[libvirt] [PATCH v4 2/4] qemu: guestinfo: handle unsupported agent commands
Michal Privoznik
mprivozn at redhat.com
Thu Aug 29 10:04:09 UTC 2019
On 8/27/19 10:35 PM, Jonathon Jongsma wrote:
> When we're collecting guest information, older agents may not support
> all agent commands. In the case where the user requested all info
> types (i.e. types == 0), ignore unsupported command errors and gather as
> much information as possible. If the agent command failed for some other
> reason, or if the user explciitly requested a specific info type (i.e.
> types != 0), abort on the first error.
>
> Signed-off-by: Jonathon Jongsma <jjongsma at redhat.com>
> ---
> src/qemu/qemu_agent.c | 70 ++++++++++++++++++++++++++++++++++++++----
> src/qemu/qemu_driver.c | 33 ++++++++++----------
> tests/qemuagenttest.c | 2 +-
> 3 files changed, 82 insertions(+), 23 deletions(-)
>
> diff --git a/src/qemu/qemu_agent.c b/src/qemu/qemu_agent.c
> index f2a8bb6263..c63db968c6 100644
> --- a/src/qemu/qemu_agent.c
> +++ b/src/qemu/qemu_agent.c
> @@ -995,6 +995,26 @@ qemuAgentStringifyErrorClass(const char *klass)
> return "unknown QEMU command error";
> }
>
> +/* Checks whether the agent reply msg is an error caused by an unsupported
> + * command.
> + *
> + * Returns true when reply is CommandNotFound or CommandDisabled
> + * false otherwise
> + */
> +static bool
> +qemuAgentErrorCommandUnsupported(virJSONValuePtr reply)
> +{
> + const char *klass;
> + virJSONValuePtr error = virJSONValueObjectGet(reply, "error");
> +
> + if (!error)
> + return false;
> +
> + klass = virJSONValueObjectGetString(error, "class");
> + return STREQ_NULLABLE(klass, "CommandNotFound") ||
> + STREQ_NULLABLE(klass, "CommandDisabled");
Huh, so whilst reviewing this I found out that qemu-ga will no longer
send us CommandDisabled class, because in 1.2.0 qemu dropped that error
class. I'm reintroducing it back here:
https://lists.nongnu.org/archive/html/qemu-devel/2019-08/msg06327.html
> +}
> +
> /* Ignoring OOM in this method, since we're already reporting
> * a more important error
> *
> @@ -1708,8 +1728,11 @@ qemuAgentGetHostname(qemuAgentPtr mon,
> return ret;
>
> if (qemuAgentCommand(mon, cmd, &reply, true,
> - VIR_DOMAIN_QEMU_AGENT_COMMAND_BLOCK) < 0)
> + VIR_DOMAIN_QEMU_AGENT_COMMAND_BLOCK) < 0) {
> + if (qemuAgentErrorCommandUnsupported(reply))
> + ret = -2;
> goto cleanup;
> + }
>
> if (!(data = virJSONValueObjectGet(reply, "return"))) {
> virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> @@ -2005,6 +2028,10 @@ qemuAgentGetFSInfoInternalDisk(virJSONValuePtr jsondisks,
> return 0;
> }
>
> +/* returns 0 on success
> + * -2 when agent command is not supported by the agent
> + * -1 otherwise
> + */
We prefer: "Returns: ..." instead of "returns ..."
> static int
> qemuAgentGetFSInfoInternal(qemuAgentPtr mon,
> qemuAgentFSInfoPtr **info,
> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> index d0e67863ea..908460bc79 100644
> --- a/src/qemu/qemu_driver.c
> +++ b/src/qemu/qemu_driver.c
> @@ -23220,6 +23220,7 @@ qemuDomainGetGuestInfo(virDomainPtr dom,
> int maxparams = 0;
> VIR_AUTOFREE(char *) hostname = NULL;
> unsigned int supportedTypes = types;
> + int status;
I prefer 'rc' or 'rv' because variables with that name are used widely
accross our code base to hold intermediate retvals from functions. The
@status name doesn't fall into that category.
>
> virCheckFlags(0, -1);
> qemuDomainGetGuestInfoCheckSupport(&supportedTypes);
> @@ -23240,30 +23241,30 @@ qemuDomainGetGuestInfo(virDomainPtr dom,
>
> agent = qemuDomainObjEnterAgent(vm);
>
> - /* Although the libvirt qemu driver supports all of these guest info types,
> - * some guest agents might be too old to support these commands. If these
> - * info categories were explicitly requested (i.e. 'types' is non-zero),
> - * abort and report an error on any failures, otherwise continue and return
> - * as much info as is supported by the guest agent. */
> + /* The agent info commands will return -2 for any commands that are not
> + * supported by the agent, or -1 for all other errors. In the case where no
> + * categories were explicitly requrested (i.e. 'types' is 0), ignore
s/requrested/requested/
> + * 'unsupported' errors and gather as much information as we can. In all
> + * other cases, abort on error. */
> if (supportedTypes & VIR_DOMAIN_GUEST_INFO_USERS) {
> - if (qemuAgentGetUsers(agent, params, nparams, &maxparams) < 0 &&
> - types != 0)
> + status = qemuAgentGetUsers(agent, params, nparams, &maxparams);
> + if (status == -1 || (status == -2 && types != 0))
Here I'd rather change this to cover just every negative value (so that
if we invent a new one, these lines don't have to be changed). Something
like:
if (rc < 0 && !(rc == -2 && types == 0))
should do.
> goto exitagent;
> }
> if (supportedTypes & VIR_DOMAIN_GUEST_INFO_OS) {
> - if (qemuAgentGetOSInfo(agent, params, nparams, &maxparams) < 0
> - && types != 0)
> + status = qemuAgentGetOSInfo(agent, params, nparams, &maxparams);
> + if (status == -1 || (status == -2 && types != 0))
> goto exitagent;
> }
> if (supportedTypes & VIR_DOMAIN_GUEST_INFO_TIMEZONE) {
> - if (qemuAgentGetTimezone(agent, params, nparams, &maxparams) < 0
> - && types != 0)
> + status = qemuAgentGetTimezone(agent, params, nparams, &maxparams);
> + if (status == -1 || (status == -2 && types != 0))
> goto exitagent;
> }
> if (supportedTypes & VIR_DOMAIN_GUEST_INFO_HOSTNAME) {
> - if (qemuAgentGetHostname(agent, &hostname) < 0) {
> - if (types != 0)
> - goto exitagent;
> + status = qemuAgentGetHostname(agent, &hostname);
> + if (status == -1 || (status == -2 && types != 0)) {
> + goto exitagent;
> } else {
> if (virTypedParamsAddString(params, nparams, &maxparams, "hostname",
> hostname) < 0)
> @@ -23271,8 +23272,8 @@ qemuDomainGetGuestInfo(virDomainPtr dom,
> }
> }
> if (supportedTypes & VIR_DOMAIN_GUEST_INFO_FILESYSTEM) {
> - if (qemuAgentGetFSInfoParams(agent, params, nparams, &maxparams, vm->def) < 0 &&
> - types != 0)
> + status = qemuAgentGetFSInfoParams(agent, params, nparams, &maxparams, vm->def);
> + if (status == -1 || (status == -2 && types != 0))
> goto exitagent;
> }
>
> diff --git a/tests/qemuagenttest.c b/tests/qemuagenttest.c
> index ae57da5989..91f19644d5 100644
> --- a/tests/qemuagenttest.c
> +++ b/tests/qemuagenttest.c
> @@ -462,7 +462,7 @@ testQemuAgentGetFSInfoParams(const void *data)
> goto cleanup;
>
> if (qemuAgentGetFSInfoParams(qemuMonitorTestGetAgent(test), ¶ms,
> - &nparams, &maxparams, def) != -1) {
> + &nparams, &maxparams, def) != -2) {
> virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> "agent get-fsinfo command should have failed");
> goto cleanup;
>
Reviewed-by: Michal Privoznik <mprivozn at redhat.com>
Michal
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