 func (c cacheControl) isEmpty() bool {
@@ -45,6 +48,19 @@ func (c cacheControl) isStale(modTime time.Time) bool {
 	if c.isEmpty() {
 		return false
 	}
+	// response will never be stale if only-if-cached is set
+	if c.onlyIfCached {
+		return false
+	}
+	// Cache-Control value no-store indicates never cache
+	if c.noStore {
+		return true
+	}
+	// Cache-Control value no-cache indicates cache entry needs to be revalidated before
+	// serving from cache
+	if c.noCache {
+		return true
+	}
 	now := time.Now()
 
 	if c.sMaxAge > 0 && c.sMaxAge < int(now.Sub(modTime).Seconds()) {
@@ -88,6 +104,19 @@ func cacheControlOpts(o ObjectInfo) (c cacheControl) {
 	vals := strings.Split(headerVal, ",")
 	for _, val := range vals {
 		val = strings.TrimSpace(val)
+
+		if val == "no-store" {
+			c.noStore = true
+			continue
+		}
+		if val == "only-if-cached" {
+			c.onlyIfCached = true
+			continue
+		}
+		if val == "no-cache" {
+			c.noCache = true
+			continue
+		}
 		p := strings.Split(val, "=")
 
 		if len(p) != 2 {

cmd/disk-cache.go

@@ -185,12 +185,17 @@ func (c *cacheObjects) GetObjectNInfo(ctx context.Context, bucket, object string
 	cacheReader, cacheErr := c.get(ctx, dcache, bucket, object, rs, h, opts)
 	if cacheErr == nil {
 		cc = cacheControlOpts(cacheReader.ObjInfo)
-		if !cc.isStale(cacheReader.ObjInfo.ModTime) {
+		if (!cc.isEmpty() && !cc.isStale(cacheReader.ObjInfo.ModTime)) ||
+			cc.onlyIfCached {
 			// This is a cache hit, mark it so
 			c.cacheStats.incHit()
 			c.cacheStats.incBytesServed(cacheReader.ObjInfo.Size)
 			return cacheReader, nil
 		}
+		if cc.noStore {
+			c.cacheStats.incMiss()
+			return c.GetObjectNInfo(ctx, bucket, object, rs, h, lockType, opts)
+		}
 	}
 
 	// Reaching here implies cache miss