util: introduce sethostname_idempotent

Function queries system hostname and applies changes only when necessary. Also,
migrate all client of sethostname to sethostname_idempotent while at it.

2 files changed, 22 insertions, 0 deletions

diff --git a/src/shared/util.c b/src/shared/util.c
index bc97c67f76..7d94a28302 100644
--- a/src/shared/util.c
+++ b/src/shared/util.c
@@ -7175,3 +7175,23 @@ int free_and_strdup(char **p, const char *s) {
 
         return 0;
 }
+
+int sethostname_idempotent(const char *s) {
+        int r;
+        char buf[HOST_NAME_MAX + 1] = {};
+
+        assert(s);
+
+        r = gethostname(buf, sizeof(buf));
+        if (r < 0)
+                return -errno;
+
+        if (streq(buf, s))
+                return 0;
+
+        r = sethostname(buf, strlen(buf));
+        if (r < 0)
+                return -errno;
+
+        return 1;
+}
diff --git a/src/shared/util.h b/src/shared/util.h
index 887cdc4a44..35584467c1 100644
--- a/src/shared/util.h
+++ b/src/shared/util.h
@@ -997,3 +997,5 @@ int unquote_first_word(const char **p, char **ret);
 int unquote_many_words(const char **p, ...) _sentinel_;
 
 int free_and_strdup(char **p, const char *s);
+
+int sethostname_idempotent(const char *s);