guest agent: add RPC blacklist command-line option

This adds a command-line option, -b/--blacklist, that accepts a
comma-seperated list of RPCs to disable, or prints a list of
available RPCs if passed "?".

In consequence this also adds general blacklisting and RPC listing
facilities to the new QMP dispatch/registry facilities, should the
QMP monitor ever have a need for such a thing.

Ideally, to avoid support/compatability issues in the future,
blacklisting guest agent functionality will be the exceptional
case, but we add the functionality here to handle guest administrators
with specific requirements.

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

3 files changed, 45 insertions, 5 deletions

diff --git a/qapi/qmp-core.h b/qapi/qmp-core.h
index f1c26e4..3cf1781 100644
--- a/qapi/qmp-core.h
+++ b/qapi/qmp-core.h
@@ -31,11 +31,14 @@ typedef struct QmpCommand
     QmpCommandType type;
     QmpCommandFunc *fn;
     QTAILQ_ENTRY(QmpCommand) node;
+    bool enabled;
 } QmpCommand;
 
 void qmp_register_command(const char *name, QmpCommandFunc *fn);
 QmpCommand *qmp_find_command(const char *name);
 QObject *qmp_dispatch(QObject *request);
+void qmp_disable_command(const char *name);
+char **qmp_get_command_list(void);
 
 #endif
 
diff --git a/qapi/qmp-dispatch.c b/qapi/qmp-dispatch.c
index 5584693..43f640a 100644
--- a/qapi/qmp-dispatch.c
+++ b/qapi/qmp-dispatch.c
@@ -79,6 +79,10 @@ static QObject *do_qmp_dispatch(QObject *request, Error **errp)
         error_set(errp, QERR_COMMAND_NOT_FOUND, command);
         return NULL;
     }
+    if (!cmd->enabled) {
+        error_set(errp, QERR_COMMAND_DISABLED, command);
+        return NULL;
+    }
 
     if (!qdict_haskey(dict, "arguments")) {
         args = qdict_new();
diff --git a/qapi/qmp-registry.c b/qapi/qmp-registry.c
index 5ff99cf..abafa34 100644
--- a/qapi/qmp-registry.c
+++ b/qapi/qmp-registry.c
@@ -14,7 +14,7 @@
 
 #include "qapi/qmp-core.h"
 
-static QTAILQ_HEAD(, QmpCommand) qmp_commands =
+static QTAILQ_HEAD(QmpCommandList, QmpCommand) qmp_commands =
     QTAILQ_HEAD_INITIALIZER(qmp_commands);
 
 void qmp_register_command(const char *name, QmpCommandFunc *fn)
@@ -24,17 +24,50 @@ void qmp_register_command(const char *name, QmpCommandFunc *fn)
     cmd->name = name;
     cmd->type = QCT_NORMAL;
     cmd->fn = fn;
+    cmd->enabled = true;
     QTAILQ_INSERT_TAIL(&qmp_commands, cmd, node);
 }
 
 QmpCommand *qmp_find_command(const char *name)
 {
-    QmpCommand *i;
+    QmpCommand *cmd;
 
-    QTAILQ_FOREACH(i, &qmp_commands, node) {
-        if (strcmp(i->name, name) == 0) {
-            return i;
+    QTAILQ_FOREACH(cmd, &qmp_commands, node) {
+        if (strcmp(cmd->name, name) == 0) {
+            return cmd;
         }
     }
     return NULL;
 }
+
+void qmp_disable_command(const char *name)
+{
+    QmpCommand *cmd;
+
+    QTAILQ_FOREACH(cmd, &qmp_commands, node) {
+        if (strcmp(cmd->name, name) == 0) {
+            cmd->enabled = false;
+            return;
+        }
+    }
+}
+
+char **qmp_get_command_list(void)
+{
+    QmpCommand *cmd;
+    int count = 1;
+    char **list_head, **list;
+
+    QTAILQ_FOREACH(cmd, &qmp_commands, node) {
+        count++;
+    }
+
+    list_head = list = g_malloc0(count * sizeof(char *));
+
+    QTAILQ_FOREACH(cmd, &qmp_commands, node) {
+        *list = strdup(cmd->name);
+        list++;
+    }
+
+    return list_head;
+}