In src/network/networkd-link.c link_save():

--
  1365	                        fprintf(f, "%s%s", *address,
  1366	                                (address + 1 ? " " : ""));
--
  1380	                        fprintf(f, "%s%s", *address,
  1381	                                (address + 1 ? " " : ""));
--
  1395	                        fprintf(f, "%s%s", *domain,
  1396	                                (domain + 1 ? " " : ""));

THIS DOES NOT MAKE SENSE!

address and domain will almost never equal ((char*)NULL)-1 because they are pointers to allocated storage and (usually) the higher half of the address space is reserved for the kernel.

You probably meant *(address+1) and *(domain+1). That would make sense however it would break DHCP (you append an address/domain and then append " "). Therefore the behavior should be preserved and spaces should always be appended.

I know your love for patches submitted through bugzilla. I will never send the following patch to the mailing list:

--- a/src/network/networkd-link.c
+++ b/src/network/networkd-link.c
@@ -1727,8 +1727,7 @@
                 fputs("DNS=", f);
 
                 STRV_FOREACH(address, link->network->dns)
-                        fprintf(f, "%s%s", *address,
-                                (address + 1 ? " " : ""));
+                        fprintf(f, "%s ", *address);
 
                 if (link->network->dhcp_dns &&
                     link->dhcp_lease) {
@@ -1747,8 +1746,7 @@
                 fprintf(f, "NTP=");
 
                 STRV_FOREACH(address, link->network->ntp)
-                        fprintf(f, "%s%s", *address,
-                                (address + 1 ? " " : ""));
+                        fprintf(f, "%s ", *address);
 
                 if (link->network->dhcp_ntp &&
                     link->dhcp_lease) {
@@ -1767,8 +1765,7 @@
                 fprintf(f, "DOMAINS=");
 
                 STRV_FOREACH(domain, link->network->domains)
-                        fprintf(f, "%s%s", *domain,
-                                (domain + 1 ? " " : ""));
+                        fprintf(f, "%s ", *domain);
 
                 if (link->network->dhcp_domains &&
                     link->dhcp_lease) {


P.S.: Thanks for implementing domains.