From b963149d4eddaf92d9e2a9d3bf5474c2d0a3b55d Mon Sep 17 00:00:00 2001 From: Alex Brainman Date: Mon, 22 Jul 2019 19:09:33 +1000 Subject: [PATCH] net: do not call Windows TransmitFile for large files TransmitFile does not allow for number of bytes that can be transmitted to be larger than 2147483646. See https://docs.microsoft.com/en-us/windows/win32/api/mswsock/nf-mswsock-transmitfile for details. So adjust sendFile accordingly. No test added, because this would require creating large file (more than 2GB file). Fixes #33193. Change-Id: I82e0cb104d112264e4ea363bb20b6d02ac30b38e Reviewed-on: https://go-review.googlesource.com/c/go/+/187037 Run-TryBot: Alex Brainman TryBot-Result: Gobot Gobot Reviewed-by: Emmanuel Odeke --- src/net/sendfile_windows.go | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/src/net/sendfile_windows.go b/src/net/sendfile_windows.go index bccd8b149f..a223e2562e 100644 --- a/src/net/sendfile_windows.go +++ b/src/net/sendfile_windows.go @@ -29,6 +29,13 @@ func sendFile(fd *netFD, r io.Reader) (written int64, err error, handled bool) { if n <= 0 { return 0, nil, true } + // TransmitFile can be invoked in one call with at most + // 2,147,483,646 bytes: the maximum value for a 32-bit integer minus 1. + // See https://docs.microsoft.com/en-us/windows/win32/api/mswsock/nf-mswsock-transmitfile + const maxSendBytes = 0x7fffffff - 1 + if n > maxSendBytes { + return 0, nil, false + } } f, ok := r.(*os.File) if !ok {