/*      $NetBSD: in6_offload.c,v 1.13 2024/07/05 04:31:54 rin Exp $     */

/*
 * Copyright (c)2006 YAMAMOTO Takashi,
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: in6_offload.c,v 1.13 2024/07/05 04:31:54 rin Exp $");

#include <sys/param.h>
#include <sys/mbuf.h>

#include <net/if.h>

#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip6.h>
#include <netinet/tcp.h>
#include <netinet6/in6_var.h>
#include <netinet6/ip6_var.h>
#include <netinet6/nd6.h>
#include <netinet6/in6_offload.h>

/*
 * Handle M_CSUM_TSOv6 in software. Split the TCP payload in chunks of
 * size MSS, and return mbuf chain consists of them.
 */
struct mbuf *
tcp6_segment(struct mbuf *m, int off)
{
        int mss;
        int iphlen;
        int thlen;
        int hlen;
        int len;
        struct ip6_hdr *iph;
        struct tcphdr *th;
        uint32_t tcpseq;
        uint16_t phsum;
        struct mbuf *hdr = NULL;
        struct mbuf *m0 = NULL;
        struct mbuf *prev = NULL;
        struct mbuf *n, *t;
        int nsegs;

        KASSERT((m->m_flags & M_PKTHDR) != 0);
        KASSERT((m->m_pkthdr.csum_flags & M_CSUM_TSOv6) != 0);

        m->m_pkthdr.csum_flags = 0;

        len = m->m_pkthdr.len;
        KASSERT(len >= off + sizeof(*iph) + sizeof(*th));

        hlen = off + sizeof(*iph);
        if (m->m_len < hlen) {
                m = m_pullup(m, hlen);
                if (m == NULL)
                        goto quit;
        }
        iph = (void *)(mtod(m, char *) + off);
        iphlen = sizeof(*iph);
        KASSERT((iph->ip6_vfc & IPV6_VERSION_MASK) == IPV6_VERSION);
        KASSERT(iph->ip6_nxt == IPPROTO_TCP);

        hlen = off + iphlen + sizeof(*th);
        if (m->m_len < hlen) {
                m = m_pullup(m, hlen);
                if (m == NULL)
                        goto quit;
        }
        th = (void *)(mtod(m, char *) + off + iphlen);
        tcpseq = ntohl(th->th_seq);
        thlen = th->th_off * 4;
        hlen = off + iphlen + thlen;

        mss = m->m_pkthdr.segsz;
        KASSERT(mss != 0);
        KASSERT(len > hlen);

        t = m_split(m, hlen, M_NOWAIT);
        if (t == NULL)
                goto quit;
        hdr = m;
        m = t;

        len -= hlen;
        KASSERT(len % mss == 0);

        iph = (void *)(mtod(hdr, char *) + off);
        iph->ip6_plen = htons(thlen + mss);
        phsum = in6_cksum_phdr(&iph->ip6_src, &iph->ip6_dst, htonl(thlen + mss),
            htonl(IPPROTO_TCP));

        for (nsegs = len / mss; nsegs > 0; nsegs--) {
                if (nsegs > 1) {
                        n = m_dup(hdr, 0, hlen, M_NOWAIT);
                        if (n == NULL)
                                goto quit;
                } else
                        n = hdr;
                KASSERT(n->m_len == hlen); /* XXX */

                if (nsegs > 1) {
                        t = m_split(m, mss, M_NOWAIT);
                        if (t == NULL) {
                                m_freem(n);
                                goto quit;
                        }
                } else
                        t = m;
                m_cat(n, m);
                m = t;

                KASSERT(n->m_len >= hlen); /* XXX */

                if (m0 == NULL)
                        m0 = n;

                if (prev != NULL)
                        prev->m_nextpkt = n;

                n->m_pkthdr.len = hlen + mss;
                n->m_nextpkt = NULL;    /* XXX */

                th = (void *)(mtod(n, char *) + off + iphlen);
                th->th_seq = htonl(tcpseq);
                th->th_sum = phsum;
                th->th_sum = in6_cksum(n, 0, off + iphlen, thlen + mss);

                tcpseq += mss;
                prev = n;
        }
        return m0;

quit:
        m_freem(hdr);
        m_freem(m);
        for (m = m0; m != NULL; m = n) {
                n = m->m_nextpkt;
                m_freem(m);
        }

        return NULL;
}

int
ip6_tso_output(struct ifnet *ifp, struct ifnet *origifp, struct mbuf *m,
    const struct sockaddr_in6 *dst, struct rtentry *rt)
{
        struct mbuf *n;
        int error = 0;

        m = tcp6_segment(m, 0);
        if (m == NULL)
                return ENOMEM;
        do {
                n = m->m_nextpkt;
                if (error == 0)
                        error = ip6_if_output(ifp, origifp, m, dst, rt);
                else
                        m_freem(m);
                m = n;
        } while (m != NULL);
        return error;
}

/*
 * Compute now in software the IP and TCP/UDP checksums. Cancel the
 * hardware offloading.
 */
void
in6_undefer_cksum(struct mbuf *m, size_t hdrlen, int csum_flags)
{
        const size_t ip6_plen_offset =
            hdrlen + offsetof(struct ip6_hdr, ip6_plen);
        size_t l4hdroff;
        size_t l4offset;
        uint16_t plen;
        uint16_t csum;

        KASSERT(m->m_flags & M_PKTHDR);
        KASSERT((m->m_pkthdr.csum_flags & csum_flags) == csum_flags);
        KASSERT(csum_flags == M_CSUM_UDPv6 || csum_flags == M_CSUM_TCPv6);

        if (__predict_true(hdrlen + sizeof(struct ip6_hdr) <= m->m_len)) {
                plen = *(uint16_t *)(mtod(m, char *) + ip6_plen_offset);
        } else {
                m_copydata(m, ip6_plen_offset, sizeof(plen), &plen);
        }
        plen = ntohs(plen);

        l4hdroff = M_CSUM_DATA_IPv6_IPHL(m->m_pkthdr.csum_data);
        l4offset = hdrlen + l4hdroff;
        csum = in6_cksum(m, 0, l4offset,
            plen - (l4hdroff - sizeof(struct ip6_hdr)));

        if (csum == 0 && (csum_flags & M_CSUM_UDPv6) != 0)
                csum = 0xffff;

        l4offset += M_CSUM_DATA_IPv6_OFFSET(m->m_pkthdr.csum_data);

        if (__predict_true((l4offset + sizeof(uint16_t)) <= m->m_len)) {
                *(uint16_t *)(mtod(m, char *) + l4offset) = csum;
        } else {
                m_copyback(m, l4offset, sizeof(csum), (void *) &csum);
        }

        m->m_pkthdr.csum_flags ^= csum_flags;
}

/*
 * Compute now in software the TCP/UDP checksum. Cancel the hardware
 * offloading.
 */
void
in6_undefer_cksum_tcpudp(struct mbuf *m)
{
        uint16_t csum, offset;

        KASSERT((m->m_pkthdr.csum_flags & (M_CSUM_UDPv6|M_CSUM_TCPv6)) != 0);
        KASSERT((~m->m_pkthdr.csum_flags & (M_CSUM_UDPv6|M_CSUM_TCPv6)) != 0);
        KASSERT((m->m_pkthdr.csum_flags
            & (M_CSUM_UDPv4|M_CSUM_TCPv4|M_CSUM_TSOv4)) == 0);

        offset = M_CSUM_DATA_IPv6_IPHL(m->m_pkthdr.csum_data);
        csum = in6_cksum(m, 0, offset, m->m_pkthdr.len - offset);
        if (csum == 0 && (m->m_pkthdr.csum_flags & M_CSUM_UDPv6) != 0) {
                csum = 0xffff;
        }

        offset += M_CSUM_DATA_IPv6_OFFSET(m->m_pkthdr.csum_data);
        if ((offset + sizeof(csum)) > m->m_len) {
                m_copyback(m, offset, sizeof(csum), &csum);
        } else {
                *(uint16_t *)(mtod(m, char *) + offset) = csum;
        }
}