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@xxxxxxxxxx>
---
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@xxxxxxxxxx>
Michal
