From f75e79047a527ff756b47e54398de5e299f93680 Mon Sep 17 00:00:00 2001
From: jyxjjj <773933146@qq.com>
Date: Sun, 20 Sep 2026 00:55:25 +0800
Subject: [PATCH] fix(webdav): stabilize fallback ETags

- Use second-precision modification times for reproducible fallback ETags
- Cover ETag stability across cache refresh timestamp normalization

Co-authored-by: Codex <267193182+codex@users.noreply.github.com>
Signed-off-by: jyxjjj <16695261+jyxjjj@users.noreply.github.com>
---
 server/common/etag_test.go | 21 +++++++++++----------
 server/common/proxy.go     |  5 +++--
 2 files changed, 14 insertions(+), 12 deletions(-)

diff --git a/server/common/etag_test.go b/server/common/etag_test.go
index d80d6deb8..d4784727e 100644
--- a/server/common/etag_test.go
+++ b/server/common/etag_test.go
@@ -8,18 +8,19 @@ import (
 	"github.com/OpenListTeam/OpenList/v4/pkg/utils"
 )
 
-func TestGetEtagSubsecondChanges(t *testing.T) {
-	file := &model.Object{Size: 4, Modified: time.Unix(1700000000, 100)}
-	before := GetEtag(file, file.Size)
-	if got := GetEtag(file, file.Size); got != before {
-		t.Fatalf("unchanged file ETag = %q, want %q", got, before)
+func TestGetEtagStableAcrossCacheRefresh(t *testing.T) {
+	uploaded := &model.Object{Size: 4, Modified: time.Unix(1700000000, 123456789)}
+	before := GetEtag(uploaded, uploaded.Size)
+	refreshed := &model.Object{Size: uploaded.Size, Modified: time.Unix(1700000000, 0)}
+	if got := GetEtag(refreshed, refreshed.Size); got != before {
+		t.Fatalf("refreshed file ETag = %q, want %q", got, before)
 	}
-	file.Modified = file.Modified.Add(time.Nanosecond)
-	if got := GetEtag(file, file.Size); got == before {
-		t.Errorf("same-size overwrite within one second retained ETag %q", got)
+	refreshed.Modified = refreshed.Modified.Add(time.Second)
+	if got := GetEtag(refreshed, refreshed.Size); got == before {
+		t.Errorf("changed modification second retained ETag %q", got)
 	}
-	file.Modified = file.Modified.Add(-time.Nanosecond)
-	if got := GetEtag(file, file.Size+1); got == before {
+	refreshed.Modified = uploaded.Modified
+	if got := GetEtag(refreshed, refreshed.Size+1); got == before {
 		t.Errorf("changed size retained ETag %q", got)
 	}
 }
diff --git a/server/common/proxy.go b/server/common/proxy.go
index b67aaa43b..5579eeca1 100644
--- a/server/common/proxy.go
+++ b/server/common/proxy.go
@@ -97,8 +97,9 @@ func GetEtag(file model.Obj, size int64) string {
 	if len(hash) > 0 {
 		return fmt.Sprintf(`"%s"`, hash)
 	}
-	// Preserve sub-second changes when files of the same size are overwritten.
-	return fmt.Sprintf(`"%x-%x"`, file.ModTime().UnixNano(), size)
+	// Storage backends may not preserve sub-second timestamps across cache
+	// refreshes, so only use the reproducible second precision here.
+	return fmt.Sprintf(`"%x-%x"`, file.ModTime().Unix(), size)
 }
 
 func ProxyRange(ctx context.Context, link *model.Link, size int64) *model.Link {