[PATCH proxmox v3 3/5] rest-server: connection: log cause of TLS handshake check errors

["Max R. Carrara" <m.carrara@proxmox.com>]

Errors from checking for a TLS handshake were logged with only their
outermost context, which hid the underlying OS error. For example, a
failed peek was only reported as "couldn't peek into incoming TCP
stream", without saying why it failed.

Log the whole error chain on a single line instead, so that the actual
reason shows up in the logs.

Also, do not keep the error from `tokio::time::timeout` in the error
context, because it doesn't tell us any additional information.

Signed-off-by: Max R. Carrara <m.carrara@proxmox.com>
---
 proxmox-rest-server/src/connection.rs | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/proxmox-rest-server/src/connection.rs b/proxmox-rest-server/src/connection.rs
index 00ee771b..9b3c1371 100644
--- a/proxmox-rest-server/src/connection.rs
+++ b/proxmox-rest-server/src/connection.rs
@@ -489,11 +489,11 @@ impl AcceptBuilder {
                         "[{peer}] failed to accept connection - connection channel closed: {send_err}"
                     );
                 }
             }
             Err(err) => {
-                log::error!("[{peer}] failed to check for TLS handshake: {err}");
+                log::error!("[{peer}] failed to check for TLS handshake: {err:#}");
             }
         }
     }
 
     async fn wait_for_client_tls_handshake(
@@ -550,13 +550,15 @@ impl AcceptBuilder {
                 })
                 .await
                 .context("couldn't peek into incoming TCP stream")
         };
 
-        tokio::time::timeout(timeout, future)
-            .await
-            .context("timed out while waiting for client to initiate TLS handshake")?
+        // The elapsed error carries no information beyond the timeout itself, so do not keep it as
+        // the cause.
+        tokio::time::timeout(timeout, future).await.map_err(|_| {
+            format_err!("timed out while waiting for client to initiate TLS handshake")
+        })?
     }
 }
 
 /// Checks whether an [SSL 3.0 / TLS plaintext fragment][0] being part of a
 /// SSL / TLS handshake is contained in the given buffer.
@@ -654,11 +656,11 @@ mod tests {
 
     fn assert_timeout_error(result: Result<TlsHandshakeCheck, Error>) {
         let err = result.expect_err("check must time out");
         assert_eq!(
             format!("{err:#}"),
-            "timed out while waiting for client to initiate TLS handshake: deadline has elapsed",
+            "timed out while waiting for client to initiate TLS handshake",
         );
     }
 
     #[tokio::test]
     async fn a_tls_client_is_detected() {
-- 
2.47.3