glib-aux: ensure alignment for nm_ether_addr_zero

In practice, this does not cause an issue, because NMEtherAddr quite
quite obviously only contains uint8 values and has alignment 1.

It's still ugly to case nm_ip_addr_zero to NMEtherAddr if they are
entirely unrelated types.

Fixes: 58e2ba053535 ('glib-aux: drop ethernet fields from NMIPAddr union')

2 files changed, 6 insertions, 1 deletions

diff --git a/src/libnm-glib-aux/nm-inet-utils.h b/src/libnm-glib-aux/nm-inet-utils.h
index af7620179c..40ba60c653 100644
--- a/src/libnm-glib-aux/nm-inet-utils.h
+++ b/src/libnm-glib-aux/nm-inet-utils.h
@@ -8,6 +8,11 @@ typedef union _NMIPAddr {
     in_addr_t       addr4;
     struct in_addr  addr4_struct;
     struct in6_addr addr6;
+
+    /* This union field only exists, so that it's guaranteed that NMIPAddr has
+     * a suitable alignment. We use that with nm_ether_addr_zero macro, that
+     * aliases nm_ip_addr_zero. */
+    NMEtherAddr _ether_addr;
 } NMIPAddr;
 
 #define NM_IP_ADDR_INIT   \
diff --git a/src/libnm-glib-aux/nm-shared-utils.h b/src/libnm-glib-aux/nm-shared-utils.h
index 618e34853b..accdd47063 100644
--- a/src/libnm-glib-aux/nm-shared-utils.h
+++ b/src/libnm-glib-aux/nm-shared-utils.h
@@ -206,7 +206,7 @@ extern const union _NMIPAddr nm_ip_addr_zero;
 
 /* Let's reuse nm_ip_addr_zero also for nm_ether_addr_zero. It's a union that
  * also contains a NMEtherAddr field. */
-#define nm_ether_addr_zero (*((const NMEtherAddr *) ((gconstpointer) &nm_ip_addr_zero)))
+#define nm_ether_addr_zero (*((const NMEtherAddr *) &nm_ip_addr_zero))
 
 static inline int
 nm_ether_addr_cmp(const NMEtherAddr *a, const NMEtherAddr *b)