nghttpd: Add -p, --push option to configure server push

The option syntax is <PATH>=<PUSH_PATH,...>.
Push resources PUSH_PATHs when PATH is requested. This option can be used
repeatedly to specify multiple push configurations. For example,
  -p/=/foo.png -p/doc=/bar.css
PATH and PUSH_PATHs are relative to document root.

src/HttpServer.cc

@@ -501,6 +501,32 @@ int Http2Handler::submit_response(const std::string& status,
                                  data_prd);
 }
 
+int Http2Handler::submit_push_promise(Request *req,
+                                      const std::string& push_path)
+{
+  std::string authority;
+  auto itr = std::lower_bound(std::begin(req->headers),
+                              std::end(req->headers),
+                              std::make_pair(std::string(":authority"),
+                                             std::string("")));
+  if(itr == std::end(req->headers) || (*itr).first != ":authority") {
+    itr = std::lower_bound(std::begin(req->headers),
+                           std::end(req->headers),
+                           std::make_pair(std::string("host"),
+                                          std::string("")));
+  }
+  auto nva = std::vector<nghttp2_nv>{
+    http2::make_nv_ll(":method", "GET"),
+    http2::make_nv_ls(":path", push_path),
+    get_config()->no_tls ?
+    http2::make_nv_ll(":scheme", "http") :
+    http2::make_nv_ll(":scheme", "https"),
+    http2::make_nv_ls(":authority", (*itr).second)
+  };
+  return nghttp2_submit_push_promise(session_, NGHTTP2_FLAG_END_PUSH_PROMISE,
+                                     req->stream_id, nva.data(), nva.size());
+}
+
 void Http2Handler::add_stream(int32_t stream_id, std::unique_ptr<Request> req)
 {
   id2req_[stream_id] = std::move(req);
@@ -644,8 +670,9 @@ void prepare_status_response(Request *req, Http2Handler *hd,
 } // namespace
 
 namespace {
-void prepare_response(Request *req, Http2Handler *hd)
+void prepare_response(Request *req, Http2Handler *hd, bool allow_push = true)
 {
+  int rv;
   auto url = (*std::lower_bound(std::begin(req->headers),
                                 std::end(req->headers),
                                 std::make_pair(std::string(":path"),
@@ -675,6 +702,16 @@ void prepare_response(Request *req, Http2Handler *hd)
     prepare_status_response(req, hd, STATUS_404);
     return;
   }
+  auto push_itr = hd->get_config()->push.find(url);
+  if(push_itr != std::end(hd->get_config()->push)) {
+    for(auto& push_path : (*push_itr).second) {
+      rv = hd->submit_push_promise(req, push_path);
+      if(rv != 0) {
+        std::cerr << "nghttp2_submit_push_promise() returned error: "
+                  << nghttp2_strerror(rv) << std::endl;
+      }
+    }
+  }
   std::string path = hd->get_config()->htdocs+url;
   if(path[path.size()-1] == '/') {
     path += DEFAULT_HTML;
@@ -783,7 +820,7 @@ int htdocs_on_request_recv_callback
   auto hd = reinterpret_cast<Http2Handler*>(user_data);
   auto stream = hd->get_stream(stream_id);
   if(stream) {
-    prepare_response(hd->get_stream(stream_id), hd);
+    prepare_response(stream, hd);
   }
   return 0;
 }
@@ -794,6 +831,17 @@ int hd_on_frame_send_callback
  void *user_data)
 {
   auto hd = reinterpret_cast<Http2Handler*>(user_data);
+  if(frame->hd.type == NGHTTP2_PUSH_PROMISE) {
+    auto req = util::make_unique<Request>
+      (frame->push_promise.promised_stream_id);
+    auto nva = http2::sort_nva(frame->push_promise.nva,
+                               frame->push_promise.nvlen);
+    append_nv(req.get(), nva);
+    auto req_ptr = req.get();
+    auto stream_id = req->stream_id;
+    hd->add_stream(stream_id, std::move(req));
+    prepare_response(req_ptr, hd, /*allow_push */ false);
+  }
   if(hd->get_config()->verbose) {
     print_session_id(hd->session_id());
     on_frame_send_callback(session, frame, user_data);

src/HttpServer.h

@@ -47,6 +47,7 @@
 namespace nghttp2 {
 
 struct Config {
+  std::map<std::string, std::vector<std::string>> push;
   std::string htdocs;
   std::string host;
   std::string private_key_file;
@@ -107,6 +108,8 @@ public:
    const std::vector<std::pair<std::string, std::string>>& headers,
    nghttp2_data_provider *data_prd);
 
+  int submit_push_promise(Request *req, const std::string& push_path);
+
   void add_stream(int32_t stream_id, std::unique_ptr<Request> req);
   void remove_stream(int32_t stream_id);
   Request* get_stream(int32_t stream_id);

src/nghttpd.cc

@@ -42,6 +42,33 @@
 
 namespace nghttp2 {
 
+namespace {
+int parse_push_config(Config& config, const char *optarg)
+{
+  const char *eq = strchr(optarg, '=');
+  if(eq == NULL) {
+    return -1;
+  }
+  auto paths = std::vector<std::string>();
+  auto optarg_end = optarg + strlen(optarg);
+  const char *i = eq + 1;
+  for(;;) {
+    const char *j = strchr(i, ',');
+    if(j == NULL) {
+      j = optarg_end;
+    }
+    paths.emplace_back(i, j);
+    if(j == optarg_end) {
+      break;
+    }
+    i = j;
+    ++i;
+  }
+  config.push[std::string(optarg, eq)] = std::move(paths);
+  return 0;
+}
+} // namespace
+
 namespace {
 void print_usage(std::ostream& out)
 {
@@ -79,6 +106,14 @@ void print_help(std::ostream& out)
       << "    -c, --header-table-size=<N>\n"
       << "                       Specify decoder header table size.\n"
       << "    --color            Force colored log output.\n"
+      << "    -p, --push=<PATH>=<PUSH_PATH,...>\n"
+      << "                       Push resources PUSH_PATHs when PATH is\n"
+      << "                       requested. This option can be used\n"
+      << "                       repeatedly to specify multiple push\n"
+      << "                       configurations. For example,\n"
+      << "                         -p/=/foo.png -p/doc=/bar.css\n"
+      << "                       PATH and PUSH_PATHs are relative to document\n"
+      << "                       root. See --htdocs option.\n"
       << "    -h, --help         Print this help.\n"
       << std::endl;
 }
@@ -98,12 +133,13 @@ int main(int argc, char **argv)
       {"verify-client", no_argument, nullptr, 'V'},
       {"no-flow-control", no_argument, nullptr, 'f'},
       {"header-table-size", required_argument, nullptr, 'c'},
+      {"push", required_argument, nullptr, 'p'},
       {"no-tls", no_argument, &flag, 1},
       {"color", no_argument, &flag, 2},
       {nullptr, 0, nullptr, 0}
     };
     int option_index = 0;
-    int c = getopt_long(argc, argv, "DVc:d:fhv", long_options, &option_index);
+    int c = getopt_long(argc, argv, "DVc:d:fhp:v", long_options, &option_index);
     char *end;
     if(c == -1) {
       break;
@@ -134,6 +170,11 @@ int main(int argc, char **argv)
         exit(EXIT_FAILURE);
       }
       break;
+    case 'p':
+      if(parse_push_config(config, optarg) != 0) {
+        std::cerr << "-p: Bad option value: " << optarg << std::endl;
+      }
+      break;
     case '?':
       exit(EXIT_FAILURE);
     case 0: