http con man: set response flag on downstream protocol error (#8522)

Signed-off-by: Spencer Lewis <slewis@squareup.com>

Mirrored from https://github.com/envoyproxy/envoy @ 6b3df463f5289e13076b9a55d37e289661ed6f42

envoy/config/filter/accesslog/v2/accesslog.proto

@@ -200,6 +200,7 @@ message ResponseFlagFilter {
         in: "URX"
         in: "SI"
         in: "IH"
+        in: "DPE"
       }
     }
   }];

envoy/config/filter/accesslog/v3alpha/accesslog.proto

@@ -200,6 +200,7 @@ message ResponseFlagFilter {
         in: "URX"
         in: "SI"
         in: "IH"
+        in: "DPE"
       }
     }
   }];

envoy/data/accesslog/v2/accesslog.proto

@@ -165,7 +165,7 @@ message AccessLogCommon {
 }
 
 // Flags indicating occurrences during request/response processing.
-// [#next-free-field: 19]
+// [#next-free-field: 20]
 message ResponseFlags {
   message Unauthorized {
     // Reasons why the request was unauthorized
@@ -233,6 +233,9 @@ message ResponseFlags {
   // Indicates that the request was rejected because an envoy request header failed strict
   // validation.
   bool invalid_envoy_request_headers = 18;
+
+  // Indicates there was an HTTP protocol error on the downstream request.
+  bool downstream_protocol_error = 19;
 }
 
 // Properties of a negotiated TLS connection.

envoy/data/accesslog/v3alpha/accesslog.proto

@@ -165,7 +165,7 @@ message AccessLogCommon {
 }
 
 // Flags indicating occurrences during request/response processing.
-// [#next-free-field: 19]
+// [#next-free-field: 20]
 message ResponseFlags {
   message Unauthorized {
     // Reasons why the request was unauthorized
@@ -233,6 +233,9 @@ message ResponseFlags {
   // Indicates that the request was rejected because an envoy request header failed strict
   // validation.
   bool invalid_envoy_request_headers = 18;
+
+  // Indicates there was an HTTP protocol error on the downstream request.
+  bool downstream_protocol_error = 19;
 }
 
 // Properties of a negotiated TLS connection.