Instead of duplicating the code from virGet{User,Group}IDByName(), which are
static anyway, extend those functions to accept NULL pointers for the result and
a boolean for controlling the error reporting.

Signed-off-by: Martin Kletzander <mkletzan@redhat.com>
---
Feel free to suggest any other way of doing this, I just felt like this is the
most readable way of doing things

 src/libvirt_private.syms |  2 ++
 src/util/virutil.c       | 40 ++++++++++++++++++++++++++++++++--------
 src/util/virutil.h       |  4 ++++
 3 files changed, 38 insertions(+), 8 deletions(-)

diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index a0d229a79f0c..e7a4d61f25fd 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -3090,6 +3090,8 @@ virUSBDeviceSetUsedBy;
 
 
 # util/virutil.h
+virDoesGroupExist;
+virDoesUserExist;
 virDoubleToStr;
 virEnumFromString;
 virEnumToString;
diff --git a/src/util/virutil.c b/src/util/virutil.c
index a908422feb7f..2290020e494e 100644
--- a/src/util/virutil.c
+++ b/src/util/virutil.c
@@ -971,9 +971,11 @@ char *virGetGroupName(gid_t gid)
 
 /* Search in the password database for a user id that matches the user name
  * `name`. Returns 0 on success, -1 on failure or 1 if name cannot be found.
+ *
+ * Warns if @missing_ok is false
  */
 static int
-virGetUserIDByName(const char *name, uid_t *uid)
+virGetUserIDByName(const char *name, uid_t *uid, bool missing_ok)
 {
     char *strbuf = NULL;
     struct passwd pwbuf;
@@ -996,7 +998,7 @@ virGetUserIDByName(const char *name, uid_t *uid)
     }
 
     if (!pw) {
-        if (rc != 0) {
+        if (rc != 0 && !missing_ok) {
             char buf[1024];
             /* log the possible error from getpwnam_r. Unfortunately error
              * reporting from this function is bad and we can't really
@@ -1009,7 +1011,8 @@ virGetUserIDByName(const char *name, uid_t *uid)
         goto cleanup;
     }
 
-    *uid = pw->pw_uid;
+    if (uid)
+        *uid = pw->pw_uid;
     ret = 0;
 
  cleanup:
@@ -1032,7 +1035,7 @@ virGetUserID(const char *user, uid_t *uid)
     if (*user == '+') {
         user++;
     } else {
-        int rc = virGetUserIDByName(user, uid);
+        int rc = virGetUserIDByName(user, uid, false);
         if (rc <= 0)
             return rc;
     }
@@ -1051,9 +1054,11 @@ virGetUserID(const char *user, uid_t *uid)
 
 /* Search in the group database for a group id that matches the group name
  * `name`. Returns 0 on success, -1 on failure or 1 if name cannot be found.
+ *
+ * Warns if @missing_ok is false
  */
 static int
-virGetGroupIDByName(const char *name, gid_t *gid)
+virGetGroupIDByName(const char *name, gid_t *gid, bool missing_ok)
 {
     char *strbuf = NULL;
     struct group grbuf;
@@ -1076,7 +1081,7 @@ virGetGroupIDByName(const char *name, gid_t *gid)
     }
 
     if (!gr) {
-        if (rc != 0) {
+        if (rc != 0 && !missing_ok) {
             char buf[1024];
             /* log the possible error from getgrnam_r. Unfortunately error
              * reporting from this function is bad and we can't really
@@ -1089,7 +1094,8 @@ virGetGroupIDByName(const char *name, gid_t *gid)
         goto cleanup;
     }
 
-    *gid = gr->gr_gid;
+    if (gid)
+        *gid = gr->gr_gid;
     ret = 0;
 
  cleanup:
@@ -1112,7 +1118,7 @@ virGetGroupID(const char *group, gid_t *gid)
     if (*group == '+') {
         group++;
     } else {
-        int rc = virGetGroupIDByName(group, gid);
+        int rc = virGetGroupIDByName(group, gid, false);
         if (rc <= 0)
             return rc;
     }
@@ -1129,6 +1135,24 @@ virGetGroupID(const char *group, gid_t *gid)
     return 0;
 }
 
+/* Silently checks if User @name exists.
+ * Returns if the user exists and fallbacks to false on error.
+ */
+int
+virDoesUserExist(const char *name, bool *exists)
+{
+    return virGetUserIDByName(name, NULL, true) == 0;
+}
+
+/* Silently checks if Group @name exists.
+ * Returns if the group exists and fallbacks to false on error.
+ */
+int
+virDoesGroupExist(const char *name)
+{
+    return virGetGroupIDByName(name, NULL, true) == 0;
+}
+
 
 /* Compute the list of primary and supplementary groups associated
  * with @uid, and including @gid in the list (unless it is -1),
diff --git a/src/util/virutil.h b/src/util/virutil.h
index 1ba9635bd991..8a27cca523c8 100644
--- a/src/util/virutil.h
+++ b/src/util/virutil.h
@@ -152,6 +152,10 @@ int virGetUserID(const char *name,
 int virGetGroupID(const char *name,
                   gid_t *gid) ATTRIBUTE_RETURN_CHECK;
 
+int virDoesUserExist(const char *name, bool *exists);
+int virDoesGroupExist(const char *name, bool *exists);
+
+
 bool virIsDevMapperDevice(const char *dev_name) ATTRIBUTE_NONNULL(1);
 
 bool virValidateWWN(const char *wwn);
-- 
2.18.0

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On Wed, Sep 12, 2018 at 05:09:12PM +0200, Martin Kletzander wrote:
>Instead of duplicating the code from virGet{User,Group}IDByName(), which are
>static anyway, extend those functions to accept NULL pointers for the result and
>a boolean for controlling the error reporting.
>
>Signed-off-by: Martin Kletzander <mkletzan@redhat.com>
>---
>Feel free to suggest any other way of doing this, I just felt like this is the
>most readable way of doing things
>
> src/libvirt_private.syms |  2 ++
> src/util/virutil.c       | 40 ++++++++++++++++++++++++++++++++--------
> src/util/virutil.h       |  4 ++++
> 3 files changed, 38 insertions(+), 8 deletions(-)
>

>+/* Silently checks if Group @name exists.
>+ * Returns if the group exists and fallbacks to false on error.
>+ */
>+int
>+virDoesGroupExist(const char *name)

util/virutil.c:1142:42: error: unused parameter 'exists' [-Werror,-Wunused-parameter]
virDoesUserExist(const char *name, bool *exists)
                                         ^
util/virutil.c:1151:1: error: conflicting types for 'virDoesGroupExist'
virDoesGroupExist(const char *name)


>+{
>+    return virGetGroupIDByName(name, NULL, true) == 0;
>+}
>+
>
> /* Compute the list of primary and supplementary groups associated
>  * with @uid, and including @gid in the list (unless it is -1),
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