On 9/25/26 23:00, Eric Blake wrote:
On Fri, Sep 25, 2026 at 05:53:45PM +0200, Guillaume Vincke wrote:
When a server closes the connection after a successful handshake but
before running any operations, the channel returned by
nbd_co_establish_connection() is the closed one and the connect thread
is not started.
When configured with reconnect-delay=0 (the default), this situation
generates at least two IO errors. The first one happens when trying to
issue an operation to the closed socket. The connect thread will be
started on the next request, which may happen long after, and will
create the second error as nbd_co_establish_connection() returns a NULL
channel.
Peeking the channel to detect FIN or RST avoids the first IO error and
does not delay the starting of the connect thread.
Signed-off-by: Guillaume Vincke <[email protected]>
---
nbd/client-connection.c | 35 +++++++++++++++++++++++++++++++++++
1 file changed, 35 insertions(+)
diff --git a/nbd/client-connection.c b/nbd/client-connection.c
index 6a4f080717..878219fede 100644
--- a/nbd/client-connection.c
+++ b/nbd/client-connection.c
@@ -274,6 +274,26 @@ void nbd_client_connection_release(NBDClientConnection
*conn)
}
}
+/* only true when the peer closed the channel. Does not detect if dead */
For consistent style, I would use
/* Only true when the peer closed the channel. Does not detect if dead. */
+static bool nbd_channel_is_closed(QIOChannel *ioc)
+{
+ char data;
+ struct iovec iov = { .iov_base = &data, .iov_len = 1 };
+ ssize_t len = -1;
+
+ if (!qio_channel_has_feature(ioc, QIO_CHANNEL_FEATURE_READ_MSG_PEEK)) {
+ return false;
+ }
+
+ len = qio_channel_readv_full(
+ ioc, &iov, 1, NULL, NULL, QIO_CHANNEL_READ_FLAG_MSG_PEEK, NULL);
+
+ if (len == 0 || (len < 0 && len != QIO_CHANNEL_ERR_BLOCK)) {
+ return true;
+ }
+ return false;
The last group could be shortened to:
return len == 0 || (len < 0 && len != QIO_CHANNEL_ERR_BLOCK);
Thanks, I will make sure to include those changes in v2 once patch 2/2
is reviewed, to avoid a new submission for these alone.
but that is not mandatory.
Reviewed-by: Eric Blake <[email protected]>
