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[libvirt] [PATCH v2] daemon: add option to read host uuid from /etc/machine-id



Daemon config parameter switch between reading host uuid
either from smbios or machine-id:

host_uuid_source = "smbios|machine-id"

Signed-off-by: Nikolay Shirokovskiy <nshirokovskiy virtuozzo com>
---

difference from version 1:

* move file reading function to virfile.c and generalize it
* change comments and documentation as suggested by reviewer (see NOTES)

NOTES

Cole, I eventually found the way you suggested to document host_uuid 
slightly misguided. It sounds like it is applied only if
dmidecode fail. So documentation is slightly different from
that is your reply.

 daemon/libvirtd-config.c |  2 ++
 daemon/libvirtd-config.h |  1 +
 daemon/libvirtd.c        | 38 +++++++++++++++++++++++++++++++++++---
 daemon/libvirtd.conf     | 15 +++++++++++----
 src/libvirt_private.syms |  2 ++
 src/util/virfile.c       | 24 ++++++++++++++++++++++++
 src/util/virfile.h       |  2 ++
 src/util/viruuid.c       | 11 ++---------
 8 files changed, 79 insertions(+), 16 deletions(-)

diff --git a/daemon/libvirtd-config.c b/daemon/libvirtd-config.c
index 7a448f9..45280e9 100644
--- a/daemon/libvirtd-config.c
+++ b/daemon/libvirtd-config.c
@@ -374,6 +374,7 @@ daemonConfigFree(struct daemonConfig *data)
     VIR_FREE(data->crl_file);
 
     VIR_FREE(data->host_uuid);
+    VIR_FREE(data->host_uuid_source);
     VIR_FREE(data->log_filters);
     VIR_FREE(data->log_outputs);
 
@@ -463,6 +464,7 @@ daemonConfigLoadOptions(struct daemonConfig *data,
     GET_CONF_UINT(conf, filename, audit_logging);
 
     GET_CONF_STR(conf, filename, host_uuid);
+    GET_CONF_STR(conf, filename, host_uuid_source);
 
     GET_CONF_UINT(conf, filename, log_level);
     GET_CONF_STR(conf, filename, log_filters);
diff --git a/daemon/libvirtd-config.h b/daemon/libvirtd-config.h
index 3e1971d..672e9ad 100644
--- a/daemon/libvirtd-config.h
+++ b/daemon/libvirtd-config.h
@@ -28,6 +28,7 @@
 
 struct daemonConfig {
     char *host_uuid;
+    char *host_uuid_source;
 
     int listen_tls;
     int listen_tcp;
diff --git a/daemon/libvirtd.c b/daemon/libvirtd.c
index 7ec02ad..a489136 100644
--- a/daemon/libvirtd.c
+++ b/daemon/libvirtd.c
@@ -1076,6 +1076,39 @@ static int migrateProfile(void)
     return ret;
 }
 
+static int
+daemonSetupHostUUID(const struct daemonConfig *config)
+{
+    static const char *machine_id = "/etc/machine-id";
+    char buf[VIR_UUID_STRING_BUFLEN];
+    const char *uuid;
+
+    if (config->host_uuid) {
+        uuid = config->host_uuid;
+    } else if (!config->host_uuid_source ||
+               STREQ(config->host_uuid_source, "smbios")) {
+        /* smbios UUID is fetched on demand in virGetHostUUID */
+        return 0;
+    } else if (STREQ(config->host_uuid_source, "machine-id")) {
+        if (virFileReadBufQuiet(machine_id, buf, sizeof(buf)) < 0) {
+            VIR_ERROR(_("Can't read %s"), machine_id);
+            return -1;
+        }
+
+        uuid = buf;
+    } else {
+        VIR_ERROR(_("invalid UUID source: %s"), config->host_uuid_source);
+        return -1;
+    }
+
+    if (virSetHostUUIDStr(uuid)) {
+        VIR_ERROR(_("invalid host UUID: %s"), uuid);
+        return -1;
+    }
+
+    return 0;
+}
+
 /* Print command-line usage. */
 static void
 daemonUsage(const char *argv0, bool privileged)
@@ -1295,9 +1328,8 @@ int main(int argc, char **argv) {
         exit(EXIT_FAILURE);
     }
 
-    if (config->host_uuid &&
-        virSetHostUUIDStr(config->host_uuid) < 0) {
-        VIR_ERROR(_("invalid host UUID: %s"), config->host_uuid);
+    if (daemonSetupHostUUID(config) < 0) {
+        VIR_ERROR(_("Can't setup host uuid"));
         exit(EXIT_FAILURE);
     }
 
diff --git a/daemon/libvirtd.conf b/daemon/libvirtd.conf
index d2c439c..1c1fa7f 100644
--- a/daemon/libvirtd.conf
+++ b/daemon/libvirtd.conf
@@ -410,10 +410,16 @@
 
 ###################################################################
 # UUID of the host:
-# Provide the UUID of the host here in case the command
-# 'dmidecode -s system-uuid' does not provide a valid uuid. In case
-# 'dmidecode' does not provide a valid UUID and none is provided here, a
-# temporary UUID will be generated.
+# Host UUID is read from one of the sources specified in host_uuid_source.
+#
+# - 'smbios': fetch the UUID from 'dmidecode -s system-uuid'
+# - 'machine-id': fetch the UUID from /etc/machine-id
+#
+# The host_uuid_source default is 'smbios'. If 'dmidecode' does not provide
+# a valid UUID a temporary UUID will be generated.
+#
+# Another option is to specify host UUID in host_uuid.
+#
 # Keep the format of the example UUID below. UUID must not have all digits
 # be the same.
 
@@ -421,6 +427,7 @@
 # it with the output of the 'uuidgen' command and then
 # uncomment this entry
 #host_uuid = "00000000-0000-0000-0000-000000000000"
+#host_uuid_source = "smbios"
 
 ###################################################################
 # Keepalive protocol:
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 0de35ef..98e9ac5 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -1510,6 +1510,7 @@ virFileOpenTty;
 virFilePrintf;
 virFileReadAll;
 virFileReadAllQuiet;
+virFileReadBufQuiet;
 virFileReadHeaderFD;
 virFileReadLimFD;
 virFileRelLinkPointsTo;
@@ -2537,6 +2538,7 @@ virUUIDFormat;
 virUUIDGenerate;
 virUUIDIsValid;
 virUUIDParse;
+virUUIDRead;
 
 
 # util/virxml.h
diff --git a/src/util/virfile.c b/src/util/virfile.c
index 730c08d..4d7b510 100644
--- a/src/util/virfile.c
+++ b/src/util/virfile.c
@@ -1401,6 +1401,30 @@ virFileReadAllQuiet(const char *path, int maxlen, char **buf)
     return len;
 }
 
+/* Read @file into preallocated buffer @buf of size @len.
+ * Return value is -errno in case of errors and size
+ * of data read (no trailing zero) in case of success.
+ * If there is more data then @len - 1 then data will be
+ * truncated. */
+int
+virFileReadBufQuiet(const char *file, char *buf, int len)
+{
+    int fd;
+    ssize_t sz;
+
+    fd = open(file, O_RDONLY);
+    if (fd < 0)
+        return -errno;
+
+    sz = saferead(fd, buf, len - 1);
+    VIR_FORCE_CLOSE(fd);
+    if (sz < 0)
+        return -errno;
+
+    buf[sz] = '\0';
+    return sz;
+}
+
 /* Truncate @path and write @str to it.  If @mode is 0, ensure that
    @path exists; otherwise, use @mode if @path must be created.
    Return 0 for success, nonzero for failure.
diff --git a/src/util/virfile.h b/src/util/virfile.h
index 312f226..dc62eab 100644
--- a/src/util/virfile.h
+++ b/src/util/virfile.h
@@ -131,6 +131,8 @@ int virFileReadAll(const char *path, int maxlen, char **buf)
     ATTRIBUTE_RETURN_CHECK ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(3);
 int virFileReadAllQuiet(const char *path, int maxlen, char **buf)
     ATTRIBUTE_RETURN_CHECK ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(3);
+int virFileReadBufQuiet(const char *file, char *buf, int len)
+    ATTRIBUTE_RETURN_CHECK ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2);
 
 int virFileWriteStr(const char *path, const char *str, mode_t mode)
     ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2) ATTRIBUTE_RETURN_CHECK;
diff --git a/src/util/viruuid.c b/src/util/viruuid.c
index 16e57db..3cbaae0 100644
--- a/src/util/viruuid.c
+++ b/src/util/viruuid.c
@@ -231,15 +231,8 @@ getDMISystemUUID(char *uuid, int len)
     };
 
     while (paths[i]) {
-        int fd = open(paths[i], O_RDONLY);
-        if (fd >= 0) {
-            if (saferead(fd, uuid, len - 1) == len - 1) {
-                uuid[len - 1] = '\0';
-                VIR_FORCE_CLOSE(fd);
-                return 0;
-            }
-            VIR_FORCE_CLOSE(fd);
-        }
+        if (virFileReadBufQuiet(paths[i], uuid, len) == len - 1)
+            return 0;
         i++;
     }
 
-- 
1.8.3.1


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