From a2458b6f6998c9a079f710ed7495d5c6f037e942 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= Date: Mon, 19 Nov 2018 13:42:28 +0000 Subject: io: return 0 for EOF in TLS session read after shutdown MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit GNUTLS takes a paranoid approach when seeing 0 bytes returned by the underlying OS read() function. It will consider this an error and return GNUTLS_E_PREMATURE_TERMINATION instead of propagating the 0 return value. It expects apps to arrange for clean termination at the protocol level and not rely on seeing EOF from a read call to detect shutdown. This is to harden apps against a malicious 3rd party causing termination of the sockets layer. This is unhelpful for the QEMU NBD code which does have a clean protocol level shutdown, but still relies on seeing 0 from the I/O channel read in the coroutine handling incoming replies. The upshot is that when using a plain NBD connection shutdown is silent, but when using TLS, the client spams the console with Cannot read from TLS channel: Broken pipe The NBD connection has, however, called qio_channel_shutdown() at this point to indicate that it is done with I/O. This gives the opportunity to optimize the code such that when the channel has been shutdown in the read direction, the error code GNUTLS_E_PREMATURE_TERMINATION gets turned into a '0' return instead of an error. Signed-off-by: Daniel P. Berrangé Message-Id: <20181119134228.11031-1-berrange@redhat.com> Reviewed-by: Eric Blake Signed-off-by: Eric Blake --- io/channel-tls.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'io') diff --git a/io/channel-tls.c b/io/channel-tls.c index 9628e6f..c98ead2 100644 --- a/io/channel-tls.c +++ b/io/channel-tls.c @@ -275,6 +275,9 @@ static ssize_t qio_channel_tls_readv(QIOChannel *ioc, } else { return QIO_CHANNEL_ERR_BLOCK; } + } else if (errno == ECONNABORTED && + (tioc->shutdown & QIO_CHANNEL_SHUTDOWN_READ)) { + return 0; } error_setg_errno(errp, errno, @@ -357,6 +360,8 @@ static int qio_channel_tls_shutdown(QIOChannel *ioc, { QIOChannelTLS *tioc = QIO_CHANNEL_TLS(ioc); + tioc->shutdown |= how; + return qio_channel_shutdown(tioc->master, how, errp); } -- cgit v1.1