qapi: net: Add query-netdev command

The query-netdev command is used to get the configuration of the current
network device backends (netdevs).
This is the QMP analog of the HMP command "info network" but only for
netdevs (i.e. excluding NIC and hubports).

The query-netdev command returns an array of objects of the NetdevInfo
type, which are an extension of Netdev type. It means that response can
be used for netdev-add after small modification. This can be useful for
recreate the same netdev configuration.

Information about the network device is filled in when it is created or
modified and is available through the NetClientState->stored_config.

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

12 files changed, 477 insertions, 9 deletions

diff --git a/include/net/net.h b/include/net/net.h
index 4f56cae..dc3679f 100644
--- a/include/net/net.h
+++ b/include/net/net.h
@@ -5,6 +5,8 @@
 #include "qapi/qapi-types-net.h"
 #include "net/queue.h"
 #include "hw/qdev-properties-system.h"
+#include "qapi/clone-visitor.h"
+#include "qapi/qapi-visit-net.h"
 
 #define MAC_FMT "%02X:%02X:%02X:%02X:%02X:%02X"
 #define MAC_ARG(x) ((uint8_t *)(x))[0], ((uint8_t *)(x))[1], \
@@ -93,6 +95,7 @@ struct NetClientState {
     char *model;
     char *name;
     char info_str[256];
+    NetdevInfo *stored_config;
     unsigned receive_disabled : 1;
     NetClientDestructor *destructor;
     unsigned int queue_index;
diff --git a/net/l2tpv3.c b/net/l2tpv3.c
index e4d4218..8aa0a3e 100644
--- a/net/l2tpv3.c
+++ b/net/l2tpv3.c
@@ -723,6 +723,13 @@ int net_init_l2tpv3(const Netdev *netdev,
 
     l2tpv3_read_poll(s, true);
 
+    /* Store startup parameters */
+    nc->stored_config = g_new0(NetdevInfo, 1);
+    nc->stored_config->type = NET_BACKEND_L2TPV3;
+
+    QAPI_CLONE_MEMBERS(NetdevL2TPv3Options,
+                       &nc->stored_config->u.l2tpv3, l2tpv3);
+
     snprintf(s->nc.info_str, sizeof(s->nc.info_str),
              "l2tpv3: connected");
     return 0;
diff --git a/net/net.c b/net/net.c
index edf9b95..9a2a6ab 100644
--- a/net/net.c
+++ b/net/net.c
@@ -36,7 +36,6 @@
 #include "monitor/monitor.h"
 #include "qemu/help_option.h"
 #include "qapi/qapi-commands-net.h"
-#include "qapi/qapi-visit-net.h"
 #include "qapi/qmp/qdict.h"
 #include "qapi/qmp/qerror.h"
 #include "qemu/error-report.h"
@@ -353,6 +352,7 @@ static void qemu_free_net_client(NetClientState *nc)
     }
     g_free(nc->name);
     g_free(nc->model);
+    qapi_free_NetdevInfo(nc->stored_config);
     if (nc->destructor) {
         nc->destructor(nc);
     }
@@ -1289,6 +1289,34 @@ RxFilterInfoList *qmp_query_rx_filter(bool has_name, const char *name,
     return filter_list;
 }
 
+NetdevInfoList *qmp_query_netdev(Error **errp)
+{
+    NetdevInfoList *list = NULL;
+    NetClientState *nc;
+
+    QTAILQ_FOREACH(nc, &net_clients, next) {
+        /*
+         * Only look at netdevs (backend network devices), not for each queue
+         * or NIC / hubport
+         */
+        if (nc->stored_config) {
+            NetdevInfo *element = QAPI_CLONE(NetdevInfo, nc->stored_config);
+
+            g_free(element->id); /* Need to dealloc empty id after clone */
+            element->id = g_strdup(nc->name);
+
+            element->has_peer_id = nc->peer != NULL;
+            if (element->has_peer_id) {
+                element->peer_id = g_strdup(nc->peer->name);
+            }
+
+            QAPI_LIST_PREPEND(list, element);
+        }
+    }
+
+    return list;
+}
+
 void hmp_info_network(Monitor *mon, const QDict *qdict)
 {
     NetClientState *nc, *peer;
diff --git a/net/netmap.c b/net/netmap.c
index 350f097..ad59d4a 100644
--- a/net/netmap.c
+++ b/net/netmap.c
@@ -427,6 +427,13 @@ int net_init_netmap(const Netdev *netdev,
     pstrcpy(s->ifname, sizeof(s->ifname), netmap_opts->ifname);
     netmap_read_poll(s, true); /* Initially only poll for reads. */
 
+    /* Store startup parameters */
+    nc->stored_config = g_new0(NetdevInfo, 1);
+    nc->stored_config->type = NET_BACKEND_NETMAP;
+
+    QAPI_CLONE_MEMBERS(NetdevNetmapOptions,
+                       &nc->stored_config->u.netmap, netmap_opts);
+
     return 0;
 }
 
diff --git a/net/slirp.c b/net/slirp.c
index be914c0..6ab348b 100644
--- a/net/slirp.c
+++ b/net/slirp.c
@@ -377,6 +377,9 @@ static int net_slirp_init(NetClientState *peer, const char *model,
     int shift;
     char *end;
     struct slirp_config_str *config;
+    NetdevUserOptions *stored;
+    StringList **stored_hostfwd;
+    StringList **stored_guestfwd;
 
     if (!ipv4 && (vnetwork || vhost || vnameserver)) {
         error_setg(errp, "IPv4 disabled but netmask/host/dns provided");
@@ -552,6 +555,115 @@ static int net_slirp_init(NetClientState *peer, const char *model,
 
     nc = qemu_new_net_client(&net_slirp_info, peer, model, name);
 
+    /* Store startup parameters */
+    nc->stored_config = g_new0(NetdevInfo, 1);
+    nc->stored_config->type = NET_BACKEND_USER;
+    stored = &nc->stored_config->u.user;
+
+    if (vhostname) {
+        stored->has_hostname = true;
+        stored->hostname = g_strdup(vhostname);
+    }
+
+    stored->has_q_restrict = true;
+    stored->q_restrict = restricted;
+
+    stored->has_ipv4 = true;
+    stored->ipv4 = ipv4;
+
+    stored->has_ipv6 = true;
+    stored->ipv6 = ipv6;
+
+    if (ipv4) {
+        uint8_t *net_bytes = (uint8_t *)&net;
+        uint8_t *mask_bytes = (uint8_t *)&mask;
+
+        stored->has_net = true;
+        stored->net = g_strdup_printf("%d.%d.%d.%d/%d.%d.%d.%d",
+                                      net_bytes[0], net_bytes[1],
+                                      net_bytes[2], net_bytes[3],
+                                      mask_bytes[0], mask_bytes[1],
+                                      mask_bytes[2], mask_bytes[3]);
+
+        stored->has_host = true;
+        stored->host = g_strdup(inet_ntoa(host));
+    }
+
+    if (tftp_export) {
+        stored->has_tftp = true;
+        stored->tftp = g_strdup(tftp_export);
+    }
+
+    if (bootfile) {
+        stored->has_bootfile = true;
+        stored->bootfile = g_strdup(bootfile);
+    }
+
+    if (vdhcp_start) {
+        stored->has_dhcpstart = true;
+        stored->dhcpstart = g_strdup(vdhcp_start);
+    }
+
+    if (ipv4) {
+        stored->has_dns = true;
+        stored->dns = g_strdup(inet_ntoa(dns));
+    }
+
+    if (dnssearch) {
+        stored->has_dnssearch = true;
+        StringList **stored_list = &stored->dnssearch;
+
+        for (int i = 0; dnssearch[i]; i++) {
+            String *element = g_new0(String, 1);
+
+            element->str = g_strdup(dnssearch[i]);
+            QAPI_LIST_APPEND(stored_list, element);
+        }
+    }
+
+    if (vdomainname) {
+        stored->has_domainname = true;
+        stored->domainname = g_strdup(vdomainname);
+    }
+
+    if (ipv6) {
+        char addrstr[INET6_ADDRSTRLEN];
+        const char *res;
+
+        stored->has_ipv6_prefix = true;
+        stored->ipv6_prefix = g_strdup(vprefix6);
+
+        stored->has_ipv6_prefixlen = true;
+        stored->ipv6_prefixlen = vprefix6_len;
+
+        res = inet_ntop(AF_INET6, &ip6_host,
+                        addrstr, sizeof(addrstr));
+
+        stored->has_ipv6_host = true;
+        stored->ipv6_host = g_strdup(res);
+
+        res = inet_ntop(AF_INET6, &ip6_dns,
+                        addrstr, sizeof(addrstr));
+
+        stored->has_ipv6_dns = true;
+        stored->ipv6_dns = g_strdup(res);
+    }
+
+    if (smb_export) {
+        stored->has_smb = true;
+        stored->smb = g_strdup(smb_export);
+    }
+
+    if (vsmbserver) {
+        stored->has_smbserver = true;
+        stored->smbserver = g_strdup(vsmbserver);
+    }
+
+    if (tftp_server_name) {
+        stored->has_tftp_server_name = true;
+        stored->tftp_server_name = g_strdup(tftp_server_name);
+    }
+
     snprintf(nc->info_str, sizeof(nc->info_str),
              "net=%s,restrict=%s", inet_ntoa(net),
              restricted ? "on" : "off");
@@ -581,15 +693,25 @@ static int net_slirp_init(NetClientState *peer, const char *model,
     s->poll_notifier.notify = net_slirp_poll_notify;
     main_loop_poll_add_notifier(&s->poll_notifier);
 
+    stored_hostfwd = &stored->hostfwd;
+    stored_guestfwd = &stored->guestfwd;
+
     for (config = slirp_configs; config; config = config->next) {
+        String *element = g_new0(String, 1);
+
+        element->str = g_strdup(config->str);
         if (config->flags & SLIRP_CFG_HOSTFWD) {
             if (slirp_hostfwd(s, config->str, errp) < 0) {
                 goto error;
             }
+            stored->has_hostfwd = true;
+            QAPI_LIST_APPEND(stored_hostfwd, element);
         } else {
             if (slirp_guestfwd(s, config->str, errp) < 0) {
                 goto error;
             }
+            stored->has_guestfwd = true;
+            QAPI_LIST_APPEND(stored_guestfwd, element);
         }
     }
 #ifndef _WIN32
diff --git a/net/socket.c b/net/socket.c
index 15b410e..1614523 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -342,6 +342,7 @@ static NetSocketState *net_socket_fd_init_dgram(NetClientState *peer,
     NetSocketState *s;
     SocketAddress *sa;
     SocketAddressType sa_type;
+    NetdevSocketOptions *stored;
 
     sa = socket_local_address(fd, errp);
     if (!sa) {
@@ -385,8 +386,19 @@ static NetSocketState *net_socket_fd_init_dgram(NetClientState *peer,
     net_socket_rs_init(&s->rs, net_socket_rs_finalize, false);
     net_socket_read_poll(s, true);
 
+    /* Store startup parameters */
+    nc->stored_config = g_new0(NetdevInfo, 1);
+    nc->stored_config->type = NET_BACKEND_SOCKET;
+    stored = &nc->stored_config->u.socket;
+
+    stored->has_fd = true;
+    stored->fd = g_strdup_printf("%d", fd);
+
     /* mcast: save bound address as dst */
     if (is_connected && mcast != NULL) {
+        stored->has_mcast = true;
+        stored->mcast = g_strdup(mcast);
+
         s->dgram_dst = saddr;
         snprintf(nc->info_str, sizeof(nc->info_str),
                  "socket: fd=%d (cloned mcast=%s:%d)",
@@ -428,6 +440,7 @@ static NetSocketState *net_socket_fd_init_stream(NetClientState *peer,
 {
     NetClientState *nc;
     NetSocketState *s;
+    NetdevSocketOptions *stored;
 
     nc = qemu_new_net_client(&net_socket_info, peer, model, name);
 
@@ -447,6 +460,15 @@ static NetSocketState *net_socket_fd_init_stream(NetClientState *peer,
     } else {
         qemu_set_fd_handler(s->fd, NULL, net_socket_connect, s);
     }
+
+    /* Store startup parameters */
+    nc->stored_config = g_new0(NetdevInfo, 1);
+    nc->stored_config->type = NET_BACKEND_SOCKET;
+    stored = &nc->stored_config->u.socket;
+
+    stored->has_fd = true;
+    stored->fd = g_strdup_printf("%d", fd);
+
     return s;
 }
 
@@ -483,6 +505,7 @@ static void net_socket_accept(void *opaque)
     struct sockaddr_in saddr;
     socklen_t len;
     int fd;
+    NetdevSocketOptions *stored;
 
     for(;;) {
         len = sizeof(saddr);
@@ -498,6 +521,13 @@ static void net_socket_accept(void *opaque)
     s->fd = fd;
     s->nc.link_down = false;
     net_socket_connect(s);
+
+    /* Store additional startup parameters (extend net_socket_listen_init) */
+    stored = &s->nc.stored_config->u.socket;
+
+    stored->has_fd = true;
+    stored->fd = g_strdup_printf("%d", fd);
+
     snprintf(s->nc.info_str, sizeof(s->nc.info_str),
              "socket: connection from %s:%d",
              inet_ntoa(saddr.sin_addr), ntohs(saddr.sin_port));
@@ -513,6 +543,7 @@ static int net_socket_listen_init(NetClientState *peer,
     NetSocketState *s;
     struct sockaddr_in saddr;
     int fd, ret;
+    NetdevSocketOptions *stored;
 
     if (parse_host_port(&saddr, host_str, errp) < 0) {
         return -1;
@@ -549,6 +580,15 @@ static int net_socket_listen_init(NetClientState *peer,
     net_socket_rs_init(&s->rs, net_socket_rs_finalize, false);
 
     qemu_set_fd_handler(s->listen_fd, net_socket_accept, NULL, s);
+
+    /* Store startup parameters */
+    nc->stored_config = g_new0(NetdevInfo, 1);
+    nc->stored_config->type = NET_BACKEND_SOCKET;
+    stored = &nc->stored_config->u.socket;
+
+    stored->has_listen = true;
+    stored->listen = g_strdup(host_str);
+
     return 0;
 }
 
@@ -561,6 +601,7 @@ static int net_socket_connect_init(NetClientState *peer,
     NetSocketState *s;
     int fd, connected, ret;
     struct sockaddr_in saddr;
+    NetdevSocketOptions *stored;
 
     if (parse_host_port(&saddr, host_str, errp) < 0) {
         return -1;
@@ -598,6 +639,12 @@ static int net_socket_connect_init(NetClientState *peer,
         return -1;
     }
 
+    /* Store additional startup parameters (extend net_socket_fd_init) */
+    stored = &s->nc.stored_config->u.socket;
+
+    stored->has_connect = true;
+    stored->connect = g_strdup(host_str);
+
     snprintf(s->nc.info_str, sizeof(s->nc.info_str),
              "socket: connect to %s:%d",
              inet_ntoa(saddr.sin_addr), ntohs(saddr.sin_port));
@@ -615,6 +662,7 @@ static int net_socket_mcast_init(NetClientState *peer,
     int fd;
     struct sockaddr_in saddr;
     struct in_addr localaddr, *param_localaddr;
+    NetdevSocketOptions *stored;
 
     if (parse_host_port(&saddr, host_str, errp) < 0) {
         return -1;
@@ -643,6 +691,19 @@ static int net_socket_mcast_init(NetClientState *peer,
 
     s->dgram_dst = saddr;
 
+    /* Store additional startup parameters (extend net_socket_fd_init) */
+    stored = &s->nc.stored_config->u.socket;
+
+    if (!stored->has_mcast) {
+        stored->has_mcast = true;
+        stored->mcast = g_strdup(host_str);
+    }
+
+    if (localaddr_str) {
+        stored->has_localaddr = true;
+        stored->localaddr = g_strdup(localaddr_str);
+    }
+
     snprintf(s->nc.info_str, sizeof(s->nc.info_str),
              "socket: mcast=%s:%d",
              inet_ntoa(saddr.sin_addr), ntohs(saddr.sin_port));
@@ -660,6 +721,7 @@ static int net_socket_udp_init(NetClientState *peer,
     NetSocketState *s;
     int fd, ret;
     struct sockaddr_in laddr, raddr;
+    NetdevSocketOptions *stored;
 
     if (parse_host_port(&laddr, lhost, errp) < 0) {
         return -1;
@@ -698,6 +760,15 @@ static int net_socket_udp_init(NetClientState *peer,
 
     s->dgram_dst = raddr;
 
+    /* Store additional startup parameters (extend net_socket_fd_init) */
+    stored = &s->nc.stored_config->u.socket;
+
+    stored->has_localaddr = true;
+    stored->localaddr = g_strdup(lhost);
+
+    stored->has_udp = true;
+    stored->udp = g_strdup(rhost);
+
     snprintf(s->nc.info_str, sizeof(s->nc.info_str),
              "socket: udp=%s:%d",
              inet_ntoa(raddr.sin_addr), ntohs(raddr.sin_port));
diff --git a/net/tap-win32.c b/net/tap-win32.c
index 2b5dcda..b60933b 100644
--- a/net/tap-win32.c
+++ b/net/tap-win32.c
@@ -768,6 +768,7 @@ static int tap_win32_init(NetClientState *peer, const char *model,
     NetClientState *nc;
     TAPState *s;
     tap_win32_overlapped_t *handle;
+    NetdevTapOptions *stored;
 
     if (tap_win32_open(&handle, ifname) < 0) {
         printf("tap: Could not open '%s'\n", ifname);
@@ -778,6 +779,14 @@ static int tap_win32_init(NetClientState *peer, const char *model,
 
     s = DO_UPCAST(TAPState, nc, nc);
 
+    /* Store startup parameters */
+    nc->stored_config = g_new0(NetdevInfo, 1);
+    nc->stored_config->type = NET_BACKEND_TAP;
+    stored = &nc->stored_config->u.tap;
+
+    stored->has_ifname = true;
+    stored->ifname = g_strdup(ifname);
+
     snprintf(s->nc.info_str, sizeof(s->nc.info_str),
              "tap: ifname=%s", ifname);
 
diff --git a/net/tap.c b/net/tap.c
index b751285..8041245 100644
--- a/net/tap.c
+++ b/net/tap.c
@@ -590,6 +590,7 @@ int net_init_bridge(const Netdev *netdev, const char *name,
     const char *helper, *br;
     TAPState *s;
     int fd, vnet_hdr;
+    NetdevBridgeOptions *stored;
 
     assert(netdev->type == NET_CLIENT_DRIVER_BRIDGE);
     bridge = &netdev->u.bridge;
@@ -609,6 +610,21 @@ int net_init_bridge(const Netdev *netdev, const char *name,
     }
     s = net_tap_fd_init(peer, "bridge", name, fd, vnet_hdr);
 
+    /* Store startup parameters */
+    s->nc.stored_config = g_new0(NetdevInfo, 1);
+    s->nc.stored_config->type = NET_BACKEND_BRIDGE;
+    stored = &s->nc.stored_config->u.bridge;
+
+    if (br) {
+        stored->has_br = true;
+        stored->br = g_strdup(br);
+    }
+
+    if (helper) {
+        stored->has_helper = true;
+        stored->helper = g_strdup(helper);
+    }
+
     snprintf(s->nc.info_str, sizeof(s->nc.info_str), "helper=%s,br=%s", helper,
              br);
 
@@ -656,11 +672,13 @@ static void net_init_tap_one(const NetdevTapOptions *tap, NetClientState *peer,
                              const char *model, const char *name,
                              const char *ifname, const char *script,
                              const char *downscript, const char *vhostfdname,
-                             int vnet_hdr, int fd, Error **errp)
+                             int vnet_hdr, int fd, NetdevInfo **common_stored,
+                             Error **errp)
 {
     Error *err = NULL;
     TAPState *s = net_tap_fd_init(peer, model, name, fd, vnet_hdr);
     int vhostfd;
+    NetdevTapOptions *stored;
 
     tap_set_sndbuf(s->fd, tap, &err);
     if (err) {
@@ -668,12 +686,65 @@ static void net_init_tap_one(const NetdevTapOptions *tap, NetClientState *peer,
         return;
     }
 
+    /* Store startup parameters */
+    if (!*common_stored) {
+        *common_stored = g_new0(NetdevInfo, 1);
+        (*common_stored)->type = NET_BACKEND_TAP;
+        s->nc.stored_config = *common_stored;
+    }
+    stored = &(*common_stored)->u.tap;
+
+    if (tap->has_sndbuf && !stored->has_sndbuf) {
+        stored->has_sndbuf = true;
+        stored->sndbuf = tap->sndbuf;
+    }
+
+    if (vnet_hdr && !stored->has_vnet_hdr) {
+        stored->has_vnet_hdr = true;
+        stored->vnet_hdr = true;
+    }
+
     if (tap->has_fd || tap->has_fds) {
+        if (!stored->has_fds) {
+            stored->has_fds = true;
+            stored->fds = g_strdup_printf("%d", fd);
+        } else {
+            char *tmp_s = stored->fds;
+            stored->fds = g_strdup_printf("%s:%d", stored->fds, fd);
+            g_free(tmp_s);
+        }
+
         snprintf(s->nc.info_str, sizeof(s->nc.info_str), "fd=%d", fd);
     } else if (tap->has_helper) {
+        if (!stored->has_helper) {
+            stored->has_helper = true;
+            stored->helper = g_strdup(tap->helper);
+        }
+
+        if (!stored->has_br) {
+            stored->has_br = true;
+            stored->br = tap->has_br ? g_strdup(tap->br) :
+                                       g_strdup(DEFAULT_BRIDGE_INTERFACE);
+        }
+
         snprintf(s->nc.info_str, sizeof(s->nc.info_str), "helper=%s",
                  tap->helper);
     } else {
+        if (ifname && !stored->has_ifname) {
+            stored->has_ifname = true;
+            stored->ifname = g_strdup(ifname);
+        }
+
+        if (script && !stored->has_script) {
+            stored->has_script = true;
+            stored->script = g_strdup(script);
+        }
+
+        if (downscript && !stored->has_downscript) {
+            stored->has_downscript = true;
+            stored->downscript = g_strdup(downscript);
+        }
+
         snprintf(s->nc.info_str, sizeof(s->nc.info_str),
                  "ifname=%s,script=%s,downscript=%s", ifname, script,
                  downscript);
@@ -689,9 +760,20 @@ static void net_init_tap_one(const NetdevTapOptions *tap, NetClientState *peer,
         vhostfdname || (tap->has_vhostforce && tap->vhostforce)) {
         VhostNetOptions options;
 
+        stored->has_vhost = true;
+        stored->vhost = true;
+
+        if (tap->has_vhostforce && tap->vhostforce) {
+            stored->has_vhostforce = true;
+            stored->vhostforce = true;
+        }
+
         options.backend_type = VHOST_BACKEND_TYPE_KERNEL;
         options.net_backend = &s->nc;
         if (tap->has_poll_us) {
+            stored->has_poll_us = true;
+            stored->poll_us = tap->poll_us;
+
             options.busyloop_timeout = tap->poll_us;
         } else {
             options.busyloop_timeout = 0;
@@ -731,6 +813,15 @@ static void net_init_tap_one(const NetdevTapOptions *tap, NetClientState *peer,
         }
         options.opaque = (void *)(uintptr_t)vhostfd;
 
+        if (!stored->has_vhostfds) {
+            stored->has_vhostfds = true;
+            stored->vhostfds = g_strdup_printf("%d", vhostfd);
+        } else {
+            char *tmp_s = stored->vhostfds;
+            stored->vhostfds = g_strdup_printf("%s:%d", stored->fds, vhostfd);
+            g_free(tmp_s);
+        }
+
         s->vhost_net = vhost_net_init(&options);
         if (!s->vhost_net) {
             if (tap->has_vhostforce && tap->vhostforce) {
@@ -783,6 +874,7 @@ int net_init_tap(const Netdev *netdev, const char *name,
     const char *vhostfdname;
     char ifname[128];
     int ret = 0;
+    NetdevInfo *common_stored = NULL; /* will store configuration */
 
     assert(netdev->type == NET_CLIENT_DRIVER_TAP);
     tap = &netdev->u.tap;
@@ -829,7 +921,7 @@ int net_init_tap(const Netdev *netdev, const char *name,
 
         net_init_tap_one(tap, peer, "tap", name, NULL,
                          script, downscript,
-                         vhostfdname, vnet_hdr, fd, &err);
+                         vhostfdname, vnet_hdr, fd, &common_stored, &err);
         if (err) {
             error_propagate(errp, err);
             close(fd);
@@ -892,7 +984,7 @@ int net_init_tap(const Netdev *netdev, const char *name,
             net_init_tap_one(tap, peer, "tap", name, ifname,
                              script, downscript,
                              tap->has_vhostfds ? vhost_fds[i] : NULL,
-                             vnet_hdr, fd, &err);
+                             vnet_hdr, fd, &common_stored, &err);
             if (err) {
                 error_propagate(errp, err);
                 ret = -1;
@@ -935,7 +1027,7 @@ free_fail:
 
         net_init_tap_one(tap, peer, "bridge", name, ifname,
                          script, downscript, vhostfdname,
-                         vnet_hdr, fd, &err);
+                         vnet_hdr, fd, &common_stored, &err);
         if (err) {
             error_propagate(errp, err);
             close(fd);
@@ -981,7 +1073,8 @@ free_fail:
             net_init_tap_one(tap, peer, "tap", name, ifname,
                              i >= 1 ? "no" : script,
                              i >= 1 ? "no" : downscript,
-                             vhostfdname, vnet_hdr, fd, &err);
+                             vhostfdname, vnet_hdr, fd,
+                             &common_stored, &err);
             if (err) {
                 error_propagate(errp, err);
                 close(fd);
diff --git a/net/vde.c b/net/vde.c
index 99189cc..b0b8800 100644
--- a/net/vde.c
+++ b/net/vde.c
@@ -84,6 +84,7 @@ static int net_vde_init(NetClientState *peer, const char *model,
     VDECONN *vde;
     char *init_group = (char *)group;
     char *init_sock = (char *)sock;
+    NetdevVdeOptions *stored;
 
     struct vde_open_args args = {
         .port = port,
@@ -108,6 +109,27 @@ static int net_vde_init(NetClientState *peer, const char *model,
 
     qemu_set_fd_handler(vde_datafd(s->vde), vde_to_qemu, NULL, s);
 
+    /* Store startup parameters */
+    nc->stored_config = g_new0(NetdevInfo, 1);
+    nc->stored_config->type = NET_BACKEND_VDE;
+    stored = &nc->stored_config->u.vde;
+
+    if (sock) {
+        stored->has_sock = true;
+        stored->sock = g_strdup(sock);
+    }
+
+    stored->has_port = true;
+    stored->port = port;
+
+    if (group) {
+        stored->has_group = true;
+        stored->group = g_strdup(group);
+    }
+
+    stored->has_mode = true;
+    stored->mode = mode;
+
     return 0;
 }
 
diff --git a/net/vhost-user.c b/net/vhost-user.c
index ffbd94d..5b7056b 100644
--- a/net/vhost-user.c
+++ b/net/vhost-user.c
@@ -311,14 +311,15 @@ static void net_vhost_user_event(void *opaque, QEMUChrEvent event)
 }
 
 static int net_vhost_user_init(NetClientState *peer, const char *device,
-                               const char *name, Chardev *chr,
-                               int queues)
+                               const char *name, const char *chardev,
+                               Chardev *chr, int queues)
 {
     Error *err = NULL;
     NetClientState *nc, *nc0 = NULL;
     NetVhostUserState *s = NULL;
     VhostUserState *user;
     int i;
+    NetdevVhostUserOptions *stored;
 
     assert(name);
     assert(queues > 0);
@@ -355,6 +356,16 @@ static int net_vhost_user_init(NetClientState *peer, const char *device,
 
     assert(s->vhost_net);
 
+    /* Store startup parameters */
+    nc0->stored_config = g_new0(NetdevInfo, 1);
+    nc0->stored_config->type = NET_BACKEND_VHOST_USER;
+    stored = &nc0->stored_config->u.vhost_user;
+
+    stored->chardev = g_strdup(chardev);
+
+    stored->has_queues = true;
+    stored->queues = queues;
+
     return 0;
 
 err:
@@ -446,5 +457,6 @@ int net_init_vhost_user(const Netdev *netdev, const char *name,
         return -1;
     }
 
-    return net_vhost_user_init(peer, "vhost_user", name, chr, queues);
+    return net_vhost_user_init(peer, "vhost_user", name,
+                               vhost_user_opts->chardev, chr, queues);
 }
diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index fe659ec..8c27ea0 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -184,8 +184,22 @@ static int net_vhost_vdpa_init(NetClientState *peer, const char *device,
     VhostVDPAState *s;
     int vdpa_device_fd = -1;
     int ret = 0;
+    NetdevVhostVDPAOptions *stored;
+
     assert(name);
     nc = qemu_new_net_client(&net_vhost_vdpa_info, peer, device, name);
+
+    /* Store startup parameters */
+    nc->stored_config = g_new0(NetdevInfo, 1);
+    nc->stored_config->type = NET_BACKEND_VHOST_VDPA;
+    stored = &nc->stored_config->u.vhost_vdpa;
+
+    stored->has_vhostdev = true;
+    stored->vhostdev = g_strdup(vhostdev);
+
+    stored->has_queues = true;
+    stored->queues = 1; /* TODO: change when support multiqueue */
+
     snprintf(nc->info_str, sizeof(nc->info_str), TYPE_VHOST_VDPA);
     nc->queue_index = 0;
     s = DO_UPCAST(VhostVDPAState, nc, nc);
diff --git a/qapi/net.json b/qapi/net.json
index c31748c8..87361eb 100644
--- a/qapi/net.json
+++ b/qapi/net.json
@@ -714,3 +714,83 @@
 ##
 { 'event': 'FAILOVER_NEGOTIATED',
   'data': {'device-id': 'str'} }
+
+##
+# @NetBackend:
+#
+# Available netdev backend drivers.
+#
+# Since: 6.0
+##
+{ 'enum': 'NetBackend',
+  'data': [ 'bridge', 'l2tpv3', 'netmap', 'socket', 'tap', 'user', 'vde',
+            'vhost-user', 'vhost-vdpa' ] }
+
+##
+# @NetdevInfo:
+#
+# Configuration of a network backend device (netdev).
+#
+# @id: Device identifier.
+#
+# @type: Specify the driver used for interpreting remaining arguments.
+#
+# @peer-id: The connected frontend network device name (absent if no frontend
+#           is connected).
+#
+# Since: 6.0
+##
+{ 'union': 'NetdevInfo',
+  'base': { 'id': 'str',
+            'type': 'NetBackend',
+            '*peer-id': 'str' },
+  'discriminator': 'type',
+  'data': {
+      'bridge':     'NetdevBridgeOptions',
+      'l2tpv3':     'NetdevL2TPv3Options',
+      'netmap':     'NetdevNetmapOptions',
+      'socket':     'NetdevSocketOptions',
+      'tap':        'NetdevTapOptions',
+      'user':       'NetdevUserOptions',
+      'vde':        'NetdevVdeOptions',
+      'vhost-user': 'NetdevVhostUserOptions',
+      'vhost-vdpa': 'NetdevVhostVDPAOptions' } }
+
+##
+# @query-netdev:
+#
+# Get a list of @NetdevInfo for all virtual network backend devices (netdevs).
+#
+# Returns: a list of @NetdevInfo describing each netdev.
+#
+# Since: 6.0
+#
+# Example:
+#
+# -> { "execute": "query-netdev" }
+# <- { "return": [
+#          {
+#              "ipv6": true,
+#              "ipv4": true,
+#              "host": "10.0.2.2",
+#              "ipv6-dns": "fec0::3",
+#              "ipv6-prefix": "fec0::",
+#              "net": "10.0.2.0/255.255.255.0",
+#              "ipv6-host": "fec0::2",
+#              "type": "user",
+#              "peer-id": "net0",
+#              "dns": "10.0.2.3",
+#              "hostfwd": [
+#                  {
+#                      "str": "tcp::20004-:22"
+#                  }
+#              ],
+#              "ipv6-prefixlen": 64,
+#              "id": "netdev0",
+#              "restrict": false
+#          }
+#      ]
+#    }
+#
+##
+{ 'command': 'query-netdev', 'returns': ['NetdevInfo'] }