/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2002, 2003 Sam Leffler, Errno Consulting
 * 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.
 */

/*
 * IPsec-specific mbuf routines.
 */

#include "opt_ipsec.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/socket.h>

#include <net/vnet.h>
#include <netinet/in.h>
#include <netipsec/ipsec.h>

/*
 * Make space for a new header of length hlen at skip bytes
 * into the packet.  When doing this we allocate new mbufs only
 * when absolutely necessary.  The mbuf where the new header
 * is to go is returned together with an offset into the mbuf.
 * If NULL is returned then the mbuf chain may have been modified;
 * the caller is assumed to always free the chain.
 */
struct mbuf *
m_makespace(struct mbuf *m0, int skip, int hlen, int *off)
{
        struct mbuf *m;
        unsigned remain;

        IPSEC_ASSERT(m0 != NULL, ("null mbuf"));
        IPSEC_ASSERT(hlen < MHLEN, ("hlen too big: %u", hlen));

        for (m = m0; m && skip > m->m_len; m = m->m_next)
                skip -= m->m_len;
        if (m == NULL)
                return (NULL);
        /*
         * At this point skip is the offset into the mbuf m
         * where the new header should be placed.  Figure out
         * if there's space to insert the new header.  If so,
         * and copying the remainder makes sense then do so.
         * Otherwise insert a new mbuf in the chain, splitting
         * the contents of m as needed.
         */
        remain = m->m_len - skip;               /* data to move */
        if (remain > skip &&
            hlen + max_linkhdr < M_LEADINGSPACE(m)) {
                /*
                 * mbuf has enough free space at the beginning.
                 * XXX: which operation is the most heavy - copying of
                 *      possible several hundred of bytes or allocation
                 *      of new mbuf? We can remove max_linkhdr check
                 *      here, but it is possible that this will lead
                 *      to allocation of new mbuf in Layer 2 code.
                 */
                m->m_data -= hlen;
                bcopy(mtodo(m, hlen), mtod(m, caddr_t), skip);
                m->m_len += hlen;
                *off = skip;
        } else if (hlen > M_TRAILINGSPACE(m)) {
                struct mbuf *n0, *n, **np;
                int todo, len, done;

                n0 = NULL;
                np = &n0;
                done = 0;
                todo = remain;
                while (todo > 0) {
                        if (todo > MHLEN) {
                                n = m_getcl(M_NOWAIT, m->m_type, 0);
                                len = MCLBYTES;
                        }
                        else {
                                n = m_get(M_NOWAIT, m->m_type);
                                len = MHLEN;
                        }
                        if (n == NULL) {
                                m_freem(n0);
                                return NULL;
                        }
                        *np = n;
                        np = &n->m_next;
                        len = min(todo, len);
                        memcpy(n->m_data, mtod(m, char *) + skip + done, len);
                        n->m_len = len;
                        done += len;
                        todo -= len;
                }

                if (hlen <= M_TRAILINGSPACE(m) + remain) {
                        m->m_len = skip + hlen;
                        *off = skip;
                        if (n0 != NULL) {
                                *np = m->m_next;
                                m->m_next = n0;
                        }
                }
                else {
                        n = m_get(M_NOWAIT, m->m_type);
                        if (n == NULL) {
                                m_freem(n0);
                                return NULL;
                        }

                        if ((n->m_next = n0) == NULL)
                                np = &n->m_next;
                        n0 = n;

                        *np = m->m_next;
                        m->m_next = n0;

                        n->m_len = hlen;
                        m->m_len = skip;

                        m = n;                  /* header is at front ... */
                        *off = 0;               /* ... of new mbuf */
                }
                IPSECSTAT_INC(ips_mbinserted);
        } else {
                /*
                 * Copy the remainder to the back of the mbuf
                 * so there's space to write the new header.
                 */
                bcopy(mtod(m, caddr_t) + skip,
                    mtod(m, caddr_t) + skip + hlen, remain);
                m->m_len += hlen;
                *off = skip;
        }
        m0->m_pkthdr.len += hlen;               /* adjust packet length */
        return m;
}

/*
 * m_pad(m, n) pads <m> with <n> bytes at the end. The packet header
 * length is updated, and a pointer to the first byte of the padding
 * (which is guaranteed to be all in one mbuf) is returned.
 */
caddr_t
m_pad(struct mbuf *m, int n)
{
        struct mbuf *m0, *m1;
        int len, pad;
        caddr_t retval;

        if (n <= 0) {  /* No stupid arguments. */
                DPRINTF(("%s: pad length invalid (%d)\n", __func__, n));
                m_freem(m);
                return NULL;
        }

        len = m->m_pkthdr.len;
        pad = n;
        m0 = m;

        while (m0->m_len < len) {
                len -= m0->m_len;
                m0 = m0->m_next;
        }

        if (m0->m_len != len) {
                DPRINTF(("%s: length mismatch (should be %d instead of %d)\n",
                        __func__, m->m_pkthdr.len,
                        m->m_pkthdr.len + m0->m_len - len));

                m_freem(m);
                return NULL;
        }

        /* Check for zero-length trailing mbufs, and find the last one. */
        for (m1 = m0; m1->m_next; m1 = m1->m_next) {
                if (m1->m_next->m_len != 0) {
                        DPRINTF(("%s: length mismatch (should be %d instead "
                                "of %d)\n", __func__,
                                m->m_pkthdr.len,
                                m->m_pkthdr.len + m1->m_next->m_len));

                        m_freem(m);
                        return NULL;
                }

                m0 = m1->m_next;
        }

        if (pad > M_TRAILINGSPACE(m0)) {
                /* Add an mbuf to the chain. */
                MGET(m1, M_NOWAIT, MT_DATA);
                if (m1 == NULL) {
                        m_freem(m0);
                        DPRINTF(("%s: unable to get extra mbuf\n", __func__));
                        return NULL;
                }

                m0->m_next = m1;
                m0 = m1;
                m0->m_len = 0;
        }

        retval = m0->m_data + m0->m_len;
        m0->m_len += pad;
        m->m_pkthdr.len += pad;

        return retval;
}

/*
 * Remove hlen data at offset skip in the packet.  This is used by
 * the protocols strip protocol headers and associated data (e.g. IV,
 * authenticator) on input.
 */
int
m_striphdr(struct mbuf *m, int skip, int hlen)
{
        struct mbuf *m1;
        int roff;

        /* Find beginning of header */
        m1 = m_getptr(m, skip, &roff);
        if (m1 == NULL)
                return (EINVAL);

        /* Remove the header and associated data from the mbuf. */
        if (roff == 0) {
                /* The header was at the beginning of the mbuf */
                IPSECSTAT_INC(ips_input_front);
                m_adj(m1, hlen);
                if (m1 != m)
                        m->m_pkthdr.len -= hlen;
        } else if (roff + hlen >= m1->m_len) {
                struct mbuf *mo;
                int adjlen;

                /*
                 * Part or all of the header is at the end of this mbuf,
                 * so first let's remove the remainder of the header from
                 * the beginning of the remainder of the mbuf chain, if any.
                 */
                IPSECSTAT_INC(ips_input_end);
                if (roff + hlen > m1->m_len) {
                        adjlen = roff + hlen - m1->m_len;

                        /* Adjust the next mbuf by the remainder */
                        m_adj(m1->m_next, adjlen);

                        /* The second mbuf is guaranteed not to have a pkthdr... */
                        m->m_pkthdr.len -= adjlen;
                }

                /* Now, let's unlink the mbuf chain for a second...*/
                mo = m1->m_next;
                m1->m_next = NULL;

                /* ...and trim the end of the first part of the chain...sick */
                adjlen = m1->m_len - roff;
                m_adj(m1, -adjlen);
                if (m1 != m)
                        m->m_pkthdr.len -= adjlen;

                /* Finally, let's relink */
                m1->m_next = mo;
        } else {
                /*
                 * The header lies in the "middle" of the mbuf; copy
                 * the remainder of the mbuf down over the header.
                 */
                IPSECSTAT_INC(ips_input_middle);
                bcopy(mtod(m1, u_char *) + roff + hlen,
                      mtod(m1, u_char *) + roff,
                      m1->m_len - (roff + hlen));
                m1->m_len -= hlen;
                m->m_pkthdr.len -= hlen;
        }
        return (0);
}

/*
 * Diagnostic routine to check mbuf alignment as required by the
 * crypto device drivers (that use DMA).
 */
void
m_checkalignment(const char* where, struct mbuf *m0, int off, int len)
{
        int roff;
        struct mbuf *m = m_getptr(m0, off, &roff);
        caddr_t addr;

        if (m == NULL)
                return;
        printf("%s (off %u len %u): ", where, off, len);
        addr = mtod(m, caddr_t) + roff;
        do {
                int mlen;

                if (((uintptr_t) addr) & 3) {
                        printf("addr misaligned %p,", addr);
                        break;
                }
                mlen = m->m_len;
                if (mlen > len)
                        mlen = len;
                len -= mlen;
                if (len && (mlen & 3)) {
                        printf("len mismatch %u,", mlen);
                        break;
                }
                m = m->m_next;
                addr = m ? mtod(m, caddr_t) : NULL;
        } while (m && len > 0);
        for (m = m0; m; m = m->m_next)
                printf(" [%p:%u]", mtod(m, caddr_t), m->m_len);
        printf("\n");
}