Implementing the Cache-Control "must-revalidate" directive

bin/varnishd/cache/cache_rfc2616.c

@@ -220,6 +220,17 @@ RFC2616_Ttl(struct busyobj *bo, vtim_real now, vtim_real *t_origin,
 		*grace = rfc2616_time(p);
 	}
 
+	/*
+	 * The "must-revalidate" directive prohibits 
+	 * the cache from serving stale data,
+	 * according to RFC7234, 5.2.2.1.
+	 * This sets the grace to zero.
+	 */
+	if (*ttl >= 0 && http_GetHdrField(hp, H_Cache_Control,
+	    "must-revalidate", &p)) { // rfc7234,l,1303,1305
+		*grace = 0.;
+	}	
+
 	VSLb(bo->vsl, SLT_TTL,
 	    "RFC %.0f %.0f %.0f %.0f %.0f %.0f %.0f %u %s",
 	    *ttl, *grace, *keep, now,

bin/varnishtest/tests/b00073.vtc

@@ -0,0 +1,31 @@
+varnishtest "Test must-revalidate"
+
+server s1 {
+	rxreq
+	txresp -hdr "Cache-Control: max-age=30"
+	rxreq
+	txresp -hdr "Cache-Control: max-age=30, must-revalidate"	
+	rxreq
+	txresp -hdr "Cache-Control: max-age=30, must-revalidate, stale-while-revalidate=100"		
+} -start
+
+varnish v1 -vcl+backend {
+	sub vcl_backend_response {
+		set beresp.http.grace = beresp.grace;
+		set beresp.http.ttl = beresp.ttl;
+	}
+} -start
+
+client c1 {
+	txreq -url /1
+	rxresp
+	expect resp.http.grace == 10.000
+
+	txreq -url /2
+	rxresp
+	expect resp.http.grace == 0.000
+
+	txreq -url /3
+	rxresp
+	expect resp.http.grace == 0.000
+} -run