qemu: command: Generate -netdev command line via JSON->cmdline conversion

The 'netdev_add' command was recently formally described in qemu via the
QMP schema. This means that it also requires the arguments to be
properly formatted. Our current approach is to generate the command line
and then use qemuMonitorJSONKeywordStringToJSON to get the JSON
properties for the monitor. This will not work if we need to pass some
fields as numbers or booleans.

In this step we re-do internals of qemuBuildHostNetStr to format a JSON
object which is converted back via virQEMUBuildNetdevCommandlineFromJSON
to the equivalent command line. This will later allow fixing of the
monitor code to use the JSON object directly rather than rely on the
conversion.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

src/qemu/qemu_command.c

@@ -3564,7 +3564,7 @@ qemuBuildNicDevStr(virDomainDefPtr def,
 }
 
 
-char *
+virJSONValuePtr
 qemuBuildHostNetStr(virDomainNetDefPtr net,
                     char **tapfd,
                     size_t tapfdSize,
@@ -3573,10 +3573,11 @@ qemuBuildHostNetStr(virDomainNetDefPtr net,
                     const char *slirpfd)
 {
     bool is_tap = false;
-    g_auto(virBuffer) buf = VIR_BUFFER_INITIALIZER;
     virDomainNetType netType = virDomainNetGetActualType(net);
     size_t i;
 
+    g_autoptr(virJSONValue) netprops = NULL;
+
     if (net->script && netType != VIR_DOMAIN_NET_TYPE_ETHERNET) {
         virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
                        _("scripts are not supported on interfaces of type %s"),
@@ -3594,54 +3595,75 @@ qemuBuildHostNetStr(virDomainNetDefPtr net,
     case VIR_DOMAIN_NET_TYPE_NETWORK:
     case VIR_DOMAIN_NET_TYPE_DIRECT:
     case VIR_DOMAIN_NET_TYPE_ETHERNET:
-        virBufferAddLit(&buf, "tap,");
+        if (virJSONValueObjectCreate(&netprops, "s:type", "tap", NULL) < 0)
+            return NULL;
+
         /* for one tapfd 'fd=' shall be used,
          * for more than one 'fds=' is the right choice */
         if (tapfdSize == 1) {
-            virBufferAsprintf(&buf, "fd=%s,", tapfd[0]);
+            if (virJSONValueObjectAdd(netprops, "s:fd", tapfd[0], NULL) < 0)
+                return NULL;
         } else {
-            virBufferAddLit(&buf, "fds=");
-            for (i = 0; i < tapfdSize; i++) {
-                if (i)
-                    virBufferAddChar(&buf, ':');
-                virBufferAdd(&buf, tapfd[i], -1);
-            }
-            virBufferAddChar(&buf, ',');
+            g_auto(virBuffer) fdsbuf = VIR_BUFFER_INITIALIZER;
+
+            for (i = 0; i < tapfdSize; i++)
+                virBufferAsprintf(&fdsbuf, "%s:", tapfd[i]);
+
+            virBufferTrim(&fdsbuf, ":");
+
+            if (virJSONValueObjectAdd(netprops,
+                                      "s:fds", virBufferCurrentContent(&fdsbuf),
+                                      NULL) < 0)
+                return NULL;
         }
+
         is_tap = true;
         break;
 
     case VIR_DOMAIN_NET_TYPE_CLIENT:
-        virBufferAsprintf(&buf, "socket,connect=%s:%d,",
-                          net->data.socket.address,
-                          net->data.socket.port);
+        if (virJSONValueObjectCreate(&netprops, "s:type", "socket", NULL) < 0 ||
+            virJSONValueObjectAppendStringPrintf(netprops, "connect", "%s:%d",
+                                                 net->data.socket.address,
+                                                 net->data.socket.port) < 0)
+            return NULL;
         break;
 
     case VIR_DOMAIN_NET_TYPE_SERVER:
-        virBufferAsprintf(&buf, "socket,listen=%s:%d,",
-                          NULLSTR_EMPTY(net->data.socket.address),
-                          net->data.socket.port);
+        if (virJSONValueObjectCreate(&netprops, "s:type", "socket", NULL) < 0 ||
+            virJSONValueObjectAppendStringPrintf(netprops, "listen", "%s:%d",
+                                                 NULLSTR_EMPTY(net->data.socket.address),
+                                                 net->data.socket.port) < 0)
+            return NULL;
         break;
 
     case VIR_DOMAIN_NET_TYPE_MCAST:
-        virBufferAsprintf(&buf, "socket,mcast=%s:%d,",
-                          net->data.socket.address,
-                          net->data.socket.port);
+        if (virJSONValueObjectCreate(&netprops, "s:type", "socket", NULL) < 0 ||
+            virJSONValueObjectAppendStringPrintf(netprops, "mcast", "%s:%d",
+                                                 net->data.socket.address,
+                                                 net->data.socket.port) < 0)
+            return NULL;
         break;
 
     case VIR_DOMAIN_NET_TYPE_UDP:
-        virBufferAsprintf(&buf, "socket,udp=%s:%d,localaddr=%s:%d,",
-                          net->data.socket.address,
-                          net->data.socket.port,
-                          net->data.socket.localaddr,
-                          net->data.socket.localport);
+        if (virJSONValueObjectCreate(&netprops, "s:type", "socket", NULL) < 0 ||
+            virJSONValueObjectAppendStringPrintf(netprops, "udp", "%s:%d",
+                                                 net->data.socket.address,
+                                                 net->data.socket.port) < 0 ||
+            virJSONValueObjectAppendStringPrintf(netprops, "localaddr", "%s:%d",
+                                                 net->data.socket.localaddr,
+                                                 net->data.socket.localport) < 0)
+            return NULL;
         break;
 
     case VIR_DOMAIN_NET_TYPE_USER:
         if (slirpfd) {
-            virBufferAsprintf(&buf, "socket,fd=%s,", slirpfd);
+            if (virJSONValueObjectCreate(&netprops, "s:type", "socket", NULL) < 0 ||
+                virJSONValueObjectAppendString(netprops, "fd", slirpfd) < 0)
+                return NULL;
         } else {
-            virBufferAddLit(&buf, "user,");
+            if (virJSONValueObjectCreate(&netprops, "s:type", "user", NULL) < 0)
+                return NULL;
+
             for (i = 0; i < net->guestIP.nips; i++) {
                 const virNetDevIPAddr *ip = net->guestIP.ips[i];
                 g_autofree char *addr = NULL;
@@ -3650,29 +3672,40 @@ qemuBuildHostNetStr(virDomainNetDefPtr net,
                     return NULL;
 
                 if (VIR_SOCKET_ADDR_IS_FAMILY(&ip->address, AF_INET)) {
-                    virBufferAsprintf(&buf, "net=%s", addr);
+                    g_autofree char *ipv4netaddr = NULL;
+
                     if (ip->prefix)
-                        virBufferAsprintf(&buf, "/%u", ip->prefix);
-                    virBufferAddChar(&buf, ',');
+                        ipv4netaddr = g_strdup_printf("%s/%u", addr, ip->prefix);
+                    else
+                        ipv4netaddr = g_strdup(addr);
+
+                    if (virJSONValueObjectAppendString(netprops, "net", ipv4netaddr) < 0)
+                        return NULL;
                 } else if (VIR_SOCKET_ADDR_IS_FAMILY(&ip->address, AF_INET6)) {
-                    virBufferAsprintf(&buf, "ipv6-prefix=%s,", addr);
-                    if (ip->prefix)
-                        virBufferAsprintf(&buf, "ipv6-prefixlen=%u,", ip->prefix);
+                    if (virJSONValueObjectAppendString(netprops, "ipv6-prefix", addr) < 0)
+                        return NULL;
+                    if (ip->prefix &&
+                        virJSONValueObjectAppendNumberUlong(netprops, "ipv6-prefixlen",
+                                                            ip->prefix) < 0)
+                        return NULL;
                 }
             }
         }
         break;
 
     case VIR_DOMAIN_NET_TYPE_INTERNAL:
-        virBufferAddLit(&buf, "user,");
+        if (virJSONValueObjectCreate(&netprops, "s:type", "user", NULL) < 0)
+            return NULL;
         break;
 
     case VIR_DOMAIN_NET_TYPE_VHOSTUSER:
-        virBufferAsprintf(&buf, "vhost-user,chardev=char%s,",
-                          net->info.alias);
-        if (net->driver.virtio.queues > 1)
-            virBufferAsprintf(&buf, "queues=%u,",
-                              net->driver.virtio.queues);
+        if (virJSONValueObjectCreate(&netprops, "s:type", "vhost-user", NULL) < 0 ||
+            virJSONValueObjectAppendStringPrintf(netprops, "chardev", "char%s", net->info.alias) < 0)
+            return NULL;
+
+        if (net->driver.virtio.queues > 1 &&
+            virJSONValueObjectAppendNumberUlong(netprops, "queues", net->driver.virtio.queues) < 0)
+            return NULL;
         break;
 
     case VIR_DOMAIN_NET_TYPE_HOSTDEV:
@@ -3681,31 +3714,38 @@ qemuBuildHostNetStr(virDomainNetDefPtr net,
         break;
     }
 
-    virBufferAsprintf(&buf, "id=host%s,", net->info.alias);
+    if (virJSONValueObjectAppendStringPrintf(netprops, "id", "host%s", net->info.alias) < 0)
+        return NULL;
 
     if (is_tap) {
         if (vhostfdSize) {
-            virBufferAddLit(&buf, "vhost=on,");
+            if (virJSONValueObjectAppendBoolean(netprops, "vhost", true) < 0)
+                return NULL;
+
             if (vhostfdSize == 1) {
-                virBufferAsprintf(&buf, "vhostfd=%s,", vhostfd[0]);
+                if (virJSONValueObjectAdd(netprops, "s:vhostfd", vhostfd[0], NULL) < 0)
+                    return NULL;
             } else {
-                virBufferAddLit(&buf, "vhostfds=");
-                for (i = 0; i < vhostfdSize; i++) {
-                    if (i)
-                        virBufferAddChar(&buf, ':');
-                    virBufferAdd(&buf, vhostfd[i], -1);
-                }
-                virBufferAddChar(&buf, ',');
+                g_auto(virBuffer) fdsbuf = VIR_BUFFER_INITIALIZER;
+
+                for (i = 0; i < vhostfdSize; i++)
+                    virBufferAsprintf(&fdsbuf, "%s:", vhostfd[i]);
+
+                virBufferTrim(&fdsbuf, ":");
+
+                if (virJSONValueObjectAdd(netprops,
+                                          "s:vhostfds", virBufferCurrentContent(&fdsbuf),
+                                          NULL) < 0)
+                    return NULL;
             }
         }
-        if (net->tune.sndbuf_specified)
-            virBufferAsprintf(&buf, "sndbuf=%lu,", net->tune.sndbuf);
+
+        if (net->tune.sndbuf_specified &&
+            virJSONValueObjectAppendNumberUlong(netprops, "sndbuf", net->tune.sndbuf) < 0)
+            return NULL;
     }
 
-
-    virBufferTrim(&buf, ",");
-
-    return virBufferContentAndReset(&buf);
+    return g_steal_pointer(&netprops);
 }
 
 
@@ -7680,6 +7720,7 @@ qemuBuildInterfaceCommandLine(virQEMUDriverPtr driver,
     bool requireNicdev = false;
     qemuSlirpPtr slirp;
     size_t i;
+    g_autoptr(virJSONValue) hostnetprops = NULL;
 
 
     if (!bootindex)
@@ -7883,11 +7924,15 @@ qemuBuildInterfaceCommandLine(virQEMUDriverPtr driver,
     if (chardev)
         virCommandAddArgList(cmd, "-chardev", chardev, NULL);
 
-    if (!(host = qemuBuildHostNetStr(net,
-                                     tapfdName, tapfdSize,
-                                     vhostfdName, vhostfdSize,
-                                     slirpfdName)))
+    if (!(hostnetprops = qemuBuildHostNetStr(net,
+                                             tapfdName, tapfdSize,
+                                             vhostfdName, vhostfdSize,
+                                             slirpfdName)))
         goto cleanup;
+
+    if (!(host = virQEMUBuildNetdevCommandlineFromJSON(hostnetprops)))
+        goto cleanup;
+
     virCommandAddArgList(cmd, "-netdev", host, NULL);
 
     /* Possible combinations:

src/qemu/qemu_command.h

@@ -89,12 +89,12 @@ qemuBuildChrDeviceStr(char **deviceStr,
 char *
 qemuBuildChannelGuestfwdNetdevProps(virDomainChrDefPtr chr);
 
-char *qemuBuildHostNetStr(virDomainNetDefPtr net,
-                          char **tapfd,
-                          size_t tapfdSize,
-                          char **vhostfd,
-                          size_t vhostfdSize,
-                          const char *slirpfd);
+virJSONValuePtr qemuBuildHostNetStr(virDomainNetDefPtr net,
+                                    char **tapfd,
+                                    size_t tapfdSize,
+                                    char **vhostfd,
+                                    size_t vhostfdSize,
+                                    const char *slirpfd);
 
 /* Current, best practice */
 char *qemuBuildNicDevStr(virDomainDefPtr def,

src/qemu/qemu_hotplug.c

@@ -54,6 +54,7 @@
 #include "virstoragefile.h"
 #include "virstring.h"
 #include "virtime.h"
+#include "virqemu.h"
 
 #define VIR_FROM_THIS VIR_FROM_QEMU
 
@@ -1157,6 +1158,7 @@ qemuDomainAttachNetDevice(virQEMUDriverPtr driver,
     size_t vhostfdSize = 0;
     size_t queueSize = 0;
     g_autofree char *nicstr = NULL;
+    g_autoptr(virJSONValue) netprops = NULL;
     g_autofree char *netstr = NULL;
     int ret = -1;
     bool releaseaddr = false;
@@ -1382,10 +1384,13 @@ qemuDomainAttachNetDevice(virQEMUDriverPtr driver,
     for (i = 0; i < vhostfdSize; i++)
         vhostfdName[i] = g_strdup_printf("vhostfd-%s%zu", net->info.alias, i);
 
-    if (!(netstr = qemuBuildHostNetStr(net,
-                                       tapfdName, tapfdSize,
-                                       vhostfdName, vhostfdSize,
-                                       slirpfdName)))
+    if (!(netprops = qemuBuildHostNetStr(net,
+                                         tapfdName, tapfdSize,
+                                         vhostfdName, vhostfdSize,
+                                         slirpfdName)))
+        goto cleanup;
+
+    if (!(netstr = virQEMUBuildNetdevCommandlineFromJSON(netprops)))
         goto cleanup;
 
     qemuDomainObjEnterMonitor(driver, vm);