[lxc-devel] [lxd/master] Network: Don't generate volatile.bridge.hwaddr in fan mode or allow static hwaddr to be set

[tomponline on Github]

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From a059598f46665a38e89369052c74a9c128a61ee4 Mon Sep 17 00:00:00 2001
From: Thomas Parrott <thomas.parrott at canonical.com>
Date: Fri, 7 Aug 2020 12:31:29 +0100
Subject: [PATCH 1/2] lxd/network/driver/bridge: Don't allow stable volatile
 MAC with fan network

Breaks host<->fan traffic.

Signed-off-by: Thomas Parrott <thomas.parrott at canonical.com>
---
 lxd/network/driver_bridge.go | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/lxd/network/driver_bridge.go b/lxd/network/driver_bridge.go
index 5518259f0a..997a805184 100644
--- a/lxd/network/driver_bridge.go
+++ b/lxd/network/driver_bridge.go
@@ -48,6 +48,13 @@ type bridge struct {
 
 // fillHwaddr populates the volatile.bridge.hwaddr in config if it, nor bridge.hwaddr, are already set.
 func (n *bridge) fillHwaddr(config map[string]string) error {
+	// Fan bridge doesn't support having the same MAC on all nodes (it breaks host<->fan traffic).
+	// Presumably because the host's MAC address is used for routing across the fan network.
+	if config["bridge.mode"] == "fan" {
+		return nil
+	}
+
+	// Don't generate a volatile stable MAC if network already has stable MAC.
 	if config["bridge.hwaddr"] != "" || config["volatile.bridge.hwaddr"] != "" {
 		return nil
 	}

From 0a111a8ae198e5d74b0551eeb54c028a7be51bca Mon Sep 17 00:00:00 2001
From: Thomas Parrott <thomas.parrott at canonical.com>
Date: Fri, 7 Aug 2020 12:53:13 +0100
Subject: [PATCH 2/2] lxd/network/driver/bridge: Don't allow hwaddr to be set
 in fan mode

Fan mode doesn't support static MAC address across all nodes.

Signed-off-by: Thomas Parrott <thomas.parrott at canonical.com>
---
 lxd/network/driver_bridge.go | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lxd/network/driver_bridge.go b/lxd/network/driver_bridge.go
index 997a805184..cb098e4b88 100644
--- a/lxd/network/driver_bridge.go
+++ b/lxd/network/driver_bridge.go
@@ -162,6 +162,10 @@ func (n *bridge) Validate(config map[string]string) error {
 				return nil
 			}
 
+			if n.config["bridge.mode"] == "fan" {
+				return fmt.Errorf("Cannot specify static MAC address when using fan mode")
+			}
+
 			return validate.IsNetworkMAC(value)
 		},
 		"volatile.bridge.hwaddr": func(value string) error {