net/http: ignore the Unix epoch time in ServeContent

ServeContent ignored zero time.Time{} values when generating Last-Modified response headers and checking If-Modified-Since request headers. Do the same for a time.Time representing the Unix epoch zero value, as this is a common bogus value. Callers who really want to send that value (incredibly unlikely) can add a nanosecond to it and it will be truncated to second granularity anyway. Fixes #9842 Change-Id: I69f697bfc4017404a92a34e3fe57e2711c1e299d Reviewed-on: https://go-review.googlesource.com/7915 Reviewed-by: David Symonds <dsymonds@golang.org>
golang · Mar 23, 2015 · a0fb8f8 · a0fb8f8
1 parent 25bf792
commit a0fb8f8
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Showing 2 changed files with 16 additions and 5 deletions.
diff --git a/src/net/http/fs.go b/src/net/http/fs.go
@@ -102,10 +102,10 @@ func dirList(w ResponseWriter, f File) {
 // The name is otherwise unused; in particular it can be empty and is
 // never sent in the response.
 //
-// If modtime is not the zero time, ServeContent includes it in a
-// Last-Modified header in the response.  If the request includes an
-// If-Modified-Since header, ServeContent uses modtime to decide
-// whether the content needs to be sent at all.
+// If modtime is not the zero time or Unix epoch, ServeContent
+// includes it in a Last-Modified header in the response.  If the
+// request includes an If-Modified-Since header, ServeContent uses
+// modtime to decide whether the content needs to be sent at all.
 //
 // The content's Seek method must work: ServeContent uses
 // a seek to the end of the content to determine its size.
@@ -258,10 +258,15 @@ func serveContent(w ResponseWriter, r *Request, name string, modtime time.Time,
 	}
 }
 
+var unixEpochTime = time.Unix(0, 0)
+
 // modtime is the modification time of the resource to be served, or IsZero().
 // return value is whether this request is now complete.
 func checkLastModified(w ResponseWriter, r *Request, modtime time.Time) bool {
-	if modtime.IsZero() {
+	if modtime.IsZero() || modtime.Equal(unixEpochTime) {
+		// If the file doesn't have a modtime (IsZero), or the modtime
+		// is obviously garbage (Unix time == 0), then ignore modtimes
+		// and don't process the If-Modified-Since header.
 		return false
 	}
 

diff --git a/src/net/http/fs_test.go b/src/net/http/fs_test.go
@@ -751,6 +751,12 @@ func TestServeContent(t *testing.T) {
 			wantContentType: "text/css; charset=utf-8",
 			wantLastMod:     "Wed, 25 Jun 2014 17:12:18 GMT",
 		},
+		"unix_zero_modtime": {
+			content:         strings.NewReader("<html>foo"),
+			modtime:         time.Unix(0, 0),
+			wantStatus:      StatusOK,
+			wantContentType: "text/html; charset=utf-8",
+		},
 	}
 	for testName, tt := range tests {
 		var content io.ReadSeeker