When sending on inactive slaves, use a random MAC address

diff --git a/src/lldpd.c b/src/lldpd.c
index 9f6dd1f7a97b0260363abd92976c8f901f85832d..f29c9d6bb74a96da801d0bff804f4ceb75ec9ce1 100644 (file)
--- a/src/lldpd.c
+++ b/src/lldpd.c
@@ -1171,23 +1171,50 @@ lldpd_recv_all(struct lldpd *cfg)
        } while ((rc != 0) || (time(NULL) - cfg->g_lastsent < cfg->g_delay));
 }
 
+void static
+get_random_ether(u_int8_t *lladdr)
+{
+       /* We use a simple law to generate random bytes of the MAC address and
+        * initialize (or re-initialize) the seed using microseconds part of
+        * gettimeofday. */
+       static u_int64_t next = 0;
+       u_int8_t random;
+       int i = 0;
+       struct timeval tv;
+       if (next == 0) {
+               gettimeofday(&tv, NULL);
+               next = tv.tv_usec;
+       }
+       do {
+               next = next * 1103515245 + 12345;
+               random = (next/65536)%256;
+               memcpy(lladdr + i, &random, 1);
+       } while (++i < ETHER_ADDR_LEN);
+       lladdr[0] &= 0xfe;      /* clear multicast bit */
+       lladdr[0] |= 0x02;      /* set local assignment bit (IEEE802) */
+}
+
 void
 lldpd_send_all(struct lldpd *cfg)
 {
        struct lldpd_hardware *hardware;
-       int i;
+       u_int8_t saved_lladdr[ETHER_ADDR_LEN];
+       int i, altermac;
+
        cfg->g_lastsent = time(NULL);
        TAILQ_FOREACH(hardware, &cfg->g_hardware, h_entries) {
                /* Ignore if interface is down */
                if ((hardware->h_flags & IFF_UP) == 0)
                        continue;
-               /* Don't send on inactive slaves */
+
+               /* When sending on inactive slaves, just send using a random address */
+               altermac = 0;
                if ((hardware->h_raw_real > 0) &&
                    (!iface_is_slave_active(cfg, hardware->h_master,
                        hardware->h_ifname))) {
-                       LLOG_DEBUG("%s is inactive, don't send anything",
-                               hardware->h_ifname);
-                       continue;
+                       altermac = 1;
+                       memcpy(saved_lladdr, hardware->h_lladdr, ETHER_ADDR_LEN);
+                       get_random_ether(hardware->h_lladdr);
                }
 
                for (i=0; cfg->g_protocols[i].mode != 0; i++) {
@@ -1197,6 +1224,9 @@ lldpd_send_all(struct lldpd *cfg)
                            (cfg->g_protocols[i].mode == LLDPD_MODE_LLDP))
                                cfg->g_protocols[i].send(cfg, &cfg->g_lchassis, hardware);
                }
+               /* Restore MAC if needed */
+               if (altermac)
+                       memcpy(hardware->h_lladdr, saved_lladdr, ETHER_ADDR_LEN);
        }
 }