PORTING: Add hint to adjust the default fail-mode, for hardware ports.

[sliver-openvswitch.git] / PORTING

diff --git a/PORTING b/PORTING
index 5281d50..ffde296 100644 (file)
--- a/PORTING
+++ b/PORTING
@@ -245,6 +245,17 @@ ovs_be64 as fixed-width types in network byte order.  Each of the
 latter is equivalent to the one of the former, but the difference in
 name makes the intended use obvious.
 
 latter is equivalent to the one of the former, but the difference in
 name makes the intended use obvious.
 

+The default "fail-mode" for Open vSwitch bridges is "standalone",
+meaning that, when the OpenFlow controllers cannot be contacted, Open
+vSwitch acts as a regular MAC-learning switch.  This works well in
+virtualization environments where there is normally just one uplink
+(either a single physical interface or a bond).  In a more general
+environment, it can create loops.  So, if you are porting to a
+general-purpose switch platform, you should consider changing the
+default "fail-mode" to "secure", which does not behave this way.  See
+documentation for the "fail-mode" column in the Bridge table in
+ovs-vswitchd.conf.db(5) for more information.
+

 lib/entropy.c assumes that it can obtain high-quality random number
 seeds at startup by reading from /dev/urandom.  You will need to
 modify it if this is not true on your platform.
 lib/entropy.c assumes that it can obtain high-quality random number
 seeds at startup by reading from /dev/urandom.  You will need to
 modify it if this is not true on your platform.