From f885c5d6ae763b4e1fda9c89945b2986dcfdad1e Mon Sep 17 00:00:00 2001
From: Eliza Weisman <eliza@buoyant.io>
Date: Mon, 23 Nov 2020 09:56:00 -0800
Subject: [PATCH 1/3] errors: set `content-type` for synthesized grpc errors

The proxy will synthesize responses for some error conditions.
Currently, there's special logic for synthesizing errors for gRPC
requests: we emit `grpc-status` and `grpc-message` trailers rather than
HTTP status codes for gRPC requests. However, we *don't* currently set a
`content-type` header for gRPC error responses. This makes some clients
angry.

This commit adds a `content-type: application/grpc` header to
synthesized error responses for gRPC requests.

Fixes linkerd/linkerd2#5273
---
 linkerd/app/core/src/errors.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/linkerd/app/core/src/errors.rs b/linkerd/app/core/src/errors.rs
index 931909fa64..c35cd780d1 100644
--- a/linkerd/app/core/src/errors.rs
+++ b/linkerd/app/core/src/errors.rs
@@ -200,6 +200,7 @@ impl<RspB: Default + hyper::body::HttpBody> respond::Respond<http::Response<RspB
                     let mut rsp = http::Response::builder()
                         .version(http::Version::HTTP_2)
                         .header(http::header::CONTENT_LENGTH, "0")
+                        .header(http::header::CONTENT_TYPE, "application/grpc")
                         .body(ResponseBody::default())
                         .expect("app::errors response is valid");
                     let code = set_grpc_status(&*error, rsp.headers_mut());

From df95890bb9c2931227d36ac097b34e7297a13a2f Mon Sep 17 00:00:00 2001
From: Eliza Weisman <eliza@buoyant.io>
Date: Mon, 23 Nov 2020 10:21:42 -0800
Subject: [PATCH 2/3] you know what, let's make it a const

Signed-off-by: Eliza Weisman <eliza@buoyant.io>
---
 linkerd/app/core/src/errors.rs | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/linkerd/app/core/src/errors.rs b/linkerd/app/core/src/errors.rs
index c35cd780d1..a8131df375 100644
--- a/linkerd/app/core/src/errors.rs
+++ b/linkerd/app/core/src/errors.rs
@@ -68,6 +68,8 @@ pub enum ResponseBody<B> {
     },
 }
 
+const GRPC_CONTENT_TYPE: &'static str = "application/grpc";
+
 impl<B: hyper::body::HttpBody> hyper::body::HttpBody for ResponseBody<B>
 where
     B::Error: Into<Error>,
@@ -149,7 +151,7 @@ impl<ReqB, RspB: Default + hyper::body::HttpBody>
                 let is_grpc = req
                     .headers()
                     .get(http::header::CONTENT_TYPE)
-                    .and_then(|v| v.to_str().ok().map(|s| s.starts_with("application/grpc")))
+                    .and_then(|v| v.to_str().ok().map(|s| s.starts_with("GRPC_CONTENT_TYPE")))
                     .unwrap_or(false);
                 Respond {
                     is_grpc,
@@ -200,7 +202,7 @@ impl<RspB: Default + hyper::body::HttpBody> respond::Respond<http::Response<RspB
                     let mut rsp = http::Response::builder()
                         .version(http::Version::HTTP_2)
                         .header(http::header::CONTENT_LENGTH, "0")
-                        .header(http::header::CONTENT_TYPE, "application/grpc")
+                        .header(http::header::CONTENT_TYPE, GRPC_CONTENT_TYPE)
                         .body(ResponseBody::default())
                         .expect("app::errors response is valid");
                     let code = set_grpc_status(&*error, rsp.headers_mut());

From 3c809576949794334a35d996eb603a9f37a3cb1b Mon Sep 17 00:00:00 2001
From: Eliza Weisman <eliza@buoyant.io>
Date: Mon, 23 Nov 2020 11:18:08 -0800
Subject: [PATCH 3/3] Update linkerd/app/core/src/errors.rs

---
 linkerd/app/core/src/errors.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/linkerd/app/core/src/errors.rs b/linkerd/app/core/src/errors.rs
index a8131df375..c4f17c5775 100644
--- a/linkerd/app/core/src/errors.rs
+++ b/linkerd/app/core/src/errors.rs
@@ -151,7 +151,7 @@ impl<ReqB, RspB: Default + hyper::body::HttpBody>
                 let is_grpc = req
                     .headers()
                     .get(http::header::CONTENT_TYPE)
-                    .and_then(|v| v.to_str().ok().map(|s| s.starts_with("GRPC_CONTENT_TYPE")))
+                    .and_then(|v| v.to_str().ok().map(|s| s.starts_with(GRPC_CONTENT_TYPE)))
                     .unwrap_or(false);
                 Respond {
                     is_grpc,