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/** @file
A plugin to parse Link headers from an origin server's response and initiate H2 Server Push for preload links.
@section license License
Licensed to the Apache Software Foundation (ASF) under one
or more contributor license agreements. See the NOTICE file
distributed with this work for additional information
regarding copyright ownership. The ASF licenses this file
to you under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
#include <iostream>
#include <regex>
#include <set>
#include <sstream>
#include <ts/ts.h>
#include "tscpp/api/GlobalPlugin.h"
#include "tscpp/api/RemapPlugin.h"
#include "tscpp/api/TransactionPlugin.h"
#define PLUGIN_NAME "server_push_preload"
#define PRELOAD_PARAM "rel=preload"
#define NOPUSH_OPTION "nopush"
using namespace std;
using namespace atscppapi;
static regex linkRegexp("<([^>]+)>;(.+)");
namespace
{
GlobalPlugin *globalPlugin;
RemapPlugin *remapPlugin;
} // namespace
class ServerPushTransaction : public TransactionPlugin
{
public:
explicit ServerPushTransaction(Transaction &transaction) : TransactionPlugin(transaction)
{
TransactionPlugin::registerHook(HOOK_SEND_RESPONSE_HEADERS);
}
void
handleSendResponseHeaders(Transaction &transaction) override
{
serverPush(transaction);
transaction.resume();
}
void
serverPush(Transaction &transaction)
{
TSHttpTxn txnp = static_cast<TSHttpTxn>(transaction.getAtsHandle());
if (TSHttpTxnClientProtocolStackContains(txnp, "h2") == nullptr) {
return;
}
ClientRequest &request = transaction.getClientRequest();
Response &response = transaction.getClientResponse();
Headers &headers = response.getHeaders();
const Url &clientUrl = request.getPristineUrl();
for (header_field_iterator it = headers.find("Link"); it != headers.end(); it.nextDup()) {
HeaderField field = *it;
for (header_field_value_iterator hit = field.begin(); hit != field.end(); ++hit) {
const string &link = *hit;
TSDebug(PLUGIN_NAME, "Parsing link header: %s", link.c_str());
smatch matches;
if (regex_search(link, matches, linkRegexp)) {
string url = matches[1].str();
TSDebug(PLUGIN_NAME, "Found link header match: %s", url.c_str());
set<string> params = split(matches[2].str(), ';');
auto preload = params.find(PRELOAD_PARAM);
if (preload == params.end()) {
continue;
}
auto noPush = params.find(NOPUSH_OPTION);
if (noPush != params.end()) {
TSDebug(PLUGIN_NAME, "Skipping nopush link: %s", link.c_str());
continue;
}
Request request(url);
Url &linkUrl = request.getUrl();
if (linkUrl.getHost().empty()) {
linkUrl.setHost(clientUrl.getHost());
linkUrl.setScheme(clientUrl.getScheme());
}
if (0 != clientUrl.getPort()) {
linkUrl.setPort(clientUrl.getPort());
}
string lu = linkUrl.getUrlString();
TSDebug(PLUGIN_NAME, "Push preloaded content: %s", lu.c_str());
TSHttpTxnServerPush(txnp, lu.c_str(), lu.length());
} else {
TSDebug(PLUGIN_NAME, "No match found for link header: %s", link.c_str());
}
}
}
}
set<string>
split(const string ¶ms, char delim)
{
stringstream ss(params);
string s;
set<string> tokens;
while (getline(ss, s, delim)) {
s.erase(find_if(s.rbegin(), s.rend(), [](unsigned char c) { return !std::isspace(c); }).base(), s.end()); // trim left
s.erase(s.begin(), find_if(s.begin(), s.end(), [](unsigned char c) { return !std::isspace(c); })); // trim right
tokens.insert(s);
}
return tokens;
}
};
class ServerPushRemap : public RemapPlugin
{
public:
explicit ServerPushRemap(void **instance_handle) : RemapPlugin(instance_handle) {}
Result
doRemap(const Url &map_from_url, const Url &map_to_url, Transaction &transaction, bool &redirect) override
{
transaction.addPlugin(new ServerPushTransaction(transaction));
return RESULT_DID_REMAP;
}
};
class ServerPushGlobal : public GlobalPlugin
{
public:
ServerPushGlobal() { GlobalPlugin::registerHook(HOOK_READ_REQUEST_HEADERS_PRE_REMAP); }
void
handleReadRequestHeadersPreRemap(Transaction &transaction) override
{
transaction.addPlugin(new ServerPushTransaction(transaction));
transaction.resume();
}
};
void
TSPluginInit(int argc ATSCPPAPI_UNUSED, const char *argv[] ATSCPPAPI_UNUSED)
{
TSDebug(PLUGIN_NAME, "Init");
if (!RegisterGlobalPlugin("ServerPushPreloadPlugin", PLUGIN_NAME, "dev@trafficserver.apache.org")) {
return;
}
globalPlugin = new ServerPushGlobal();
}
TSReturnCode
TSRemapNewInstance(int argc ATSCPPAPI_UNUSED, char *argv[] ATSCPPAPI_UNUSED, void **instance_handle, char *errbuf ATSCPPAPI_UNUSED,
int errbuf_size ATSCPPAPI_UNUSED)
{
TSDebug(PLUGIN_NAME, "New Instance");
remapPlugin = new ServerPushRemap(instance_handle);
return TS_SUCCESS;
}
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