siphash24: change result argument to uint64_t

Change the "out" parameter from uint8_t[8] to uint64_t. On architectures which
enforce pointer alignment this fixes crashes when we previously cast an
unaligned array to uint64_t*, and on others this should at least improve
performance as the compiler now aligns these properly.

This also simplifies the code in most cases by getting rid of typecasts. The
only place which we can't change is struct duid's en.id, as that is _packed_
and public API, so we can't enforce alignment of the "id" field and have to
use memcpy instead.

1 files changed, 6 insertions, 4 deletions

diff --git a/src/libsystemd-network/dhcp-identifier.c b/src/libsystemd-network/dhcp-identifier.c
index 51ee7bcce4..368525c40a 100644
--- a/src/libsystemd-network/dhcp-identifier.c
+++ b/src/libsystemd-network/dhcp-identifier.c
@@ -35,6 +35,7 @@
 
 int dhcp_identifier_set_duid_en(struct duid *duid, size_t *len) {
         sd_id128_t machine_id;
+        uint64_t hash;
         int r;
 
         assert(duid);
@@ -50,8 +51,9 @@ int dhcp_identifier_set_duid_en(struct duid *duid, size_t *len) {
         *len = sizeof(duid->type) + sizeof(duid->en);
 
         /* a bit of snake-oil perhaps, but no need to expose the machine-id
-           directly */
-        siphash24(duid->en.id, &machine_id, sizeof(machine_id), HASH_KEY.bytes);
+           directly; duid->en.id might not be aligned, so we need to copy */
+        siphash24(&hash, &machine_id, sizeof(machine_id), HASH_KEY.bytes);
+        memcpy(duid->en.id, &hash, sizeof(duid->en.id));
 
         return 0;
 }
@@ -84,10 +86,10 @@ int dhcp_identifier_set_iaid(int ifindex, uint8_t *mac, size_t mac_len, void *_i
         }
 
         if (name)
-                siphash24((uint8_t*)&id, name, strlen(name), HASH_KEY.bytes);
+                siphash24(&id, name, strlen(name), HASH_KEY.bytes);
         else
                 /* fall back to MAC address if no predictable name available */
-                siphash24((uint8_t*)&id, mac, mac_len, HASH_KEY.bytes);
+                siphash24(&id, mac, mac_len, HASH_KEY.bytes);
 
         /* fold into 32 bits */
         unaligned_write_be32(_id, (id & 0xffffffff) ^ (id >> 32));