28/01/2024 10:39, Ori Kam: > During the encapsulation of a packet, it is expected to calculate the > hash value which is based on the original packet (the outer values, > which will become the inner values).
It is not clear what the hash is for. > The tunnel protocol defines which tunnel field should hold this hash, > but it doesn't define the hash calculation algorithm. If the hash is stored in the packet header, I expect it to be reproducible when being checked. How the algorithm may be undefined? > An application that uses flow offloads gets the first few packets > and then decides to offload the flow. As a result, there are two > different paths that a packet from a given flow may take. > SW for the first few packets or HW for the rest. > When the packet goes through the SW, the SW encapsulates the packet > and must use the same hash calculation as the HW will do for > the rest of the packets in this flow. > > This patch gives the SW a way to query the hash value > for a given packet as if the packet was passed through the HW. > > Signed-off-by: Ori Kam <or...@nvidia.com> > --- > +Calculate encap hash > +~~~~~~~~~~~~~~~~~~~~ > + > +Calculating hash of a packet in SW as it would be calculated in HW for the > encap action We should give the real full name of the flow action. > + > +When the HW execute an encapsulation action, it may calculate an hash value > which is based > +on the original packet. This hash is stored depending on the encapsulation > protocol, in one > +of the outer fields. Give an example of such encapsulation protocol? > +This function allows the application to calculate the hash for a given > packet as if the > +encapsulation was done in HW. > + > +.. code-block:: c > + > + int > + rte_flow_calc_encap_hash(uint16_t port_id, > + const struct rte_flow_item pattern[], > + enum rte_flow_encap_hash_field > dest_field, > + uint8_t hash_len, > + uint8_t *hash, > + struct rte_flow_error *error); I don't think we should add the complete prototype in this guide. [...] > +/** > + * @warning > + * @b EXPERIMENTAL: this API may change without prior notice. > + * > + * Simulates HW hash calculation that is done when encap action is being > used. s/Simulates/Simulate/ > + * > + * @param[in] port_id > + * Port identifier of Ethernet device. > + * @param[in] pattern > + * The values to be used in the hash calculation. > + * @param[in] dest_field > + * Type of destination field for hash calculation. > + * @param[in] hash_len > + * The length of the hash pointer in bytes. Should be according to > encap_hash_field. > + * @param[out] hash > + * Used to return the calculated hash. It will be written in network order, > + * so hash[0] is the MSB. > + * The number of bytes is based on the destination field type. > + * @param[out] error > + * Perform verbose error reporting if not NULL. > + * PMDs initialize this structure in case of error only. > + * > + * @return > + * - (0) if success. > + * - (-ENODEV) if *port_id* invalid. > + * - (-ENOTSUP) if underlying device does not support this functionality. > + * - (-EINVAL) if *pattern* doesn't hold enough information to calculate > the hash > + * or the dest is not supported. > + */ > +__rte_experimental > +int > +rte_flow_calc_encap_hash(uint16_t port_id, const struct rte_flow_item > pattern[], > + enum rte_flow_encap_hash_field dest_field, uint8_t > hash_len, > + uint8_t *hash, struct rte_flow_error *error);
