/*      $NetBSD: ipsec_mbuf.c,v 1.30 2018/12/22 13:11:38 maxv Exp $     */

/*
 * 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.
 *
 * $FreeBSD: sys/netipsec/ipsec_mbuf.c,v 1.5.2.2 2003/03/28 20:32:53 sam Exp $
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: ipsec_mbuf.c,v 1.30 2018/12/22 13:11:38 maxv Exp $");

/*
 * IPsec-specific mbuf routines.
 */

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

#include <netipsec/ipsec.h>
#include <netipsec/ipsec_var.h>
#include <netipsec/ipsec_private.h>

/*
 * Create a writable copy of the mbuf chain.  While doing this
 * we compact the chain with a goal of producing a chain with
 * at most two mbufs.  The second mbuf in this chain is likely
 * to be a cluster.  The primary purpose of this work is to create
 * a writable packet for encryption, compression, etc.  The
 * secondary goal is to linearize the data so the data can be
 * passed to crypto hardware in the most efficient manner possible.
 */
struct mbuf *
m_clone(struct mbuf *m0)
{
        struct mbuf *m, *mprev;
        struct mbuf *n, *mfirst, *mlast;
        int len, off;

        KASSERT(m0 != NULL);

        mprev = NULL;
        for (m = m0; m != NULL; m = mprev->m_next) {
                /*
                 * Regular mbufs are ignored unless there's a cluster
                 * in front of it that we can use to coalesce.
                 */
                if ((m->m_flags & M_EXT) == 0) {
                        if (mprev && (mprev->m_flags & M_EXT) &&
                            m->m_len <= M_TRAILINGSPACE(mprev)) {
                                memcpy(mtod(mprev, char *) + mprev->m_len,
                                    mtod(m, char *), m->m_len);
                                mprev->m_len += m->m_len;
                                mprev->m_next = m_free(m);
                                IPSEC_STATINC(IPSEC_STAT_MBCOALESCED);
                        } else {
                                mprev = m;
                        }
                        continue;
                }

                /*
                 * Writable mbufs are left alone.
                 */
                if (!M_READONLY(m)) {
                        mprev = m;
                        continue;
                }

                /*
                 * Not writable, replace with a copy or coalesce with
                 * the previous mbuf if possible (since we have to copy
                 * it anyway, we try to reduce the number of mbufs and
                 * clusters so that future work is easier).
                 */

                /* We only coalesce into a cluster. */
                if (mprev != NULL && (mprev->m_flags & M_EXT) &&
                    m->m_len <= M_TRAILINGSPACE(mprev)) {
                        memcpy(mtod(mprev, char *) + mprev->m_len,
                            mtod(m, char *), m->m_len);
                        mprev->m_len += m->m_len;
                        mprev->m_next = m_free(m);
                        IPSEC_STATINC(IPSEC_STAT_CLCOALESCED);
                        continue;
                }

                /*
                 * Allocate new space to hold the copy...
                 */
                if (mprev == NULL && (m->m_flags & M_PKTHDR)) {
                        MGETHDR(n, M_DONTWAIT, m->m_type);
                        if (n == NULL) {
                                m_freem(m0);
                                return NULL;
                        }
                        m_move_pkthdr(n, m);
                        MCLGET(n, M_DONTWAIT);
                        if ((n->m_flags & M_EXT) == 0) {
                                m_free(n);
                                m_freem(m0);
                                return NULL;
                        }
                } else {
                        n = m_getcl(M_DONTWAIT, m->m_type, m->m_flags);
                        if (n == NULL) {
                                m_freem(m0);
                                return NULL;
                        }
                }

                /*
                 * ... and copy the data.  We deal with jumbo mbufs
                 * (i.e. m_len > MCLBYTES) by splitting them into
                 * clusters.  We could just malloc a buffer and make
                 * it external but too many device drivers don't know
                 * how to break up the non-contiguous memory when
                 * doing DMA.
                 */
                len = m->m_len;
                off = 0;
                mfirst = n;
                mlast = NULL;
                for (;;) {
                        const int cc = uimin(len, MCLBYTES);
                        memcpy(mtod(n, char *), mtod(m, char *) + off, cc);
                        n->m_len = cc;
                        if (mlast != NULL)
                                mlast->m_next = n;
                        mlast = n;
                        IPSEC_STATINC(IPSEC_STAT_CLCOPIED);

                        len -= cc;
                        if (len <= 0)
                                break;
                        off += cc;

                        n = m_getcl(M_DONTWAIT, m->m_type, m->m_flags);
                        if (n == NULL) {
                                m_freem(mfirst);
                                m_freem(m0);
                                return NULL;
                        }
                }
                n->m_next = m->m_next;
                if (mprev == NULL)
                        m0 = mfirst;            /* new head of chain */
                else
                        mprev->m_next = mfirst; /* replace old mbuf */
                m_free(m);                      /* release old mbuf */
                mprev = mfirst;
        }

        return m0;
}

/*
 * 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;

        KASSERT(m0 != NULL);
        KASSERT(m0->m_flags & M_PKTHDR);
        KASSERTMSG(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 (hlen > M_TRAILINGSPACE(m)) {
                struct mbuf *n0, *n, **np;
                int todo, len, done, alloc;

                n0 = NULL;
                np = &n0;
                alloc = 0;
                done = 0;
                todo = remain;
                while (todo > 0) {
                        if (todo > MHLEN) {
                                n = m_getcl(M_DONTWAIT, m->m_type, 0);
                                len = MCLBYTES;
                        } else {
                                n = m_get(M_DONTWAIT, m->m_type);
                                len = MHLEN;
                        }
                        if (n == NULL) {
                                m_freem(n0);
                                return NULL;
                        }
                        *np = n;
                        np = &n->m_next;
                        alloc++;
                        len = uimin(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_DONTWAIT, m->m_type);
                        if (n == NULL) {
                                m_freem(n0);
                                return NULL;
                        }
                        alloc++;

                        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 */
                }

                IPSEC_STATADD(IPSEC_STAT_MBINSERTED, alloc);
        } else {
                /*
                 * Copy the remainder to the back of the mbuf
                 * so there's space to write the new header.
                 */
                /* XXX can this be memcpy? does it handle overlap? */
                memmove(mtod(m, char *) + skip + hlen,
                        mtod(m, char *) + skip, 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.
 */
void *
m_pad(struct mbuf *m, int n)
{
        register struct mbuf *m0, *m1;
        register int len, pad;
        void *retval;

        if (__predict_false(n > MLEN)) {
                panic("%s: %d > MLEN", __func__, n);
        }
        KASSERT(m->m_flags & M_PKTHDR);

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

        while (m0->m_len < len) {
                KASSERTMSG(m0->m_next != NULL,
                    "m0 null, len %u m_len %u", len, m0->m_len);
                len -= m0->m_len;
                m0 = m0->m_next;
        }

        if (m0->m_len != len) {
                IPSECLOG(LOG_DEBUG,
                    "length mismatch (should be %d instead of %d)\n",
                    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) {
                        IPSECLOG(LOG_DEBUG,
                            "length mismatch (should be %d instead of %d)\n",
                            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_DONTWAIT, MT_DATA);
                if (m1 == NULL) {
                        m_freem(m);
                        IPSECLOG(LOG_DEBUG, "unable to get extra mbuf\n");
                        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;

        KASSERT(m->m_flags & M_PKTHDR);

        /* 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 */
                IPSEC_STATINC(IPSEC_STAT_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.
                 */
                IPSEC_STATINC(IPSEC_STAT_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.
                 */
                IPSEC_STATINC(IPSEC_STAT_INPUT_MIDDLE);
                memmove(mtod(m1, u_char *) + roff,
                      mtod(m1, u_char *) + roff + hlen,
                      m1->m_len - (roff + hlen));
                m1->m_len -= hlen;
                m->m_pkthdr.len -= hlen;
        }

        return 0;
}