hmp: Use QAPI NetdevInfo in hmp_info_network

Replace usage of legacy field info_str of NetClientState for backend
network devices with QAPI NetdevInfo stored_config that already used
in QMP query-netdev.

This change increases the detail of the "info network" output and takes
a more general approach to composing the output.

NIC and hubports still use legacy info_str field.

Signed-off-by: Alexey Kirillov <lekiravi@yandex-team.ru>
Signed-off-by: Jason Wang <jasowang@redhat.com>

include/qapi/hmp-output-visitor.h

@@ -0,0 +1,30 @@
+/*
+ * HMP string output Visitor
+ *
+ * Copyright Yandex N.V., 2021
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#ifndef HMP_OUTPUT_VISITOR_H
+#define HMP_OUTPUT_VISITOR_H
+
+#include "qapi/visitor.h"
+
+typedef struct HMPOutputVisitor HMPOutputVisitor;
+
+/**
+ * Create a HMP string output visitor for @obj
+ *
+ * Flattens dicts/structures, only shows arrays borders.
+ *
+ * Errors are not expected to happen.
+ *
+ * The caller is responsible for freeing the visitor with
+ * visit_free().
+ */
+Visitor *hmp_output_visitor_new(char **result);
+
+#endif

net/net.c

@@ -55,6 +55,7 @@
 #include "sysemu/sysemu.h"
 #include "net/filter.h"
 #include "qapi/string-output-visitor.h"
+#include "qapi/hmp-output-visitor.h"
 
 /* Net bridge is currently not supported for W32. */
 #if !defined(_WIN32)
@@ -1221,14 +1222,42 @@ static void netfilter_print_info(Monitor *mon, NetFilterState *nf)
     monitor_printf(mon, "\n");
 }
 
+static char *generate_info_str(NetClientState *nc)
+{
+    NetdevInfo *ni = nc->stored_config;
+    char *ret_out = NULL;
+    Visitor *v;
+
+    /* Use legacy field info_str for NIC and hubports */
+    if ((nc->info->type == NET_CLIENT_DRIVER_NIC) ||
+        (nc->info->type == NET_CLIENT_DRIVER_HUBPORT)) {
+        return g_strdup(nc->info_str ? nc->info_str : "");
+    }
+
+    if (!ni) {
+        return g_malloc0(1);
+    }
+
+    v = hmp_output_visitor_new(&ret_out);
+    if (visit_type_NetdevInfo(v, "", &ni, NULL)) {
+        visit_complete(v, &ret_out);
+    }
+    visit_free(v);
+
+    return ret_out;
+}
+
 void print_net_client(Monitor *mon, NetClientState *nc)
 {
     NetFilterState *nf;
+    char *info_str = generate_info_str(nc);
 
     monitor_printf(mon, "%s: index=%d,type=%s,%s\n", nc->name,
                    nc->queue_index,
                    NetClientDriver_str(nc->info->type),
-                   nc->info_str ? nc->info_str : "");
+                   info_str);
+    g_free(info_str);
+
     if (!QTAILQ_EMPTY(&nc->filters)) {
         monitor_printf(mon, "filters:\n");
     }

qapi/hmp-output-visitor.c

@@ -0,0 +1,193 @@
+/*
+ * HMP string output Visitor
+ *
+ * Copyright Yandex N.V., 2021
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/cutils.h"
+#include "qapi/hmp-output-visitor.h"
+#include "qapi/visitor-impl.h"
+
+struct HMPOutputVisitor {
+    Visitor visitor;
+    char **result;
+    GString *buffer;
+    bool is_continue;
+};
+
+static HMPOutputVisitor *to_hov(Visitor *v)
+{
+    return container_of(v, HMPOutputVisitor, visitor);
+}
+
+static void hmp_output_append_formatted(Visitor *v, const char *fmt, ...)
+{
+    HMPOutputVisitor *ov = to_hov(v);
+    va_list args;
+
+    if (ov->is_continue) {
+        g_string_append(ov->buffer, ",");
+    } else {
+        ov->is_continue = true;
+    }
+
+    va_start(args, fmt);
+    g_string_append_vprintf(ov->buffer, fmt, args);
+    va_end(args);
+}
+
+static void hmp_output_skip_comma(Visitor *v)
+{
+    HMPOutputVisitor *ov = to_hov(v);
+
+    ov->is_continue = false;
+}
+
+static bool hmp_output_start_struct(Visitor *v, const char *name,
+                                    void **obj, size_t unused, Error **errp)
+{
+    return true;
+}
+
+static void hmp_output_end_struct(Visitor *v, void **obj) {}
+
+static bool hmp_output_start_list(Visitor *v, const char *name,
+                                  GenericList **listp, size_t size,
+                                  Error **errp)
+{
+    hmp_output_append_formatted(v, "%s=[", name);
+    /* First element in array without comma before it */
+    hmp_output_skip_comma(v);
+
+    return true;
+}
+
+static GenericList *hmp_output_next_list(Visitor *v, GenericList *tail,
+                                         size_t size)
+{
+    return tail->next;
+}
+
+static void hmp_output_end_list(Visitor *v, void **obj)
+{
+    /* Don't need comma after last array element */
+    hmp_output_skip_comma(v);
+    hmp_output_append_formatted(v, "]");
+}
+
+static bool hmp_output_type_int64(Visitor *v, const char *name,
+                                  int64_t *obj, Error **errp)
+{
+    hmp_output_append_formatted(v, "%s=%" PRId64, name, *obj);
+
+    return true;
+}
+
+static bool hmp_output_type_uint64(Visitor *v, const char *name,
+                                   uint64_t *obj, Error **errp)
+{
+    hmp_output_append_formatted(v, "%s=%" PRIu64, name, *obj);
+
+    return true;
+}
+
+static bool hmp_output_type_bool(Visitor *v, const char *name, bool *obj,
+                                 Error **errp)
+{
+    hmp_output_append_formatted(v, "%s=%s", name, *obj ? "true" : "false");
+
+    return true;
+}
+
+static bool hmp_output_type_str(Visitor *v, const char *name, char **obj,
+                                Error **errp)
+{
+    /* Skip already printed or unused fields */
+    if (!*obj || g_str_equal(name, "id") || g_str_equal(name, "type")) {
+        return true;
+    }
+
+    /* Do not print stub name for StringList elements */
+    if (g_str_equal(name, "str")) {
+        hmp_output_append_formatted(v, "%s", *obj);
+    } else {
+        hmp_output_append_formatted(v, "%s=%s", name, *obj);
+    }
+
+    return true;
+}
+
+static bool hmp_output_type_number(Visitor *v, const char *name,
+                                   double *obj, Error **errp)
+{
+    hmp_output_append_formatted(v, "%s=%.17g", name, *obj);
+
+    return true;
+}
+
+/* TODO: remove this function? */
+static bool hmp_output_type_any(Visitor *v, const char *name,
+                                QObject **obj, Error **errp)
+{
+    return true;
+}
+
+static bool hmp_output_type_null(Visitor *v, const char *name,
+                                 QNull **obj, Error **errp)
+{
+    hmp_output_append_formatted(v, "%s=NULL", name);
+
+    return true;
+}
+
+static void hmp_output_complete(Visitor *v, void *opaque)
+{
+    HMPOutputVisitor *ov = to_hov(v);
+
+    *ov->result = g_string_free(ov->buffer, false);
+    ov->buffer = NULL;
+}
+
+static void hmp_output_free(Visitor *v)
+{
+    HMPOutputVisitor *ov = to_hov(v);
+
+    if (ov->buffer) {
+        g_string_free(ov->buffer, true);
+    }
+    g_free(v);
+}
+
+Visitor *hmp_output_visitor_new(char **result)
+{
+    HMPOutputVisitor *v;
+
+    v = g_malloc0(sizeof(*v));
+
+    v->visitor.type = VISITOR_OUTPUT;
+    v->visitor.start_struct = hmp_output_start_struct;
+    v->visitor.end_struct = hmp_output_end_struct;
+    v->visitor.start_list = hmp_output_start_list;
+    v->visitor.next_list = hmp_output_next_list;
+    v->visitor.end_list = hmp_output_end_list;
+    v->visitor.type_int64 = hmp_output_type_int64;
+    v->visitor.type_uint64 = hmp_output_type_uint64;
+    v->visitor.type_bool = hmp_output_type_bool;
+    v->visitor.type_str = hmp_output_type_str;
+    v->visitor.type_number = hmp_output_type_number;
+    v->visitor.type_any = hmp_output_type_any;
+    v->visitor.type_null = hmp_output_type_null;
+    v->visitor.complete = hmp_output_complete;
+    v->visitor.free = hmp_output_free;
+
+    v->result = result;
+    v->buffer = g_string_new("");
+    v->is_continue = false;
+
+    return &v->visitor;
+}

qapi/meson.build

@@ -8,6 +8,7 @@ util_ss.add(files(
   'qobject-output-visitor.c',
   'string-input-visitor.c',
   'string-output-visitor.c',
+  'hmp-output-visitor.c',
 ))
 if have_system or have_tools
   util_ss.add(files(