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Message-Id: <20200826160535.1460065-1-maheshb@google.com>
Date: Wed, 26 Aug 2020 09:05:35 -0700
From: Mahesh Bandewar <maheshb@...gle.com>
To: Netdev <netdev@...r.kernel.org>
Cc: David Miller <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
Eric Dumazet <edumazet@...gle.com>,
Mahesh Bandewar <mahesh@...dewar.net>,
Mahesh Bandewar <maheshb@...gle.com>,
Maciej Zenczykowski <maze@...gle.com>,
Jian Yang <jianyang@...gle.com>,
Randy Dunlap <rdunlap@...radead.org>
Subject: [PATCHv3 next] net: add option to not create fall-back tunnels in
root-ns as well
The sysctl that was added earlier by commit 79134e6ce2c ("net: do
not create fallback tunnels for non-default namespaces") to create
fall-back only in root-ns. This patch enhances that behavior to provide
option not to create fallback tunnels in root-ns as well. Since modules
that create fallback tunnels could be built-in and setting the sysctl
value after booting is pointless, so added a kernel cmdline options to
change this default. The default setting is preseved for backward
compatibility. The kernel command line option of fb_tunnels=initns will
set the sysctl value to 1 and will create fallback tunnels only in initns
while kernel cmdline fb_tunnels=none will set the sysctl value to 2 and
fallback tunnels are skipped in every netns.
Signed-off-by: Mahesh Bandewar <maheshb@...gle.com>
Cc: Eric Dumazet <edumazet@...gle.com>
Cc: Maciej Zenczykowski <maze@...gle.com>
Cc: Jian Yang <jianyang@...gle.com>
Cc: Randy Dunlap <rdunlap@...radead.org>
---
v1->v2
Removed the Kconfig option which would force rebuild and replaced with
kcmd-line option
v2->v3
Removed CONFIG_SYSCTL check -and-
Moved the fb_tunnels documentation to correct pseudo-sorted place.
---
.../admin-guide/kernel-parameters.txt | 5 +++++
Documentation/admin-guide/sysctl/net.rst | 20 +++++++++++++------
include/linux/netdevice.h | 8 ++++++--
net/core/sysctl_net_core.c | 17 ++++++++++++++--
4 files changed, 40 insertions(+), 10 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index a1068742a6df..8af893ef0d46 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1338,6 +1338,11 @@
Format: <interval>,<probability>,<space>,<times>
See also Documentation/fault-injection/.
+ fb_tunnels= [NET]
+ Format: { initns | none }
+ See Documentation/admin-guide/sysctl/net.rst for
+ fb_tunnels_only_for_init_ns
+
floppy= [HW]
See Documentation/admin-guide/blockdev/floppy.rst.
diff --git a/Documentation/admin-guide/sysctl/net.rst b/Documentation/admin-guide/sysctl/net.rst
index 42cd04bca548..57fd6ce68fe0 100644
--- a/Documentation/admin-guide/sysctl/net.rst
+++ b/Documentation/admin-guide/sysctl/net.rst
@@ -300,7 +300,6 @@ Note:
0: 0 1 2 3 4 5 6 7
RSS hash key:
84:50:f4:00:a8:15:d1:a7:e9:7f:1d:60:35:c7:47:25:42:97:74:ca:56:bb:b6:a1:d8:43:e3:c9:0c:fd:17:55:c2:3a:4d:69:ed:f1:42:89
-
netdev_tstamp_prequeue
----------------------
@@ -321,11 +320,20 @@ fb_tunnels_only_for_init_net
----------------------------
Controls if fallback tunnels (like tunl0, gre0, gretap0, erspan0,
-sit0, ip6tnl0, ip6gre0) are automatically created when a new
-network namespace is created, if corresponding tunnel is present
-in initial network namespace.
-If set to 1, these devices are not automatically created, and
-user space is responsible for creating them if needed.
+sit0, ip6tnl0, ip6gre0) are automatically created. There are 3 possibilities
+(a) value = 0; respective fallback tunnels are created when module is
+loaded in every net namespaces (backward compatible behavior).
+(b) value = 1; [kcmd value: initns] respective fallback tunnels are
+created only in init net namespace and every other net namespace will
+not have them.
+(c) value = 2; [kcmd value: none] fallback tunnels are not created
+when a module is loaded in any of the net namespace. Setting value to
+"2" is pointless after boot if these modules are built-in, so there is
+a kernel command-line option that can change this default. Please refer to
+Documentation/admin-guide/kernel-parameters.txt for additional details.
+
+Not creating fallback tunnels gives control to userspace to create
+whatever is needed only and avoid creating devices which are redundant.
Default : 0 (for compatibility reasons)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index b0e303f6603f..32e570dc8e78 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -640,10 +640,14 @@ struct netdev_queue {
extern int sysctl_fb_tunnels_only_for_init_net;
extern int sysctl_devconf_inherit_init_net;
+/*
+ * sysctl_fb_tunnels_only_for_init_net == 0 : For all netns
+ * == 1 : For initns only
+ * == 2 : For none.
+ */
static inline bool net_has_fallback_tunnels(const struct net *net)
{
- return net == &init_net ||
- !IS_ENABLED(CONFIG_SYSCTL) ||
+ return (net == &init_net && sysctl_fb_tunnels_only_for_init_net == 1) ||
!sysctl_fb_tunnels_only_for_init_net;
}
diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index 6ada114bbcca..d86d8d11cfe4 100644
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -22,7 +22,7 @@
#include <net/busy_poll.h>
#include <net/pkt_sched.h>
-static int two __maybe_unused = 2;
+static int two = 2;
static int three = 3;
static int min_sndbuf = SOCK_MIN_SNDBUF;
static int min_rcvbuf = SOCK_MIN_RCVBUF;
@@ -546,7 +546,7 @@ static struct ctl_table net_core_table[] = {
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ZERO,
- .extra2 = SYSCTL_ONE,
+ .extra2 = &two,
},
{
.procname = "devconf_inherit_init_net",
@@ -587,6 +587,19 @@ static struct ctl_table netns_core_table[] = {
{ }
};
+static int __init fb_tunnels_only_for_init_net_sysctl_setup(char *str)
+{
+ /* fallback tunnels for initns only */
+ if (!strncmp(str, "initns", 6))
+ sysctl_fb_tunnels_only_for_init_net = 1;
+ /* no fallback tunnels anywhere */
+ else if (!strncmp(str, "none", 4))
+ sysctl_fb_tunnels_only_for_init_net = 2;
+
+ return 1;
+}
+__setup("fb_tunnels=", fb_tunnels_only_for_init_net_sysctl_setup);
+
static __net_init int sysctl_core_net_init(struct net *net)
{
struct ctl_table *tbl;
--
2.28.0.297.g1956fa8f8d-goog
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