Dumpcap: Improve an error message.

Dumpcap doesn't yet support capturing pcapng from stdin. On Windows,
make sure we invalidate our file handle so that instead of printing

  "Error reading from pipe: The operation completed successfully. (error 0)"

we show the more useful

  "Capturing from a pipe doesn't support pcapng format."

Change-Id: I472c1bf5c8520c9ee3fe4b6299a6e0250262ea51
Reviewed-on: https://code.wireshark.org/review/19876
Petri-Dish: Gerald Combs <gerald@wireshark.org>
Reviewed-by: Alexis La Goutte <alexis.lagoutte@gmail.com>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Gerald Combs <gerald@wireshark.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/dumpcap.c b/dumpcap.c
index 632dda33f8..6f07b63225 100644
--- a/dumpcap.c
+++ b/dumpcap.c
@@ -1849,6 +1849,9 @@ error:
     pcap_opts->cap_pipe_err = PIPERR;
     cap_pipe_close(fd, pcap_opts->from_cap_socket);
     pcap_opts->cap_pipe_fd = -1;
+#ifdef _WIN32
+    pcap_opts->cap_pipe_h = INVALID_HANDLE_VALUE;
+#endif
 }