volume: check If-None-Match before If-Modified-Since and match ETag lists (#12027)

* filer: match If-Match and If-None-Match against "*" and ETag lists

checkPreconditions compared the whole header as one ETag, so "*", a
list of ETags and a weak W/ tag in If-None-Match never matched
(RFC 9110 13.1.1, 13.1.2).

* volume: check If-None-Match before If-Modified-Since and match ETag lists

A volume GET answered 304 from If-Modified-Since even when If-None-Match
named a different ETag, and compared If-None-Match as one exact string,
so "*", lists and weak tags never matched (RFC 9110 13.1.2, 13.2.2).

* filer: split etag lists only outside quoted tags

A comma inside a quoted opaque tag is a legal etagc, not a list
separator; strings.Split cut such tags into fragments that
CanonicalizeETag could turn into a false match.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

* filer: match repeated If-Match and If-None-Match header lines

Header.Get reads only the first field line, so a match on a later
repeated header was missed; join all field values like any other
comma-separated list.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

* volume: match repeated If-None-Match header lines

Header.Get reads only the first field line; join all field values so a
match on a later repeated header is seen. Also covers a comma inside a
quoted opaque tag.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

* volume: send the etag on a 304 like the filer does

RFC 9110 15.4.5 lists ETag among the fields a 304 must carry when a 200
would send it; SetEtag now runs before the notModified check.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

* volume: mirror the conditional-GET fixes in the rust server

not_modified_response now checks If-None-Match before If-Modified-Since,
matches "*", weak tags, quoted commas and repeated field lines through
the same list rules, and sends the etag on a 304.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

* volume: treat an empty If-None-Match like the Go server does

* filer: ignore empty elements in etag precondition lists

* volume: ignore empty elements in etag lists like the filer

* filer: let a present-but-empty precondition line suppress the date check

* volume: gate If-Modified-Since on a present If-None-Match line

* volume: gate If-Modified-Since on header presence like the Go server

---------

Co-authored-by: user.email <chrislusf@users.noreply.github.com>
Co-authored-by: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>
Co-authored-by: chrislusf <chris.lu@gmail.com>

weed/server/volume_server_handlers_read.go

@@ -149,6 +149,20 @@ func (vs *VolumeServer) proxyReqToTargetServer(w http.ResponseWriter, r *http.Re
 	}
 }
 
+// notModified checks If-Modified-Since only when there is no If-None-Match
+// (RFC 9110 13.2.2).
+func notModified(r *http.Request, etag string, lastModified uint64) bool {
+	if inm := r.Header.Values("If-None-Match"); len(inm) != 0 {
+		return etagListMatches(strings.Join(inm, ","), etag, true)
+	}
+	ims := r.Header.Get("If-Modified-Since")
+	if ims == "" || lastModified == 0 {
+		return false
+	}
+	t, err := time.Parse(http.TimeFormat, ims)
+	return err == nil && t.Unix() >= int64(lastModified)
+}
+
 func (vs *VolumeServer) GetOrHeadHandler(w http.ResponseWriter, r *http.Request) {
 	n := new(needle.Needle)
 	vid, fid, filename, ext, _ := parseURLPath(r.URL.Path)
@@ -244,21 +258,9 @@ func (vs *VolumeServer) GetOrHeadHandler(w http.ResponseWriter, r *http.Request)
 	}
 	if n.LastModified != 0 {
 		w.Header().Set("Last-Modified", time.Unix(int64(n.LastModified), 0).UTC().Format(http.TimeFormat))
-		if r.Header.Get("If-Modified-Since") != "" {
-			if t, parseError := time.Parse(http.TimeFormat, r.Header.Get("If-Modified-Since")); parseError == nil {
-				if t.Unix() >= int64(n.LastModified) {
-					if readOption.IsMetaOnly {
-						if v := vs.store.GetVolume(volumeId); v != nil {
-							v.NoteMetaOnlySuccess()
-						}
-					}
-					w.WriteHeader(http.StatusNotModified)
-					return
-				}
-			}
-		}
 	}
-	if inm := r.Header.Get("If-None-Match"); inm == "\""+n.Etag()+"\"" {
+	SetEtag(w, n.Etag())
+	if notModified(r, n.Etag(), n.LastModified) {
 		if readOption.IsMetaOnly {
 			if v := vs.store.GetVolume(volumeId); v != nil {
 				v.NoteMetaOnlySuccess()
@@ -267,7 +269,6 @@ func (vs *VolumeServer) GetOrHeadHandler(w http.ResponseWriter, r *http.Request)
 		w.WriteHeader(http.StatusNotModified)
 		return
 	}
-	SetEtag(w, n.Etag())
 
 	if n.HasPairs() {
 		pairMap := make(map[string]string)

weed/server/volume_server_handlers_read_test.go

@@ -6,6 +6,7 @@ import (
 	"net/http/httptest"
 	"strings"
 	"testing"
+	"time"
 )
 
 func TestInternalErrorWritesTheReadError(t *testing.T) {
@@ -59,3 +60,39 @@ func TestShouldAttemptStreamWrite(t *testing.T) {
 		}
 	}
 }
+
+func TestNotModifiedChecksIfNoneMatchFirst(t *testing.T) {
+	const etag = "353dd8be"
+	const lastModified = 1700000000
+	before := time.Unix(lastModified-60, 0).UTC().Format(http.TimeFormat)
+	after := time.Unix(lastModified+60, 0).UTC().Format(http.TimeFormat)
+
+	tests := []struct {
+		name    string
+		headers [][2]string
+		want    bool
+	}{
+		{"matching etag", [][2]string{{"If-None-Match", `"353dd8be"`}}, true},
+		{"weak etag", [][2]string{{"If-None-Match", `W/"353dd8be"`}}, true},
+		{"etag in a list", [][2]string{{"If-None-Match", `"x", "353dd8be"`}}, true},
+		{"star", [][2]string{{"If-None-Match", `*`}}, true},
+		{"other etag", [][2]string{{"If-None-Match", `"x"`}}, false},
+		{"etag across repeated lines", [][2]string{{"If-None-Match", `"x"`}, {"If-None-Match", `"353dd8be"`}}, true},
+		{"comma inside quotes", [][2]string{{"If-None-Match", `"353dd8be,old"`}}, false},
+		{"other etag ignores If-Modified-Since", [][2]string{{"If-None-Match", `"x"`}, {"If-Modified-Since", after}}, false},
+		{"empty If-None-Match ignores If-Modified-Since", [][2]string{{"If-None-Match", ``}, {"If-Modified-Since", after}}, false},
+		{"not modified since", [][2]string{{"If-Modified-Since", after}}, true},
+		{"modified since", [][2]string{{"If-Modified-Since", before}}, false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			r := httptest.NewRequest(http.MethodGet, "/3,01637037d6", nil)
+			for _, kv := range tt.headers {
+				r.Header.Add(kv[0], kv[1])
+			}
+			if got := notModified(r, etag, lastModified); got != tt.want {
+				t.Errorf("notModified = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}