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84214ab468
When function igc_rx_hash() was introduced in v4.20 via commit0507ef8a03("igc: Add transmit and receive fastpath and interrupt handlers"), the hardware wasn't configured to provide RSS hash, thus it made sense to not enable net_device NETIF_F_RXHASH feature bit. The NIC hardware was configured to enable RSS hash info in v5.2 via commit2121c2712f("igc: Add multiple receive queues control supporting"), but forgot to set the NETIF_F_RXHASH feature bit. The original implementation of igc_rx_hash() didn't extract the associated pkt_hash_type, but statically set PKT_HASH_TYPE_L3. The largest portions of this patch are about extracting the RSS Type from the hardware and mapping this to enum pkt_hash_types. This was based on Foxville i225 software user manual rev-1.3.1 and tested on Intel Ethernet Controller I225-LM (rev 03). For UDP it's worth noting that RSS (type) hashing have been disabled both for IPv4 and IPv6 (see IGC_MRQC_RSS_FIELD_IPV4_UDP + IGC_MRQC_RSS_FIELD_IPV6_UDP) because hardware RSS doesn't handle fragmented pkts well when enabled (can cause out-of-order). This results in PKT_HASH_TYPE_L3 for UDP packets, and hash value doesn't include UDP port numbers. Not being PKT_HASH_TYPE_L4, have the effect that netstack will do a software based hash calc calling into flow_dissect, but only when code calls skb_get_hash(), which doesn't necessary happen for local delivery. For QA verification testing I wrote a small bpftrace prog: [0] https://github.com/xdp-project/xdp-project/blob/master/areas/hints/monitor_skb_hash_on_dev.bt Fixes:2121c2712f("igc: Add multiple receive queues control supporting") Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Song Yoong Siang <yoong.siang.song@intel.com> Link: https://lore.kernel.org/bpf/168182464270.616355.11391652654430626584.stgit@firesoul
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.