source: ReferenceDesigns/w3_802.11/c/wlan_mac_high_framework/wlan_mac_eth_util.c

/** @file wlan_mac_eth_util.c
 *  @brief Ethernet Framework
 *
 *  Contains code for using Ethernet, including encapsulation and de-encapsulation.
 *
 *  @copyright Copyright 2013-2019, Mango Communications. All rights reserved.
 *          Distributed under the Mango Communications Reference Design License
 *              See LICENSE.txt included in the design archive or
 *              at http://mangocomm.com/802.11/license
 *
 *  This file is part of the Mango 802.11 Reference Design (https://mangocomm.com/802.11)
 */

/***************************** Include Files *********************************/





#include "stdlib.h"
#include "stddef.h"
#include "xil_types.h"
#include "string.h"

#include "wlan_platform_high.h"
#include "wlan_mac_high.h"
#include "wlan_mac_common.h"
#include "wlan_mac_eth_util.h"
#include "wlan_mac_dl_list.h"
#include "wlan_mac_queue.h"
#include "wlan_mac_station_info.h"
#include "wlan_mac_802_11_defs.h"
#include "wlan_mac_pkt_buf_util.h"

#include "wlan_mac_high_sw_config.h"

/*************************** Variable Definitions ****************************/

#if WLAN_SW_CONFIG_ENABLE_ETH_BRIDGE

// Ethernet Station MAC Address
//
//   The station code's implementation of encapsulation and de-encapsulation has an important
// limitation: only one device may be plugged into the station's Ethernet port. The station
// does not provide NAT. It assumes that the last received Ethernet src MAC address is used
// as the destination MAC address on any Ethernet transmissions. This is fine when there is
// only one device on the station's Ethernet port, but will definitely not work if the station
// is plugged into a switch with more than one device.
//
static u8 mac_addr_to_overwrite[6];


/*********************** Global Variable Definitions *************************/

// Controls whether or not portal behaviors will be enabled
static u8 gl_portal_en;
static int _portal_eth_rx_qid;
static int _portal_eth_tx_qid;

// Callback for top-level processing of Ethernet received packets
static function_ptr_t eth_rx_callback;


/*************************** Functions Prototypes ****************************/

void _portal_eth_rx_queue_occupancy_change(int callback_arg, u32 queue_len);
void _portal_eth_tx_queue_occupancy_change(int callback_arg, u32 queue_len);

#if PERF_MON_ETH_BD
void     print_bd_high_water_mark() { xil_printf("BD HWM = %d\n", bd_high_water_mark); }
#endif


/*****************************************************************************/
/**
 * @brief Initialize the Ethernet utility sub-system
 *
 * Initialize Ethernet A hardware and framework for handling Ethernet Tx/Rx via
 * the DMA.  This function must be called once at boot, before any Ethernet
 * configuration or Tx/Rx operations.
 *
 * @return WLAN_SUCCESS
 */
int wlan_eth_util_init() {

    // Open a queue for Rx Ethernet frames
    _portal_eth_rx_qid = queue_open((void*)_portal_eth_rx_queue_occupancy_change, 0, PORTAL_MAX_QUEUE_LEN);

    // Open a queue for Tx Ethernet frames
    _portal_eth_tx_qid = queue_open((void*)_portal_eth_tx_queue_occupancy_change, 0, PORTAL_MAX_QUEUE_LEN);

    if((_portal_eth_rx_qid == -1) || (_portal_eth_tx_qid == -1)) xil_printf("Error in wlan_eth_util_init(), unable to open queue\n");

    // Initialize Callback
    eth_rx_callback = (function_ptr_t)wlan_null_callback;

    // Enable bridging of the wired-wireless networks (a.k.a. the "portal" between networks)
    wlan_eth_portal_en(1);
    return WLAN_SUCCESS;
}

/*****************************************************************************/
/**
 * @brief Sets the MAC callback to process Ethernet receptions
 *
 * The framework will call the MAC's callback for each Ethernet reception that is a candidate
 * for wireless transmission. The framework may reject some packets for malformed or unrecognized
 * Ethernet headers. The MAC may reject more, based on Ethernet address or packet contents.
 *
 * @param void(*callback)
 *  -Function pointer to the MAC's Ethernet Rx callback
 */
void wlan_mac_util_set_eth_rx_callback(void(*callback)()) {
    eth_rx_callback = (function_ptr_t)callback;
}

int wlan_enqueue_eth_rx(eth_rx_queue_buffer_t* eth_rx_queue_buffer){
    u8 is_claimed = 0;
    int status;
    status = queue_enqueue(_portal_eth_rx_qid, eth_rx_queue_buffer->pyld_queue_hdr.dle);
    if(status == 0) is_claimed = 1;
    return is_claimed;
}

int wlan_enqueue_eth_tx(dl_entry* queue_entry){
    int status;
    status = queue_enqueue(_portal_eth_tx_qid, queue_entry);
    return status;
}

u32 wlan_poll_eth_rx_queue(){
    dl_entry* packet_to_process;
    int ret;
    u32 i;

    for(i = 0; i < WLAN_MIN(queue_length(_portal_eth_rx_qid), WLAN_MAX_ETH_RX_PROCESS_PER_ISR); i++){
        packet_to_process = queue_dequeue(_portal_eth_rx_qid);
        if(packet_to_process == NULL) return WLAN_SUCCESS; // should not be possible
        ret = wlan_process_eth_rx((eth_rx_queue_buffer_t*)(packet_to_process->data));
        if( ret != 0 ){
            // This Ethernet packet was rejected so we must return
            //  the entry back to the free list.
            queue_checkin(packet_to_process);
        }
    }

    return queue_length(_portal_eth_rx_qid);
}

u32 wlan_poll_eth_tx_queue(){
    dl_entry* packet_to_process;
    u32 i;
    int status;

    for(i = 0; i < WLAN_MIN(queue_length(_portal_eth_tx_qid), WLAN_MAX_ETH_TX_PROCESS_PER_ISR); i++){
        packet_to_process = queue_dequeue(_portal_eth_tx_qid);
        if(packet_to_process == NULL) return WLAN_SUCCESS; // should not be possible

        // Platform Ethernet Send functions are required to check in
        //  packet_to_process when they are done with them if they were successful.
        status = wlan_platform_portal_eth_send((eth_tx_queue_buffer_t*)(packet_to_process->data));

        if(status != 0){
            // We were unable to transmit this packet. This is mostly likely due to an ongoing transmission
            //  causing there to be no free BDs. Re-enqueue this packet back into the head of the _eth_tx_qid
            //  queue;

            status = enqueue_head(_portal_eth_tx_qid, packet_to_process);

            if( status == -1 ){
                queue_checkin(packet_to_process);
            }
        }
    }

    return queue_length(_portal_eth_tx_qid);
}

/*****************************************************************************/
/**
 * @brief Process an Ethernet packet that has been received by the ETH DMA
 *
 * This function processes an Ethernet DMA buffer descriptor.  This design assumes
 * a 1-to-1 correspondence between buffer descriptors and Ethernet packets.  For
 * each packet, this function encapsulates the Ethernet packet and calls the
 * MAC's callback to either enqueue (for eventual wireless Tx) or reject the packet.
 *
 * NOTE:  Processed ETH DMA buffer descriptors are freed but not resubmitted to
 * hardware for use by future Ethernet receptions.  This is the responsibility of
 * higher level code (see comment at the end of the function if this behavior needs
 * to change).
 *
 * This function requires the MAC implement a function (assigned to the eth_rx_callback
 * function pointer) that returns 0 or 1, indicating the MAC's handling of the packet:
 *     0: Packet was not enqueued and will not be processed by wireless MAC; framework
 *        should immediately discard
 *     1: Packet was enqueued for eventual wireless transmission; MAC will check in
 *        occupied queue entry when finished
 *
 */
int wlan_process_eth_rx(eth_rx_queue_buffer_t* eth_rx_queue_buffer) {

    int return_value = -1;
    int packet_claimed = 0;

#if PERF_MON_ETH_PROCESS_RX
    wlan_mac_set_dbg_hdr_out(0x4);
#endif

    // Check arguments
    if( eth_rx_queue_buffer == NULL ) {
        xil_printf("ERROR:  Tried to process NULL Ethernet packet\n");
        return return_value;
    }

    ////////////////////
    // 1. The first potential claimant for this packet is wlan_exp. It is expected that wlan_exp
    //    processing will be light and will simply save the packet away for future processing if
    //    it decides to claim it.
        // TODO:
    // wlan_exp_process_this_packet(pyld_queue_eth)
    packet_claimed = 0; //wlan_exp should return 1 if it is holding on to this packet

    if(packet_claimed == 0){
        ////////////////////
        // 2. The second potential claimant for this packet is the 802.11 portal.
        packet_claimed = eth_rx_callback(eth_rx_queue_buffer);
        if (packet_claimed) {
                return_value = 0;
        }
    }
#if PERF_MON_ETH_PROCESS_RX
    wlan_mac_clear_dbg_hdr_out(0x4);
#endif
    return return_value;
}

void wlan_eth_portal_en(u8 enable){
    gl_portal_en = enable;
}



#endif /* WLAN_SW_CONFIG_ENABLE_ETH_BRIDGE */


/*****************************************************************************/
/**
 * @brief Encapsulates Ethernet packets for wireless transmission
 *
 * This function implements the encapsulation process for 802.11 transmission of
 * Ethernet packets
 *
 * The encapsulation process depends on the node's role:
 *
 * AP:
 *     - Copy original packet's source and destination addresses to temporary space
 *     - Add an LLC header (8 bytes) in front of the Ethernet payload
 *         - LLC header includes original packet's ETHER_TYPE field; only IPV4 and ARP
 *           are currently supported
 *
 * STA:
 *    - Copy original packet's source and destination addresses to temporary space
 *    - Add an LLC header (8 bytes) in front of the Ethernet payload
 *        - LLC header includes original packet's ETHER_TYPE field; only IPV4 and ARP
 *          are currently supported
 *    - If packet is ARP Request, overwrite ARP header's source address with STA
 *      wireless MAC address
 *    - If packet is UDP packet containing a DHCP request
 *        - Assert DHCP header's BROADCAST flag
 *        - Disable the UDP packet checksum (otherwise it would be invliad after
 *          modifying the BROADCAST flag)
 *
 */
tx_80211_queue_buffer_t* wlan_eth_encap( eth_rx_queue_buffer_t* eth_rx_queue_buffer, u32 flags ) {
#if WLAN_SW_CONFIG_ENABLE_ETH_BRIDGE
    ethernet_header_t* eth_hdr;
    llc_header_t* llc_hdr;
    ipv4_header_t* ip_hdr;
    arp_ipv4_packet_t* arp;
    udp_header_t* udp;
    dhcp_packet* dhcp;

    //Cast the Rx Ethernet Stencil as a Tx 802.11 Stencil
    tx_80211_queue_buffer_t* tx_queue_buffer = (tx_80211_queue_buffer_t*)eth_rx_queue_buffer;

    // Calculate actual wireless Tx len (eth payload - eth header + wireless header)
    tx_queue_buffer->length = eth_rx_queue_buffer->length - sizeof(ethernet_header_t)  + sizeof(llc_header_t) + sizeof(mac_header_80211) + WLAN_PHY_FCS_NBYTES;

    // Update metadata so dequeue operation knows how to construct contiguous series of bytes that form the MPDU
    //  1) The C0 section starting at tx_queue_buffer->pkt contains an 802.11 header and an LLC header.
    tx_queue_buffer->seg0_len = sizeof(mac_header_80211) + sizeof(llc_header_t);

    //  2) The C1 section starts after both the C0 section and an Ethernet header. The Ethernet header must remain
    //     in this buffer for other processes in this framework, but the bytes themselves are not copied to CPU_LOW
    //     on dequeue. This offset allows the dequeue operation to skip these bytes.
    tx_queue_buffer->seg1_offset = tx_queue_buffer->seg0_len + sizeof(ethernet_header_t);

    //  3) Together, the C0 and C1 section lengths total the wireless Tx length calculated above in tx_queue_buffer->pyld_queue_hdr.length
    tx_queue_buffer->seg1_len = tx_queue_buffer->length - tx_queue_buffer->seg0_len;

    // Read pointers to interpret fields in the new MPDU
    eth_hdr = (ethernet_header_t*)eth_rx_queue_buffer->pkt;

    // Write pointers to fill fields in the new MPDU
    llc_hdr = (llc_header_t*)(tx_queue_buffer->pkt + sizeof(mac_header_80211));

    // Prepare the MPDU LLC header
    llc_hdr->dsap = LLC_SNAP;
    llc_hdr->ssap = LLC_SNAP;
    llc_hdr->control_field = LLC_CNTRL_UNNUMBERED;
    bzero((void *)(llc_hdr->org_code), 3); //Org Code 0x000000: Encapsulated Ethernet
    if( flags & WLAN_ETH_ENCAP_FLAGS_OVERWRITE_PYLD_ADDRS ){
            memcpy(mac_addr_to_overwrite, eth_hdr->src_mac_addr, 6);
    }
    switch(eth_hdr->ethertype){
            case ETH_TYPE_ARP:
                    llc_hdr->type = LLC_TYPE_ARP;
                    if( flags & WLAN_ETH_ENCAP_FLAGS_OVERWRITE_PYLD_ADDRS ){
                            arp = (arp_ipv4_packet_t*)((void*)eth_hdr + sizeof(ethernet_header_t));
                            memcpy(arp->sender_haddr, get_mac_hw_addr_wlan(), 6);
                    }
            break;
            case ETH_TYPE_IP:
                    llc_hdr->type = LLC_TYPE_IP;
                    if( flags & WLAN_ETH_ENCAP_FLAGS_OVERWRITE_PYLD_ADDRS ){
                            // Check if IPv4 packet is a DHCP Discover in a UDP frame
                                ip_hdr = (ipv4_header_t*)((void*)eth_hdr + sizeof(ethernet_header_t));
                                if (ip_hdr->protocol == IPV4_PROT_UDP) {
                                        udp = (udp_header_t*)((void*)ip_hdr + 4*((u8)(ip_hdr->version_ihl) & 0xF));
                                        // All Bootstrap Protocol packets contain the client MAC address as part of the
                                        // payload. For STA encapsulation, we need to replace the wired MAC address of
                                        // the client with the wireless MAC address of the STA.
                                        if ((Xil_Ntohs(udp->src_port) == UDP_SRC_PORT_BOOTPC) ||
                                                (Xil_Ntohs(udp->src_port) == UDP_SRC_PORT_BOOTPS)) {
                                                // Disable the checksum since this will change the bytes in the packet
                                                udp->checksum = 0;
                                                dhcp = (dhcp_packet*)((void*)udp + sizeof(udp_header_t));
                                                if (Xil_Ntohl(dhcp->magic_cookie) == DHCP_MAGIC_COOKIE) {
                                                        // Overwrite DHCP client MAC address with the station's wireless MAC address
                                                        memcpy(dhcp->chaddr, get_mac_hw_addr_wlan(), 6);
                                                } // END is DHCP valid
                                        } // END is DHCP
                                } // END is UDP
                    }
            break;
            default:
                    return NULL;
            break;
    }
    return tx_queue_buffer;
#else
    return NULL;
#endif
}

int wlan_eth_decap_and_send( u8* rx_mac_payload,
                             u8* addr_da,
                             u8* addr_sa,
                             u16 rx_length,
                             u32 flags ) {

#if WLAN_SW_CONFIG_ENABLE_ETH_BRIDGE
    eth_tx_queue_buffer_t* eth_tx_queue_buffer;
    dl_entry* eth_tx_queue_entry;
    mac_header_80211* rx80211_hdr;
    u32 eth_length;
    llc_header_t* llc_hdr;
    u16 pre_llc_offset;
    int status;

    // Read pointers -- these point to Rx packet buffers
    u8* eth_payload_read;
    arp_ipv4_packet_t* arp_read;
    ipv4_header_t* ip_hdr_read;
    udp_header_t* udp_read;
    dhcp_packet* dhcp_read;

    // Write pointers -- these point into Queue buffer in DRAM
    ethernet_header_t* eth_hdr_write;
    arp_ipv4_packet_t* arp_write;
    ipv4_header_t* ip_hdr_write;
    udp_header_t* udp_write;
    dhcp_packet* dhcp_write;

    u8 addr_da_localcopy[MAC_ADDR_LEN];
    u8 addr_sa_localcopy[MAC_ADDR_LEN];

    // Because the decapsulation procedure is destructive to the 802.11 header,
    // we need to make copies of the addr_da and addr_sa arguments
    if( flags & WLAN_ETH_ENCAP_FLAGS_OVERWRITE_PYLD_ADDRS ){
        memcpy(addr_da_localcopy, mac_addr_to_overwrite, MAC_ADDR_LEN);
    } else {
        memcpy(addr_da_localcopy, addr_da, MAC_ADDR_LEN);
    }
    memcpy(addr_sa_localcopy, addr_sa, MAC_ADDR_LEN);

    // Get helper pointers to various byte offsets in the packet payload
    rx80211_hdr = (mac_header_80211*)(rx_mac_payload);

    switch(rx80211_hdr->frame_control_1){
        case MAC_FRAME_CTRL1_SUBTYPE_QOSDATA:
            pre_llc_offset = sizeof(qos_control);
        break;
        case MAC_FRAME_CTRL1_SUBTYPE_DATA:
            pre_llc_offset = 0;
        break;
        default:
            // Unrecognized type -- cannot decapsulate
            return WLAN_FAILURE;
        break;
    }

    llc_hdr = (llc_header_t*)(rx_mac_payload + sizeof(mac_header_80211) + pre_llc_offset);
    eth_payload_read = (u8*)(rx_mac_payload + sizeof(mac_header_80211) + sizeof(llc_header_t) + pre_llc_offset);
    eth_length = rx_length - sizeof(mac_header_80211) - sizeof(llc_header_t) - pre_llc_offset - WLAN_PHY_FCS_NBYTES + sizeof(ethernet_header_t);

    if(eth_length <= sizeof(ethernet_header_t)){
        //This packet has no payload, we should quit now.
        return WLAN_FAILURE;
    }

    // Speculatively check out a queue buffer and begin CDMA of the payload. This enables decapsulation
    //  processing to be pipelined with the bulk of the copy

    eth_tx_queue_entry = queue_checkout();

    if(eth_tx_queue_entry == NULL){
        return WLAN_FAILURE;
    }

    eth_tx_queue_buffer = (eth_tx_queue_buffer_t*)(eth_tx_queue_entry->data);
    eth_hdr_write = (ethernet_header_t*)(eth_tx_queue_buffer->seg0);
    eth_tx_queue_buffer->seg0_len = eth_length;
    eth_tx_queue_buffer->seg1_len = 0;

    // Start the transfer
    wlan_mac_high_cdma_start_transfer((u8*)eth_hdr_write + sizeof(ethernet_header_t),
                                      eth_payload_read,
                                      eth_length - sizeof(ethernet_header_t));

    // Create Ethernet Header
    switch(llc_hdr->type){
        case LLC_TYPE_ARP:
            eth_hdr_write->ethertype = ETH_TYPE_ARP;
        break;

        case LLC_TYPE_IP:
            eth_hdr_write->ethertype = ETH_TYPE_IP;
        break;

        default:
            // Unrecognized type -- cannot decapsulate
            wlan_mac_high_cdma_finish_transfer();
            queue_checkin(eth_tx_queue_entry);
            return WLAN_FAILURE;
        break;
    }
    memcpy(eth_hdr_write->dest_mac_addr, addr_da_localcopy, MAC_ADDR_LEN);
    memcpy(eth_hdr_write->src_mac_addr,  addr_sa_localcopy, MAC_ADDR_LEN);

    // (Optional) -- overwrite MAC address present in the payload of the Ethernet frame
    // with one stored previously during encapsulation
    if( flags & WLAN_ETH_ENCAP_FLAGS_OVERWRITE_PYLD_ADDRS ){

        // We are about to start modifying bytes deep into the payload of the packet. We should
        //  wait for the CDMA operation to finish so we avoid a race.
        wlan_mac_high_cdma_finish_transfer();

        switch(llc_hdr->type){
            case LLC_TYPE_ARP:
                // If the ARP packet is addressed to this wireless address, replace the ARP dest address
                // with the connected wired device's MAC address
                arp_read = (arp_ipv4_packet_t *)(eth_payload_read); //eth_payload_read
                arp_write = (arp_ipv4_packet_t *)((u8*)eth_hdr_write + sizeof(ethernet_header_t));
                if (wlan_addr_eq(arp_read->target_haddr, get_mac_hw_addr_wlan())) {
                    memcpy(arp_write->target_haddr, mac_addr_to_overwrite, MAC_ADDR_LEN);
                }
            break;

            case ETH_TYPE_IP:
                ip_hdr_read = (ipv4_header_t*)(eth_payload_read);
                ip_hdr_write = (ipv4_header_t*)((u8*)eth_hdr_write + sizeof(ethernet_header_t));

                if (ip_hdr_read->protocol == IPV4_PROT_UDP) {
                    udp_read = (udp_header_t*)((void*)ip_hdr_read + 4*((u8)(ip_hdr_read->version_ihl) & 0xF));
                    udp_write = (udp_header_t*)((void*)ip_hdr_write + 4*((u8)(ip_hdr_read->version_ihl) & 0xF));

                    // All Bootstrap Protocol packets contain the client MAC address as part of the
                    // payload. For STA de-encapsulation, we need to replace the wireless MAC address
                    // of the STA with the wired MAC address of the client
                    if ((Xil_Ntohs(udp_read->src_port) == UDP_SRC_PORT_BOOTPC) ||
                        (Xil_Ntohs(udp_read->src_port) == UDP_SRC_PORT_BOOTPS)) {

                        // Disable the checksum since this will change the bytes in the packet
                        udp_write->checksum = 0;

                        dhcp_read = (dhcp_packet*)((u8*)udp_read + sizeof(udp_header_t));
                        dhcp_write = (dhcp_packet*)((u8*)udp_write + sizeof(udp_header_t));

                        if (Xil_Ntohl(dhcp_read->magic_cookie) == DHCP_MAGIC_COOKIE) {
                            // Overwrite DHCP client MAC address with the station's wireless MAC address
                            memcpy(dhcp_write->chaddr, mac_addr_to_overwrite, MAC_ADDR_LEN);
                        } // END is DHCP valid
                    } // END is DHCP
                } // END is UDP

            break;

            default:
            break;
        }
    }

    // Wait for CDMA to finish. If ~WLAN_ETH_ENCAP_FLAGS_OVERWRITE_PYLD_ADDRS, we have not called this yet
    wlan_mac_high_cdma_finish_transfer();

    // Add it to the Tx queue
    status = wlan_enqueue_eth_tx(eth_tx_queue_entry);

    if(status == -1){
        queue_checkin(eth_tx_queue_entry);
        return WLAN_FAILURE;
    } else {
        return WLAN_SUCCESS;
    }
#else
    return WLAN_FAILURE;
#endif
}

#if WLAN_SW_CONFIG_ENABLE_ETH_BRIDGE
// Local functions

void _portal_eth_rx_queue_occupancy_change(int callback_arg, u32 queue_len){
    // callback_arg is not used. It was set to 0 when opening the queue

    if(queue_len == 0){
        wlan_platform_clear_sw_intr(SW_INTR_ID_PORTAL_ETH_RX);
    } else {
        wlan_platform_assert_sw_intr(SW_INTR_ID_PORTAL_ETH_RX);
    }
}

void _portal_eth_tx_queue_occupancy_change(int callback_arg, u32 queue_len){
    // callback_arg is not used. It was set to 0 when opening the queue

    if(queue_len == 0){
        wlan_platform_clear_sw_intr(SW_INTR_ID_PORTAL_ETH_TX);
    } else {
        wlan_platform_assert_sw_intr(SW_INTR_ID_PORTAL_ETH_TX);
    }
}
#endif