/*      $NetBSD: in_offload.c,v 1.15 2024/07/05 04:31:54 rin Exp $      */

/*
 * Copyright (c)2005, 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: in_offload.c,v 1.15 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/ip.h>
#include <netinet/ip_var.h>
#include <netinet/tcp.h>
#include <netinet/in_offload.h>

/*
 * Handle M_CSUM_TSOv4 in software. Split the TCP payload in chunks of
 * size MSS, and return mbuf chain consists of them.
 */
struct mbuf *
tcp4_segment(struct mbuf *m, int off)
{
        int mss;
        int iphlen, thlen;
        int hlen, len;
        struct ip *ip;
        struct tcphdr *th;
        uint16_t ipid, phsum;
        uint32_t tcpseq;
        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_TSOv4) != 0);

        m->m_pkthdr.csum_flags = 0;

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

        hlen = off + sizeof(*ip);
        if (m->m_len < hlen) {
                m = m_pullup(m, hlen);
                if (m == NULL)
                        goto quit;
        }
        ip = (void *)(mtod(m, char *) + off);
        iphlen = ip->ip_hl * 4;
        KASSERT(ip->ip_v == IPVERSION);
        KASSERT(iphlen >= sizeof(*ip));
        KASSERT(ip->ip_p == IPPROTO_TCP);
        ipid = ntohs(ip->ip_id);

        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);

        ip = (void *)(mtod(hdr, char *) + off);
        ip->ip_len = htons(iphlen + thlen + mss);
        phsum = in_cksum_phdr(ip->ip_src.s_addr, ip->ip_dst.s_addr,
            htons((uint16_t)(thlen + mss) + 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 */

                ip = (void *)(mtod(n, char *) + off);
                ip->ip_id = htons(ipid);
                ip->ip_sum = 0;
                ip->ip_sum = in4_cksum(n, 0, off, iphlen);

                th = (void *)(mtod(n, char *) + off + iphlen);
                th->th_seq = htonl(tcpseq);
                th->th_sum = phsum;
                th->th_sum = in4_cksum(n, 0, off + iphlen, thlen + mss);

                tcpseq += mss;
                ipid++;
                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
ip_tso_output(struct ifnet *ifp, struct mbuf *m, const struct sockaddr *sa,
    struct rtentry *rt)
{
        struct mbuf *n;
        int error = 0;

        m = tcp4_segment(m, 0);
        if (m == NULL)
                return ENOMEM;
        do {
                n = m->m_nextpkt;
                if (error == 0)
                        error = ip_if_output(ifp, m, sa, 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
in_undefer_cksum(struct mbuf *mh, size_t hdrlen, int csum_flags)
{
        const size_t iphdrlen = M_CSUM_DATA_IPv4_IPHL(mh->m_pkthdr.csum_data);
        uint16_t csum;
        uint16_t ip_len;
        uint16_t *csump;
        struct mbuf *m = mh;

        KASSERT(mh->m_flags & M_PKTHDR);
        KASSERT(mh->m_pkthdr.len > hdrlen);
        KASSERT((mh->m_pkthdr.csum_flags & csum_flags) == csum_flags);

        /*
         * Deal with prepended frame header as done by e.g. ether_output().
         * If first mbuf in chain has just the header, use second mbuf
         * for the actual checksum. in4_csum() expects the passed mbuf
         * to have the whole (struct ip) area contiguous.
         */
        if (m->m_len <= hdrlen) {
                hdrlen -= m->m_len;
                m = m->m_next;
                KASSERT(m != NULL);
        }

        if (__predict_true(hdrlen + sizeof(struct ip) <= m->m_len)) {
                struct ip *ip = (struct ip *)(mtod(m, uint8_t *) + hdrlen);

                ip_len = ip->ip_len;
                csump = &ip->ip_sum;
        } else {
                const size_t ip_len_offset =
                    hdrlen + offsetof(struct ip, ip_len);

                m_copydata(m, ip_len_offset, sizeof(ip_len), &ip_len);
                csump = NULL;
        }
        ip_len = ntohs(ip_len);

        if (csum_flags & M_CSUM_IPv4) {
                csum = in4_cksum(m, 0, hdrlen, iphdrlen);
                if (csump != NULL) {
                        *csump = csum;
                } else {
                        const size_t offset = hdrlen +
                            offsetof(struct ip, ip_sum);

                        m_copyback(m, offset, sizeof(uint16_t), &csum);
                }
        }

        if (csum_flags & (M_CSUM_UDPv4|M_CSUM_TCPv4)) {
                size_t l4offset = hdrlen + iphdrlen;

                csum = in4_cksum(m, 0, l4offset, ip_len - iphdrlen);
                if (csum == 0 && (csum_flags & M_CSUM_UDPv4) != 0)
                        csum = 0xffff;

                l4offset += M_CSUM_DATA_IPv4_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);
                }
        }

        mh->m_pkthdr.csum_flags ^= csum_flags;
}

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

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

        ip = mtod(m, struct ip *);
        offset = ip->ip_hl << 2;

        csum = in4_cksum(m, 0, offset, ntohs(ip->ip_len) - offset);
        if (csum == 0 && (m->m_pkthdr.csum_flags & M_CSUM_UDPv4) != 0)
                csum = 0xffff;

        offset += M_CSUM_DATA_IPv4_OFFSET(m->m_pkthdr.csum_data);

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