// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2014 Fraunhofer ITWM
 *
 * Written by:
 * Phoebe Buckheister <phoebe.buckheister@itwm.fraunhofer.de>
 */

#include <linux/ieee802154.h>

#include <net/mac802154.h>
#include <net/ieee802154_netdev.h>

static int
ieee802154_hdr_push_addr(u8 *buf, const struct ieee802154_addr *addr,
                         bool omit_pan)
{
        int pos = 0;

        if (addr->mode == IEEE802154_ADDR_NONE)
                return 0;

        if (!omit_pan) {
                memcpy(buf + pos, &addr->pan_id, 2);
                pos += 2;
        }

        switch (addr->mode) {
        case IEEE802154_ADDR_SHORT:
                memcpy(buf + pos, &addr->short_addr, 2);
                pos += 2;
                break;

        case IEEE802154_ADDR_LONG:
                memcpy(buf + pos, &addr->extended_addr, IEEE802154_ADDR_LEN);
                pos += IEEE802154_ADDR_LEN;
                break;

        default:
                return -EINVAL;
        }

        return pos;
}

static int
ieee802154_hdr_push_sechdr(u8 *buf, const struct ieee802154_sechdr *hdr)
{
        int pos = 5;

        memcpy(buf, hdr, 1);
        memcpy(buf + 1, &hdr->frame_counter, 4);

        switch (hdr->key_id_mode) {
        case IEEE802154_SCF_KEY_IMPLICIT:
                return pos;

        case IEEE802154_SCF_KEY_INDEX:
                break;

        case IEEE802154_SCF_KEY_SHORT_INDEX:
                memcpy(buf + pos, &hdr->short_src, 4);
                pos += 4;
                break;

        case IEEE802154_SCF_KEY_HW_INDEX:
                memcpy(buf + pos, &hdr->extended_src, IEEE802154_ADDR_LEN);
                pos += IEEE802154_ADDR_LEN;
                break;
        }

        buf[pos++] = hdr->key_id;

        return pos;
}

int
ieee802154_hdr_push(struct sk_buff *skb, struct ieee802154_hdr *hdr)
{
        u8 buf[IEEE802154_MAX_HEADER_LEN];
        int pos = 2;
        int rc;
        struct ieee802154_hdr_fc *fc = &hdr->fc;

        buf[pos++] = hdr->seq;

        fc->dest_addr_mode = hdr->dest.mode;

        rc = ieee802154_hdr_push_addr(buf + pos, &hdr->dest, false);
        if (rc < 0)
                return -EINVAL;
        pos += rc;

        fc->source_addr_mode = hdr->source.mode;

        if (hdr->source.pan_id == hdr->dest.pan_id &&
            hdr->dest.mode != IEEE802154_ADDR_NONE)
                fc->intra_pan = true;

        rc = ieee802154_hdr_push_addr(buf + pos, &hdr->source, fc->intra_pan);
        if (rc < 0)
                return -EINVAL;
        pos += rc;

        if (fc->security_enabled) {
                fc->version = 1;

                rc = ieee802154_hdr_push_sechdr(buf + pos, &hdr->sec);
                if (rc < 0)
                        return -EINVAL;

                pos += rc;
        }

        memcpy(buf, fc, 2);

        memcpy(skb_push(skb, pos), buf, pos);

        return pos;
}
EXPORT_SYMBOL_GPL(ieee802154_hdr_push);

int ieee802154_mac_cmd_push(struct sk_buff *skb, void *f,
                            const void *pl, unsigned int pl_len)
{
        struct ieee802154_mac_cmd_frame *frame = f;
        struct ieee802154_mac_cmd_pl *mac_pl = &frame->mac_pl;
        struct ieee802154_hdr *mhr = &frame->mhr;
        int ret;

        skb_reserve(skb, sizeof(*mhr));
        ret = ieee802154_hdr_push(skb, mhr);
        if (ret < 0)
                return ret;

        skb_reset_mac_header(skb);
        skb->mac_len = ret;

        skb_put_data(skb, mac_pl, sizeof(*mac_pl));
        skb_put_data(skb, pl, pl_len);

        return 0;
}
EXPORT_SYMBOL_GPL(ieee802154_mac_cmd_push);

int ieee802154_beacon_push(struct sk_buff *skb,
                           struct ieee802154_beacon_frame *beacon)
{
        struct ieee802154_beacon_hdr *mac_pl = &beacon->mac_pl;
        struct ieee802154_hdr *mhr = &beacon->mhr;
        int ret;

        skb_reserve(skb, sizeof(*mhr));
        ret = ieee802154_hdr_push(skb, mhr);
        if (ret < 0)
                return ret;

        skb_reset_mac_header(skb);
        skb->mac_len = ret;

        skb_put_data(skb, mac_pl, sizeof(*mac_pl));

        if (mac_pl->pend_short_addr_count || mac_pl->pend_ext_addr_count)
                return -EOPNOTSUPP;

        return 0;
}
EXPORT_SYMBOL_GPL(ieee802154_beacon_push);

static int
ieee802154_hdr_get_addr(const u8 *buf, int mode, bool omit_pan,
                        struct ieee802154_addr *addr)
{
        int pos = 0;

        addr->mode = mode;

        if (mode == IEEE802154_ADDR_NONE)
                return 0;

        if (!omit_pan) {
                memcpy(&addr->pan_id, buf + pos, 2);
                pos += 2;
        }

        if (mode == IEEE802154_ADDR_SHORT) {
                memcpy(&addr->short_addr, buf + pos, 2);
                return pos + 2;
        } else {
                memcpy(&addr->extended_addr, buf + pos, IEEE802154_ADDR_LEN);
                return pos + IEEE802154_ADDR_LEN;
        }
}

static int ieee802154_hdr_addr_len(int mode, bool omit_pan)
{
        int pan_len = omit_pan ? 0 : 2;

        switch (mode) {
        case IEEE802154_ADDR_NONE: return 0;
        case IEEE802154_ADDR_SHORT: return 2 + pan_len;
        case IEEE802154_ADDR_LONG: return IEEE802154_ADDR_LEN + pan_len;
        default: return -EINVAL;
        }
}

static int
ieee802154_hdr_get_sechdr(const u8 *buf, struct ieee802154_sechdr *hdr)
{
        int pos = 5;

        memcpy(hdr, buf, 1);
        memcpy(&hdr->frame_counter, buf + 1, 4);

        switch (hdr->key_id_mode) {
        case IEEE802154_SCF_KEY_IMPLICIT:
                return pos;

        case IEEE802154_SCF_KEY_INDEX:
                break;

        case IEEE802154_SCF_KEY_SHORT_INDEX:
                memcpy(&hdr->short_src, buf + pos, 4);
                pos += 4;
                break;

        case IEEE802154_SCF_KEY_HW_INDEX:
                memcpy(&hdr->extended_src, buf + pos, IEEE802154_ADDR_LEN);
                pos += IEEE802154_ADDR_LEN;
                break;
        }

        hdr->key_id = buf[pos++];

        return pos;
}

static int ieee802154_sechdr_lengths[4] = {
        [IEEE802154_SCF_KEY_IMPLICIT] = 5,
        [IEEE802154_SCF_KEY_INDEX] = 6,
        [IEEE802154_SCF_KEY_SHORT_INDEX] = 10,
        [IEEE802154_SCF_KEY_HW_INDEX] = 14,
};

static int ieee802154_hdr_sechdr_len(u8 sc)
{
        return ieee802154_sechdr_lengths[IEEE802154_SCF_KEY_ID_MODE(sc)];
}

static int ieee802154_hdr_minlen(const struct ieee802154_hdr *hdr)
{
        int dlen, slen;

        dlen = ieee802154_hdr_addr_len(hdr->fc.dest_addr_mode, false);
        slen = ieee802154_hdr_addr_len(hdr->fc.source_addr_mode,
                                       hdr->fc.intra_pan);

        if (slen < 0 || dlen < 0)
                return -EINVAL;

        return 3 + dlen + slen + hdr->fc.security_enabled;
}

static int
ieee802154_hdr_get_addrs(const u8 *buf, struct ieee802154_hdr *hdr)
{
        int pos = 0;

        pos += ieee802154_hdr_get_addr(buf + pos, hdr->fc.dest_addr_mode,
                                       false, &hdr->dest);
        pos += ieee802154_hdr_get_addr(buf + pos, hdr->fc.source_addr_mode,
                                       hdr->fc.intra_pan, &hdr->source);

        if (hdr->fc.intra_pan)
                hdr->source.pan_id = hdr->dest.pan_id;

        return pos;
}

int
ieee802154_hdr_pull(struct sk_buff *skb, struct ieee802154_hdr *hdr)
{
        int pos = 3, rc;

        if (!pskb_may_pull(skb, 3))
                return -EINVAL;

        memcpy(hdr, skb->data, 3);

        rc = ieee802154_hdr_minlen(hdr);
        if (rc < 0 || !pskb_may_pull(skb, rc))
                return -EINVAL;

        pos += ieee802154_hdr_get_addrs(skb->data + pos, hdr);

        if (hdr->fc.security_enabled) {
                int want = pos + ieee802154_hdr_sechdr_len(skb->data[pos]);

                if (!pskb_may_pull(skb, want))
                        return -EINVAL;

                pos += ieee802154_hdr_get_sechdr(skb->data + pos, &hdr->sec);
        }

        skb_pull(skb, pos);
        return pos;
}
EXPORT_SYMBOL_GPL(ieee802154_hdr_pull);

int ieee802154_mac_cmd_pl_pull(struct sk_buff *skb,
                               struct ieee802154_mac_cmd_pl *mac_pl)
{
        if (!pskb_may_pull(skb, sizeof(*mac_pl)))
                return -EINVAL;

        memcpy(mac_pl, skb->data, sizeof(*mac_pl));
        skb_pull(skb, sizeof(*mac_pl));

        return 0;
}
EXPORT_SYMBOL_GPL(ieee802154_mac_cmd_pl_pull);

int
ieee802154_hdr_peek_addrs(const struct sk_buff *skb, struct ieee802154_hdr *hdr)
{
        const u8 *buf = skb_mac_header(skb);
        int pos = 3, rc;

        if (buf + 3 > skb_tail_pointer(skb))
                return -EINVAL;

        memcpy(hdr, buf, 3);

        rc = ieee802154_hdr_minlen(hdr);
        if (rc < 0 || buf + rc > skb_tail_pointer(skb))
                return -EINVAL;

        pos += ieee802154_hdr_get_addrs(buf + pos, hdr);
        return pos;
}
EXPORT_SYMBOL_GPL(ieee802154_hdr_peek_addrs);

int
ieee802154_hdr_peek(const struct sk_buff *skb, struct ieee802154_hdr *hdr)
{
        const u8 *buf = skb_mac_header(skb);
        int pos;

        pos = ieee802154_hdr_peek_addrs(skb, hdr);
        if (pos < 0)
                return -EINVAL;

        if (hdr->fc.security_enabled) {
                u8 key_id_mode = IEEE802154_SCF_KEY_ID_MODE(*(buf + pos));
                int want = pos + ieee802154_sechdr_lengths[key_id_mode];

                if (buf + want > skb_tail_pointer(skb))
                        return -EINVAL;

                pos += ieee802154_hdr_get_sechdr(buf + pos, &hdr->sec);
        }

        return pos;
}
EXPORT_SYMBOL_GPL(ieee802154_hdr_peek);

int ieee802154_max_payload(const struct ieee802154_hdr *hdr)
{
        int hlen = ieee802154_hdr_minlen(hdr);

        if (hdr->fc.security_enabled) {
                hlen += ieee802154_sechdr_lengths[hdr->sec.key_id_mode] - 1;
                hlen += ieee802154_sechdr_authtag_len(&hdr->sec);
        }

        return IEEE802154_MTU - hlen - IEEE802154_MFR_SIZE;
}
EXPORT_SYMBOL_GPL(ieee802154_max_payload);