[libvirt PATCH 2/3] qemu: add reconnect=5 to passt qemu commandline options when available

[Laine Stump <laine@redhat.com>]

QEMU's "reconnect" option of "-netdev stream" tells QEMU to
periodically (period is given in seconds as an argument to the option)
attempt to reconnect to the same passt socket to which it had
originally connected to. This is useful in cases where the passt
process terminates, and libvirtd starts a new passt process in its
place (which doesn't happen yet, but will happen automatically after
an upcoming patch in this series).

Since there is no real hueristic for determining the "best" value of
the reconnect interval, rather than clutter up config with a knob that
nobody knows how to properly twiddle, we just set the reconnect timer
to 5 seconds.

"-netdev stream" first appeared in QEMU 7.2.0, but the reconnect
option won't be available until QEMU 8.0.0, so we need to check QEMU
capabilities just in case someone is using QEMU 7.2.0 (and thus can
support passt backend, but not reconnect)

Signed-off-by: Laine Stump <laine@redhat.com>
---
 src/qemu/qemu_passt.c                         | 11 ++++++
 .../net-user-passt.x86_64-7.2.0.args          | 37 +++++++++++++++++++
 .../net-user-passt.x86_64-latest.args         |  2 +-
 tests/qemuxml2argvtest.c                      |  1 +
 4 files changed, 50 insertions(+), 1 deletion(-)
 create mode 100644 tests/qemuxml2argvdata/net-user-passt.x86_64-7.2.0.args

diff --git a/src/qemu/qemu_passt.c b/src/qemu/qemu_passt.c
index 1217a6a087..55199c9d36 100644
--- a/src/qemu/qemu_passt.c
+++ b/src/qemu/qemu_passt.c
@@ -83,6 +83,8 @@ qemuPasstAddNetProps(virDomainObj *vm,
 {
     g_autofree char *passtSocketName = qemuPasstCreateSocketPath(vm, net);
     g_autoptr(virJSONValue) addrprops = NULL;
+    qemuDomainObjPrivate *priv = vm->privateData;
+    virQEMUCaps *qemuCaps = priv->qemuCaps;
 
     if (virJSONValueObjectAdd(&addrprops,
                               "s:type", "unix",
@@ -98,6 +100,15 @@ qemuPasstAddNetProps(virDomainObj *vm,
                               NULL) < 0) {
         return -1;
     }
+
+    /* a narrow range of QEMU releases support -netdev stream, but
+     * don't support its "reconnect" option
+     */
+    if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_NETDEV_STREAM_RECONNECT) &&
+        virJSONValueObjectAdd(netprops, "u:reconnect", 5, NULL) < 0) {
+        return -1;
+    }
+
     return 0;
 }
 
diff --git a/tests/qemuxml2argvdata/net-user-passt.x86_64-7.2.0.args b/tests/qemuxml2argvdata/net-user-passt.x86_64-7.2.0.args
new file mode 100644
index 0000000000..037dabb87d
--- /dev/null
+++ b/tests/qemuxml2argvdata/net-user-passt.x86_64-7.2.0.args
@@ -0,0 +1,37 @@
+LC_ALL=C \
+PATH=/bin \
+HOME=/tmp/lib/domain--1-QEMUGuest1 \
+USER=test \
+LOGNAME=test \
+XDG_DATA_HOME=/tmp/lib/domain--1-QEMUGuest1/.local/share \
+XDG_CACHE_HOME=/tmp/lib/domain--1-QEMUGuest1/.cache \
+XDG_CONFIG_HOME=/tmp/lib/domain--1-QEMUGuest1/.config \
+/usr/bin/qemu-system-x86_64 \
+-name guest=QEMUGuest1,debug-threads=on \
+-S \
+-object '{"qom-type":"secret","id":"masterKey0","format":"raw","file":"/tmp/lib/domain--1-QEMUGuest1/master-key.aes"}' \
+-machine pc-i440fx-7.2,usb=off,dump-guest-core=off,memory-backend=pc.ram \
+-accel tcg \
+-cpu qemu64 \
+-m 214 \
+-object '{"qom-type":"memory-backend-ram","id":"pc.ram","size":224395264}' \
+-overcommit mem-lock=off \
+-smp 1,sockets=1,cores=1,threads=1 \
+-uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \
+-display none \
+-no-user-config \
+-nodefaults \
+-chardev socket,id=charmonitor,fd=1729,server=on,wait=off \
+-mon chardev=charmonitor,id=monitor,mode=control \
+-rtc base=utc \
+-no-shutdown \
+-no-acpi \
+-boot strict=on \
+-blockdev '{"driver":"host_device","filename":"/dev/HostVG/QEMUGuest1","node-name":"libvirt-1-storage","auto-read-only":true,"discard":"unmap"}' \
+-blockdev '{"node-name":"libvirt-1-format","read-only":false,"driver":"raw","file":"libvirt-1-storage"}' \
+-device '{"driver":"ide-hd","bus":"ide.0","unit":0,"drive":"libvirt-1-format","id":"ide0-0-0","bootindex":1}' \
+-netdev '{"type":"stream","addr":{"type":"unix","path":"/bad-test-used-env-xdg-runtime-dir/libvirt/qemu/run/passt/-1-QEMUGuest1-net0.socket"},"server":false,"id":"hostnet0"}' \
+-device '{"driver":"rtl8139","netdev":"hostnet0","id":"net0","mac":"00:11:22:33:44:55","bus":"pci.0","addr":"0x2"}' \
+-audiodev '{"id":"audio1","driver":"none"}' \
+-sandbox on,obsolete=deny,elevateprivileges=deny,spawn=deny,resourcecontrol=deny \
+-msg timestamp=on
diff --git a/tests/qemuxml2argvdata/net-user-passt.x86_64-latest.args b/tests/qemuxml2argvdata/net-user-passt.x86_64-latest.args
index 48e3e8ca8b..f84bec2ec1 100644
--- a/tests/qemuxml2argvdata/net-user-passt.x86_64-latest.args
+++ b/tests/qemuxml2argvdata/net-user-passt.x86_64-latest.args
@@ -30,7 +30,7 @@ XDG_CONFIG_HOME=/tmp/lib/domain--1-QEMUGuest1/.config \
 -blockdev '{"driver":"host_device","filename":"/dev/HostVG/QEMUGuest1","node-name":"libvirt-1-storage","auto-read-only":true,"discard":"unmap"}' \
 -blockdev '{"node-name":"libvirt-1-format","read-only":false,"driver":"raw","file":"libvirt-1-storage"}' \
 -device '{"driver":"ide-hd","bus":"ide.0","unit":0,"drive":"libvirt-1-format","id":"ide0-0-0","bootindex":1}' \
--netdev '{"type":"stream","addr":{"type":"unix","path":"/bad-test-used-env-xdg-runtime-dir/libvirt/qemu/run/passt/-1-QEMUGuest1-net0.socket"},"server":false,"id":"hostnet0"}' \
+-netdev '{"type":"stream","addr":{"type":"unix","path":"/bad-test-used-env-xdg-runtime-dir/libvirt/qemu/run/passt/-1-QEMUGuest1-net0.socket"},"server":false,"reconnect":5,"id":"hostnet0"}' \
 -device '{"driver":"rtl8139","netdev":"hostnet0","id":"net0","mac":"00:11:22:33:44:55","bus":"pci.0","addr":"0x2"}' \
 -audiodev '{"id":"audio1","driver":"none"}' \
 -sandbox on,obsolete=deny,elevateprivileges=deny,spawn=deny,resourcecontrol=deny \
diff --git a/tests/qemuxml2argvtest.c b/tests/qemuxml2argvtest.c
index b897814a5d..5a33c336c8 100644
--- a/tests/qemuxml2argvtest.c
+++ b/tests/qemuxml2argvtest.c
@@ -1471,6 +1471,7 @@ mymain(void)
     DO_TEST_CAPS_ARCH_LATEST_FULL("net-user", "x86_64", ARG_FLAGS, FLAG_SLIRP_HELPER);
     DO_TEST_NOCAPS("net-user-addr");
     DO_TEST_CAPS_LATEST("net-user-passt");
+    DO_TEST_CAPS_VER("net-user-passt", "7.2.0");
     DO_TEST_NOCAPS("net-virtio");
     DO_TEST_NOCAPS("net-virtio-device");
     DO_TEST_NOCAPS("net-virtio-disable-offloads");
-- 
@@ -1471,6 +1471,7 @@ mymain(void)
     DO_TEST_CAPS_ARCH_LATEST_FULL("net-user", "x86_64", ARG_FLAGS, FLAG_SLIRP_HELPER);
     DO_TEST_NOCAPS("net-user-addr");
     DO_TEST_CAPS_LATEST("net-user-passt");
+    DO_TEST_CAPS_VER("net-user-passt", "7.2.0");
     DO_TEST_NOCAPS("net-virtio");
     DO_TEST_NOCAPS("net-virtio-device");
     DO_TEST_NOCAPS("net-virtio-disable-offloads");
-- 
2.39.2