net/http: add MaxBytesError
Fixes #30715
Change-Id: Ia3712d248b6dc86abef71ccea6e705a571933d53
GitHub-Last-Rev: 6ae68402a5a7c57f7f18e945d48c69ba2b134078
GitHub-Pull-Request: golang/go#49359
Reviewed-on: https://go-review.googlesource.com/c/go/+/361397
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Damien Neil <dneil@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
diff --git a/api/next/30715.txt b/api/next/30715.txt
new file mode 100644
index 0000000..077a8d1
--- /dev/null
+++ b/api/next/30715.txt
@@ -0,0 +1,3 @@
+pkg net/http, type MaxBytesError struct #30715
+pkg net/http, type MaxBytesError struct, Limit int64 #30715
+pkg net/http, method (*MaxBytesError) Error() string #30715
diff --git a/src/net/http/request.go b/src/net/http/request.go
index 3122119..d091f3c 100644
--- a/src/net/http/request.go
+++ b/src/net/http/request.go
@@ -1126,21 +1126,34 @@
// MaxBytesReader is similar to io.LimitReader but is intended for
// limiting the size of incoming request bodies. In contrast to
// io.LimitReader, MaxBytesReader's result is a ReadCloser, returns a
-// non-EOF error for a Read beyond the limit, and closes the
+// MaxBytesError for a Read beyond the limit, and closes the
// underlying reader when its Close method is called.
//
// MaxBytesReader prevents clients from accidentally or maliciously
-// sending a large request and wasting server resources.
+// sending a large request and wasting server resources. If possible,
+// it tells the ResponseWriter to close the connection after the limit
+// has been reached.
func MaxBytesReader(w ResponseWriter, r io.ReadCloser, n int64) io.ReadCloser {
if n < 0 { // Treat negative limits as equivalent to 0.
n = 0
}
- return &maxBytesReader{w: w, r: r, n: n}
+ return &maxBytesReader{w: w, r: r, i: n, n: n}
+}
+
+// MaxBytesError is returned by MaxBytesReader when its read limit is exceeded.
+type MaxBytesError struct {
+ Limit int64
+}
+
+func (e *MaxBytesError) Error() string {
+ // Due to Hyrum's law, this text cannot be changed.
+ return "http: request body too large"
}
type maxBytesReader struct {
w ResponseWriter
r io.ReadCloser // underlying reader
+ i int64 // max bytes initially, for MaxBytesError
n int64 // max bytes remaining
err error // sticky error
}
@@ -1182,7 +1195,7 @@
if res, ok := l.w.(requestTooLarger); ok {
res.requestTooLarge()
}
- l.err = errors.New("http: request body too large")
+ l.err = &MaxBytesError{l.i}
return n, l.err
}
diff --git a/src/net/http/serve_test.go b/src/net/http/serve_test.go
index 1c85a66..404cca0 100644
--- a/src/net/http/serve_test.go
+++ b/src/net/http/serve_test.go
@@ -3035,6 +3035,13 @@
if n != limit {
t.Errorf("io.Copy = %d, want %d", n, limit)
}
+ mbErr, ok := err.(*MaxBytesError)
+ if !ok {
+ t.Errorf("expected MaxBytesError, got %T", err)
+ }
+ if mbErr.Limit != limit {
+ t.Errorf("MaxBytesError.Limit = %d, want %d", mbErr.Limit, limit)
+ }
}))
defer cst.close()
