socket: make sure we warn loudly about symlinks we can't create

Note that this change does not make symlink creation failing fatal. I am
not entirely sure about whether it should be, but I am leaning towards
not making it fatal for two reasons: symlinks like this tend to be a
compatibility feature, and hence unlikely to be essential for operation,
in a way this breaks compatibility, and while doing that is not off the
table, we should probably avoid it if we are not entirely sure it's a
good thing.

Note that this also changes plain symlink() to symlink_idempotent() so
that existing symlinks with the right destination are nothing we log
about.

Fixes: #6920

diff --git a/src/core/socket.c b/src/core/socket.c
index 3b84ffa..d1d4007 100644 (file)
--- a/src/core/socket.c
+++ b/src/core/socket.c
@@ -38,6 +38,7 @@
 #include "exit-status.h"
 #include "fd-util.h"
 #include "format-util.h"
+#include "fs-util.h"
 #include "in-addr-util.h"
 #include "io-util.h"
 #include "label.h"
@@ -1324,6 +1325,7 @@ static int mq_address_create(
 static int socket_symlink(Socket *s) {
         const char *p;
         char **i;
+        int r;
 
         assert(s);
 
@@ -1331,8 +1333,11 @@ static int socket_symlink(Socket *s) {
         if (!p)
                 return 0;
 
-        STRV_FOREACH(i, s->symlinks)
-                symlink_label(p, *i);
+        STRV_FOREACH(i, s->symlinks) {
+                r = symlink_idempotent(p, *i);
+                if (r < 0)
+                        log_unit_warning_errno(UNIT(s), r, "Failed to create symlink %s → %s, ignoring: %m", p, *i);
+        }
 
         return 0;
 }