> OK, if I understand properly here, the problem is that asking the Linux
> kernel datapath to add a bridge named "default" does two things. First,
> it fails. Second, it triggers a notifier that causes OVS to try again.
> The second part is what makes this different from other failures and
> what makes OVS use 100% CPU in this case but not other cases. Is that
> right?
>
Yes
> If I'm right, then how about something like the following instead? It
> pushes this down to Linux-specific code, which seems better because this
> is a Linux-specific issue, and it thoroughly documents the problem. It
> compiles but I have not tested it.
>
> Thanks,
>
> Ben.
>
> diff --git a/lib/netdev-linux.c b/lib/netdev-linux.c
> index 9ff1333f8e85..79e827303d07 100644
> --- a/lib/netdev-linux.c
> +++ b/lib/netdev-linux.c
> @@ -1,5 +1,5 @@
> /*
> - * Copyright (c) 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016 Nicira, Inc.
> + * Copyright (c) 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017
> Nicira, Inc.
> *
> * Licensed under the Apache License, Version 2.0 (the "License");
> * you may not use this file except in compliance with the License.
> @@ -773,10 +773,28 @@ netdev_linux_alloc(void)
> return &netdev->up;
> }
>
> -static void
> -netdev_linux_common_construct(struct netdev_linux *netdev)
> -{
> +static int
> +netdev_linux_common_construct(struct netdev *netdev_)
> +{
> + /* Prevent any attempt to create (or open) a network device named
> "default"
> + * or "all". These device names are effectively reserved on Linux
> because
> + * /proc/sys/net/ipv4/conf/ always contains directories by these names.
> By
> + * itself this wouldn't call for any special treatment, but in practice
> if
> + * a program tries to create devices with these names, it causes the
> kernel
> + * to fire a "new device" notification event even though creation failed,
> + * and in turn that causes OVS to wake up and try to create them again,
> + * which ends up as a 100% CPU loop. */
> + struct netdev_linux *netdev = netdev_linux_cast(netdev_);
> + const char *name = netdev_->name;
> + if (!strcmp(name, "default") || !strcmp(name, "all")) {
> + static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 1);
> + VLOG_WARN_RL(&rl, "%s: Linux forbids network device with this name",
> + name);
> + return EINVAL;
> + }
> +
> ovs_mutex_init(&netdev->mutex);
> + return 0;
> }
>
> /* Creates system and internal devices. */
> @@ -784,9 +802,10 @@ static int
> netdev_linux_construct(struct netdev *netdev_)
> {
> struct netdev_linux *netdev = netdev_linux_cast(netdev_);
> - int error;
> -
> - netdev_linux_common_construct(netdev);
> + int error = netdev_linux_common_construct(netdev_);
> + if (error) {
> + return error;
> + }
>
> error = get_flags(&netdev->up, &netdev->ifi_flags);
> if (error == ENODEV) {
> @@ -817,9 +836,11 @@ netdev_linux_construct_tap(struct netdev *netdev_)
> static const char tap_dev[] = "/dev/net/tun";
> const char *name = netdev_->name;
> struct ifreq ifr;
> - int error;
>
> - netdev_linux_common_construct(netdev);
> + int error = netdev_linux_common_construct(netdev_);
> + if (error) {
> + return error;
> + }
>
> /* Open tap device. */
> netdev->tap_fd = open(tap_dev, O_RDWR);
Thanks! I've tested it and it works ok.
Regards,
William
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