After IPv4 packets are forwarded, the priority of the corresponding SKB is updated according to the TOS field of IPv4 header. This overrides any prioritization done earlier by e.g. an skbedit action or ingress-qos-map defined at a vlan device.
Such overriding may not always be desirable. Even if the packet ends up being routed, which implies this is an L3 network node, an administrator may wish to preserve whatever prioritization was done earlier on in the pipeline.
Therefore this patch set introduces a sysctl that controls this behavior, net.ipv4.ip_forward_update_priority. It's value is 1 by default to preserve the current behavior.
All of the above is implemented in patch #1.
Value changes prompt a new NETEVENT_IPV4_FWD_UPDATE_PRIORITY_UPDATE notification, so that the drivers can hook up whatever logic may depend on this value. That is implemented in patch #2.
In patches #3 and #4, mlxsw is adapted to recognize the sysctl. On initialization, the RGCR register that handles router configuration is set in accordance with the sysctl. The new notification is listened to and RGCR is reconfigured as necessary.
In patches #5 to #7, a selftest is added to verify that mlxsw reflects the sysctl value as necessary. The test is expressed in terms of the recently-introduced ieee_setapp support, and works by observing how DSCP value gets rewritten depending on packet priority. For this reason, the test is added to the subdirectory drivers/net/mlxsw. Even though it's not particularly specific to mlxsw, it's not suitable for running on soft devices (which don't support the ieee_setapp et.al.).
Changes from v1 to v2:
- In patch #1, init sysctl_ip_fwd_update_priority to 1 instead of true.
Changes from RFC to v1:
- Fix wrong sysctl name in ip-sysctl.txt - Add notifications - Add mlxsw support - Add self test
Petr Machata (7): net: ipv4: Control SKB reprioritization after forwarding net: ipv4: Notify about changes to ip_forward_update_priority mlxsw: spectrum: Extract work-scheduling into a new function mlxsw: spectrum_router: Handle sysctl_ip_fwd_update_priority selftests: forwarding: Move lldpad waiting to lib.sh selftests: forwarding: Move DSCP capture to lib.sh selftests: mlxsw: Add test for ip_forward_update_priority
Documentation/networking/ip-sysctl.txt | 9 + .../net/ethernet/mellanox/mlxsw/spectrum_router.c | 56 +++-- include/net/netevent.h | 1 + include/net/netns/ipv4.h | 1 + net/ipv4/af_inet.c | 1 + net/ipv4/ip_forward.c | 3 +- net/ipv4/sysctl_net_ipv4.c | 26 +++ .../selftests/drivers/net/mlxsw/qos_dscp_bridge.sh | 65 +----- .../selftests/drivers/net/mlxsw/qos_dscp_router.sh | 233 +++++++++++++++++++++ tools/testing/selftests/net/forwarding/lib.sh | 63 ++++++ 10 files changed, 379 insertions(+), 79 deletions(-) create mode 100755 tools/testing/selftests/drivers/net/mlxsw/qos_dscp_router.sh