On a Sunday in 2023, Laine Stump wrote:
>This consists of (1) adding the necessary args to the qemu commandline
>netdev option, and (2) starting a passt process prior to starting
>qemu, and making sure that it is terminated when it's no longer
>needed. Under normal circumstances, passt will terminate itself as
>soon as qemu closes its socket, but in case of some error where qemu
>is never started, or fails to startup completely, we need to terminate
>passt manually.
>
>Signed-off-by: Laine Stump <laine@redhat.com>
>---
> meson.build                                   |   1 +
> po/POTFILES                                   |   1 +
> src/qemu/meson.build                          |   2 +
> src/qemu/qemu_command.c                       |  11 +-
> src/qemu/qemu_command.h                       |   3 +-
> src/qemu/qemu_domain.c                        |   5 +-
> src/qemu/qemu_domain.h                        |   3 +-
> src/qemu/qemu_extdevice.c                     |  25 +-
> src/qemu/qemu_hotplug.c                       |  26 +-
> src/qemu/qemu_passt.c                         | 284 ++++++++++++++++++
> src/qemu/qemu_passt.h                         |  38 +++
> src/qemu/qemu_process.c                       |   1 +
> src/qemu/qemu_validate.c                      |   9 +-
> tests/qemuxml2argvdata/net-user-passt.args    |  34 +++
> .../net-user-passt.x86_64-latest.args         |  37 +++
> tests/qemuxml2argvtest.c                      |   2 +
> 16 files changed, 470 insertions(+), 12 deletions(-)
> create mode 100644 src/qemu/qemu_passt.c
> create mode 100644 src/qemu/qemu_passt.h
> create mode 100644 tests/qemuxml2argvdata/net-user-passt.args
> create mode 100644 tests/qemuxml2argvdata/net-user-passt.x86_64-latest.args
>
>diff --git a/src/qemu/qemu_passt.c b/src/qemu/qemu_passt.c
>new file mode 100644
>index 0000000000..5941594811
>--- /dev/null
>+++ b/src/qemu/qemu_passt.c
>@@ -0,0 +1,284 @@
>+/*
>+ * qemu_passt.c: QEMU passt support
>+ *
>+ * Copyright (C) 2022 Red Hat, Inc.
>+ *
>+ * This library is free software; you can redistribute it and/or
>+ * modify it under the terms of the GNU Lesser General Public
>+ * License as published by the Free Software Foundation; either
>+ * version 2.1 of the License, or (at your option) any later version.
>+ *
>+ * This library is distributed in the hope that it will be useful,
>+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
>+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>+ * Lesser General Public License for more details.
>+ *
>+ * You should have received a copy of the GNU Lesser General Public
>+ * License along with this library.  If not, see
>+ * <http://www.gnu.org/licenses/>.
>+ */
>+
>+#include <config.h>
>+
>+#include "qemu_dbus.h"
>+#include "qemu_extdevice.h"
>+#include "qemu_security.h"
>+#include "qemu_passt.h"
>+#include "virenum.h"
>+#include "virerror.h"
>+#include "virjson.h"
>+#include "virlog.h"
>+#include "virpidfile.h"
>+
>+#define VIR_FROM_THIS VIR_FROM_NONE
>+
>+VIR_LOG_INIT("qemu.passt");
>+
>+
>+static char *
>+qemuPasstCreatePidFilename(virDomainObj *vm,
>+                           virDomainNetDef *net)
>+{
>+    qemuDomainObjPrivate *priv = vm->privateData;
>+    virQEMUDriver *driver = priv->driver;
>+    g_autoptr(virQEMUDriverConfig) cfg = virQEMUDriverGetConfig(driver);
>+    g_autofree char *name = NULL;
>+
>+    name = g_strdup_printf("%s-%s-passt", vm->def->name, net->info.alias);

Please use virDomainDefGetShortName for filename purposes.

>+
>+    return virPidFileBuildPath(cfg->passtStateDir, name);
>+}
>+
>+

[...]

>+int
>+qemuPasstAddNetProps(virDomainObj *vm,
>+                     virDomainNetDef *net,
>+                     virJSONValue **netprops)
>+{
>+    g_autofree char *passtSocketName = qemuPasstCreateSocketPath(vm, net);
>+    g_autoptr(virJSONValue) addrprops = NULL;
>+
>+    if (virJSONValueObjectAdd(&addrprops,
>+                              "s:type", "unix",
>+                              "s:path", passtSocketName,
>+                              NULL) < 0) {
>+        return -1;
>+    }
>+
>+    if (virJSONValueObjectAdd(netprops,
>+                              "s:type", "stream",
>+                              "a:addr", &addrprops,
>+                              "b:server", false,

>+                              /*  "u:reconnect", 5, */

Debugging leftover?

>+                              NULL) < 0) {
>+        return -1;
>+    }
>+    return 0;
>+}
>+
>+
>+void
>+qemuPasstStop(virDomainObj *vm,
>+              virDomainNetDef *net)
>+{
>+    g_autofree char *pidfile = qemuPasstCreatePidFilename(vm, net);
>+    virErrorPtr orig_err;
>+
>+    virErrorPreserveLast(&orig_err);
>+
>+

Extra whitespace

>+    if (virPidFileForceCleanupPath(pidfile) < 0)
>+        VIR_WARN("Unable to kill passt process");
>+
>+    virErrorRestore(&orig_err);
>+}
>+
>+

Reviewed-by: Ján Tomko <jtomko@redhat.com>

Jano