2:39 a.m.
On 12/16/20 8:17 PM, Laine Stump wrote:
On 12/16/20 1:45 PM, Michal Privoznik wrote:
> During testing of my patch v6.10.0-rc1~221 it was found that
>
> 'ovs-vsctl get Interface $name name' or
> 'ovs-vsctl find Interface options:vhost-server-path=$path'
>
> may return a string in double quotes, e.g. "vhost-user1". Later
> investigation of openvswitch code showed, that early versions
> (like 1.3.0) have somewhat restrictive set of safe characters
> (isalpha() || '_' || '-' || '.'), which is then refined with
> increasing version. For instance, version 2.11.4 has: isalnum()
> || '_' || '-' || '.'. If the string that ovs-vsctl wants to
> output contains any other character it is escaped. You want to be
> looking at ovsdb_atom_to_string() which handles outputting of a
> single string and calls string_needs_quotes() and possibly
> json_serialize_string() in openvswitch code base.
>
> Since the interfaces are usually named "vhost-userN" we are
> facing a problem where with one version we get the name in double
> quotes and with another we get plain name without funny business.
>
> Because of json involved I thought, let's make ovs-vsctl output
> into JSON format and then use our JSON parser, but guess what -
> ovs-vsctl ignores --format=json.
Yuck. Is this a known/reported problem? Is it true with current
ovs-vsctl, or just with old versions? (I guess in the end it doesn't
really matter, because we have to support old and new anyway :-/)
Honestly, I did not bother exactly because of the reason you're
mentioning: we have to support both.
> But with a little help of
> g_strdup_printf() it can be turned into JSON.
>
> Fixes: e4c29e2904197472919d050c67acfd59f0144bbc
> Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1767013
> Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com>
> ---
> src/libvirt_private.syms | 1 +
> src/util/virnetdevopenvswitch.c | 47 +++++++++++++++++++++++++++++
> src/util/virnetdevopenvswitch.h | 4 +++
> tests/virnetdevopenvswitchtest.c | 52 ++++++++++++++++++++++++++++++++
> 4 files changed, 104 insertions(+)
>
> diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
> index c7c37d9689..583fc5800e 100644
> --- a/src/libvirt_private.syms
> +++ b/src/libvirt_private.syms
> @@ -2676,6 +2676,7 @@ virNetDevOpenvswitchGetVhostuserIfname;
> virNetDevOpenvswitchInterfaceGetMaster;
> virNetDevOpenvswitchInterfaceParseStats;
> virNetDevOpenvswitchInterfaceStats;
> +virNetDevOpenvswitchMaybeUnescapeReply;
> virNetDevOpenvswitchRemovePort;
> virNetDevOpenvswitchSetMigrateData;
> virNetDevOpenvswitchSetTimeout;
> diff --git a/src/util/virnetdevopenvswitch.c
> b/src/util/virnetdevopenvswitch.c
> index 7eabaa763d..14fa294ae1 100644
> --- a/src/util/virnetdevopenvswitch.c
> +++ b/src/util/virnetdevopenvswitch.c
> @@ -460,6 +460,48 @@ virNetDevOpenvswitchInterfaceGetMaster(const char
> *ifname, char **master)
> }
> +/**
> + * virNetDevOpenvswitchMaybeUnescapeReply:
> + * @reply: a string to unescape
> + *
> + * Depending on ovs-vsctl version a string might be escaped. For
> instance:
> + * -version 2.11.4 allows only is_alpha(), an underscore, a dash or
> a dot,
> + * -version 2.14.0 allows only is_alnum(), an underscore, a dash or
> a dot,
> + * any other character causes the string to be escaped.
> + *
> + * What this function does, is it checks whether @reply string
> consists solely
> + * from safe, not escaped characters (as defined by version 2.14.0)
> and if not
> + * an error is reported. If @reply is a string enclosed in double
> quotes, but
> + * otherwise safe those double quotes are removed.
> + *
> + * Returns: 0 on success,
> + * -1 otherwise (with error reported).
> + */
> +int
> +virNetDevOpenvswitchMaybeUnescapeReply(char *reply)
> +{
> + g_autoptr(virJSONValue) json = NULL;
> + g_autofree char *jsonStr = NULL;
> + const char *tmp = NULL;
> + size_t replyLen = strlen(reply);
> +
> + if (*reply != '"')
> + return 0;
> +
> + jsonStr = g_strdup_printf("{\"name\": %s}", reply);
> + if (!(json = virJSONValueFromString(jsonStr)))
> + return -1;
> +
> + if (!(tmp = virJSONValueObjectGetString(json, "name"))) {
> + virReportError(VIR_ERR_INTERNAL_ERROR,
> + _("Malformed ovs-vsctl output"));
> + return -1;
> + }
Tricky!
There are other ways to unescape a string, but this one gets a vote for
novelty :-)
Thank you sir!
Reviewed-by: Laine Stump <laine(a)redhat.com>
Michal