On 11/16/18 9:53 AM, Daniel P. Berrangé wrote:
When sending a NBD_CMD_DISC message there is no reply expected,
however, the nbd_read_eof() coroutine is still waiting for a reply.
In a plain NBD connection this doesn't matter as it will just get an
EOF, however, on a TLS connection it will get an interrupted TLS data
packet. The nbd_read_eof() will then print an error message on the
console due to missing reply to NBD_CMD_DISC.
This can be seen with qemu-img
$ qemu-img info \
--object tls-creds-x509,dir=tlsdir,id=tls0,endpoint=client \
--image-opts driver=nbd,host=127.0.0.1,port=9000,tls-creds=tls0
qemu-img: Cannot read from TLS channel: Input/output error
image: nbd://127.0.0.1:9000
file format: nbd
virtual size: 10M (10485760 bytes)
disk size: unavailable
Simply setting the 'quit' flag after sending NBD_CMD_DISC is enough to
get the coroutine to stop waiting for a reply and thus supress the error
message.
Actually, it's not quite enough - once you actually start performing
I/O, enough coroutines are kicked off that the error still happens:
$ qemu-io -c 'r 1m 1m' -c 'w -P 0x22 1m 1m' --image-opts \
--object tls-creds-x509,dir=scratch/tls/client1,endpoint=client,id=tls0\
driver=nbd,host=localhost,port=10809,tls-creds=tls0
read 1048576/1048576 bytes at offset 1048576
1 MiB, 1 ops; 0.0430 sec (23.204 MiB/sec and 23.2040 ops/sec)
wrote 1048576/1048576 bytes at offset 1048576
1 MiB, 1 ops; 0.0152 sec (65.479 MiB/sec and 65.4793 ops/sec)
Cannot read from TLS channel: Input/output error
Squashing this in on top of your patch helps, though:
diff --git i/block/nbd-client.c w/block/nbd-client.c
index 5f63e4b8f15..e7916c78996 100644
--- i/block/nbd-client.c
+++ w/block/nbd-client.c
@@ -79,7 +79,14 @@ static coroutine_fn void nbd_read_reply_entry(void
*opaque)
assert(s->reply.handle == 0);
ret = nbd_receive_reply(s->ioc, &s->reply, &local_err);
if (local_err) {
- error_report_err(local_err);
+ /* If we are already quitting, either another error has
+ * already been reported, or we requested NBD_CMD_DISC and
+ * don't need to report anything further. */
+ if (!s->quit) {
+ error_report_err(local_err);
+ } else {
+ error_free(local_err);
+ }
}
if (ret <= 0) {
break;
But I want to do more testing to make sure I'm not missing out on
reporting an actual error if I add that.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
