Add http2 support. Start with http2 frame parsing logic

Author: muthu90tech

CMakeLists.txt

@@ -474,6 +474,12 @@ seastar_generate_ragel (
   IN_FILE ${CMAKE_CURRENT_SOURCE_DIR}/src/http/request_parser.rl
   OUT_FILE ${Seastar_GEN_BINARY_DIR}/include/seastar/http/request_parser.hh)
 
+  seastar_generate_ragel (
+    TARGET seastar_http2_frame_parser
+    VAR http2_frame_parser_file
+    IN_FILE ${CMAKE_CURRENT_SOURCE_DIR}/src/http/http2_frame_parser.rl
+    OUT_FILE ${Seastar_GEN_BINARY_DIR}/include/seastar/http/http2_frame_parser.hh)
+
 seastar_generate_ragel (
   TARGET seastar_http_response_parser
   VAR http_response_parser_file
@@ -489,6 +495,7 @@ seastar_generate_protobuf (
 add_library (seastar
   ${http_chunk_parsers_file}
   ${http_request_parser_file}
+  ${http2_frame_parser_file}
   ${proto_metrics2_files}
   ${seastar_dpdk_obj}
   include/seastar/core/abort_source.hh
@@ -600,6 +607,7 @@ add_library (seastar
   include/seastar/http/mime_types.hh
   include/seastar/http/reply.hh
   include/seastar/http/request.hh
+  include/seastar/http/http2_connection.hh
   include/seastar/http/routes.hh
   include/seastar/http/short_streams.hh
   include/seastar/http/transformers.hh
@@ -721,6 +729,7 @@ add_library (seastar
   src/http/transformers.cc
   src/http/url.cc
   src/http/client.cc
+  src/http/http2_connection.cc
   src/http/request.cc
   src/json/formatter.cc
   src/json/json_elements.cc
@@ -771,6 +780,7 @@ add_dependencies (seastar
   seastar_http_chunk_parsers
   seastar_http_request_parser
   seastar_http_response_parser
+  seastar_http2_frame_parser
   seastar_proto_metrics2)
 
 target_include_directories (seastar

include/seastar/http/http2_connection.hh

@@ -0,0 +1,93 @@
+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  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.
+ */
+/*
+ * Copyright (C) 2025 Scylladb, Ltd.
+ */
+
+#pragma once
+
+#include <seastar/core/iostream.hh>
+#include <seastar/core/gate.hh>
+#include <seastar/core/pipe.hh>
+#include <seastar/net/api.hh>
+#include <seastar/http/request.hh>
+#include <seastar/http/reply.hh>
+#include <seastar/http/routes.hh>
+#include <seastar/http/http2_frame_parser.hh>
+
+namespace seastar {
+
+namespace http {
+
+class http2_connection {
+public:
+    // Represents a single HTTP/2 stream (a request/response exchange)
+    // As per RFC 7540
+    struct h2_stream {
+        // A stream has a well-defined lifecycle (RFC 7540, Section 5.1).
+        enum class state {
+            IDLE,
+            RESERVED_LOCAL,
+            RESERVED_REMOTE,
+            OPEN,
+            HALF_CLOSED_REMOTE,
+            HALF_CLOSED_LOCAL,
+            CLOSED
+        };
+    };
+
+private:
+    httpd::routes& _routes;
+    connected_socket _fd;
+    input_stream<char> _read_buf;
+    output_stream<char> _write_buf;
+    http2_frame_header_parser _parser;
+    bool _done = false;
+
+public:
+    http2_connection(httpd::routes& routes, connected_socket&& fd, socket_address remote_addr, socket_address local_addr)
+        : _routes(routes)
+        , _fd(std::move(fd))
+        , _read_buf(_fd.input())
+        , _write_buf(_fd.output())
+    {}
+
+    // Main entry point to start processing the HTTP/2 connection.
+    future<> process();
+
+    #ifdef SEASTAR_HTTP2_TEST
+        http2_frame_header_parser& get_parser_for_testing() { return _parser; }
+    #endif
+
+private:
+    // The main loop for reading and dispatching frames.
+    future<> read_loop();
+    future<> read_one_frame();
+
+    // Frame-specific handlers.
+    future<> handle_settings_frame(const temporary_buffer<char>& payload);
+    future<> handle_headers_frame(uint32_t stream_id, uint8_t flags, const temporary_buffer<char>& payload);
+    future<> handle_data_frame(uint32_t stream_id, uint8_t flags, const temporary_buffer<char>& payload);
+    // ... other frame handlers (GOAWAY, RST_STREAM, etc.)
+};
+
+
+
+} // namespace http
+
+} // namespace seastar 

src/http/http2_connection.cc

@@ -0,0 +1,54 @@
+#include "seastar/core/future.hh"
+#include <seastar/http/http2_connection.hh>
+#include <seastar/core/loop.hh>
+#include <seastar/core/do_with.hh>
+#include <seastar/core/when_all.hh>
+#include <seastar/core/print.hh>
+#include <seastar/core/future-util.hh>
+#include <seastar/core/temporary_buffer.hh>
+#include <seastar/core/iostream.hh>
+#include <seastar/util/log.hh>
+#include <cstring>
+
+namespace seastar {
+namespace http {
+
+static logger h2log("http2");
+
+future<> http2_connection::process() {
+    h2log.info("Starting HTTP/2 connection processing");
+    return read_loop();
+}
+
+future<> http2_connection::read_loop() {
+    h2log.info("Entering HTTP/2 read loop");
+    return do_until([this] { return _done; }, [this] {
+        return read_one_frame();
+    });
+}
+
+future<> http2_connection::read_one_frame() {
+    // Read 9-byte HTTP/2 frame header
+    // According to the HTTP/2 spec, the frame header is always 9 bytes long.
+    // https://datatracker.ietf.org/doc/html/rfc7540#section-4.1
+    return _read_buf.read_exactly(9).then([this](temporary_buffer<char> hdr_buf) {
+        if (hdr_buf.size() < 9) {
+            h2log.error("Connection closed or incomplete frame header");
+            _done = true;
+            return make_ready_future<>();
+        }
+        // Parse the frame header
+        _parser.init();
+        _parser.parse(hdr_buf.get_write(), hdr_buf.get_write() + 9);
+        uint32_t frame_len = _parser._length;
+        uint8_t frame_type = _parser._type;
+        //TODO: parse frame flags and streamid
+        h2log.info("Frame: type={} len={}", frame_type, frame_len);
+        _done = true;
+        // Depending on the the frame type, call the appropriate handler
+        return make_ready_future<>();
+    });
+}
+
+} // namespace http
+} // namespace seastar 

src/http/http2_frame_parser.rl

@@ -0,0 +1,87 @@
+/*
+ * HTTP/2 Frame Header Parser
+ * Parses the 9-byte HTTP/2 frame header into a struct.
+ */
+
+#pragma once
+
+#include <seastar/core/ragel.hh>
+#include <cstdint>
+
+namespace seastar {
+
+%%{
+    machine http2_frame_parser;
+
+    access _fsm_;
+
+    action mark_start {
+        _frame_start = p;
+    }
+
+    action store_length1 { 
+        _length = (uint32_t)(uint8_t)_frame_start[0] << 16; 
+    }
+    action store_length2 {
+        _length |= (uint32_t)(uint8_t)_frame_start[1] << 8; 
+    }
+    action store_length3 { 
+        _length |= (uint32_t)(uint8_t)_frame_start[2]; 
+    }
+    action store_type { 
+        _type = (uint8_t)_frame_start[3]; 
+    }
+    action store_flags { 
+        _flags = (uint8_t)_frame_start[4]; 
+    }
+
+    main := (
+        any >mark_start
+        any @store_length1
+        any @store_length2
+        any @store_length3
+        any @store_type
+        any @store_flags
+    );
+}%%
+
+class http2_frame_header_parser : public ragel_parser_base<http2_frame_header_parser> {
+    %% write data nofinal noprefix;
+private:
+    const char* _frame_start = nullptr;
+
+public:
+    uint32_t _length = 0;
+    uint8_t _type = 0;
+    uint8_t _flags = 0;
+
+    void init() {
+        init_base();
+        _length = 0;
+        _type = 0;
+        _flags = 0;
+        %% write init;
+    }
+
+    // Returns pointer to next byte after header if parsed, nullptr otherwise
+    char* parse(char* p, char* pe) {
+        char* start = p;
+#ifdef __clang__
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wmisleading-indentation"
+#endif
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wimplicit-fallthrough"
+        %% write exec;
+#pragma GCC diagnostic pop
+#ifdef __clang__
+#pragma clang diagnostic pop
+#endif
+        if (p - start >= 9) {
+            return p;
+        }
+        return nullptr;
+    }
+};
+
+} // namespace seastar 

tests/unit/httpd_test.cc

@@ -1,7 +1,8 @@
 /*
  * Copyright 2015 Cloudius Systems
  */
-
+    
+#define SEASTAR_HTTP2_TEST
 #include <seastar/http/function_handlers.hh>
 #include <seastar/http/httpd.hh>
 #include <seastar/http/handlers.hh>
@@ -20,6 +21,7 @@
 #include <seastar/testing/test_case.hh>
 #include <seastar/testing/thread_test_case.hh>
 #include "loopback_socket.hh"
+#include "seastar/http/http2_connection.hh"
 #include <boost/algorithm/string.hpp>
 #include <seastar/core/thread.hh>
 #include <seastar/util/noncopyable_function.hh>
@@ -2176,5 +2178,43 @@ SEASTAR_TEST_CASE(test_client_close_connection) {
 
             when_all(std::move(server), std::move(client)).discard_result().get();
         }
+
+    });
+}
+
+SEASTAR_TEST_CASE(test_http2_frame_parsing) {
+
+    return seastar::async([] {
+        // Set up loopback connection factory and server socket
+        loopback_connection_factory lcf(1);
+        auto server_sock = lcf.get_server_socket();
+        loopback_socket_impl lsi(lcf);
+
+        // Start server coroutine to handle HTTP/2 connection
+        auto server = seastar::async([&] {
+            auto ar = server_sock.accept().get();
+            // Create HTTP/2 connection object
+            seastar::httpd::routes dummy_routes;
+            seastar::http::http2_connection h2conn(dummy_routes, std::move(ar.connection), ar.remote_address, ar.remote_address);
+            h2conn.process().get();
+            fmt::print("after http2 connection process, frame type {}\n", h2conn.get_parser_for_testing()._type);
+            BOOST_REQUIRE(h2conn.get_parser_for_testing()._type == 0x4); // 0x4 is the SETTINGS frame type
+    
+            fmt::print("finished processing http2 frame!!\n");
+        });
+
+        // Client coroutine: connect and send a SETTINGS frame
+        auto client = seastar::async([&] {
+            connected_socket sock = lsi.connect(socket_address(ipv4_addr()), socket_address(ipv4_addr())).get();
+            auto out = sock.output();
+
+            // 1. Send a SETTINGS frame (empty payload, just header)
+            char settings_frame[9] = {0,0,0, 0x4, 0x0, 0,0,0,0}; // length=0, type=4 (SETTINGS), flags=0, stream_id=0
+            out.write(settings_frame, 9).get();
+            out.flush().get();
+            out.close().get();
+        });
+        // Wait for both client and server to finish
+        when_all(std::move(server), std::move(client)).get();
     });
 }