Disable HTTP2 for S3 backend with ?disable_http2=true option

s3/client.go

@@ -62,17 +62,10 @@ type Client struct {
 func New(config *Config) *Client {
 	httpClient := config.HTTPClient
 	if httpClient == nil {
-		// Force HTTP/1.1 to avoid HTTP/2 stream errors with S3-compatible providers
-		// (e.g. DigitalOcean Spaces). HTTP/2 can cause non-retryable failures on
-		// streaming uploads when the server resets the stream mid-transfer.
-		httpClient = &http.Client{
-			Transport: &http.Transport{
-				TLSClientConfig: &tls.Config{
-					MinVersion: tls.VersionTLS12,
-				},
-				ForceAttemptHTTP2: false,
-				TLSNextProto:      make(map[string]func(string, *tls.Conn) http.RoundTripper),
-			},
+		if config.DisableHTTP2 {
+			httpClient = newHTTP1Client()
+		} else {
+			httpClient = http.DefaultClient
 		}
 	}
 	return &Client{
@@ -312,3 +305,20 @@ func (c *Client) do(ctx context.Context, op, method, reqURL string, body []byte,
 	}
 	return respBody, nil
 }
+
+// newHTTP1Client creates an HTTP client that forces HTTP/1.1 by disabling HTTP/2
+// ALPN negotiation. This works around HTTP/2 stream errors with some S3-compatible
+// providers (e.g. DigitalOcean Spaces) that can cause non-retryable failures on
+// streaming uploads when the server resets the stream mid-transfer.
+// See https://github.com/rclone/rclone/issues/4673, https://github.com/golang/go/issues/42777
+func newHTTP1Client() *http.Client {
+	return &http.Client{
+		Transport: &http.Transport{
+			TLSClientConfig: &tls.Config{
+				MinVersion: tls.VersionTLS12,
+			},
+			ForceAttemptHTTP2: false,
+			TLSNextProto:      make(map[string]func(string, *tls.Conn) http.RoundTripper),
+		},
+	}
+}

s3/client_test.go

@@ -92,6 +92,18 @@ func TestParseURL_EmptyBucket(t *testing.T) {
 	require.Contains(t, err.Error(), "bucket")
 }
 
+func TestParseURL_DisableHTTP2(t *testing.T) {
+	cfg, err := ParseURL("s3://AKID:SECRET@my-bucket?region=us-east-1&disable_http2=true")
+	require.Nil(t, err)
+	require.True(t, cfg.DisableHTTP2)
+}
+
+func TestParseURL_DisableHTTP2_NotSet(t *testing.T) {
+	cfg, err := ParseURL("s3://AKID:SECRET@my-bucket?region=us-east-1")
+	require.Nil(t, err)
+	require.False(t, cfg.DisableHTTP2)
+}
+
 // --- Unit tests: URL construction ---
 
 func TestConfig_BucketURL_PathStyle(t *testing.T) {

s3/types.go

@@ -11,14 +11,15 @@ import (
 
 // Config holds the parsed fields from an S3 URL. Use ParseURL to create one from a URL string.
 type Config struct {
-	Endpoint   string // host[:port] only, e.g. "s3.us-east-1.amazonaws.com"
-	PathStyle  bool
-	Bucket     string
-	Prefix     string
-	Region     string
-	AccessKey  string
-	SecretKey  string
-	HTTPClient *http.Client // if nil, http.DefaultClient is used
+	Endpoint     string // host[:port] only, e.g. "s3.us-east-1.amazonaws.com"
+	PathStyle    bool
+	Bucket       string
+	Prefix       string
+	Region       string
+	AccessKey    string
+	SecretKey    string
+	DisableHTTP2 bool         // Force HTTP/1.1 to work around HTTP/2 issues with some S3-compatible providers
+	HTTPClient   *http.Client // if nil, a default client is created (respecting DisableHTTP2)
 }
 
 // BucketURL returns the base URL for bucket-level operations.

s3/util.go

@@ -10,6 +10,7 @@ import (
 	"net/http"
 	"net/url"
 	"sort"
+	"strconv"
 	"strings"
 )
 
@@ -41,9 +42,11 @@ const (
 
 // ParseURL parses an S3 URL of the form:
 //
-//	s3://ACCESS_KEY:SECRET_KEY@BUCKET[/PREFIX]?region=REGION[&endpoint=ENDPOINT]
+//	s3://ACCESS_KEY:SECRET_KEY@BUCKET[/PREFIX]?region=REGION[&endpoint=ENDPOINT][&disable_http2=true]
 //
 // When endpoint is specified, path-style addressing is enabled automatically.
+// When disable_http2=true is set, the client forces HTTP/1.1 to work around
+// HTTP/2 stream errors with some S3-compatible providers (e.g. DigitalOcean Spaces).
 func ParseURL(s3URL string) (*Config, error) {
 	u, err := url.Parse(s3URL)
 	if err != nil {
@@ -80,14 +83,16 @@ func ParseURL(s3URL string) (*Config, error) {
 		endpoint = fmt.Sprintf("s3.%s.amazonaws.com", region)
 		pathStyle = false
 	}
+	disableHTTP2, _ := strconv.ParseBool(u.Query().Get("disable_http2"))
 	return &Config{
-		Endpoint:  endpoint,
-		PathStyle: pathStyle,
-		Bucket:    bucket,
-		Prefix:    prefix,
-		Region:    region,
-		AccessKey: accessKey,
-		SecretKey: secretKey,
+		Endpoint:     endpoint,
+		PathStyle:    pathStyle,
+		Bucket:       bucket,
+		Prefix:       prefix,
+		Region:       region,
+		AccessKey:    accessKey,
+		SecretKey:    secretKey,
+		DisableHTTP2: disableHTTP2,
 	}, nil
 }