udhcpc6: additional fix for ppp interface type

Invent a fictitious MAC only once

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/networking/udhcp/d6_socket.c b/networking/udhcp/d6_socket.c
index f9082ee9d..315c8d98a 100644
--- a/networking/udhcp/d6_socket.c
+++ b/networking/udhcp/d6_socket.c
@@ -69,8 +69,12 @@ int FAST_FUNC d6_read_interface(const char *interface, int *ifindex, struct in6_
                 if (ioctl(fd, SIOCGIFINDEX, &ifr) == 0) {
                         *ifindex = ifr.ifr_ifindex;
                         log2("ifindex %d", *ifindex);
-                        ((uint32_t*)mac)[0] = rand();
-                        ((uint16_t*)mac)[2] = rand();
+                        if (((uint32_t*)mac)[0] == 0) {
+                                /* invent a fictitious MAC (once) */
+                                ((uint32_t*)mac)[0] = rand();
+                                ((uint16_t*)mac)[2] = rand();
+                                mac[0] &= 0xfc; /* make sure it's not bcast */
+                        }
                         retval &= (3 - (1<<0));
                 }
                 close(fd);