nghttpx: Add --frontend-quic-congestion-controller option

gennghttpxfun.py

@@ -191,6 +191,7 @@ OPTIONS = [
     "frontend-quic-early-data",
     "frontend-quic-qlog-dir",
     "frontend-quic-require-token",
+    "frontend-quic-congestion-controller",
 ]
 
 LOGVARS = [

src/shrpx.cc

@@ -1854,6 +1854,8 @@ void fill_default_config(Config *config) {
 
     auto &bpfconf = quicconf.bpf;
     bpfconf.prog_file = StringRef::from_lit(PKGLIBDIR "/reuseport_kern.o");
+
+    upstreamconf.congestion_controller = NGTCP2_CC_ALGO_CUBIC;
   }
 
   auto &http3conf = config->http3;
@@ -3226,6 +3228,15 @@ HTTP/3 and QUIC:
               Require an address validation  token for a frontend QUIC
               connection.   Server sends  a token  in Retry  packet or
               NEW_TOKEN frame in the previous connection.
+  --frontend-quic-congestion-controller=<CC>
+              Specify a congestion controller algorithm for a frontend
+              QUIC  connection.   <CC>  should be  either  "cubic"  or
+              "bbr".
+              Default: )"
+      << (config->quic.upstream.congestion_controller == NGTCP2_CC_ALGO_CUBIC
+              ? "cubic"
+              : "bbr")
+      << R"(
   --no-quic-bpf
               Disable eBPF.
   --frontend-http3-window-size=<SIZE>
@@ -4022,6 +4033,8 @@ int main(int argc, char **argv) {
          181},
         {SHRPX_OPT_FRONTEND_QUIC_REQUIRE_TOKEN.c_str(), no_argument, &flag,
          182},
+        {SHRPX_OPT_FRONTEND_QUIC_CONGESTION_CONTROLLER.c_str(),
+         required_argument, &flag, 183},
         {nullptr, 0, nullptr, 0}};
 
     int option_index = 0;
@@ -4894,6 +4907,11 @@ int main(int argc, char **argv) {
         cmdcfgs.emplace_back(SHRPX_OPT_FRONTEND_QUIC_REQUIRE_TOKEN,
                              StringRef::from_lit("yes"));
         break;
+      case 183:
+        // --frontend-quic-congestion-controller
+        cmdcfgs.emplace_back(SHRPX_OPT_FRONTEND_QUIC_CONGESTION_CONTROLLER,
+                             StringRef{optarg});
+        break;
       default:
         break;
       }

src/shrpx_config.cc

@@ -2571,6 +2571,9 @@ int option_lookup_token(const char *name, size_t namelen) {
       if (util::strieq_l("frontend-http2-dump-response-heade", name, 34)) {
         return SHRPX_OPTID_FRONTEND_HTTP2_DUMP_RESPONSE_HEADER;
       }
+      if (util::strieq_l("frontend-quic-congestion-controlle", name, 34)) {
+        return SHRPX_OPTID_FRONTEND_QUIC_CONGESTION_CONTROLLER;
+      }
       break;
     }
     break;
@@ -3997,6 +4000,19 @@ int parse_config(Config *config, int optid, const StringRef &opt,
     config->quic.upstream.require_token = util::strieq_l("yes", optarg);
 #endif // ENABLE_HTTP3
 
+    return 0;
+  case SHRPX_OPTID_FRONTEND_QUIC_CONGESTION_CONTROLLER:
+#ifdef ENABLE_HTTP3
+    if (util::strieq_l("cubic", optarg)) {
+      config->quic.upstream.congestion_controller = NGTCP2_CC_ALGO_CUBIC;
+    } else if (util::strieq_l("bbr", optarg)) {
+      config->quic.upstream.congestion_controller = NGTCP2_CC_ALGO_BBR;
+    } else {
+      LOG(ERROR) << opt << ": must be either cubic or bbr";
+      return -1;
+    }
+#endif // ENABLE_HTTP3
+
     return 0;
   case SHRPX_OPTID_CONF:
     LOG(WARN) << "conf: ignored";

src/shrpx_config.h

@@ -389,6 +389,8 @@ constexpr auto SHRPX_OPT_FRONTEND_QUIC_QLOG_DIR =
     StringRef::from_lit("frontend-quic-qlog-dir");
 constexpr auto SHRPX_OPT_FRONTEND_QUIC_REQUIRE_TOKEN =
     StringRef::from_lit("frontend-quic-require-token");
+constexpr auto SHRPX_OPT_FRONTEND_QUIC_CONGESTION_CONTROLLER =
+    StringRef::from_lit("frontend-quic-congestion-controller");
 
 constexpr size_t SHRPX_OBFUSCATED_NODE_LENGTH = 8;
 
@@ -756,6 +758,7 @@ struct QUICConfig {
     struct {
       StringRef dir;
     } qlog;
+    ngtcp2_cc_algo congestion_controller;
     bool early_data;
     bool require_token;
   } upstream;
@@ -1210,6 +1213,7 @@ enum {
   SHRPX_OPTID_FRONTEND_KEEP_ALIVE_TIMEOUT,
   SHRPX_OPTID_FRONTEND_MAX_REQUESTS,
   SHRPX_OPTID_FRONTEND_NO_TLS,
+  SHRPX_OPTID_FRONTEND_QUIC_CONGESTION_CONTROLLER,
   SHRPX_OPTID_FRONTEND_QUIC_DEBUG_LOG,
   SHRPX_OPTID_FRONTEND_QUIC_EARLY_DATA,
   SHRPX_OPTID_FRONTEND_QUIC_IDLE_TIMEOUT,

src/shrpx_http3_upstream.cc

@@ -573,7 +573,7 @@ int Http3Upstream::init(const UpstreamAddr *faddr, const Address &remote_addr,
   }
 
   settings.initial_ts = quic_timestamp();
-  settings.cc_algo = NGTCP2_CC_ALGO_BBR;
+  settings.cc_algo = quicconf.upstream.congestion_controller;
   settings.max_window = http3conf.upstream.max_connection_window_size;
   settings.max_stream_window = http3conf.upstream.max_window_size;
   settings.max_udp_payload_size = SHRPX_QUIC_MAX_UDP_PAYLOAD_SIZE;
@@ -665,6 +665,13 @@ int Http3Upstream::write_streams() {
   ngtcp2_path_storage_zero(&ps);
   ngtcp2_path_storage_zero(&prev_ps);
 
+  auto config = get_config();
+  auto &quicconf = config->quic;
+
+  if (quicconf.upstream.congestion_controller != NGTCP2_CC_ALGO_BBR) {
+    max_pktcnt = std::min(max_pktcnt, static_cast<size_t>(10));
+  }
+
   for (;;) {
     int64_t stream_id = -1;
     int fin = 0;