From 0c77d6b943cab4661ba4d8a921874da96bcfd2dd Mon Sep 17 00:00:00 2001
From: Tatsuhiro Tsujikawa <tatsuhiro.t@gmail.com>
Date: Mon, 16 May 2022 21:20:40 +0900
Subject: [PATCH] Better pack UDP packets in one GSO write

---
 src/h2load_quic.cc          |  8 ++++++--
 src/shrpx_http3_upstream.cc | 10 ++++++++--
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/src/h2load_quic.cc b/src/h2load_quic.cc
index 437f5754..0e9a210c 100644
--- a/src/h2load_quic.cc
+++ b/src/h2load_quic.cc
@@ -711,6 +711,8 @@ int Client::write_quic() {
   std::array<nghttp3_vec, 16> vec;
   size_t pktcnt = 0;
   auto max_udp_payload_size = ngtcp2_conn_get_max_udp_payload_size(quic.conn);
+  auto path_max_udp_payload_size =
+      ngtcp2_conn_get_path_max_udp_payload_size(quic.conn);
   size_t max_pktcnt =
 #ifdef UDP_SEGMENT
       worker->config->no_udp_gso
@@ -803,7 +805,9 @@ int Client::write_quic() {
 
     if (pktcnt == 0) {
       gso_size = nwrite;
-    } else if (static_cast<size_t>(nwrite) != gso_size) {
+    } else if (static_cast<size_t>(nwrite) > gso_size ||
+               (gso_size > path_max_udp_payload_size &&
+                static_cast<size_t>(nwrite) != gso_size)) {
       auto data = quic.tx.data.get();
       auto datalen = bufpos - quic.tx.data.get() - nwrite;
       rv = write_udp(ps.path.remote.addr, ps.path.remote.addrlen, data, datalen,
@@ -825,7 +829,7 @@ int Client::write_quic() {
     }
 
     // Assume that the path does not change.
-    if (++pktcnt == max_pktcnt) {
+    if (++pktcnt == max_pktcnt || static_cast<size_t>(nwrite) < gso_size) {
       auto data = quic.tx.data.get();
       auto datalen = bufpos - quic.tx.data.get();
       rv = write_udp(ps.path.remote.addr, ps.path.remote.addrlen, data, datalen,
diff --git a/src/shrpx_http3_upstream.cc b/src/shrpx_http3_upstream.cc
index f8e6048f..0232728b 100644
--- a/src/shrpx_http3_upstream.cc
+++ b/src/shrpx_http3_upstream.cc
@@ -706,6 +706,10 @@ int Http3Upstream::on_write() {
 int Http3Upstream::write_streams() {
   std::array<nghttp3_vec, 16> vec;
   auto max_udp_payload_size = ngtcp2_conn_get_max_udp_payload_size(conn_);
+#ifdef UDP_SEGMENT
+  auto path_max_udp_payload_size =
+      ngtcp2_conn_get_path_max_udp_payload_size(conn_);
+#endif // UDP_SEGMENT
   size_t max_pktcnt =
       std::min(static_cast<size_t>(64_k), ngtcp2_conn_get_send_quantum(conn_)) /
       max_udp_payload_size;
@@ -860,7 +864,9 @@ int Http3Upstream::write_streams() {
       gso_size = nwrite;
     } else if (!ngtcp2_path_eq(&prev_ps.path, &ps.path) ||
                prev_pi.ecn != pi.ecn ||
-               static_cast<size_t>(nwrite) != gso_size) {
+               static_cast<size_t>(nwrite) > gso_size ||
+               (gso_size > path_max_udp_payload_size &&
+                static_cast<size_t>(nwrite) != gso_size)) {
       auto faddr = static_cast<UpstreamAddr *>(prev_ps.path.user_data);
       auto data = tx_.data.get();
       auto datalen = bufpos - data - nwrite;
@@ -902,7 +908,7 @@ int Http3Upstream::write_streams() {
       return 0;
     }
 
-    if (++pktcnt == max_pktcnt) {
+    if (++pktcnt == max_pktcnt || static_cast<size_t>(nwrite) < gso_size) {
       auto faddr = static_cast<UpstreamAddr *>(ps.path.user_data);
       auto data = tx_.data.get();
       auto datalen = bufpos - data;