IFLIBTXTX(9)

💖 IFLIBTXTX(9) — the Kernel Developer's Manual glow-up 💖

okay so bestie, welcome to IFLIBTXTX(9) from the Kernel Developer's Manual. This is the page for iflibtxrx — Device Dependent Transmit and Receive Functions. It’s giving “the exact facts, but make it group chat” energy, and the facts do not change. No cap. 💖

🌸 NAME 🌸

iflibtxrx — Device Dependent Transmit and Receive Functions

✨ SYNOPSIS ✨

Here’s the include, bestie — exact energy only, no renaming, no merging. periodt.

#include <ifdi_if.h>

💅 Interface Manipulation Functions 💅

int
isc_txd_encap(void *sc, if_pkt_info_t pi);

void
isc_txd_flush(void *sc, uint16_t qid, uint32_t _pidx_or_credits_);

int
isc_txd_credits_update(void *sc, uint16_t qid, bool clear);

int
isc_rxd_available(void *sc, uint16_t qsid, uint32_t cidx);

void
isc_rxd_refill(void *sc, uint16_t qsid, uint8_t flid, uint32_t pidx,
    uint64_t *paddrs, caddr_t *vaddrs, uint16_t count);

void
isc_rxd_flush(void *sc, uint16_t qsid, uint8_t flid, uint32_t pidx);

int
isc_rxd_pkt_get(void *sc, if_rxd_info_t ri);

🌈 Global Variables 🌈

And the synopsis also lists this global variable, literally:

extern struct if_txrx

bestie, it’s written like that in the original — no semicolon added, no “fixing” the vibe. 🫶

🦋 DATA STRUCTURES 🦋

The device dependent mechanisms for handling packet transmit and receive are primarily defined by the functions named above. The if_pkt_info data structure contains statistics and identifying info necessary for packet transmission. While the data structure for packet receipt is the if_rxd_info structure.

🎀 The if_pkt_info Structure 🎀

The fields of struct if_pkt_info are as follows:

• ipi_len (uint32_t) — Denotes the size of packet to be sent on the transmit queue.
• ipi_segs (bus_dma_segment_t *) — A pointer to the bus_dma_segment of the device independent transfer queue defined in iflib.
• ipi_qsidx — Unique index value assigned sequentially to each transmit queue. Used to reference the currently transmitting queue.
• ipi_nsegs (uint16_t) — Number of descriptors to be read into the device dependent transfer descriptors.
• ipi_ndescs (uint16_t) — Number of descriptors in use. Calculated by subtracting the old pidx value from the new pidx value.
• ipi_flags (uint16_t) — Flags defined on a per packet basis.
• ipi_pidx (uint32_t) — Value of first pidx sent to the isc_encap function for encapsulation and subsequent transmission.
• ipi_new_pidx (uint32_t) — Value set after the termination of the isc_encap function. This value will become the first pidx sent to the isc-encap the next time that the function is called.

💅 The Following Fields Are Used For Offload Handling 💅

• ipi_csum_flags (uint64_t) — Flags describing the checksum values, used on a per packet basis.
• ipi_tso_segsz (uint16_t) — Size of the TSO Segment Size.
• ipi_mflags (uint16_t) — Flags describing the operational parameters of the mbuf.
• ipi_vtag (uint16_t) — Contains the VLAN information in the Ethernet Frame.
• ipi_etype (uint16_t) — Type of ethernet header protocol as contained by the struct ether_vlan_header.
• ipi_ehrdlen (uint8_t) — Length of the Ethernet Header.
• ipi_ip_hlen (uint8_t) — Length of the TCP Header.
• ipi_tcp_hlen (uint8_t) — Length of the TCP Header.
• ipi_tcp_hflags (uint8_t) — Flags describing the operational parameters of the TCP Header.
• ipi_ipproto (uint8_t) — Specifies the type of IP Protocol in use. Example TCP, UDP, or SCTP.

🌸 The if_rxd_info Structure 🌸

The fields of struct if_rxd_info are as follows:

• iri_qsidx (uint16_t) — Unique index value assigned sequentially to each receive queue. Used to reference the currently receiving queue.
• iri_vtag (uint16_t) — Contains the VLAN information in the Ethernet Frame.
• iri_len (uint16_t) — Denotes the size of a received packet.
• iri_next_offset (uint16_t) — Denotes the offset value for the next packet to be receive. A Null value signifies the end of packet.
• iri_cidx (uint32_t) — Denotes the index value of the packet currently being processed in the consumer queue.
• iri_flowid (uint32_t) — Value of the RSS hash for the packet.
• iri_flags (uint) — Flags describing the operational parameters of the mbuf contained in the receive packet.
• iri_csum_flags (uint32_t) — Flags describing the checksum value contained in the receive packet.
• iri_csum_data (uint32_t) — Checksum data contained in the mbuf(9) packet header.
• iri_m (struct mbuf *) — A mbuf for drivers that manage their own receive queues.
• iri_ifp (struct ifnet *) — A link back to the interface structure. Utilized by drivers that have multiple interface per softc.
• iri_rsstype (uint8_t) — The value of the RSS hash type.
• iri_pad (uint8_t) — The length of any padding contained by the received data.
• iri_qidx (uint8_t) — Represents the type of queue event. If value >= 0 then it is the freelist id otherwise it is a completion queue event.

🔥 FUNCTIONS 🔥

All function calls are associated exclusively with either packet transmission or receipt. The void *sc passed as the first argument to all of the following functions represents the driver’s softc. iykyk 💅

🚀 Transmit Packet Functions 🚀

• isc_txd_encap() — Transmit function that sends a packet on an interface. The if_pkt_info data structure contains data information fields describing the packet. This function returns 0 if successful, otherwise an error value is returned.
• isc_txd_flush() — Flush function is called immediately after the isc_txd_encap function transmits a packet. It updates the hardware producer index or increments the descriptors used to pidx_or_credits in the queue designated by the qid number. This is often referred to as poking the doorbell register.
• isc_txd_credits_update() — Credit function advances the buffer ring and calculates the credits (descriptors) processed. Until the I/O is complete it cleans the range in case of multisegments and updates the count of processed packets. The function returns the number of processed credits.

💌 Receive Packet Functions 💌

• isc_rxd_available() — Function calculates the remaining number of descriptors from a position given by idx. The function returns this value.
• isc_rxd_refill() — Starting with the physical address paddrs, the function reads a packet into the rx_ring until a value designated by count is reached. vaddrs is typically not needed and is provided for devices that place their own metadata in the packet header.
• isc_rxd_flush() — Flush function updates the producer pointer on the free list flid in queue set number qid to pidx to reflect the presence of new buffers.
• isc_rxd_pkt_get() — Process a single software descriptor. rxr->rx_base[i] contains a descriptor that describes a received packet. Hardware specific information about the buffer referred to by ri is returned in the data structure if_rxd_info.

🌈 SEE ALSO 🌈

• iflibdd(9)
• iflibdi(9)
• mbuf(9)

👑 AUTHORS 👑

This manual page was written by Nicole Graziano.

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okay bestie, that’s the whole page 💖 source/version: Debian; date: December 17, 2020; page: IFLIBTXTX(9). periodt ✨