Automated g4 rollback of changelist 666964686. *** Reason for rollback *** b/668502670 Looks like this changes behavior in the flag=false case. *** Original change description *** Allow HTTP/3 requests to have a "host" header, per the RFC *** PiperOrigin-RevId: 668974611

diff --git a/quiche/common/quiche_feature_flags_list.h b/quiche/common/quiche_feature_flags_list.h
index 1ae371f..a1240e5 100755
--- a/quiche/common/quiche_feature_flags_list.h
+++ b/quiche/common/quiche_feature_flags_list.h

@@ -12,7 +12,6 @@
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_act_upon_invalid_header, true, true, "If true, reject or send error response code upon receiving invalid request or response headers.")
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_add_stream_info_to_idle_close_detail, false, true, "If true, include stream information in idle timeout connection close detail.")
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_allow_client_enabled_bbr_v2, true, true, "If true, allow client to enable BBRv2 on server via connection option 'B2ON'.")
-QUICHE_FLAG(bool, quiche_reloadable_flag_quic_allow_host_in_request, false, false, "If true, requests with a host header will be allowed.")
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_bbr2_enable_bbpd_by_default, true, true, "If true, QUIC BBR2 will use a 0.91 PROBE_DOWN gain by default.")
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_bbr2_extra_acked_window, false, true, "When true, the BBR4 copt sets the extra_acked window to 20 RTTs and BBR5 sets it to 40 RTTs.")
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_bbr2_probe_two_rounds, true, true, "When true, the BB2U copt causes BBR2 to wait two rounds with out draining the queue before exiting PROBE_UP and BB2S has the same effect in STARTUP.")

diff --git a/quiche/quic/core/http/quic_spdy_server_stream_base.cc b/quiche/quic/core/http/quic_spdy_server_stream_base.cc
index e53d8b4..0302542 100644
--- a/quiche/quic/core/http/quic_spdy_server_stream_base.cc
+++ b/quiche/quic/core/http/quic_spdy_server_stream_base.cc

@@ -4,7 +4,6 @@
 
 #include "quiche/quic/core/http/quic_spdy_server_stream_base.h"
 
-#include <optional>
 #include <string>
 #include <utility>
 
@@ -15,7 +14,6 @@
 #include "quiche/quic/platform/api/quic_flag_utils.h"
 #include "quiche/quic/platform/api/quic_flags.h"
 #include "quiche/quic/platform/api/quic_logging.h"
-#include "quiche/common/platform/api/quiche_flag_utils.h"
 #include "quiche/common/quiche_text_utils.h"
 
 namespace quic {
@@ -65,9 +63,7 @@
   bool saw_path = false;
   bool saw_scheme = false;
   bool saw_method = false;
-  std::optional<std::string> authority;
-  std::optional<std::string> host;
-
+  bool saw_authority = false;
   bool is_extended_connect = false;
   // Check if it is missing any required headers and if there is any disallowed
   // ones.
@@ -90,14 +86,12 @@
     } else if (pair.first == ":path") {
       saw_path = true;
     } else if (pair.first == ":authority") {
-      authority = pair.second;
+      saw_authority = true;
     } else if (absl::StrContains(pair.first, ":")) {
       set_invalid_request_details(
           absl::StrCat("Unexpected ':' in header ", pair.first, "."));
       QUIC_DLOG(ERROR) << invalid_request_details();
       return false;
-    } else if (pair.first == "host") {
-      host = pair.second;
     }
     if (is_extended_connect) {
       if (!spdy_session()->allow_extended_connect()) {
@@ -116,27 +110,8 @@
     }
   }
 
-  if (GetQuicReloadableFlag(quic_allow_host_in_request)) {
-    // If the :scheme pseudo-header field identifies a scheme that has a
-    // mandatory authority component (including "http" and "https"), the
-    // request MUST contain either an :authority pseudo-header field or a
-    // Host header field. If these fields are present, they MUST NOT be
-    // empty. If both fields are present, they MUST contain the same value.
-    // If the scheme does not have a mandatory authority component and none
-    // is provided in the request target, the request MUST NOT contain the
-    // :authority pseudo-header or Host header fields.
-    //
-    // https://datatracker.ietf.org/doc/html/rfc9114#section-4.3.1
-    QUICHE_RELOADABLE_FLAG_COUNT_N(quic_allow_host_in_request, 2, 3);
-    if (host && (!authority || authority != host)) {
-      QUIC_CODE_COUNT(http3_host_header_does_not_match_authority);
-      set_invalid_request_details("Host header does not match authority");
-      return false;
-    }
-  }
-
   if (is_extended_connect) {
-    if (saw_scheme && saw_path && authority) {
+    if (saw_scheme && saw_path && saw_authority) {
       // Saw all the required pseudo headers.
       return true;
     }
@@ -157,13 +132,10 @@
     return true;
   }
   // Check non-CONNECT request.
-  if (saw_method && authority && saw_path && saw_scheme) {
+  if (saw_method && saw_authority && saw_path && saw_scheme) {
     return true;
   }
-  set_invalid_request_details(
-      absl::StrCat("Missing required pseudo headers. saw_method=", saw_method,
-                   ", authority=", authority.has_value(),
-                   ", saw_path=", saw_path, ", saw_scheme=", saw_scheme));
+  set_invalid_request_details("Missing required pseudo headers.");
   QUIC_DLOG(ERROR) << invalid_request_details();
   return false;
 }

diff --git a/quiche/quic/core/http/quic_spdy_server_stream_base_test.cc b/quiche/quic/core/http/quic_spdy_server_stream_base_test.cc
index ae43178..b136fa7 100644
--- a/quiche/quic/core/http/quic_spdy_server_stream_base_test.cc
+++ b/quiche/quic/core/http/quic_spdy_server_stream_base_test.cc

@@ -289,63 +289,6 @@
   EXPECT_TRUE(stream_->rst_sent());
 }
 
-TEST_F(QuicSpdyServerStreamBaseTest, HostHeaderWithoutAuthority) {
-  SetQuicReloadableFlag(quic_act_upon_invalid_header, true);
-  SetQuicReloadableFlag(quic_allow_host_in_request, true);
-  // A request with host but without authority should be rejected.
-  QuicHeaderList header_list;
-  header_list.OnHeader("host", "www.google.com:4433");
-  header_list.OnHeader(":scheme", "http");
-  header_list.OnHeader(":method", "POST");
-  header_list.OnHeader(":path", "/path");
-  header_list.OnHeaderBlockEnd(128, 128);
-
-  EXPECT_CALL(
-      session_,
-      MaybeSendRstStreamFrame(
-          _, QuicResetStreamError::FromInternal(QUIC_BAD_APPLICATION_PAYLOAD),
-          _));
-  stream_->OnStreamHeaderList(/*fin=*/false, 0, header_list);
-  EXPECT_TRUE(stream_->rst_sent());
-}
-
-TEST_F(QuicSpdyServerStreamBaseTest, HostHeaderWitDifferentAuthority) {
-  SetQuicReloadableFlag(quic_act_upon_invalid_header, true);
-  SetQuicReloadableFlag(quic_allow_host_in_request, true);
-  // A request with host that does not match authority should be rejected.
-  QuicHeaderList header_list;
-  header_list.OnHeader(":authority", "www.google.com:4433");
-  header_list.OnHeader(":scheme", "http");
-  header_list.OnHeader(":method", "POST");
-  header_list.OnHeader(":path", "/path");
-  header_list.OnHeader("host", "mail.google.com:4433");
-  header_list.OnHeaderBlockEnd(128, 128);
-
-  EXPECT_CALL(
-      session_,
-      MaybeSendRstStreamFrame(
-          _, QuicResetStreamError::FromInternal(QUIC_BAD_APPLICATION_PAYLOAD),
-          _));
-  stream_->OnStreamHeaderList(/*fin=*/false, 0, header_list);
-  EXPECT_TRUE(stream_->rst_sent());
-}
-
-TEST_F(QuicSpdyServerStreamBaseTest, ValidHostHeader) {
-  SetQuicReloadableFlag(quic_act_upon_invalid_header, true);
-  SetQuicReloadableFlag(quic_allow_host_in_request, true);
-  // A request with host that matches authority should be accepted.
-  QuicHeaderList header_list;
-  header_list.OnHeader(":authority", "www.google.com:4433");
-  header_list.OnHeader(":scheme", "http");
-  header_list.OnHeader(":method", "POST");
-  header_list.OnHeader(":path", "/path");
-  header_list.OnHeader("host", "www.google.com:4433");
-  header_list.OnHeaderBlockEnd(128, 128);
-
-  stream_->OnStreamHeaderList(/*fin=*/false, 0, header_list);
-  EXPECT_FALSE(stream_->rst_sent());
-}
-
 TEST_F(QuicSpdyServerStreamBaseTest, EmptyHeaders) {
   SetQuicReloadableFlag(quic_act_upon_invalid_header, true);
   quiche::HttpHeaderBlock empty_header;

diff --git a/quiche/quic/core/http/quic_spdy_stream.cc b/quiche/quic/core/http/quic_spdy_stream.cc
index e3e10f2..933cd50 100644
--- a/quiche/quic/core/http/quic_spdy_stream.cc
+++ b/quiche/quic/core/http/quic_spdy_stream.cc

@@ -1787,18 +1787,11 @@
       return false;
     }
     if (name == ":status") {
-      // Note: remove this when deprecating quic_allow_host_in_request.
       is_response = !pair.second.empty();
     }
-    if (name == "host") {
-      if (GetQuicReloadableFlag(quic_allow_host_in_request)) {
-        QUICHE_RELOADABLE_FLAG_COUNT_N(quic_allow_host_in_request, 1, 3);
-        continue;
-      }
-      if (is_response) {
-        // Host header is allowed in response.
-        continue;
-      }
+    if (is_response && name == "host") {
+      // Host header is allowed in response.
+      continue;
     }
     if (http2::GetInvalidHttp2HeaderSet().contains(name)) {
       invalid_request_details_ = absl::StrCat(name, " header is not allowed");

diff --git a/quiche/quic/core/http/quic_spdy_stream_test.cc b/quiche/quic/core/http/quic_spdy_stream_test.cc
index a7efd70..5ede717 100644
--- a/quiche/quic/core/http/quic_spdy_stream_test.cc
+++ b/quiche/quic/core/http/quic_spdy_stream_test.cc

@@ -3520,22 +3520,6 @@
             stream_->invalid_request_details());
 }
 
-TEST_P(QuicSpdyStreamTest, HostHeaderInRequest) {
-  if (!UsesHttp3()) {
-    return;
-  }
-
-  Initialize(kShouldProcessData);
-
-  headers_["host"] = "foo";
-  if (GetQuicReloadableFlag(quic_allow_host_in_request)) {
-    EXPECT_TRUE(stream_->ValidateReceivedHeaders(AsHeaderList(headers_)));
-  } else {
-    EXPECT_FALSE(stream_->ValidateReceivedHeaders(AsHeaderList(headers_)));
-    EXPECT_EQ("host header is not allowed", stream_->invalid_request_details());
-  }
-}
-
 }  // namespace
 }  // namespace test
 }  // namespace quic