/* SPDX-License-Identifier: BSD-3-Clause
 * Copyright(c) 2010-2014 Intel Corporation
 */

#include <stddef.h>

#include <rte_memcpy.h>

#include "ip_frag_common.h"

/**
 * @file
 * IPv6 reassemble
 *
 * Implementation of IPv6 reassembly.
 *
 */

static inline void
ip_frag_memmove(char *dst, char *src, int len)
{
        int i;

        /* go backwards to make sure we don't overwrite anything important */
        for (i = len - 1; i >= 0; i--)
                dst[i] = src[i];
}

/*
 * Reassemble fragments into one packet.
 */
struct rte_mbuf *
ipv6_frag_reassemble(struct ip_frag_pkt *fp)
{
        struct rte_ipv6_hdr *ip_hdr;
        struct ipv6_extension_fragment *frag_hdr;
        struct rte_mbuf *m, *prev;
        uint32_t i, n, ofs, first_len;
        uint32_t last_len, move_len, payload_len;
        uint32_t curr_idx = 0;

        first_len = fp->frags[IP_FIRST_FRAG_IDX].len;
        n = fp->last_idx - 1;

        /*start from the last fragment. */
        m = fp->frags[IP_LAST_FRAG_IDX].mb;
        ofs = fp->frags[IP_LAST_FRAG_IDX].ofs;
        last_len = fp->frags[IP_LAST_FRAG_IDX].len;
        curr_idx = IP_LAST_FRAG_IDX;

        payload_len = ofs + last_len;

        while (ofs != first_len) {

                prev = m;

                for (i = n; i != IP_FIRST_FRAG_IDX && ofs != first_len; i--) {

                        /* previous fragment found. */
                        if (fp->frags[i].ofs + fp->frags[i].len == ofs) {

                                RTE_ASSERT(curr_idx != i);

                                /* adjust start of the last fragment data. */
                                rte_pktmbuf_adj(m,
                                        (uint16_t)(m->l2_len + m->l3_len));
                                rte_pktmbuf_chain(fp->frags[i].mb, m);

                                /* this mbuf should not be accessed directly */
                                fp->frags[curr_idx].mb = NULL;
                                curr_idx = i;

                                /* update our last fragment and offset. */
                                m = fp->frags[i].mb;
                                ofs = fp->frags[i].ofs;
                        }
                }

                /* error - hole in the packet. */
                if (m == prev) {
                        return NULL;
                }
        }

        /* chain with the first fragment. */
        rte_pktmbuf_adj(m, (uint16_t)(m->l2_len + m->l3_len));
        rte_pktmbuf_chain(fp->frags[IP_FIRST_FRAG_IDX].mb, m);
        fp->frags[curr_idx].mb = NULL;
        m = fp->frags[IP_FIRST_FRAG_IDX].mb;
        fp->frags[IP_FIRST_FRAG_IDX].mb = NULL;

        /* update ipv6 header for the reassembled datagram */
        ip_hdr = rte_pktmbuf_mtod_offset(m, struct rte_ipv6_hdr *, m->l2_len);

        ip_hdr->payload_len = rte_cpu_to_be_16(payload_len);

        /*
         * remove fragmentation header. note that per RFC2460, we need to update
         * the last non-fragmentable header with the "next header" field to contain
         * type of the first fragmentable header, but we currently don't support
         * other headers, so we assume there are no other headers and thus update
         * the main IPv6 header instead.
         */
        move_len = m->l2_len + m->l3_len - sizeof(*frag_hdr);
        frag_hdr = (struct ipv6_extension_fragment *) (ip_hdr + 1);
        ip_hdr->proto = frag_hdr->next_header;

        ip_frag_memmove(rte_pktmbuf_mtod_offset(m, char *, sizeof(*frag_hdr)),
                        rte_pktmbuf_mtod(m, char*), move_len);

        rte_pktmbuf_adj(m, sizeof(*frag_hdr));

        return m;
}

/*
 * Process new mbuf with fragment of IPV6 datagram.
 * Incoming mbuf should have its l2_len/l3_len fields setup correctly.
 * @param tbl
 *   Table where to lookup/add the fragmented packet.
 * @param mb
 *   Incoming mbuf with IPV6 fragment.
 * @param tms
 *   Fragment arrival timestamp.
 * @param ip_hdr
 *   Pointer to the IPV6 header.
 * @param frag_hdr
 *   Pointer to the IPV6 fragment extension header.
 * @return
 *   Pointer to mbuf for reassembled packet, or NULL if:
 *   - an error occurred.
 *   - not all fragments of the packet are collected yet.
 */
#define MORE_FRAGS(x) (((x) & 0x100) >> 8)
#define FRAG_OFFSET(x) (rte_cpu_to_be_16(x) >> 3)
struct rte_mbuf *
rte_ipv6_frag_reassemble_packet(struct rte_ip_frag_tbl *tbl,
        struct rte_ip_frag_death_row *dr, struct rte_mbuf *mb, uint64_t tms,
        struct rte_ipv6_hdr *ip_hdr, struct ipv6_extension_fragment *frag_hdr)
{
        struct ip_frag_pkt *fp;
        struct ip_frag_key key;
        uint16_t ip_ofs;
        int32_t ip_len;
        int32_t trim;

        rte_memcpy(&key.src_dst[0], ip_hdr->src_addr, 16);
        rte_memcpy(&key.src_dst[2], ip_hdr->dst_addr, 16);

        key.id = frag_hdr->id;
        key.key_len = IPV6_KEYLEN;

        ip_ofs = FRAG_OFFSET(frag_hdr->frag_data) * 8;

        /*
         * as per RFC2460, payload length contains all extension headers
         * as well.
         * since we don't support anything but frag headers,
         * this is what we remove from the payload len.
         */
        ip_len = rte_be_to_cpu_16(ip_hdr->payload_len) - sizeof(*frag_hdr);
        trim = mb->pkt_len - (ip_len + mb->l3_len + mb->l2_len);

        IP_FRAG_LOG(DEBUG, "%s:%d:\n"
                "mbuf: %p, tms: %" PRIu64
                ", key: <" IPv6_KEY_BYTES_FMT ", %#x>, "
                "ofs: %u, len: %d, padding: %d, flags: %#x\n"
                "tbl: %p, max_cycles: %" PRIu64 ", entry_mask: %#x, "
                "max_entries: %u, use_entries: %u\n\n",
                __func__, __LINE__,
                mb, tms, IPv6_KEY_BYTES(key.src_dst), key.id, ip_ofs, ip_len,
                trim, RTE_IPV6_GET_MF(frag_hdr->frag_data),
                tbl, tbl->max_cycles, tbl->entry_mask, tbl->max_entries,
                tbl->use_entries);

        /* check that fragment length is greater then zero. */
        if (ip_len <= 0) {
                IP_FRAG_MBUF2DR(dr, mb);
                return NULL;
        }

        if (unlikely(trim > 0))
                rte_pktmbuf_trim(mb, trim);

        /* try to find/add entry into the fragment's table. */
        fp = ip_frag_find(tbl, dr, &key, tms);
        if (fp == NULL) {
                IP_FRAG_MBUF2DR(dr, mb);
                return NULL;
        }

        IP_FRAG_LOG(DEBUG, "%s:%d:\n"
                "tbl: %p, max_entries: %u, use_entries: %u\n"
                "ipv6_frag_pkt: %p, key: <" IPv6_KEY_BYTES_FMT ", %#x>, start: %" PRIu64
                ", total_size: %u, frag_size: %u, last_idx: %u\n\n",
                __func__, __LINE__,
                tbl, tbl->max_entries, tbl->use_entries,
                fp, IPv6_KEY_BYTES(fp->key.src_dst), fp->key.id, fp->start,
                fp->total_size, fp->frag_size, fp->last_idx);


        /* process the fragmented packet. */
        mb = ip_frag_process(fp, dr, mb, ip_ofs, ip_len,
                        MORE_FRAGS(frag_hdr->frag_data));
        ip_frag_inuse(tbl, fp);

        IP_FRAG_LOG(DEBUG, "%s:%d:\n"
                "mbuf: %p\n"
                "tbl: %p, max_entries: %u, use_entries: %u\n"
                "ipv6_frag_pkt: %p, key: <" IPv6_KEY_BYTES_FMT ", %#x>, start: %" PRIu64
                ", total_size: %u, frag_size: %u, last_idx: %u\n\n",
                __func__, __LINE__, mb,
                tbl, tbl->max_entries, tbl->use_entries,
                fp, IPv6_KEY_BYTES(fp->key.src_dst), fp->key.id, fp->start,
                fp->total_size, fp->frag_size, fp->last_idx);

        return mb;
}