sd-dhcp-lease: use shared default prefixlen function

Also change the default prefixlen function to only access the first octet of the in_addr.

1 files changed, 6 insertions, 7 deletions

diff --git a/src/shared/in-addr-util.c b/src/shared/in-addr-util.c
index 5fbee6caf2..9dc9ec82b4 100644
--- a/src/shared/in-addr-util.c
+++ b/src/shared/in-addr-util.c
@@ -250,21 +250,20 @@ unsigned in_addr_netmask_to_prefixlen(const struct in_addr *addr) {
 }
 
 int in_addr_default_prefixlen(const struct in_addr *addr, unsigned char *prefixlen) {
-        uint32_t address;
+        uint8_t msb_octet = *(uint8_t*) addr;
+
+        /* addr may not be aligned, so make sure we only access it byte-wise */
 
         assert(addr);
-        assert(addr->s_addr != INADDR_ANY);
         assert(prefixlen);
 
-        address = be32toh(addr->s_addr);
-
-        if ((address >> 31) == 0x0)
+        if (msb_octet < 128)
                 /* class A, leading bits: 0 */
                 *prefixlen = 8;
-        else if ((address >> 30) == 0x2)
+        else if (msb_octet < 192)
                 /* class B, leading bits 10 */
                 *prefixlen = 16;
-        else if ((address >> 29) == 0x6)
+        else if (msb_octet < 224)
                 /* class C, leading bits 110 */
                 *prefixlen = 24;
         else