Respect xidhwaddr option for DHCPv6

diff --git a/dhcp6.c b/dhcp6.c
index 0679c2f09a4fdc6b650b526a38c18a73406fef30..5d09236bdc8ab115ced943a60b5c6d7021d4654d 100644 (file)
--- a/dhcp6.c
+++ b/dhcp6.c
@@ -328,11 +328,18 @@ dhcp6_updateelapsed(struct interface *ifp, struct dhcp6_message *m, ssize_t len)
 }
 
 static void
-dhcp6_newxid(struct dhcp6_message *m)
+dhcp6_newxid(const struct interface *ifp, struct dhcp6_message *m)
 {
        uint32_t xid;
 
-       xid = arc4random();
+       if (ifp->options->options & DHCPCD_XID_HWADDR &&
+           ifp->hwlen >= sizeof(xid)) 
+               /* The lower bits are probably more unique on the network */
+               memcpy(&xid, (ifp->hwaddr + ifp->hwlen) - sizeof(xid),
+                   sizeof(xid));
+       else
+               xid = arc4random();
+
        m->xid[0] = (xid >> 16) & 0xff;
        m->xid[1] = (xid >> 8) & 0xff;
        m->xid[2] = xid & 0xff;
@@ -451,7 +458,7 @@ dhcp6_makemessage(struct interface *ifp)
                return -1;
        }
 
-       dhcp6_newxid(state->send);
+       dhcp6_newxid(ifp, state->send);
 
        o = D6_FIRST_OPTION(state->send);
        o->code = htons(D6_OPTION_CLIENTID);