Implement a bridge mac addr forging for ipv6 dedicated bridges

The current algo only works for ipv4, as we derive the hw address
from the ipv4, but an ipv6 is too long to do that.

opensvc/core/node/linux.py

@@ -133,7 +133,35 @@ def network_route_add(self, dst=None, gw=None, dev=None, local_ip=None, brdev=No
             for line in out.splitlines():
                 self.log.info(line)
 
-    def mac_from_ip(self, ip):
+    def mac_from_ip6(self, name):
+        """
+        When the device with the lowest mac is removed from the bridge or when
+        a new device with the lowest mac is added to the bridge, all containers
+        can experience tcp hangs while the arp table resynchronizes.
+
+        Setting a mac address to the bridge explicitely avoids these mac address
+        changes.
+
+        Forge the mac address using a 6a:58 prefix followed by the bridge original
+        random address last 4 bytes.
+        """
+        cmd = ["ip", "link", "show", "dev", name]
+        out, _, _ = justcall(cmd)
+        mac = out.strip().split("\n")[-1].split()[1]
+        return "6a:58" + mac[5:]
+
+    def mac_from_ip4(self, ip):
+        """
+        When the device with the lowest mac is removed from the bridge or when
+        a new device with the lowest mac is added to the bridge, all containers
+        can experience tcp hangs while the arp table resynchronizes.
+
+        Setting a mac address to the bridge explicitely avoids these mac address
+        changes.
+
+        Forge the mac address using a 0a:58 prefix followed by the bridge ipv4
+        address converted to hexa (same algorithm used in k8s).
+        """
         mac = "0a:58"
         for i in ip.split("/", 1)[0].split("."):
             mac += ":%.2x" % int(i)
@@ -152,9 +180,12 @@ def network_bridge_add(self, name, ip):
             self.vcall(cmd)
         cmd = ["ip", "link", "show", "dev", name]
         out, _, _ = justcall(cmd)
-        mac = self.mac_from_ip(ip)
+        if ":" in ip:
+            mac = self.mac_from_ip6(name)
+        else:
+            mac = self.mac_from_ip4(ip)
         if mac not in out:
-            cmd = ["ip", "link", "set", "dev", name, "address", self.mac_from_ip(ip)]
+            cmd = ["ip", "link", "set", "dev", name, "address", mac]
             self.vcall(cmd)
         if "DOWN" in out:
             cmd = ["ip", "link", "set", "dev", name, "up"]