/*-
 * Copyright (c) 2013-2015 Gleb Smirnoff <glebius@FreeBSD.org>
 * Copyright (c) 1998, David Greenman. 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.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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 "opt_kern_tls.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/capsicum.h>
#include <sys/inotify.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/ktls.h>
#include <sys/mutex.h>
#include <sys/malloc.h>
#include <sys/mman.h>
#include <sys/mount.h>
#include <sys/mbuf.h>
#include <sys/proc.h>
#include <sys/protosw.h>
#include <sys/rwlock.h>
#include <sys/sf_buf.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/syscallsubr.h>
#include <sys/sysctl.h>
#include <sys/sysproto.h>
#include <sys/vnode.h>

#include <net/vnet.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <netinet/in_pcb.h>
#include <netinet/tcp_var.h>
#include <netinet/tcp_log_buf.h>

#include <security/audit/audit.h>
#include <security/mac/mac_framework.h>

#include <vm/vm.h>
#include <vm/vm_object.h>
#include <vm/vm_pager.h>

static MALLOC_DEFINE(M_SENDFILE, "sendfile", "sendfile dynamic memory");

#define EXT_FLAG_NOCACHE        EXT_FLAG_VENDOR2
#define EXT_FLAG_CACHE_LAST     EXT_FLAG_VENDOR3

/*
 * Structure describing a single sendfile(2) I/O, which may consist of
 * several underlying pager I/Os.
 *
 * The syscall context allocates the structure and initializes 'nios'
 * to 1.  As sendfile_swapin() runs through pages and starts asynchronous
 * paging operations, it increments 'nios'.
 *
 * Every I/O completion calls sendfile_iodone(), which decrements the 'nios',
 * and the syscall also calls sendfile_iodone() after allocating all mbufs,
 * linking them and sending to socket.  Whoever reaches zero 'nios' is
 * responsible to call pr_ready() on the socket, to notify it of readyness
 * of the data.
 */
struct sf_io {
        volatile u_int  nios;
        u_int           error;
        int             npages;
        struct socket   *so;
        struct mbuf     *m;
        vm_object_t     obj;
        vm_pindex_t     pindex0;
#ifdef KERN_TLS
        struct ktls_session *tls;
#endif
        vm_page_t       pa[];
};

counter_u64_t sfstat[sizeof(struct sfstat) / sizeof(uint64_t)];

static void
sfstat_init(const void *unused)
{

        COUNTER_ARRAY_ALLOC(sfstat, sizeof(struct sfstat) / sizeof(uint64_t),
            M_WAITOK);
}
SYSINIT(sfstat, SI_SUB_MBUF, SI_ORDER_FIRST, sfstat_init, NULL);

static int
sfstat_sysctl(SYSCTL_HANDLER_ARGS)
{
        struct sfstat s;

        COUNTER_ARRAY_COPY(sfstat, &s, sizeof(s) / sizeof(uint64_t));
        if (req->newptr)
                COUNTER_ARRAY_ZERO(sfstat, sizeof(s) / sizeof(uint64_t));
        return (SYSCTL_OUT(req, &s, sizeof(s)));
}
SYSCTL_PROC(_kern_ipc, OID_AUTO, sfstat,
    CTLTYPE_OPAQUE | CTLFLAG_RW | CTLFLAG_MPSAFE, NULL, 0,
    sfstat_sysctl, "I",
    "sendfile statistics");

static void
sendfile_free_mext(struct mbuf *m)
{
        struct sf_buf *sf;
        vm_page_t pg;
        int flags;

        KASSERT(m->m_flags & M_EXT && m->m_ext.ext_type == EXT_SFBUF,
            ("%s: m %p !M_EXT or !EXT_SFBUF", __func__, m));

        sf = m->m_ext.ext_arg1;
        pg = sf_buf_page(sf);
        flags = (m->m_ext.ext_flags & EXT_FLAG_NOCACHE) != 0 ? VPR_TRYFREE : 0;

        sf_buf_free(sf);
        vm_page_release(pg, flags);
}

static void
sendfile_free_mext_pg(struct mbuf *m)
{
        vm_page_t pg;
        int flags, i;
        bool cache_last;

        M_ASSERTEXTPG(m);

        cache_last = m->m_ext.ext_flags & EXT_FLAG_CACHE_LAST;
        flags = (m->m_ext.ext_flags & EXT_FLAG_NOCACHE) != 0 ? VPR_TRYFREE : 0;

        for (i = 0; i < m->m_epg_npgs; i++) {
                if (cache_last && i == m->m_epg_npgs - 1)
                        flags = 0;
                pg = PHYS_TO_VM_PAGE(m->m_epg_pa[i]);
                vm_page_release(pg, flags);
        }
}

/*
 * Helper function to calculate how much data to put into page i of n.
 * Only first and last pages are special.
 */
static inline off_t
xfsize(int i, int n, off_t off, off_t len)
{

        if (i == 0)
                return (omin(PAGE_SIZE - (off & PAGE_MASK), len));

        if (i == n - 1 && ((off + len) & PAGE_MASK) > 0)
                return ((off + len) & PAGE_MASK);

        return (PAGE_SIZE);
}

/*
 * Helper function to get offset within object for i page.
 */
static inline vm_ooffset_t
vmoff(int i, off_t off)
{

        if (i == 0)
                return ((vm_ooffset_t)off);

        return (trunc_page(off + i * PAGE_SIZE));
}

/*
 * Helper function used when allocation of a page or sf_buf failed.
 * Pretend as if we don't have enough space, subtract xfsize() of
 * all pages that failed.
 */
static inline void
fixspace(int old, int new, off_t off, int *space)
{

        KASSERT(old > new, ("%s: old %d new %d", __func__, old, new));

        /* Subtract last one. */
        *space -= xfsize(old - 1, old, off, *space);
        old--;

        if (new == old)
                /* There was only one page. */
                return;

        /* Subtract first one. */
        if (new == 0) {
                *space -= xfsize(0, old, off, *space);
                new++;
        }

        /* Rest of pages are full sized. */
        *space -= (old - new) * PAGE_SIZE;

        KASSERT(*space >= 0, ("%s: space went backwards", __func__));
}

/*
 * Wait for all in-flight ios to complete, we must not unwire pages
 * under them.
 */
static void
sendfile_iowait(struct sf_io *sfio, const char *wmesg)
{
        while (atomic_load_int(&sfio->nios) != 1)
                pause(wmesg, 1);
}

/*
 * I/O completion callback.
 *
 * When called via I/O path, the curvnet is not set and should be obtained
 * from the socket.  When called synchronously from vn_sendfile(), usually
 * to report error or just release the reference (all pages are valid), then
 * curvnet shall be already set.
 */
static void
sendfile_iodone(void *arg, vm_page_t *pa, int count, int error)
{
        struct sf_io *sfio = arg;
        struct socket *so;
        int i;

        if (error != 0)
                sfio->error = error;

        /*
         * Restore the valid page pointers.  They are already
         * unbusied, but still wired.
         *
         * XXXKIB since pages are only wired, and we do not
         * own the object lock, other users might have
         * invalidated them in meantime.  Similarly, after we
         * unbusied the swapped-in pages, they can become
         * invalid under us.
         */
        MPASS(count == 0 || pa[0] != bogus_page);
        for (i = 0; i < count; i++) {
                if (pa[i] == bogus_page) {
                        sfio->pa[(pa[0]->pindex - sfio->pindex0) + i] =
                            pa[i] = vm_page_relookup(sfio->obj,
                            pa[0]->pindex + i);
                        KASSERT(pa[i] != NULL,
                            ("%s: page %p[%d] disappeared",
                            __func__, pa, i));
                } else {
                        vm_page_xunbusy_unchecked(pa[i]);
                }
        }

        if (!refcount_release(&sfio->nios))
                return;

#ifdef INVARIANTS
        for (i = 1; i < sfio->npages; i++) {
                if (sfio->pa[i] == NULL)
                        break;
                KASSERT(vm_page_wired(sfio->pa[i]),
                    ("sfio %p page %d %p not wired", sfio, i, sfio->pa[i]));
                if (i == 0)
                        continue;
                KASSERT(sfio->pa[0]->object == sfio->pa[i]->object,
                    ("sfio %p page %d %p wrong owner %p %p", sfio, i,
                    sfio->pa[i], sfio->pa[0]->object, sfio->pa[i]->object));
                KASSERT(sfio->pa[0]->pindex + i == sfio->pa[i]->pindex,
                    ("sfio %p page %d %p wrong index %jx %jx", sfio, i,
                    sfio->pa[i], (uintmax_t)sfio->pa[0]->pindex,
                    (uintmax_t)sfio->pa[i]->pindex));
        }
#endif

        vm_object_pip_wakeup(sfio->obj);

        if (sfio->m == NULL) {
                /*
                 * Either I/O operation failed, or we failed to allocate
                 * buffers, or we bailed out on first busy page, or we
                 * succeeded filling the request without any I/Os. Anyway,
                 * pr_send() hadn't been executed - nothing had been sent
                 * to the socket yet.
                 */
                MPASS((curthread->td_pflags & TDP_KTHREAD) == 0);
                free(sfio, M_SENDFILE);
                return;
        }

#if defined(KERN_TLS) && defined(INVARIANTS)
        if ((sfio->m->m_flags & M_EXTPG) != 0)
                KASSERT(sfio->tls == sfio->m->m_epg_tls,
                    ("TLS session mismatch"));
        else
                KASSERT(sfio->tls == NULL,
                    ("non-ext_pgs mbuf with TLS session"));
#endif
        so = sfio->so;
        CURVNET_SET_QUIET(so->so_vnet);
        if (__predict_false(sfio->error)) {
                /*
                 * I/O operation failed.  The state of data in the socket
                 * is now inconsistent, and all what we can do is to tear
                 * it down. Protocol abort method would tear down protocol
                 * state, free all ready mbufs and detach not ready ones.
                 * We will free the mbufs corresponding to this I/O manually.
                 *
                 * The socket would be marked with EIO and made available
                 * for read, so that application receives EIO on next
                 * syscall and eventually closes the socket.
                 */
                so->so_proto->pr_abort(so);
                so->so_error = EIO;

                mb_free_notready(sfio->m, sfio->npages);
#ifdef KERN_TLS
        } else if (sfio->tls != NULL && sfio->tls->mode == TCP_TLS_MODE_SW) {
                /*
                 * I/O operation is complete, but we still need to
                 * encrypt.  We cannot do this in the interrupt thread
                 * of the disk controller, so forward the mbufs to a
                 * different thread.
                 *
                 * Donate the socket reference from sfio to rather
                 * than explicitly invoking soref().
                 */
                ktls_enqueue(sfio->m, so, sfio->npages);
                goto out_with_ref;
#endif
        } else
                (void)so->so_proto->pr_ready(so, sfio->m, sfio->npages);

        sorele(so);
#ifdef KERN_TLS
out_with_ref:
#endif
        CURVNET_RESTORE();
        free(sfio, M_SENDFILE);
}

/*
 * Iterate through pages vector and request paging for non-valid pages.
 */
static int
sendfile_swapin(vm_object_t obj, struct sf_io *sfio, int *nios, off_t off,
    off_t len, int rhpages, int flags)
{
        vm_page_t *pa;
        int a, count, count1, grabbed, i, j, npages, rv;

        pa = sfio->pa;
        npages = sfio->npages;
        *nios = 0;
        flags = (flags & SF_NODISKIO) ? VM_ALLOC_NOWAIT : 0;
        sfio->pindex0 = OFF_TO_IDX(off);

        /*
         * First grab all the pages and wire them.  Note that we grab
         * only required pages.  Readahead pages are dealt with later.
         */
        grabbed = vm_page_grab_pages_unlocked(obj, OFF_TO_IDX(off),
            VM_ALLOC_NORMAL | VM_ALLOC_WIRED | flags, pa, npages);
        if (grabbed < npages) {
                for (int i = grabbed; i < npages; i++)
                        pa[i] = NULL;
                npages = grabbed;
                rhpages = 0;
        }

        for (i = 0; i < npages;) {
                /* Skip valid pages. */
                if (vm_page_is_valid(pa[i], vmoff(i, off) & PAGE_MASK,
                    xfsize(i, npages, off, len))) {
                        vm_page_xunbusy(pa[i]);
                        SFSTAT_INC(sf_pages_valid);
                        i++;
                        continue;
                }

                /*
                 * Next page is invalid.  Check if it belongs to pager.  It
                 * may not be there, which is a regular situation for shmem
                 * pager.  For vnode pager this happens only in case of
                 * a sparse file.
                 *
                 * Important feature of vm_pager_has_page() is the hint
                 * stored in 'a', about how many pages we can pagein after
                 * this page in a single I/O.
                 */
                VM_OBJECT_RLOCK(obj);
                if (!vm_pager_has_page(obj, OFF_TO_IDX(vmoff(i, off)), NULL,
                    &a)) {
                        VM_OBJECT_RUNLOCK(obj);
                        pmap_zero_page(pa[i]);
                        vm_page_valid(pa[i]);
                        MPASS(pa[i]->dirty == 0);
                        vm_page_xunbusy(pa[i]);
                        i++;
                        continue;
                }
                VM_OBJECT_RUNLOCK(obj);

                /*
                 * We want to pagein as many pages as possible, limited only
                 * by the 'a' hint and actual request.
                 */
                count = min(a + 1, npages - i);

                /*
                 * We should not pagein into a valid page because
                 * there might be still unfinished write tracked by
                 * e.g. a buffer, thus we substitute any valid pages
                 * with the bogus one.
                 *
                 * We must not leave around xbusy pages which are not
                 * part of the run passed to vm_pager_getpages(),
                 * otherwise pager might deadlock waiting for the busy
                 * status of the page, e.g. if it constitues the
                 * buffer needed to validate other page.
                 *
                 * First trim the end of the run consisting of the
                 * valid pages, then replace the rest of the valid
                 * with bogus.
                 */
                count1 = count;
                for (j = i + count - 1; j > i; j--) {
                        if (vm_page_is_valid(pa[j], vmoff(j, off) & PAGE_MASK,
                            xfsize(j, npages, off, len))) {
                                vm_page_xunbusy(pa[j]);
                                SFSTAT_INC(sf_pages_valid);
                                count--;
                        } else {
                                break;
                        }
                }

                /*
                 * The last page in the run pa[i + count - 1] is
                 * guaranteed to be invalid by the trim above, so it
                 * is not replaced with bogus, thus -1 in the loop end
                 * condition.
                 */
                MPASS(pa[i + count - 1]->valid != VM_PAGE_BITS_ALL);
                for (j = i + 1; j < i + count - 1; j++) {
                        if (vm_page_is_valid(pa[j], vmoff(j, off) & PAGE_MASK,
                            xfsize(j, npages, off, len))) {
                                vm_page_xunbusy(pa[j]);
                                SFSTAT_INC(sf_pages_valid);
                                SFSTAT_INC(sf_pages_bogus);
                                pa[j] = bogus_page;
                        }
                }

                refcount_acquire(&sfio->nios);
                rv = vm_pager_get_pages_async(obj, pa + i, count, NULL,
                    i + count == npages ? &rhpages : NULL,
                    &sendfile_iodone, sfio);
                if (__predict_false(rv != VM_PAGER_OK)) {
                        sendfile_iowait(sfio, "sferrio");

                        /*
                         * Do remaining pages recovery before returning EIO.
                         * Pages from 0 to npages are wired.
                         * Pages from (i + count1) to npages are busied.
                         */
                        for (j = 0; j < npages; j++) {
                                if (j >= i + count1)
                                        vm_page_xunbusy(pa[j]);
                                KASSERT(pa[j] != NULL && pa[j] != bogus_page,
                                    ("%s: page %p[%d] I/O recovery failure",
                                    __func__, pa, j));
                                vm_page_unwire(pa[j], PQ_INACTIVE);
                                pa[j] = NULL;
                        }
                        return (EIO);
                }

                SFSTAT_INC(sf_iocnt);
                SFSTAT_ADD(sf_pages_read, count);
                if (i + count == npages)
                        SFSTAT_ADD(sf_rhpages_read, rhpages);

                i += count1;
                (*nios)++;
        }

        if (*nios == 0 && npages != 0)
                SFSTAT_INC(sf_noiocnt);

        return (0);
}

static int
sendfile_getobj(struct thread *td, struct file *fp, vm_object_t *obj_res,
    struct vnode **vp_res, struct shmfd **shmfd_res, off_t *obj_size)
{
        vm_object_t obj;
        struct vnode *vp;
        struct shmfd *shmfd;
        int error;

        error = 0;
        vp = *vp_res = NULL;
        obj = NULL;
        shmfd = *shmfd_res = NULL;

        /*
         * The file descriptor must be a regular file and have a
         * backing VM object.
         */
        if (fp->f_type == DTYPE_VNODE) {
                vp = fp->f_vnode;
                vn_lock(vp, LK_SHARED | LK_RETRY);
                if (vp->v_type != VREG) {
                        error = EINVAL;
                        goto out;
                }
                obj = vp->v_object;
                if (obj == NULL) {
                        error = EINVAL;
                        goto out;
                }

                /*
                 * Use the pager size when available to simplify synchronization
                 * with filesystems, which otherwise must atomically update both
                 * the vnode pager size and file size.
                 */
                if (obj->type == OBJT_VNODE) {
                        VM_OBJECT_RLOCK(obj);
                        *obj_size = obj->un_pager.vnp.vnp_size;
                } else {
                        error = vn_getsize_locked(vp, obj_size, td->td_ucred);
                        if (error != 0)
                                goto out;
                        VM_OBJECT_RLOCK(obj);
                }
        } else if (fp->f_type == DTYPE_SHM) {
                shmfd = fp->f_data;
                obj = shmfd->shm_object;
                VM_OBJECT_RLOCK(obj);
                *obj_size = shmfd->shm_size;
        } else {
                error = EINVAL;
                goto out;
        }

        if ((obj->flags & OBJ_DEAD) != 0) {
                VM_OBJECT_RUNLOCK(obj);
                error = EBADF;
                goto out;
        }

        /*
         * Temporarily increase the backing VM object's reference
         * count so that a forced reclamation of its vnode does not
         * immediately destroy it.
         */
        vm_object_reference_locked(obj);
        VM_OBJECT_RUNLOCK(obj);
        *obj_res = obj;
        *vp_res = vp;
        *shmfd_res = shmfd;

out:
        if (vp != NULL)
                VOP_UNLOCK(vp);
        return (error);
}

static int
sendfile_getsock(struct thread *td, int s, struct file **sock_fp,
    struct socket **so)
{
        int error;

        *sock_fp = NULL;
        *so = NULL;

        /*
         * The socket must be a stream socket and connected.
         */
        error = getsock(td, s, &cap_send_rights, sock_fp);
        if (error != 0)
                return (error);
        *so = (*sock_fp)->f_data;
        if ((*so)->so_type != SOCK_STREAM)
                return (EINVAL);
        /*
         * SCTP one-to-one style sockets currently don't work with
         * sendfile(). So indicate EINVAL for now.
         */
        if ((*so)->so_proto->pr_protocol == IPPROTO_SCTP)
                return (EINVAL);
        return (0);
}

/*
 * Check socket state and wait (or EAGAIN) for needed amount of space.
 */
int
sendfile_wait_generic(struct socket *so, off_t need, int *space)
{
        int error;

        MPASS(need > 0);
        MPASS(space != NULL);

        /*
         * XXXGL: the hack with sb_lowat originates from d99b0dd2c5297.  To
         * achieve high performance sending with sendfile(2) a non-blocking
         * socket needs a fairly high low watermark.  Otherwise, the socket
         * will be reported as writable too early, and sendfile(2) will send
         * just a few bytes each time.  It is important to understand that
         * we are changing sb_lowat not for the current invocation of the
         * syscall, but for the *next* syscall. So there is no way to
         * workaround the problem, e.g. provide a special version of sbspace().
         * Since this hack has been in the kernel for a long time, we
         * anticipate that there is a lot of software that will suffer if we
         * remove it.  See also b21104487324.
         */
        error = 0;
        SOCK_SENDBUF_LOCK(so);
        if (so->so_snd.sb_flags & SB_AUTOLOWAT) {
                if (so->so_snd.sb_lowat < so->so_snd.sb_hiwat / 2)
                        so->so_snd.sb_lowat = so->so_snd.sb_hiwat / 2;
                if (so->so_snd.sb_lowat < PAGE_SIZE &&
                    so->so_snd.sb_hiwat >= PAGE_SIZE)
                        so->so_snd.sb_lowat = PAGE_SIZE;
        }
retry_space:
        if (so->so_snd.sb_state & SBS_CANTSENDMORE) {
                error = EPIPE;
                goto done;
        } else if (so->so_error) {
                error = so->so_error;
                so->so_error = 0;
                goto done;
        }
        if ((so->so_state & SS_ISCONNECTED) == 0) {
                error = ENOTCONN;
                goto done;
        }

        *space = sbspace(&so->so_snd);
        if (*space < need && (*space <= 0 || *space < so->so_snd.sb_lowat)) {
                if (so->so_state & SS_NBIO) {
                        error = EAGAIN;
                        goto done;
                }
                /*
                 * sbwait() drops the lock while sleeping.  When we loop back
                 * to retry_space the state may have changed and we retest
                 * for it.
                 */
                error = sbwait(so, SO_SND);
                /*
                 * An error from sbwait() usually indicates that we've been
                 * interrupted by a signal.  If we've sent anything then return
                 * bytes sent, otherwise return the error.
                 */
                if (error != 0)
                        goto done;
                goto retry_space;
        }
done:
        SOCK_SENDBUF_UNLOCK(so);

        return (error);
}

int
vn_sendfile(struct file *fp, int sockfd, struct uio *hdr_uio,
    struct uio *trl_uio, off_t offset, size_t nbytes, off_t *sent, int flags,
    struct thread *td)
{
        struct file *sock_fp;
        struct vnode *vp;
        struct vm_object *obj;
        vm_page_t pga;
        struct socket *so;
        const struct protosw *pr;
#ifdef KERN_TLS
        struct ktls_session *tls;
#endif
        struct mbuf *m, *mh, *mhtail;
        struct sf_buf *sf;
        struct shmfd *shmfd;
        struct vattr va;
        off_t off, sbytes, rem, obj_size, nobj_size;
        int error, ext_pgs_idx, hdrlen, max_pgs, softerr;
#ifdef KERN_TLS
        int tls_enq_cnt;
#endif
        bool use_ext_pgs;

        obj = NULL;
        so = NULL;
        m = mh = NULL;
#ifdef KERN_TLS
        tls = NULL;
#endif
        hdrlen = sbytes = 0;
        softerr = 0;
        use_ext_pgs = false;

        error = sendfile_getobj(td, fp, &obj, &vp, &shmfd, &obj_size);
        if (error != 0)
                goto out;

        error = sendfile_getsock(td, sockfd, &sock_fp, &so);
        if (error != 0)
                goto out;
        pr = so->so_proto;

#ifdef MAC
        error = mac_socket_check_send(td->td_ucred, so);
        if (error != 0)
                goto out;
#endif

        SFSTAT_INC(sf_syscalls);
        SFSTAT_ADD(sf_rhpages_requested, SF_READAHEAD(flags));

        rem = nbytes ? omin(nbytes, obj_size - offset) : obj_size - offset;

        /*
         * Protect against multiple writers to the socket.
         *
         * XXXRW: Historically this has assumed non-interruptibility, so now
         * we implement that, but possibly shouldn't.
         */
        error = SOCK_IO_SEND_LOCK(so, SBL_WAIT | SBL_NOINTR);
        if (error != 0)
                goto out;
        CURVNET_SET(so->so_vnet);
#ifdef KERN_TLS
        tls = ktls_hold(so->so_snd.sb_tls_info);
#endif

        /*
         * Loop through the pages of the file, starting with the requested
         * offset. Get a file page (do I/O if necessary), map the file page
         * into an sf_buf, attach an mbuf header to the sf_buf, and queue
         * it on the socket.
         * This is done in two loops.  The inner loop turns as many pages
         * as it can, up to available socket buffer space, without blocking
         * into mbufs to have it bulk delivered into the socket send buffer.
         * The outer loop checks the state and available space of the socket
         * and takes care of the overall progress.
         */
        for (off = offset; rem > 0; ) {
                struct sf_io *sfio;
                vm_page_t *pa;
                struct mbuf *m0, *mtail;
                int nios, space, npages, rhpages;

                mtail = NULL;
                if ((error = pr->pr_sendfile_wait(so, rem, &space)) != 0)
                        goto done;
                /*
                 * At the beginning of the first loop check if any headers
                 * are specified and copy them into mbufs.  Reduce space in
                 * the socket buffer by the size of the header mbuf chain.
                 * Clear hdr_uio here and hdrlen at the end of the first loop.
                 */
                if (hdr_uio != NULL && hdr_uio->uio_resid > 0) {
                        hdr_uio->uio_td = td;
                        hdr_uio->uio_rw = UIO_WRITE;
#ifdef KERN_TLS
                        if (tls != NULL)
                                mh = m_uiotombuf(hdr_uio, M_WAITOK, space,
                                    tls->params.max_frame_len, M_EXTPG);
                        else
#endif
                                mh = m_uiotombuf(hdr_uio, M_WAITOK,
                                    space, 0, 0);
                        hdrlen = m_length(mh, &mhtail);
                        space -= hdrlen;
                        /*
                         * If header consumed all the socket buffer space,
                         * don't waste CPU cycles and jump to the end.
                         */
                        if (space == 0) {
                                sfio = NULL;
                                nios = 0;
                                goto prepend_header;
                        }
                        hdr_uio = NULL;
                }

                if (vp != NULL) {
                        error = vn_lock(vp, LK_SHARED);
                        if (error != 0)
                                goto done;

                        /*
                         * Check to see if the file size has changed.
                         */
                        if (obj->type == OBJT_VNODE) {
                                VM_OBJECT_RLOCK(obj);
                                nobj_size = obj->un_pager.vnp.vnp_size;
                                VM_OBJECT_RUNLOCK(obj);
                        } else {
                                error = VOP_GETATTR(vp, &va, td->td_ucred);
                                if (error != 0) {
                                        VOP_UNLOCK(vp);
                                        goto done;
                                }
                                nobj_size = va.va_size;
                        }
                        if (off >= nobj_size) {
                                VOP_UNLOCK(vp);
                                goto done;
                        }
                        if (nobj_size != obj_size) {
                                obj_size = nobj_size;
                                rem = nbytes ? omin(nbytes + offset, obj_size) :
                                    obj_size;
                                rem -= off;
                        }
                }

                if (space > rem)
                        space = rem;
                else if (space > PAGE_SIZE) {
                        /*
                         * Use page boundaries when possible for large
                         * requests.
                         */
                        if (off & PAGE_MASK)
                                space -= (PAGE_SIZE - (off & PAGE_MASK));
                        space = trunc_page(space);
                        if (off & PAGE_MASK)
                                space += (PAGE_SIZE - (off & PAGE_MASK));
                }

                npages = howmany(space + (off & PAGE_MASK), PAGE_SIZE);

                /*
                 * Calculate maximum allowed number of pages for readahead
                 * at this iteration.  If SF_USER_READAHEAD was set, we don't
                 * do any heuristics and use exactly the value supplied by
                 * application.  Otherwise, we allow readahead up to "rem".
                 * If application wants more, let it be, but there is no
                 * reason to go above maxphys.  Also check against "obj_size",
                 * since vm_pager_has_page() can hint beyond EOF.
                 */
                if (flags & SF_USER_READAHEAD) {
                        rhpages = SF_READAHEAD(flags);
                } else {
                        rhpages = howmany(rem + (off & PAGE_MASK), PAGE_SIZE) -
                            npages;
                        rhpages += SF_READAHEAD(flags);
                }
                rhpages = min(howmany(maxphys, PAGE_SIZE), rhpages);
                rhpages = min(howmany(obj_size - trunc_page(off), PAGE_SIZE) -
                    npages, rhpages);

                sfio = malloc(sizeof(struct sf_io) +
                    npages * sizeof(vm_page_t), M_SENDFILE, M_WAITOK);
                refcount_init(&sfio->nios, 1);
                sfio->obj = obj;
                sfio->error = 0;
                sfio->m = NULL;
                sfio->npages = npages;
#ifdef KERN_TLS
                /*
                 * This doesn't use ktls_hold() because sfio->m will
                 * also have a reference on 'tls' that will be valid
                 * for all of sfio's lifetime.
                 */
                sfio->tls = tls;
#endif
                vm_object_pip_add(obj, 1);
                error = sendfile_swapin(obj, sfio, &nios, off, space, rhpages,
                    flags);
                if (error != 0) {
                        if (vp != NULL)
                                VOP_UNLOCK(vp);
                        sendfile_iodone(sfio, NULL, 0, error);
                        goto done;
                }

                /*
                 * Loop and construct maximum sized mbuf chain to be bulk
                 * dumped into socket buffer.
                 */
                pa = sfio->pa;

                /*
                 * Use unmapped mbufs if enabled for TCP.  Unmapped
                 * bufs are restricted to TCP as that is what has been
                 * tested.  In particular, unmapped mbufs have not
                 * been tested with UNIX-domain sockets.
                 *
                 * TLS frames always require unmapped mbufs.
                 */
                if ((mb_use_ext_pgs && pr->pr_protocol == IPPROTO_TCP)
#ifdef KERN_TLS
                    || tls != NULL
#endif
                    ) {
                        use_ext_pgs = true;
#ifdef KERN_TLS
                        if (tls != NULL)
                                max_pgs = num_pages(tls->params.max_frame_len);
                        else
#endif
                                max_pgs = MBUF_PEXT_MAX_PGS;

                        /* Start at last index, to wrap on first use. */
                        ext_pgs_idx = max_pgs - 1;
                }

                for (int i = 0; i < npages; i++) {
                        /*
                         * If a page wasn't grabbed successfully, then
                         * trim the array. Can happen only with SF_NODISKIO.
                         */
                        if (pa[i] == NULL) {
                                SFSTAT_INC(sf_busy);
                                fixspace(npages, i, off, &space);
                                sfio->npages = i;
                                softerr = EBUSY;
                                break;
                        }
                        pga = pa[i];
                        if (pga == bogus_page)
                                pga = vm_page_relookup(obj, sfio->pindex0 + i);

                        if (use_ext_pgs) {
                                off_t xfs;

                                ext_pgs_idx++;
                                if (ext_pgs_idx == max_pgs) {
                                        m0 = mb_alloc_ext_pgs(M_WAITOK,
                                            sendfile_free_mext_pg, M_RDONLY);

                                        if (flags & SF_NOCACHE) {
                                                m0->m_ext.ext_flags |=
                                                    EXT_FLAG_NOCACHE;

                                                /*
                                                 * See comment below regarding
                                                 * ignoring SF_NOCACHE for the
                                                 * last page.
                                                 */
                                                if ((npages - i <= max_pgs) &&
                                                    ((off + space) & PAGE_MASK) &&
                                                    (rem > space || rhpages > 0))
                                                        m0->m_ext.ext_flags |=
                                                            EXT_FLAG_CACHE_LAST;
                                        }
                                        ext_pgs_idx = 0;

                                        /* Append to mbuf chain. */
                                        if (mtail != NULL)
                                                mtail->m_next = m0;
                                        else
                                                m = m0;
                                        mtail = m0;
                                        m0->m_epg_1st_off =
                                            vmoff(i, off) & PAGE_MASK;
                                }
                                if (nios) {
                                        mtail->m_flags |= M_NOTREADY;
                                        m0->m_epg_nrdy++;
                                }

                                m0->m_epg_pa[ext_pgs_idx] = VM_PAGE_TO_PHYS(pga);
                                m0->m_epg_npgs++;
                                xfs = xfsize(i, npages, off, space);
                                m0->m_epg_last_len = xfs;
                                MBUF_EXT_PGS_ASSERT_SANITY(m0);
                                mtail->m_len += xfs;
                                mtail->m_ext.ext_size += PAGE_SIZE;
                                continue;
                        }

                        /*
                         * Get a sendfile buf.  When allocating the
                         * first buffer for mbuf chain, we usually
                         * wait as long as necessary, but this wait
                         * can be interrupted.  For consequent
                         * buffers, do not sleep, since several
                         * threads might exhaust the buffers and then
                         * deadlock.
                         */
                        sf = sf_buf_alloc(pga,
                            m != NULL ? SFB_NOWAIT : SFB_CATCH);
                        if (sf == NULL) {
                                SFSTAT_INC(sf_allocfail);
                                sendfile_iowait(sfio, "sfnosf");
                                for (int j = i; j < npages; j++) {
                                        vm_page_unwire(pa[j], PQ_INACTIVE);
                                        pa[j] = NULL;
                                }
                                if (m == NULL)
                                        softerr = ENOBUFS;
                                fixspace(npages, i, off, &space);
                                sfio->npages = i;
                                break;
                        }

                        m0 = m_get(M_WAITOK, MT_DATA);
                        m0->m_ext.ext_buf = (char *)sf_buf_kva(sf);
                        m0->m_ext.ext_size = PAGE_SIZE;
                        m0->m_ext.ext_arg1 = sf;
                        m0->m_ext.ext_type = EXT_SFBUF;
                        m0->m_ext.ext_flags = EXT_FLAG_EMBREF;
                        m0->m_ext.ext_free = sendfile_free_mext;
                        /*
                         * SF_NOCACHE sets the page as being freed upon send.
                         * However, we ignore it for the last page in 'space',
                         * if the page is truncated, and we got more data to
                         * send (rem > space), or if we have readahead
                         * configured (rhpages > 0).
                         */
                        if ((flags & SF_NOCACHE) &&
                            (i != npages - 1 ||
                            !((off + space) & PAGE_MASK) ||
                            !(rem > space || rhpages > 0)))
                                m0->m_ext.ext_flags |= EXT_FLAG_NOCACHE;
                        m0->m_ext.ext_count = 1;
                        m0->m_flags |= (M_EXT | M_RDONLY);
                        if (nios)
                                m0->m_flags |= M_NOTREADY;
                        m0->m_data = (char *)sf_buf_kva(sf) +
                            (vmoff(i, off) & PAGE_MASK);
                        m0->m_len = xfsize(i, npages, off, space);

                        /* Append to mbuf chain. */
                        if (mtail != NULL)
                                mtail->m_next = m0;
                        else
                                m = m0;
                        mtail = m0;
                }

                if (vp != NULL)
                        VOP_UNLOCK(vp);

                /* Keep track of bytes processed. */
                off += space;
                rem -= space;

                /*
                 * Prepend header, if any.  Save pointer to first mbuf
                 * with a page.
                 */
                if (hdrlen) {
prepend_header:
                        m0 = mhtail->m_next = m;
                        m = mh;
                        mh = NULL;
                } else
                        m0 = m;

                if (m == NULL) {
                        KASSERT(softerr, ("%s: m NULL, no error", __func__));
                        error = softerr;
                        sendfile_iodone(sfio, NULL, 0, 0);
                        goto done;
                }

                /* Add the buffer chain to the socket buffer. */
                KASSERT(m_length(m, NULL) == space + hdrlen,
                    ("%s: mlen %u space %d hdrlen %d",
                    __func__, m_length(m, NULL), space, hdrlen));

#ifdef KERN_TLS
                if (tls != NULL)
                        ktls_frame(m, tls, &tls_enq_cnt, TLS_RLTYPE_APP);
#endif
                if (nios == 0) {
                        /*
                         * If sendfile_swapin() didn't initiate any I/Os,
                         * which happens if all data is cached in VM, or if
                         * the header consumed all socket buffer space and
                         * sfio is NULL, then we can send data right now
                         * without the PRUS_NOTREADY flag.
                         */
                        if (sfio != NULL)
                                sendfile_iodone(sfio, NULL, 0, 0);
#ifdef KERN_TLS
                        if (tls != NULL && tls->mode == TCP_TLS_MODE_SW) {
                                error = pr->pr_send(so, PRUS_NOTREADY, m, NULL,
                                    NULL, td);
                                if (error != 0) {
                                        m_freem(m);
                                } else {
                                        soref(so);
                                        ktls_enqueue(m, so, tls_enq_cnt);
                                }
                        } else
#endif
                                error = pr->pr_send(so, 0, m, NULL, NULL, td);
                } else {
                        sfio->so = so;
                        sfio->m = m0;
                        soref(so);
                        error = pr->pr_send(so, PRUS_NOTREADY, m, NULL, NULL,
                            td);
                        sendfile_iodone(sfio, NULL, 0, error);
                }
#ifdef TCP_REQUEST_TRK
                if (so->so_proto->pr_protocol == IPPROTO_TCP) {
                        /* log the sendfile call to the TCP log, if enabled */
                        tcp_log_sendfile(so, offset, nbytes, flags);
                }
#endif
                m = NULL;
                if (error)
                        goto done;
                sbytes += space + hdrlen;
                if (hdrlen)
                        hdrlen = 0;
                if (softerr) {
                        error = softerr;
                        goto done;
                }
        }

        /*
         * Send trailers. Wimp out and use writev(2).
         */
        if (trl_uio != NULL) {
                SOCK_IO_SEND_UNLOCK(so);
                CURVNET_RESTORE();
                error = kern_writev(td, sockfd, trl_uio);
                if (error == 0)
                        sbytes += td->td_retval[0];
                goto out;
        }

done:
        SOCK_IO_SEND_UNLOCK(so);
        CURVNET_RESTORE();
out:
        /*
         * If there was no error we have to clear td->td_retval[0]
         * because it may have been set by writev.
         */
        if (error == 0) {
                td->td_retval[0] = 0;
                if (sbytes > 0 && vp != NULL)
                        INOTIFY(vp, IN_ACCESS);
        }
        if (sent != NULL) {
                (*sent) = sbytes;
        }
        if (obj != NULL)
                vm_object_deallocate(obj);
        if (so)
                fdrop(sock_fp, td);
        if (m)
                m_freem(m);
        if (mh)
                m_freem(mh);
#ifdef KERN_TLS
        if (tls != NULL)
                ktls_free(tls);
#endif
        if (error == ERESTART)
                error = EINTR;

        return (error);
}

static int
sendfile(struct thread *td, struct sendfile_args *uap, int compat)
{
        struct sf_hdtr hdtr;
        struct uio *hdr_uio, *trl_uio;
        struct file *fp;
        off_t sbytes;
        int error;

        /*
         * File offset must be positive.  If it goes beyond EOF
         * we send only the header/trailer and no payload data.
         */
        if (uap->offset < 0)
                return (EINVAL);

        sbytes = 0;
        hdr_uio = trl_uio = NULL;

        if (uap->hdtr != NULL) {
                error = copyin(uap->hdtr, &hdtr, sizeof(hdtr));
                if (error != 0)
                        goto out;
                if (hdtr.headers != NULL) {
                        error = copyinuio(hdtr.headers, hdtr.hdr_cnt,
                            &hdr_uio);
                        if (error != 0)
                                goto out;
#ifdef COMPAT_FREEBSD4
                        /*
                         * In FreeBSD < 5.0 the nbytes to send also included
                         * the header.  If compat is specified subtract the
                         * header size from nbytes.
                         */
                        if (compat) {
                                if (uap->nbytes > hdr_uio->uio_resid)
                                        uap->nbytes -= hdr_uio->uio_resid;
                                else
                                        uap->nbytes = 0;
                        }
#endif
                }
                if (hdtr.trailers != NULL) {
                        error = copyinuio(hdtr.trailers, hdtr.trl_cnt,
                            &trl_uio);
                        if (error != 0)
                                goto out;
                }
        }

        AUDIT_ARG_FD(uap->fd);

        /*
         * sendfile(2) can start at any offset within a file so we require
         * CAP_READ+CAP_SEEK = CAP_PREAD.
         */
        if ((error = fget_read(td, uap->fd, &cap_pread_rights, &fp)) != 0)
                goto out;

        error = fo_sendfile(fp, uap->s, hdr_uio, trl_uio, uap->offset,
            uap->nbytes, &sbytes, uap->flags, td);
        fdrop(fp, td);

        if (uap->sbytes != NULL)
                (void)copyout(&sbytes, uap->sbytes, sizeof(off_t));

out:
        freeuio(hdr_uio);
        freeuio(trl_uio);
        return (error);
}

/*
 * sendfile(2)
 * 
 * int sendfile(int fd, int s, off_t offset, size_t nbytes,
 *       struct sf_hdtr *hdtr, off_t *sbytes, int flags)
 * 
 * Send a file specified by 'fd' and starting at 'offset' to a socket
 * specified by 's'. Send only 'nbytes' of the file or until EOF if nbytes ==
 * 0.  Optionally add a header and/or trailer to the socket output.  If
 * specified, write the total number of bytes sent into *sbytes.
 */
int
sys_sendfile(struct thread *td, struct sendfile_args *uap)
{

        return (sendfile(td, uap, 0));
}

#ifdef COMPAT_FREEBSD4
int
freebsd4_sendfile(struct thread *td, struct freebsd4_sendfile_args *uap)
{
        struct sendfile_args args;

        args.fd = uap->fd;
        args.s = uap->s;
        args.offset = uap->offset;
        args.nbytes = uap->nbytes;
        args.hdtr = uap->hdtr;
        args.sbytes = uap->sbytes;
        args.flags = uap->flags;

        return (sendfile(td, &args, 1));
}
#endif /* COMPAT_FREEBSD4 */