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Re: [libvirt] [PATCH v2 3/3] qemu: improve detection of UNIX path generated by libvirt



On Fri, May 12, 2017 at 02:57:56PM +0200, Pavel Hrdina wrote:
Currently we consider all UNIX paths with specific prefix as generated
by libvirt, but that's a wrong assumption.  Let's make the detection
better by actually checking whether the whole path matches one of the
paths that we generate or generated in the past.

The UNIX path isn't stored in config XML since libvirt-1.3.0.


1.3.1, I believe.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1446980

Signed-off-by: Pavel Hrdina <phrdina redhat com>
---

changes in v2:
   - dropped the magic to split the path into 3 parts and use only one
     regexp to match the path

src/qemu/qemu_domain.c                             | 51 ++++++++++++++++++----
.../qemuxml2argv-channel-unix-gen-path1.xml        | 17 ++++++++
.../qemuxml2argv-channel-unix-gen-path2.xml        | 17 ++++++++
.../qemuxml2argv-channel-unix-gen-path3.xml        | 17 ++++++++
.../qemuxml2argv-channel-unix-user-path.xml        | 17 ++++++++
.../qemuxml2xmlout-channel-unix-gen-path1.xml      | 32 ++++++++++++++
.../qemuxml2xmlout-channel-unix-gen-path2.xml      | 32 ++++++++++++++
.../qemuxml2xmlout-channel-unix-gen-path3.xml      | 32 ++++++++++++++
.../qemuxml2xmlout-channel-unix-user-path.xml      | 33 ++++++++++++++
tests/qemuxml2xmltest.c                            |  5 +++
10 files changed, 244 insertions(+), 9 deletions(-)
create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-channel-unix-gen-path1.xml
create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-channel-unix-gen-path2.xml
create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-channel-unix-gen-path3.xml
create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-channel-unix-user-path.xml
create mode 100644 tests/qemuxml2xmloutdata/qemuxml2xmlout-channel-unix-gen-path1.xml
create mode 100644 tests/qemuxml2xmloutdata/qemuxml2xmlout-channel-unix-gen-path2.xml
create mode 100644 tests/qemuxml2xmloutdata/qemuxml2xmlout-channel-unix-gen-path3.xml
create mode 100644 tests/qemuxml2xmloutdata/qemuxml2xmlout-channel-unix-user-path.xml


Just have one file that tests it all.

diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index cc02c801e1..00e37d3428 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -3154,24 +3154,57 @@ qemuDomainDefaultNetModel(const virDomainDef *def,


/*
- * Clear auto generated unix socket path, i.e., the one which starts with our
- * channel directory.
+ * Clear auto generated unix socket paths:
+ *
+ * libvirt 1.2.18 and older:
+ *     {cfg->channelTargetDir}/{dom-name}.{target-name}
+ *
+ * libvirt 1.2.19 - 1.3.2:
+ *     {cfg->channelTargetDir}/domain-{dom-name}/{target-name}
+ *
+ * libvirt 1.3.3 and newer:
+ *     {cfg->channelTargetDir}/domain-{dom-id}-{short-dom-name}/{target-name}
+ *
+ * The unix socket path was stored in config XML until libvirt 1.3.0.
+ * If someone specifies the same path as we generate, they shouldn't do it.
+ *
+ * This function clears the path for migration as well, so we need to clear
+ * the path event if we are not storing it in the XML.
 */
-static void
+static int

This ^^ is not reflected anywhere.  It's a pity that such function (that
just conditionally frees something) can fail.

qemuDomainChrDefDropDefaultPath(virDomainChrDefPtr chr,
                                virQEMUDriverPtr driver)
{
    virQEMUDriverConfigPtr cfg = virQEMUDriverGetConfig(driver);
+    virBuffer buf = VIR_BUFFER_INITIALIZER;
+    char *regexp = NULL;
+    int ret = -1;

-    if (chr->deviceType == VIR_DOMAIN_CHR_DEVICE_TYPE_CHANNEL &&
-        chr->targetType == VIR_DOMAIN_CHR_CHANNEL_TARGET_TYPE_VIRTIO &&
-        chr->source->type == VIR_DOMAIN_CHR_TYPE_UNIX &&
-        chr->source->data.nix.path &&
-        STRPREFIX(chr->source->data.nix.path, cfg->channelTargetDir)) {
+    if (chr->deviceType != VIR_DOMAIN_CHR_DEVICE_TYPE_CHANNEL ||
+        chr->targetType != VIR_DOMAIN_CHR_CHANNEL_TARGET_TYPE_VIRTIO ||
+        chr->source->type != VIR_DOMAIN_CHR_TYPE_UNIX ||
+        !chr->source->data.nix.path) {

This would be more readable if you postponed the initialization of @cfg
and just return 0 from this.  Optionally break this into multiple
conditions.

+        ret = 0;
+        goto cleanup;
+    }
+
+    virBufferEscapeRegex(&buf, "^%s", cfg->channelTargetDir);
+    virBufferAddLit(&buf, "/([^/]+\\.)|(domain-[^/]+/)");
+    virBufferEscapeRegex(&buf, "%s$", chr->target.name);
+
+    if (virBufferCheckError(&buf) < 0)
+        goto cleanup;
+

No need to do this ^^, [1]

+    regexp = virBufferContentAndReset(&buf);
+

[1] Just do this:

if ((regexp = virBufferContentAndReset(&buf)) < 0)
 goto cleanup;

or similar.

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