http: fix etag cache scoping

Currently the lookup from previous local etags was based on
filename. This leads to possibility where (misbehaving) server
may reuse the same eTag for different URLs. While using only
the filename might theoretically create more cache matches when
the same file is used via multiple URLs, I think was accidental
mistake and not intentional.

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

client/client_test.go

@@ -104,6 +104,7 @@ var allTests = []func(t *testing.T, sb integration.Sandbox){
 	testCallDiskUsage,
 	testBuildMultiMount,
 	testBuildHTTPSource,
+	testBuildHTTPSourceEtagScope,
 	testBuildPushAndValidate,
 	testBuildExportWithUncompressed,
 	testBuildExportScratch,
@@ -2769,6 +2770,104 @@ func testBuildHTTPSource(t *testing.T, sb integration.Sandbox) {
 	// TODO: check that second request was marked as cached
 }
 
+// docker/buildx#2803
+func testBuildHTTPSourceEtagScope(t *testing.T, sb integration.Sandbox) {
+	integration.SkipOnPlatform(t, "windows")
+	c, err := New(sb.Context(), sb.Address())
+	require.NoError(t, err)
+	defer c.Close()
+
+	modTime := time.Now().Add(-24 * time.Hour) // avoid falso positive with current time
+
+	sharedEtag := identity.NewID()
+	resp := httpserver.Response{
+		Etag:         sharedEtag,
+		Content:      []byte("content1"),
+		LastModified: &modTime,
+	}
+	resp2 := httpserver.Response{
+		Etag:         sharedEtag,
+		Content:      []byte("another"),
+		LastModified: &modTime,
+	}
+
+	server := httpserver.NewTestServer(map[string]httpserver.Response{
+		"/one/foo": resp,
+		"/two/foo": resp2,
+	})
+	defer server.Close()
+
+	// first correct request
+	st := llb.HTTP(server.URL + "/one/foo")
+
+	def, err := st.Marshal(sb.Context())
+	require.NoError(t, err)
+
+	out1 := t.TempDir()
+	_, err = c.Solve(sb.Context(), def, SolveOpt{
+		Exports: []ExportEntry{
+			{
+				Type:      ExporterLocal,
+				OutputDir: out1,
+			},
+		},
+	}, nil)
+	require.NoError(t, err)
+
+	require.Equal(t, 1, server.Stats("/one/foo").AllRequests)
+	require.Equal(t, 0, server.Stats("/one/foo").CachedRequests)
+
+	dt, err := os.ReadFile(filepath.Join(out1, "foo"))
+	require.NoError(t, err)
+	require.Equal(t, []byte("content1"), dt)
+
+	st = llb.HTTP(server.URL + "/two/foo")
+
+	def, err = st.Marshal(sb.Context())
+	require.NoError(t, err)
+
+	out2 := t.TempDir()
+	_, err = c.Solve(sb.Context(), def, SolveOpt{
+		Exports: []ExportEntry{
+			{
+				Type:      ExporterLocal,
+				OutputDir: out2,
+			},
+		},
+	}, nil)
+	require.NoError(t, err)
+
+	require.Equal(t, 1, server.Stats("/two/foo").AllRequests)
+	require.Equal(t, 0, server.Stats("/two/foo").CachedRequests)
+
+	dt, err = os.ReadFile(filepath.Join(out2, "foo"))
+	require.NoError(t, err)
+	require.Equal(t, []byte("another"), dt)
+
+	out2 = t.TempDir()
+	_, err = c.Solve(sb.Context(), def, SolveOpt{
+		Exports: []ExportEntry{
+			{
+				Type:      ExporterLocal,
+				OutputDir: out2,
+			},
+		},
+	}, nil)
+	require.NoError(t, err)
+
+	require.Equal(t, 2, server.Stats("/two/foo").AllRequests)
+	require.Equal(t, 1, server.Stats("/two/foo").CachedRequests)
+
+	allReqs := server.Stats("/two/foo").Requests
+	require.Equal(t, 2, len(allReqs))
+	require.Equal(t, http.MethodGet, allReqs[0].Method)
+	require.Equal(t, "gzip", allReqs[0].Header.Get("Accept-Encoding"))
+	require.Equal(t, http.MethodHead, allReqs[1].Method)
+	require.Equal(t, "gzip", allReqs[1].Header.Get("Accept-Encoding"))
+
+	require.NoError(t, os.RemoveAll(filepath.Join(out2, "foo")))
+}
+
 func testResolveAndHosts(t *testing.T, sb integration.Sandbox) {
 	requiresLinux(t)
 	c, err := New(sb.Context(), sb.Address())

source/http/source.go

@@ -1,6 +1,7 @@
 package http
 
 import (
+	"bytes"
 	"context"
 	"crypto/sha256"
 	"encoding/json"
@@ -126,13 +127,16 @@ func (hs *httpSourceHandler) client(g session.Group) *http.Client {
 // this package.
 func (hs *httpSourceHandler) urlHash() (digest.Digest, error) {
 	dt, err := json.Marshal(struct {
-		Filename       string
+		Filename       []byte
 		Perm, UID, GID int
 	}{
-		Filename: getFileName(hs.src.URL, hs.src.Filename, nil),
-		Perm:     hs.src.Perm,
-		UID:      hs.src.UID,
-		GID:      hs.src.GID,
+		Filename: bytes.Join([][]byte{
+			[]byte(hs.src.URL),
+			[]byte(hs.src.Filename),
+		}, []byte{0}),
+		Perm: hs.src.Perm,
+		UID:  hs.src.UID,
+		GID:  hs.src.GID,
 	})
 	if err != nil {
 		return "", err