// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2013-2018, 2021, 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_map_header *map_header = (void *)skb->data;
        struct rmnet_endpoint *ep;
        u16 len, pad;
        u8 mux_id;

        if (map_header->flags & MAP_CMD_FLAG) {
                /* Packet contains a MAP command (not data) */
                if (port->data_format & RMNET_FLAGS_INGRESS_MAP_COMMANDS)
                        return rmnet_map_command(skb, port);

                goto free_skb;
        }

        mux_id = map_header->mux_id;
        pad = map_header->flags & MAP_PAD_LEN_MASK;
        len = ntohs(map_header->pkt_len) - 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;

        if ((port->data_format & RMNET_FLAGS_INGRESS_MAP_CKSUMV5) &&
            (map_header->flags & MAP_NEXT_HEADER_FLAG)) {
                if (rmnet_map_process_next_hdr_packet(skb, len))
                        goto free_skb;
                skb_pull(skb, sizeof(*map_header));
                rmnet_set_skb_proto(skb);
        } else {
                /* Subtract MAP header */
                skb_pull(skb, sizeof(*map_header));
                rmnet_set_skb_proto(skb);
                if (port->data_format & RMNET_FLAGS_INGRESS_MAP_CKSUMV4 &&
                    !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, csum_type = 0;
        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);
                csum_type = RMNET_FLAGS_EGRESS_MAP_CKSUMV4;
        } else if (port->data_format & RMNET_FLAGS_EGRESS_MAP_CKSUMV5) {
                additional_header_len = sizeof(struct rmnet_map_v5_csum_header);
                csum_type = RMNET_FLAGS_EGRESS_MAP_CKSUMV5;
        }

        required_headroom += additional_header_len;

        if (skb_cow_head(skb, required_headroom) < 0)
                return -ENOMEM;

        if (csum_type)
                rmnet_map_checksum_uplink_packet(skb, port, orig_dev,
                                                 csum_type);

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

        map_header->mux_id = mux_id;

        if (READ_ONCE(port->egress_agg_params.count) > 1) {
                unsigned int len;

                len = rmnet_map_tx_aggregate(skb, port, orig_dev);
                if (likely(len)) {
                        rmnet_vnd_tx_fixup_len(len, orig_dev);
                        return -EINPROGRESS;
                }
                return -ENOMEM;
        }

        skb->protocol = htons(ETH_P_MAP);
        return 0;
}

static void
rmnet_bridge_handler(struct sk_buff *skb, struct net_device *bridge_dev)
{
        if (skb_mac_header_was_set(skb))
                skb_push(skb, skb->mac_len);

        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_linearize(skb)) {
                kfree_skb(skb);
                goto done;
        }

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

        dev = skb->dev;
        port = rmnet_get_port_rcu(dev);
        if (unlikely(!port)) {
                dev_core_stats_rx_nohandler_inc(skb->dev);
                kfree_skb(skb);
                goto done;
        }

        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;
        int err;

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

        err = rmnet_map_egress_handler(skb, port, mux_id, orig_dev);
        if (err == -ENOMEM)
                goto drop;
        else if (err == -EINPROGRESS)
                return;

        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);
}