From f636eec33bc8bcdbdb7d8597422236c2611a868b Mon Sep 17 00:00:00 2001
From: unkn0wn-root <unkn0wn_root@tuta.io>
Date: Sat, 4 Jan 2025 20:48:34 +0100
Subject: [PATCH] fix(proxy): handle client disconnect from round tripper using
 proxy error

---
 internal/pool/errors.go | 14 +++++++-------
 internal/pool/proxy.go  | 10 +++++++---
 2 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/internal/pool/errors.go b/internal/pool/errors.go
index efca01f..e2a760b 100644
--- a/internal/pool/errors.go
+++ b/internal/pool/errors.go
@@ -24,6 +24,13 @@ const (
 	RetryAfterSec = 5
 )
 
+// ErrorResponse represents the structure of error responses sent to clients
+type ErrorResponse struct {
+	Status     string `json:"status"`
+	Message    string `json:"message"`
+	RetryAfter int    `json:"retry_after,omitempty"`
+}
+
 // ProxyErrorCode represents specific error conditions in the proxy
 type ProxyErrorCode int
 
@@ -189,13 +196,6 @@ func NewProxyError(op string, err error) *ProxyError {
 	return pe
 }
 
-// ErrorResponse represents the structure of error responses sent to clients
-type ErrorResponse struct {
-	Status     string `json:"status"`
-	Message    string `json:"message"`
-	RetryAfter int    `json:"retry_after,omitempty"`
-}
-
 // WriteErrorResponse writes a structured error response to the client
 func WriteErrorResponse(w http.ResponseWriter, err error) {
 	var pe *ProxyError
diff --git a/internal/pool/proxy.go b/internal/pool/proxy.go
index 73b7bdb..4f3ca8f 100644
--- a/internal/pool/proxy.go
+++ b/internal/pool/proxy.go
@@ -1,7 +1,6 @@
 package pool
 
 import (
-	"context"
 	"crypto/tls"
 	"errors"
 	"fmt"
@@ -242,10 +241,15 @@ func (p *URLRewriteProxy) errorHandler(w http.ResponseWriter, r *http.Request, e
 	// so as for Go 1.23 this is still an issue and we have to live with it
 	// We don't want to overflow logs with this error as this can happen quite often
 	// so we just ignore it for now until Go team provide a better solution
-	if errors.Is(err, context.Canceled) {
-		return
+	var proxyErr *ProxyError
+	if errors.As(err, &proxyErr) {
+		if proxyErr.Code == ErrCodeClientDisconnect {
+			return
+		}
 	}
 
+	// log every error even if error could be non-proxy
+	// WriteErrorResponse will handle all non-proxy errors but it should not happen (just in case)
 	p.logger.Error("Proxy error",
 		zap.Error(err),
 		zap.String("method", r.Method),