kernel/linux.git/net/ethtool/rss.c, branch v6.19.11

net: rss: fix reporting RXH_XFRM_NO_CHANGE as input_xfrm for contexts

2026-02-03T01:09:48+00:00

Initializing input_xfrm to RXH_XFRM_NO_CHANGE in RSS contexts is problematic. I think I did this to make it clear that the context does not have its own settings applied. But unlike ETH_RSS_HASH_NO_CHANGE which is zero, RXH_XFRM_NO_CHANGE is 0xff. We need to be careful when reading the value back, and remember to treat 0xff as 0. Remove the initialization and switch to storing 0. This lets us also remove the workaround in ethnl_rss_set(). Get side does not need any adjustments and context get no longer reports: RSS input transformation: symmetric-xor: on symmetric-or-xor: on Unknown bits in RSS input transformation: 0xfc for NICs which don't support input_xfrm. Remove the init of hfunc to ETH_RSS_HASH_NO_CHANGE while at it. As already mentioned this is a noop since ETH_RSS_HASH_NO_CHANGE is 0 and struct is zalloc'd. But as this fix exemplifies storing NO_CHANGE as state is fragile. This issue is implicitly caught by running our selftests because YNL in selftests errors out on unknown bits. Fixes: d3e2c7bab124 ("ethtool: rss: support setting input-xfrm via Netlink") Link: https://patch.msgid.link/20260130190311.811129-1-kuba@kernel.org Signed-off-by: Jakub Kicinski

net: ethtool: use the new helper in rss_set_prep_indir()

2025-09-18T14:07:38+00:00

Refactor rss_set_prep_indir() to utilize the new ethtool_get_rx_ring_count() helper for determining the number of RX rings, replacing the direct use of get_rxnfc with ETHTOOL_GRXRINGS. This ensures compatibility with both legacy and new ethtool_ops interfaces by transparently multiplexing between them. Signed-off-by: Breno Leitao Link: https://patch.msgid.link/20250917-gxrings-v4-7-dae520e2e1cb@debian.org Signed-off-by: Jakub Kicinski

net: ethtool: support including Flow Label in the flow hash for RSS

2025-08-14T09:40:13+00:00

Some modern NICs support including the IPv6 Flow Label in the flow hash for RSS queue selection. This is outside the old "Microsoft spec", but was included in the OCP NIC spec: [ ] RSS include flow label in the hash (configurable) https://www.opencompute.org/w/index.php?title=Core_Offloads#Receive_Side_Scaling RSS Flow Label hashing allows TCP Protective Load Balancing (PLB) to recover from receiver congestion / overload. Rx CPU/queue hotspots are relatively common for data ingest workloads, and so far we had to try to detect the condition at the RPC layer and reopen the connection. PLB lets us change the Flow Label and therefore Rx CPU on RTO, with minimal packet reordering. PLB reaction times are much faster, and can happen at any point in the connection, not just at RPC boundaries. Due to the nature of host processing (relatively long queues, other kernel subsystems masking IRQs for 100s of msecs) the risk of reordering within the host is higher than in the network. But for applications which need it - it is far preferable to potentially persistent overload of subset of queues. It is expected that the hash communicated to the host may change if the Flow Label changes. This may be surprising to some host software, but I don't expect the devices can compute two Toeplitz hashes, one with the Flow Label for queue selection and one without for the rx hash communicated to the host. Besides, changing the hash may potentially help to change the path thru host queues. User can disable NETIF_F_RXHASH if they require a stable flow hash. The name RXH_IP6_FL was chosen based on what we call Flow Label variables in IPv6 processing (fl). I prefer fl_lbl but that appears to be an fbnic-only spelling. We could spell out RXH_IP6_FLOW_LABEL but existing RXH_ defines are a lot more terse. Willem notes [1] that Flow Label is defined as identifying the flow and therefore including both the flow label _and_ the L4 header fields is not generally necessary. But it should not hurt so it's not explicitly prevented if the driver supports hashing on both at the same time. Link: https://lore.kernel.org/68483433b45e2_3cd66f29440@willemb.c.googlers.com.notmuch [1] Signed-off-by: Jakub Kicinski Reviewed-by: Joe Damato Link: https://patch.msgid.link/20250811234212.580748-2-kuba@kernel.org Signed-off-by: Paolo Abeni

ethtool: rss: support removing contexts via Netlink

2025-07-22T01:21:19+00:00

Implement removing additional RSS contexts via Netlink. Technically it'd be possible to shoehorn the delete operation into ethnl_request_ops-compatible handler. The code ends up longer than open coded version, and I think we'll need a custom way of sending notifications at some stage (if we allow tying the context lifetime to the netlink socket, in the future). Link: https://patch.msgid.link/20250717234343.2328602-8-kuba@kernel.org Signed-off-by: Jakub Kicinski

ethtool: rss: support creating contexts via Netlink

2025-07-22T01:20:43+00:00

Support creating contexts via Netlink. Setting flow hashing fields on the new context is not supported at this stage, it can be added later. An empty indirection table is not supported. This is a carry over from the IOCTL interface where empty indirection table meant delete. We can repurpose empty indirection table in Netlink but for now to avoid confusion reject it using the policy. Support letting user choose the ID for the new context. This was not possible in IOCTL since the context ID field for the create action had to be set to the ETH_RXFH_CONTEXT_ALLOC magic value. Link: https://patch.msgid.link/20250717234343.2328602-7-kuba@kernel.org Signed-off-by: Jakub Kicinski

ethtool: rss: factor out populating response from context

2025-07-22T01:20:19+00:00

Similarly to previous change, factor out populating the response. We will use this after the context was allocated to send a notification so this time factor out from the additional context handling, rather than context 0 handling (for request context didn't exist, for response it does). Reviewed-by: Gal Pressman Link: https://patch.msgid.link/20250717234343.2328602-5-kuba@kernel.org Signed-off-by: Jakub Kicinski

ethtool: rss: factor out allocating memory for response

2025-07-22T01:20:19+00:00

To ease the code reuse for RSS_CREATE we'll want to prepare struct rss_reply_data for the new context. Unfortunately we can't depend on the exiting scaffolding because the context doesn't exist (ctx=NULL) when we start preparing. Factor out the portion of the context 0 handling responsible for allocation of request memory, so that we can call it directly. Link: https://patch.msgid.link/20250717234343.2328602-4-kuba@kernel.org Signed-off-by: Jakub Kicinski

ethtool: rejig the RSS notification machinery for more types

2025-07-22T01:20:19+00:00

In anticipation for CREATE and DELETE notifications - explicitly pass the notification type to ethtool_rss_notify(), when calling from the IOCTL code. Reviewed-by: Gal Pressman Link: https://patch.msgid.link/20250717234343.2328602-3-kuba@kernel.org Signed-off-by: Jakub Kicinski

ethtool: rss: support setting flow hashing fields

2025-07-17T23:13:59+00:00

Add support for ETHTOOL_SRXFH (setting hashing fields) in RSS_SET. The tricky part is dealing with symmetric hashing. In netlink user can change the hashing fields and symmetric hash in one request, in IOCTL the two used to be set via different uAPI requests. Since fields and hash function config are still separate driver callbacks - changes to the two are not atomic. Keep things simple and validate the settings against both pre- and post- change ones. Meaning that we will reject the config request if user tries to correct the flow fields and set input_xfrm in one request, or disables input_xfrm and makes flow fields non-symmetric. We can adjust it later if there's a real need. Starting simple feels right, and potentially partially applying the settings isn't nice, either. Reviewed-by: Gal Pressman Link: https://patch.msgid.link/20250716000331.1378807-11-kuba@kernel.org Signed-off-by: Jakub Kicinski

ethtool: rss: support setting input-xfrm via Netlink

2025-07-17T23:13:59+00:00

Support configuring symmetric hashing via Netlink. We have the flow field config prepared as part of SET handling, so scan it for conflicts instead of querying the driver again. Reviewed-by: Gal Pressman Link: https://patch.msgid.link/20250716000331.1378807-10-kuba@kernel.org Signed-off-by: Jakub Kicinski