nghttpx: Don't push resource if link header has non empty loadpolicy

src/http2.cc

@@ -718,6 +718,30 @@ InputIt skip_to_right_dquote(InputIt first, InputIt last) {
 }
 } // namespace
 
+namespace {
+// Returns true if link-param does not match pattern |pat| of length
+// |patlen| or it has empty value ("").  |pat| should be parmname
+// followed by "=".
+bool check_link_param_empty(const char *first, const char *last,
+                            const char *pat, size_t patlen) {
+  if (first + patlen <= last) {
+    if (std::equal(pat, pat + patlen, first, util::CaseCmp())) {
+      // we only accept URI if pat is followd by "" (e.g.,
+      // loadpolicy="") here.
+      if (first + patlen + 2 <= last) {
+        if (*(first + patlen) != '"' || *(first + patlen + 1) != '"') {
+          return false;
+        }
+      } else {
+        // here we got invalid production (anchor=") or anchor=?
+        return false;
+      }
+    }
+  }
+  return true;
+}
+} // namespace
+
 namespace {
 std::pair<LinkHeader, const char *>
 parse_next_link_header_once(const char *first, const char *last) {
@@ -836,18 +860,17 @@ parse_next_link_header_once(const char *first, const char *last) {
     // we have to reject URI if we have nonempty anchor parameter.
     static const char ANCHOR[] = "anchor=";
     static const size_t ANCHORLEN = sizeof(ANCHOR) - 1;
-    if (!ign && first + ANCHORLEN <= last) {
-      if (std::equal(ANCHOR, ANCHOR + ANCHORLEN, first, util::CaseCmp())) {
-        // we only accept URI if anchor="" here.
-        if (first + ANCHORLEN + 2 <= last) {
-          if (*(first + ANCHORLEN) != '"' || *(first + ANCHORLEN + 1) != '"') {
-            ign = true;
-          }
-        } else {
-          // here we got invalid production (anchor=") or anchor=?
-          ign = true;
-        }
-      }
+    if (!ign && !check_link_param_empty(first, last, ANCHOR, ANCHORLEN)) {
+      ign = true;
+    }
+
+    // reject URI if we have non-empty loadpolicy.  This could be
+    // tightened up to just pick up "next" or "insert".
+    static const char LOADPOLICY[] = "loadpolicy=";
+    static const size_t LOADPOLICYLEN = sizeof(LOADPOLICY) - 1;
+    if (!ign &&
+        !check_link_param_empty(first, last, LOADPOLICY, LOADPOLICYLEN)) {
+      ign = true;
     }
 
     auto param_first = first;

src/http2_test.cc

@@ -627,6 +627,19 @@ void test_http2_parse_link_header(void) {
     CU_ASSERT(1 == res.size());
     CU_ASSERT(std::make_pair(&s[36], &s[39]) == res[0].uri);
   }
+  {
+    // With loadpolicy="next", url should be ignored
+    const char s[] = R"(<url>; rel=preload; loadpolicy="next")";
+    auto res = http2::parse_link_header(s, sizeof(s) - 1);
+    CU_ASSERT(0 == res.size());
+  }
+  {
+    // url should be picked up if empty loadpolicy is specified
+    const char s[] = R"(<url>; rel=preload; loadpolicy="")";
+    auto res = http2::parse_link_header(s, sizeof(s) - 1);
+    CU_ASSERT(1 == res.size());
+    CU_ASSERT(std::make_pair(&s[1], &s[4]) == res[0].uri);
+  }
   {
     // case-insensitive match
     const char s[] = R"(<url>; rel=preload; ANCHOR="#foo", <url>; )"