Revert "Revert "networkd: netdev - set predictable mac address when creating netdev""

This reverts (and rewrites) commit 7d95c772cb.

The issue blocking this feature has now been fixed in the kernel, and backported
to the various stable kernels.

Our netdevs will now have stable MAC addresses, even if one is not specified.

src/network/networkd-netdev.c

@@ -27,6 +27,7 @@
 #include "conf-files.h"
 #include "conf-parser.h"
 #include "list.h"
+#include "siphash24.h"
 
 #define VLANID_MAX 4094
 
@@ -528,6 +529,52 @@ int netdev_set_ifindex(NetDev *netdev, sd_rtnl_message *message) {
         return 0;
 }
 
+#define HASH_KEY SD_ID128_MAKE(52,e1,45,bd,00,6f,29,96,21,c6,30,6d,83,71,04,48)
+
+static int netdev_get_mac(const char *ifname, struct ether_addr **ret) {
+        _cleanup_free_ struct ether_addr *mac = NULL;
+        uint8_t result[8];
+        size_t l, sz;
+        uint8_t *v;
+        int r;
+
+        assert(ifname);
+        assert(ret);
+
+        mac = new0(struct ether_addr, 1);
+        if (!mac)
+                return -ENOMEM;
+
+        l = strlen(ifname);
+        sz = sizeof(sd_id128_t) + l;
+        v = alloca(sz);
+
+        /* fetch some persistent data unique to the machine */
+        r = sd_id128_get_machine((sd_id128_t*) v);
+        if (r < 0)
+                return r;
+
+        /* combine with some data unique (on this machine) to this
+         * netdev */
+        memcpy(v + sizeof(sd_id128_t), ifname, l);
+
+        /* Let's hash the host machine ID plus the container name. We
+         * use a fixed, but originally randomly created hash key here. */
+        siphash24(result, v, sz, HASH_KEY.bytes);
+
+        assert_cc(ETH_ALEN <= sizeof(result));
+        memcpy(mac->ether_addr_octet, result, ETH_ALEN);
+
+        /* see eth_random_addr in the kernel */
+        mac->ether_addr_octet[0] &= 0xfe;        /* clear multicast bit */
+        mac->ether_addr_octet[0] |= 0x02;        /* set local assignment bit (IEEE802) */
+
+        *ret = mac;
+        mac = NULL;
+
+        return 0;
+}
+
 static int netdev_load_one(Manager *manager, const char *filename) {
         _cleanup_netdev_unref_ NetDev *netdev = NULL;
         _cleanup_fclose_ FILE *file = NULL;
@@ -607,14 +654,39 @@ static int netdev_load_one(Manager *manager, const char *filename) {
                              NULL, NULL, NULL, NULL, NULL, NULL) <= 0)
                 return 0;
 
+        if (!netdev->mac) {
+                r = netdev_get_mac(netdev->ifname, &netdev->mac);
+                if (r < 0) {
+                        log_error("Failed to generate predictable MAC address for %s",
+                                  netdev->ifname);
+                        return r;
+                }
+        }
+
         r = hashmap_put(netdev->manager->netdevs, netdev->ifname, netdev);
         if (r < 0)
                 return r;
 
         LIST_HEAD_INIT(netdev->callbacks);
 
-        if(netdev->kind == NETDEV_KIND_VETH)
+        if(netdev->kind == NETDEV_KIND_VETH) {
+                if (netdev->ifname_peer) {
+                        log_warning("Veth NetDev without Peer Name configured "
+                                    "in %s. Ignoring", filename);
+                        return 0;
+                }
+
+                if (!netdev->mac) {
+                        r = netdev_get_mac(netdev->ifname_peer, &netdev->mac_peer);
+                        if (r < 0) {
+                                log_error("Failed to generate predictable MAC address for %s",
+                                          netdev->ifname_peer);
+                                return r;
+                        }
+                }
+
                 return netdev_create_veth(netdev, netdev_create_handler);
+        }
 
         if (netdev->kind != NETDEV_KIND_VLAN &&
             netdev->kind != NETDEV_KIND_MACVLAN &&