This is mostly historical. Here's the whole story, as I remember it.
I guess that you remember at least some of this too.
Originally ovs-vswitchd had a text-based config file. To reconfigure,
you edited the file and then told ovs-vswitchd to reread it. When we
did the xenserver integration, we needed some better way, so we wrote
ovs-vsctl (a Python script initially) with a set of basic commands
that also edited the config file and told ovs-vswitchd to reread it.
Because XenServer also supported the Linux bridge, the ovs-vsctl
commands had to have semantics very similar to brctl commands. brctl
commands to list bridge ports, etc., don't include the local port in
the list of ports, so ovs-vsctl didn't either. That means that
"ovs-vsctl -- --if-exists del-port <bridge>" never failed, because
ovs-vsctl didn't consider <bridge> to be a port (because brctl
didn't). And we've preserved that behavior over major changes and
rewrites, until now, when we broke it.
So the short answer is that ovs-vsctl doesn't consider a bridge to be
a port in this context, and so --if-exists should just silently do
nothing.
Thanks for the review, I'll apply this to master soon.
On Tue, Jul 09, 2013 at 10:09:05AM -0700, Justin Pettit wrote:
> The behavior seems a little surprising, since the "--if-exists"
> sounds like it will be deleted if it exists, but it's actually just
> avoiding a fatal error and the port will still exist. It would be
> nicer to give some sort of non-fatal warning in that case. However,
> that's likely to cause breakage in scripts and most people know not
> to delete the local port, so I'm also fine if you prefer this
> approach.
>
> --Justin
>
>
> On Jul 8, 2013, at 10:48 AM, Ben Pfaff <b...@nicira.com> wrote:
>
> > Commit 89f3c258fe (ovs-vsctl: Improve error message for "ovs-vsctl del-port
> > <bridge>".) changed the behavior of
> > ovs-vsctl --if-exists del-port <bridge>
> > from a silent no-op to a hard failure. This commit fixes this regression.
> >
> > This caused problems on XenServer, for which the Open vSwitch integration
> > runs commands like:
> > /usr/bin/ovs-vsctl --timeout=20 \
> > -- --with-iface --if-exists del-port xapi103 \
> > -- --if-exists del-br xapi103
> >
> > Bug #18276.
> > Reported-by: Michael Hu <m...@nicira.com>
> > Signed-off-by: Ben Pfaff <b...@nicira.com>
> > ---
> > tests/ovs-vsctl.at | 2 ++
> > utilities/ovs-vsctl.c | 9 ++++++---
> > 2 files changed, 8 insertions(+), 3 deletions(-)
> >
> > diff --git a/tests/ovs-vsctl.at b/tests/ovs-vsctl.at
> > index fa2c3ff..4449f7a 100644
> > --- a/tests/ovs-vsctl.at
> > +++ b/tests/ovs-vsctl.at
> > @@ -327,6 +327,8 @@ AT_CHECK([RUN_OVS_VSCTL([del-port a])], [1], [],
> > [ovs-vsctl: cannot delete port a because it is the local port for bridge
> > a (deleting this port requires deleting the entire bridge)
> > ],
> > [OVS_VSCTL_CLEANUP])
> > +AT_CHECK([RUN_OVS_VSCTL([--if-exists del-port a])], [0], [], [],
> > + [OVS_VSCTL_CLEANUP])
> > AT_CHECK([RUN_OVS_VSCTL([--may-exist add-port a b1])], [1], [],
> > [ovs-vsctl: "--may-exist add-port a b1" but b1 is actually attached to
> > bridge b
> > ],
> > diff --git a/utilities/ovs-vsctl.c b/utilities/ovs-vsctl.c
> > index 2d8c7c7..e679e0d 100644
> > --- a/utilities/ovs-vsctl.c
> > +++ b/utilities/ovs-vsctl.c
> > @@ -2021,9 +2021,12 @@ cmd_del_port(struct vsctl_context *ctx)
> >
> > vsctl_context_populate_cache(ctx);
> > if (find_bridge(ctx, target, false)) {
> > - vsctl_fatal("cannot delete port %s because it is the local port "
> > - "for bridge %s (deleting this port requires deleting "
> > - "the entire bridge)", target, target);
> > + if (must_exist) {
> > + vsctl_fatal("cannot delete port %s because it is the local
> > port "
> > + "for bridge %s (deleting this port requires
> > deleting "
> > + "the entire bridge)", target, target);
> > + }
> > + port = NULL;
> > } else if (!with_iface) {
> > port = find_port(ctx, target, must_exist);
> > } else {
> > --
> > 1.7.2.5
> >
> > _______________________________________________
> > dev mailing list
> > dev@openvswitch.org
> > http://openvswitch.org/mailman/listinfo/dev
>
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