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authorAmit Cohen <amcohen@nvidia.com>2021-02-01 20:47:52 +0100
committerJakub Kicinski <kuba@kernel.org>2021-02-03 02:45:59 +0100
commit680aea08e78c003292415518ad270bc20f9c80b1 (patch)
tree1215e16fb0586bf8b296e70a26c6f4ccd031cd31 /Documentation/networking/ip-sysctl.rst
parentnet: ipv4: Publish fib_nlmsg_size() (diff)
downloadlinux-680aea08e78c003292415518ad270bc20f9c80b1.tar.xz
linux-680aea08e78c003292415518ad270bc20f9c80b1.zip
net: ipv4: Emit notification when fib hardware flags are changed
After installing a route to the kernel, user space receives an acknowledgment, which means the route was installed in the kernel, but not necessarily in hardware. The asynchronous nature of route installation in hardware can lead to a routing daemon advertising a route before it was actually installed in hardware. This can result in packet loss or mis-routed packets until the route is installed in hardware. It is also possible for a route already installed in hardware to change its action and therefore its flags. For example, a host route that is trapping packets can be "promoted" to perform decapsulation following the installation of an IPinIP/VXLAN tunnel. Emit RTM_NEWROUTE notifications whenever RTM_F_OFFLOAD/RTM_F_TRAP flags are changed. The aim is to provide an indication to user-space (e.g., routing daemons) about the state of the route in hardware. Introduce a sysctl that controls this behavior. Keep the default value at 0 (i.e., do not emit notifications) for several reasons: - Multiple RTM_NEWROUTE notification per-route might confuse existing routing daemons. - Convergence reasons in routing daemons. - The extra notifications will negatively impact the insertion rate. - Not all users are interested in these notifications. Signed-off-by: Amit Cohen <amcohen@nvidia.com> Acked-by: Roopa Prabhu <roopa@nvidia.com> Signed-off-by: Ido Schimmel <idosch@nvidia.com> Reviewed-by: David Ahern <dsahern@kernel.org> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'Documentation/networking/ip-sysctl.rst')
-rw-r--r--Documentation/networking/ip-sysctl.rst20
1 files changed, 20 insertions, 0 deletions
diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
index 2685ec161060..b0e800e68366 100644
--- a/Documentation/networking/ip-sysctl.rst
+++ b/Documentation/networking/ip-sysctl.rst
@@ -178,6 +178,26 @@ min_adv_mss - INTEGER
The advertised MSS depends on the first hop route MTU, but will
never be lower than this setting.
+fib_notify_on_flag_change - INTEGER
+ Whether to emit RTM_NEWROUTE notifications whenever RTM_F_OFFLOAD/
+ RTM_F_TRAP flags are changed.
+
+ After installing a route to the kernel, user space receives an
+ acknowledgment, which means the route was installed in the kernel,
+ but not necessarily in hardware.
+ It is also possible for a route already installed in hardware to change
+ its action and therefore its flags. For example, a host route that is
+ trapping packets can be "promoted" to perform decapsulation following
+ the installation of an IPinIP/VXLAN tunnel.
+ The notifications will indicate to user-space the state of the route.
+
+ Default: 0 (Do not emit notifications.)
+
+ Possible values:
+
+ - 0 - Do not emit notifications.
+ - 1 - Emit notifications.
+
IP Fragmentation:
ipfrag_high_thresh - LONG INTEGER