106 lines
4.2 KiB
Diff
106 lines
4.2 KiB
Diff
From 4364ac20ae74ae2fa4cc2dfa4e982411d9902b59 Mon Sep 17 00:00:00 2001
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From: Eric Blake <eblake@redhat.com>
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Date: Fri, 15 Nov 2024 13:55:53 -0600
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Subject: [PATCH] nbd-server: Silence server warnings on port probes
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RH-Author: Eric Blake <eblake@redhat.com>
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RH-MergeRequest: 334: nbd-server: Silence server warnings on port probes
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RH-Jira: RHEL-76908
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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RH-Commit: [1/1] a66ea3900e0a8515871b6342dfbc0d2c108b4911 (ebblake/centos-qemu-kvm)
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While testing the use of qemu-nbd in a Pod of a Kubernetes cluster, I
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got LOTS of log messages of the forms:
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qemu-nbd: option negotiation failed: Failed to read flags: Unexpected end-of-file before all data were read
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qemu-nbd: option negotiation failed: Failed to read flags: Unable to read from socket: Connection reset by peer
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While it is nice to warn about clients that aren't following protocol
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(in case it helps diagnosing bugs in those clients), a mere port probe
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(where the client never write()s any bytes, and where we might even
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hit EPIPE in trying to send our greeting to the client) is NOT
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abnormal, but merely serves to pollute the log. And Kubernetes
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_really_ likes to do port probes to determine whether a given Pod is
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up and running.
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Easy ways to demonstrate the above port probes:
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$ qemu-nbd -r -f raw path/to/file &
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$ nc localhost 10809 </dev/null
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$ bash -c 'exec </dev/tcp/localhost/10809'
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$ kill $!
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Silence the noise by not capturing errors until after our first
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successful read() from a client.
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Signed-off-by: Eric Blake <eblake@redhat.com>
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Message-ID: <20241115195638.1132007-2-eblake@redhat.com>
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Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
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(cherry picked from commit efd3dda312129b91986f85976afbda58d40f757f)
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Signed-off-by: Eric Blake <eblake@redhat.com>
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---
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nbd/server.c | 26 +++++++++++++++++---------
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1 file changed, 17 insertions(+), 9 deletions(-)
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diff --git a/nbd/server.c b/nbd/server.c
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index c30e687fc8..f64e47270c 100644
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--- a/nbd/server.c
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+++ b/nbd/server.c
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@@ -1150,8 +1150,8 @@ nbd_negotiate_meta_queries(NBDClient *client, Error **errp)
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* Return:
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* -errno on error, errp is set
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* 0 on successful negotiation, errp is not set
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- * 1 if client sent NBD_OPT_ABORT, i.e. on valid disconnect,
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- * errp is not set
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+ * 1 if client sent NBD_OPT_ABORT (i.e. on valid disconnect) or never
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+ * wrote anything (i.e. port probe); errp is not set
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*/
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static coroutine_fn int
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nbd_negotiate_options(NBDClient *client, Error **errp)
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@@ -1175,8 +1175,13 @@ nbd_negotiate_options(NBDClient *client, Error **errp)
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... Rest of request
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*/
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- if (nbd_read32(client->ioc, &flags, "flags", errp) < 0) {
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- return -EIO;
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+ /*
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+ * Intentionally ignore errors on this first read - we do not want
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+ * to be noisy about a mere port probe, but only for clients that
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+ * start talking the protocol and then quit abruptly.
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+ */
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+ if (nbd_read32(client->ioc, &flags, "flags", NULL) < 0) {
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+ return 1;
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}
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client->mode = NBD_MODE_EXPORT_NAME;
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trace_nbd_negotiate_options_flags(flags);
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@@ -1383,8 +1388,8 @@ nbd_negotiate_options(NBDClient *client, Error **errp)
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* Return:
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* -errno on error, errp is set
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* 0 on successful negotiation, errp is not set
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- * 1 if client sent NBD_OPT_ABORT, i.e. on valid disconnect,
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- * errp is not set
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+ * 1 if client sent NBD_OPT_ABORT (i.e. on valid disconnect) or never
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+ * wrote anything (i.e. port probe); errp is not set
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*/
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static coroutine_fn int nbd_negotiate(NBDClient *client, Error **errp)
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{
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@@ -1415,9 +1420,12 @@ static coroutine_fn int nbd_negotiate(NBDClient *client, Error **errp)
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stq_be_p(buf + 8, NBD_OPTS_MAGIC);
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stw_be_p(buf + 16, NBD_FLAG_FIXED_NEWSTYLE | NBD_FLAG_NO_ZEROES);
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- if (nbd_write(client->ioc, buf, 18, errp) < 0) {
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- error_prepend(errp, "write failed: ");
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- return -EINVAL;
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+ /*
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+ * Be silent about failure to write our greeting: there is nothing
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+ * wrong with a client testing if our port is alive.
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+ */
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+ if (nbd_write(client->ioc, buf, 18, NULL) < 0) {
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+ return 1;
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}
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ret = nbd_negotiate_options(client, errp);
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if (ret != 0) {
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--
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2.39.3
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