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bridge: Prohibit "default" and "all" bridge name.

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Under Linux, when users create bridge named "default" or "all", although
ovs-vsctl fails but vswitchd in the background will keep retrying it,
causing the systemd-udev to reach 100% cpu utilization. The patch prevents
any attempt to create or open a netdev named "default" or "all" because
these two names are reserved on Linux due to
/proc/sys/net/ipv4/conf/ always contains directories by these names.

The reason for high CPU utilization is due to frequent calls into kernel's
register_netdevice function, which will invoke several kernel elements who
has registered on the netdevice notifier chain.  And due to creation failed,
OVS wakes up and re-recreate the device, which ends up as a high CPU loop.

VMWare-BZ: #1842388
Signed-off-by: William Tu <u9012063@gmail.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>
Acked-by: Greg Rose <gvrose8192@gmail.com>
This commit is contained in:
William Tu 2017-04-29 06:30:59 -07:00 committed by Ben Pfaff
parent 28ff6aa279
commit 48c6733cb5
1 changed files with 29 additions and 8 deletions
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37
lib/netdev-linux.c
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@ -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);