// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2013-2018, The Linux Foundation. All rights reserved.
 *
 * RMNET Data ingress/egress handler
 */

#include <linux/netdevice.h>
#include <linux/netdev_features.h>
#include <linux/if_arp.h>
#include <net/sock.h>
#include "rmnet_private.h"
#include "rmnet_config.h"
#include "rmnet_vnd.h"
#include "rmnet_map.h"
#include "rmnet_handlers.h"

#define RMNET_IP_VERSION_4 0x40
#define RMNET_IP_VERSION_6 0x60

/* Helper Functions */

static void rmnet_set_skb_proto(struct sk_buff *skb)
{
        switch (skb->data[0] & 0xF0) {
        case RMNET_IP_VERSION_4:
                skb->protocol = htons(ETH_P_IP);
                break;
        case RMNET_IP_VERSION_6:
                skb->protocol = htons(ETH_P_IPV6);
                break;
        default:
                skb->protocol = htons(ETH_P_MAP);
                break;
        }
}

/* Generic handler */

static void
rmnet_deliver_skb(struct sk_buff *skb)
{
        struct rmnet_priv *priv = netdev_priv(skb->dev);

        skb_reset_transport_header(skb);
        skb_reset_network_header(skb);
        rmnet_vnd_rx_fixup(skb, skb->dev);

        skb->pkt_type = PACKET_HOST;
        skb_set_mac_header(skb, 0);
        gro_cells_receive(&priv->gro_cells, skb);
}

/* MAP handler */

static void
__rmnet_map_ingress_handler(struct sk_buff *skb,
                            struct rmnet_port *port)
{
        struct rmnet_endpoint *ep;
        u16 len, pad;
        u8 mux_id;

        if (RMNET_MAP_GET_CD_BIT(skb)) {
                if (port->data_format & RMNET_FLAGS_INGRESS_MAP_COMMANDS)
                        return rmnet_map_command(skb, port);

                goto free_skb;
        }

        mux_id = RMNET_MAP_GET_MUX_ID(skb);
        pad = RMNET_MAP_GET_PAD(skb);
        len = RMNET_MAP_GET_LENGTH(skb) - pad;

        if (mux_id >= RMNET_MAX_LOGICAL_EP)
                goto free_skb;

        ep = rmnet_get_endpoint(port, mux_id);
        if (!ep)
                goto free_skb;

        skb->dev = ep->egress_dev;

        /* Subtract MAP header */
        skb_pull(skb, sizeof(struct rmnet_map_header));
        rmnet_set_skb_proto(skb);

        if (port->data_format & RMNET_FLAGS_INGRESS_MAP_CKSUMV4) {
                if (!rmnet_map_checksum_downlink_packet(skb, len + pad))
                        skb->ip_summed = CHECKSUM_UNNECESSARY;
        }

        skb_trim(skb, len);
        rmnet_deliver_skb(skb);
        return;

free_skb:
        kfree_skb(skb);
}

static void
rmnet_map_ingress_handler(struct sk_buff *skb,
                          struct rmnet_port *port)
{
        struct sk_buff *skbn;

        if (skb->dev->type == ARPHRD_ETHER) {
                if (pskb_expand_head(skb, ETH_HLEN, 0, GFP_ATOMIC)) {
                        kfree_skb(skb);
                        return;
                }

                skb_push(skb, ETH_HLEN);
        }

        if (port->data_format & RMNET_FLAGS_INGRESS_DEAGGREGATION) {
                while ((skbn = rmnet_map_deaggregate(skb, port)) != NULL)
                        __rmnet_map_ingress_handler(skbn, port);

                consume_skb(skb);
        } else {
                __rmnet_map_ingress_handler(skb, port);
        }
}

static int rmnet_map_egress_handler(struct sk_buff *skb,
                                    struct rmnet_port *port, u8 mux_id,
                                    struct net_device *orig_dev)
{
        int required_headroom, additional_header_len;
        struct rmnet_map_header *map_header;

        additional_header_len = 0;
        required_headroom = sizeof(struct rmnet_map_header);

        if (port->data_format & RMNET_FLAGS_EGRESS_MAP_CKSUMV4) {
                additional_header_len = sizeof(struct rmnet_map_ul_csum_header);
                required_headroom += additional_header_len;
        }

        if (skb_headroom(skb) < required_headroom) {
                if (pskb_expand_head(skb, required_headroom, 0, GFP_ATOMIC))
                        return -ENOMEM;
        }

        if (port->data_format & RMNET_FLAGS_EGRESS_MAP_CKSUMV4)
                rmnet_map_checksum_uplink_packet(skb, orig_dev);

        map_header = rmnet_map_add_map_header(skb, additional_header_len, 0);
        if (!map_header)
                return -ENOMEM;

        map_header->mux_id = mux_id;

        skb->protocol = htons(ETH_P_MAP);

        return 0;
}

static void
rmnet_bridge_handler(struct sk_buff *skb, struct net_device *bridge_dev)
{
        if (bridge_dev) {
                skb->dev = bridge_dev;
                dev_queue_xmit(skb);
        }
}

/* Ingress / Egress Entry Points */

/* Processes packet as per ingress data format for receiving device. Logical
 * endpoint is determined from packet inspection. Packet is then sent to the
 * egress device listed in the logical endpoint configuration.
 */
rx_handler_result_t rmnet_rx_handler(struct sk_buff **pskb)
{
        struct sk_buff *skb = *pskb;
        struct rmnet_port *port;
        struct net_device *dev;

        if (!skb)
                goto done;

        if (skb->pkt_type == PACKET_LOOPBACK)
                return RX_HANDLER_PASS;

        dev = skb->dev;
        port = rmnet_get_port(dev);

        switch (port->rmnet_mode) {
        case RMNET_EPMODE_VND:
                rmnet_map_ingress_handler(skb, port);
                break;
        case RMNET_EPMODE_BRIDGE:
                rmnet_bridge_handler(skb, port->bridge_ep);
                break;
        }

done:
        return RX_HANDLER_CONSUMED;
}

/* Modifies packet as per logical endpoint configuration and egress data format
 * for egress device configured in logical endpoint. Packet is then transmitted
 * on the egress device.
 */
void rmnet_egress_handler(struct sk_buff *skb)
{
        struct net_device *orig_dev;
        struct rmnet_port *port;
        struct rmnet_priv *priv;
        u8 mux_id;

        sk_pacing_shift_update(skb->sk, 8);

        orig_dev = skb->dev;
        priv = netdev_priv(orig_dev);
        skb->dev = priv->real_dev;
        mux_id = priv->mux_id;

        port = rmnet_get_port(skb->dev);
        if (!port)
                goto drop;

        if (rmnet_map_egress_handler(skb, port, mux_id, orig_dev))
                goto drop;

        rmnet_vnd_tx_fixup(skb, orig_dev);

        dev_queue_xmit(skb);
        return;

drop:
        this_cpu_inc(priv->pcpu_stats->stats.tx_drops);
        kfree_skb(skb);
}