confd: use the system base mac as mac address on bridges

To prevent the kernel from setting a random mac address on new bridges,
before we have added any bridge ports, we create bridges using the:

  1. Custom mac address from the configuration (phys-address)
  2. System base mac from /run/system.json
  3. None, if there is no base mac address in system.json, e.g. r2s

Fixes #357

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

doc/ChangeLog.md

@@ -357,6 +357,10 @@ future releases.
 - Fix #349: minor changes to `bridge-port` settings, like setting `pvid`
   when you forget it, did not take without a reboot
 - Fix #353: impossible to remove bridge port with `no bridge-port`
+- Fix #357: EUI-64 based IPv6 autoconf address on bridges seem to be
+  randomized.  Problem caused by kernel setting a random MAC before any
+  bridge port is added.  Fixed by using the device's base MAC address on
+  bridge interfaces.  Possible to override using `phys-address` option
 - Fix #358: MAC address no longer shown for bridge interfaces in CLI
   `show interfaces` command
 - Fix #365: not possible to run `ping` from container

src/confd/src/core.c

@@ -4,7 +4,7 @@
 
 #include "core.h"
 
-static struct confd confd;
+struct confd confd;
 
 uint32_t core_hook_prio(void)
 {

src/confd/src/core.h

@@ -32,6 +32,9 @@
 #define CB_PRIO_PRIMARY   65535
 #define CB_PRIO_PASSIVE   65000
 
+extern struct confd confd;
+
+
 static inline void print_val(sr_val_t *val)
 {
 	char *str;

src/confd/src/ietf-interfaces.c

@@ -1284,15 +1284,37 @@ static int netdag_gen_bridge(sr_session_ctx_t *session, struct dagger *net, stru
 	vlan_filtering = bridge_vlan_settings(cif, &proto, &vlan_mcast);
 	fwd_mask = bridge_fwd_mask(cif);
 
+	fprintf(ip, "link %s dev %s", op, brname);
+	/*
+	 * Must set base mac on add to prevent kernel from seeding ipv6
+	 * addrgenmode eui64 with random mac, issue #357.
+	 */
+	if (add) {
+		const char *mac;
+
+		mac = lydx_get_cattr(cif, "phys-address");
+		if (!mac) {
+			struct json_t *j;
+
+			j = json_object_get(confd.root, "mac-address");
+			if (j)
+				mac = json_string_value(j);
+		}
+		if (mac)
+			fprintf(ip, " address %s", mac);
+
+		/* on failure, fall back to kernel's random mac */
+	}
+
 	/*
 	 * Issue #198: we require explicit VLAN assignment for ports
 	 *             when VLAN filtering is enabled.  We strongly
 	 *             believe this is the only sane way of doing it.
 	 * Issue #310: malplaced 'vlan_default_pvid 0'
 	 */
-	fprintf(ip, "link %s dev %s type bridge group_fwd_mask %d mcast_flood_always 1"
+	fprintf(ip, " type bridge group_fwd_mask %d mcast_flood_always 1"
 		" vlan_filtering %d vlan_default_pvid 0",
-		op, brname, fwd_mask, vlan_filtering ? 1 : 0);
+		fwd_mask, vlan_filtering ? 1 : 0);
 
 	if ((err = bridge_mcast_settings(ip, brname, cif, vlan_mcast)))
 		goto out;