kernel - Make numerous proc accesses use p->p_token instead of proc_token.

[dragonfly.git] / sys / kern / uipc_syscalls.c

/*
 * Copyright (c) 1982, 1986, 1989, 1990, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * sendfile(2) and related extensions:
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. 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.
 *
 *      @(#)uipc_syscalls.c     8.4 (Berkeley) 2/21/94
 * $FreeBSD: src/sys/kern/uipc_syscalls.c,v 1.65.2.17 2003/04/04 17:11:16 tegge Exp $
 */

#include "opt_ktrace.h"
#include "opt_sctp.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/sysproto.h>
#include <sys/malloc.h>
#include <sys/filedesc.h>
#include <sys/event.h>
#include <sys/proc.h>
#include <sys/fcntl.h>
#include <sys/file.h>
#include <sys/filio.h>
#include <sys/kern_syscall.h>
#include <sys/mbuf.h>
#include <sys/protosw.h>
#include <sys/sfbuf.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/socketops.h>
#include <sys/uio.h>
#include <sys/vnode.h>
#include <sys/lock.h>
#include <sys/mount.h>
#ifdef KTRACE
#include <sys/ktrace.h>
#endif
#include <vm/vm.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_pageout.h>
#include <vm/vm_kern.h>
#include <vm/vm_extern.h>
#include <sys/file2.h>
#include <sys/signalvar.h>
#include <sys/serialize.h>

#include <sys/thread2.h>
#include <sys/msgport2.h>
#include <sys/socketvar2.h>
#include <net/netmsg2.h>

#ifdef SCTP
#include <netinet/sctp_peeloff.h>
#endif /* SCTP */

/*
 * System call interface to the socket abstraction.
 */

extern  struct fileops socketops;

/*
 * socket_args(int domain, int type, int protocol)
 */
int
kern_socket(int domain, int type, int protocol, int *res)
{
        struct thread *td = curthread;
        struct filedesc *fdp = td->td_proc->p_fd;
        struct socket *so;
        struct file *fp;
        int fd, error;

        KKASSERT(td->td_lwp);

        error = falloc(td->td_lwp, &fp, &fd);
        if (error)
                return (error);
        error = socreate(domain, &so, type, protocol, td);
        if (error) {
                fsetfd(fdp, NULL, fd);
        } else {
                fp->f_type = DTYPE_SOCKET;
                fp->f_flag = FREAD | FWRITE;
                fp->f_ops = &socketops;
                fp->f_data = so;
                *res = fd;
                fsetfd(fdp, fp, fd);
        }
        fdrop(fp);
        return (error);
}

/*
 * MPALMOSTSAFE
 */
int
sys_socket(struct socket_args *uap)
{
        int error;

        error = kern_socket(uap->domain, uap->type, uap->protocol,
                            &uap->sysmsg_iresult);

        return (error);
}

int
kern_bind(int s, struct sockaddr *sa)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct file *fp;
        int error;

        KKASSERT(p);
        error = holdsock(p->p_fd, s, &fp);
        if (error)
                return (error);
        error = sobind((struct socket *)fp->f_data, sa, td);
        fdrop(fp);
        return (error);
}

/*
 * bind_args(int s, caddr_t name, int namelen)
 *
 * MPALMOSTSAFE
 */
int
sys_bind(struct bind_args *uap)
{
        struct sockaddr *sa;
        int error;

        error = getsockaddr(&sa, uap->name, uap->namelen);
        if (error)
                return (error);
        error = kern_bind(uap->s, sa);
        FREE(sa, M_SONAME);

        return (error);
}

int
kern_listen(int s, int backlog)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct file *fp;
        int error;

        KKASSERT(p);
        error = holdsock(p->p_fd, s, &fp);
        if (error)
                return (error);
        error = solisten((struct socket *)fp->f_data, backlog, td);
        fdrop(fp);
        return(error);
}

/*
 * listen_args(int s, int backlog)
 *
 * MPALMOSTSAFE
 */
int
sys_listen(struct listen_args *uap)
{
        int error;

        error = kern_listen(uap->s, uap->backlog);
        return (error);
}

/*
 * Returns the accepted socket as well.
 *
 * NOTE!  The sockets sitting on so_comp/so_incomp might have 0 refs, the
 *        pool token is absolutely required to avoid a sofree() race,
 *        as well as to avoid tailq handling races.
 */
static boolean_t
soaccept_predicate(struct netmsg_so_notify *msg)
{
        struct socket *head = msg->base.nm_so;
        struct socket *so;

        if (head->so_error != 0) {
                msg->base.lmsg.ms_error = head->so_error;
                return (TRUE);
        }
        lwkt_getpooltoken(head);
        if (!TAILQ_EMPTY(&head->so_comp)) {
                /* Abuse nm_so field as copy in/copy out parameter. XXX JH */
                so = TAILQ_FIRST(&head->so_comp);
                TAILQ_REMOVE(&head->so_comp, so, so_list);
                head->so_qlen--;
                soclrstate(so, SS_COMP);
                so->so_head = NULL;
                soreference(so);

                lwkt_relpooltoken(head);

                msg->base.lmsg.ms_error = 0;
                msg->base.nm_so = so;
                return (TRUE);
        }
        lwkt_relpooltoken(head);
        if (head->so_state & SS_CANTRCVMORE) {
                msg->base.lmsg.ms_error = ECONNABORTED;
                return (TRUE);
        }
        if (msg->nm_fflags & FNONBLOCK) {
                msg->base.lmsg.ms_error = EWOULDBLOCK;
                return (TRUE);
        }

        return (FALSE);
}

/*
 * The second argument to kern_accept() is a handle to a struct sockaddr.
 * This allows kern_accept() to return a pointer to an allocated struct
 * sockaddr which must be freed later with FREE().  The caller must
 * initialize *name to NULL.
 */
int
kern_accept(int s, int fflags, struct sockaddr **name, int *namelen, int *res)
{
        struct thread *td = curthread;
        struct filedesc *fdp = td->td_proc->p_fd;
        struct file *lfp = NULL;
        struct file *nfp = NULL;
        struct sockaddr *sa;
        struct socket *head, *so;
        struct netmsg_so_notify msg;
        int fd;
        u_int fflag;            /* type must match fp->f_flag */
        int error, tmp;

        *res = -1;
        if (name && namelen && *namelen < 0)
                return (EINVAL);

        error = holdsock(td->td_proc->p_fd, s, &lfp);
        if (error)
                return (error);

        error = falloc(td->td_lwp, &nfp, &fd);
        if (error) {            /* Probably ran out of file descriptors. */
                fdrop(lfp);
                return (error);
        }
        head = (struct socket *)lfp->f_data;
        if ((head->so_options & SO_ACCEPTCONN) == 0) {
                error = EINVAL;
                goto done;
        }

        if (fflags & O_FBLOCKING)
                fflags |= lfp->f_flag & ~FNONBLOCK;
        else if (fflags & O_FNONBLOCKING)
                fflags |= lfp->f_flag | FNONBLOCK;
        else
                fflags = lfp->f_flag;

        /* optimize for uniprocessor case later XXX JH */
        netmsg_init_abortable(&msg.base, head, &curthread->td_msgport,
                              0, netmsg_so_notify, netmsg_so_notify_doabort);
        msg.nm_predicate = soaccept_predicate;
        msg.nm_fflags = fflags;
        msg.nm_etype = NM_REVENT;
        error = lwkt_domsg(head->so_port, &msg.base.lmsg, PCATCH);
        if (error)
                goto done;

        /*
         * At this point we have the connection that's ready to be accepted.
         *
         * NOTE! soaccept_predicate() ref'd so for us, and soaccept() expects
         *       to eat the ref and turn it into a descriptor.
         */
        so = msg.base.nm_so;

        fflag = lfp->f_flag;

        /* connection has been removed from the listen queue */
        KNOTE(&head->so_rcv.ssb_kq.ki_note, 0);

        if (head->so_sigio != NULL)
                fsetown(fgetown(&head->so_sigio), &so->so_sigio);

        nfp->f_type = DTYPE_SOCKET;
        nfp->f_flag = fflag;
        nfp->f_ops = &socketops;
        nfp->f_data = so;
        /* Sync socket nonblocking/async state with file flags */
        tmp = fflag & FNONBLOCK;
        fo_ioctl(nfp, FIONBIO, (caddr_t)&tmp, td->td_ucred, NULL);
        tmp = fflag & FASYNC;
        fo_ioctl(nfp, FIOASYNC, (caddr_t)&tmp, td->td_ucred, NULL);

        sa = NULL;
        error = soaccept(so, &sa);

        /*
         * Set the returned name and namelen as applicable.  Set the returned
         * namelen to 0 for older code which might ignore the return value
         * from accept.
         */
        if (error == 0) {
                if (sa && name && namelen) {
                        if (*namelen > sa->sa_len)
                                *namelen = sa->sa_len;
                        *name = sa;
                } else {
                        if (sa)
                                FREE(sa, M_SONAME);
                }
        }

done:
        /*
         * If an error occured clear the reserved descriptor, else associate
         * nfp with it.
         *
         * Note that *res is normally ignored if an error is returned but
         * a syscall message will still have access to the result code.
         */
        if (error) {
                fsetfd(fdp, NULL, fd);
        } else {
                *res = fd;
                fsetfd(fdp, nfp, fd);
        }
        fdrop(nfp);
        fdrop(lfp);
        return (error);
}

/*
 * accept(int s, caddr_t name, int *anamelen)
 *
 * MPALMOSTSAFE
 */
int
sys_accept(struct accept_args *uap)
{
        struct sockaddr *sa = NULL;
        int sa_len;
        int error;

        if (uap->name) {
                error = copyin(uap->anamelen, &sa_len, sizeof(sa_len));
                if (error)
                        return (error);

                error = kern_accept(uap->s, 0, &sa, &sa_len,
                                    &uap->sysmsg_iresult);

                if (error == 0)
                        error = copyout(sa, uap->name, sa_len);
                if (error == 0) {
                        error = copyout(&sa_len, uap->anamelen,
                            sizeof(*uap->anamelen));
                }
                if (sa)
                        FREE(sa, M_SONAME);
        } else {
                error = kern_accept(uap->s, 0, NULL, 0,
                                    &uap->sysmsg_iresult);
        }
        return (error);
}

/*
 * extaccept(int s, int fflags, caddr_t name, int *anamelen)
 *
 * MPALMOSTSAFE
 */
int
sys_extaccept(struct extaccept_args *uap)
{
        struct sockaddr *sa = NULL;
        int sa_len;
        int error;
        int fflags = uap->flags & O_FMASK;

        if (uap->name) {
                error = copyin(uap->anamelen, &sa_len, sizeof(sa_len));
                if (error)
                        return (error);

                error = kern_accept(uap->s, fflags, &sa, &sa_len,
                                    &uap->sysmsg_iresult);

                if (error == 0)
                        error = copyout(sa, uap->name, sa_len);
                if (error == 0) {
                        error = copyout(&sa_len, uap->anamelen,
                            sizeof(*uap->anamelen));
                }
                if (sa)
                        FREE(sa, M_SONAME);
        } else {
                error = kern_accept(uap->s, fflags, NULL, 0,
                                    &uap->sysmsg_iresult);
        }
        return (error);
}


/*
 * Returns TRUE if predicate satisfied.
 */
static boolean_t
soconnected_predicate(struct netmsg_so_notify *msg)
{
        struct socket *so = msg->base.nm_so;

        /* check predicate */
        if (!(so->so_state & SS_ISCONNECTING) || so->so_error != 0) {
                msg->base.lmsg.ms_error = so->so_error;
                return (TRUE);
        }

        return (FALSE);
}

int
kern_connect(int s, int fflags, struct sockaddr *sa)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct file *fp;
        struct socket *so;
        int error, interrupted = 0;

        error = holdsock(p->p_fd, s, &fp);
        if (error)
                return (error);
        so = (struct socket *)fp->f_data;

        if (fflags & O_FBLOCKING)
                /* fflags &= ~FNONBLOCK; */;
        else if (fflags & O_FNONBLOCKING)
                fflags |= FNONBLOCK;
        else
                fflags = fp->f_flag;

        if (so->so_state & SS_ISCONNECTING) {
                error = EALREADY;
                goto done;
        }
        error = soconnect(so, sa, td);
        if (error)
                goto bad;
        if ((fflags & FNONBLOCK) && (so->so_state & SS_ISCONNECTING)) {
                error = EINPROGRESS;
                goto done;
        }
        if ((so->so_state & SS_ISCONNECTING) && so->so_error == 0) {
                struct netmsg_so_notify msg;

                netmsg_init_abortable(&msg.base, so,
                                      &curthread->td_msgport,
                                      0,
                                      netmsg_so_notify,
                                      netmsg_so_notify_doabort);
                msg.nm_predicate = soconnected_predicate;
                msg.nm_etype = NM_REVENT;
                error = lwkt_domsg(so->so_port, &msg.base.lmsg, PCATCH);
                if (error == EINTR || error == ERESTART)
                        interrupted = 1;
        }
        if (error == 0) {
                error = so->so_error;
                so->so_error = 0;
        }
bad:
        if (!interrupted)
                soclrstate(so, SS_ISCONNECTING);
        if (error == ERESTART)
                error = EINTR;
done:
        fdrop(fp);
        return (error);
}

/*
 * connect_args(int s, caddr_t name, int namelen)
 *
 * MPALMOSTSAFE
 */
int
sys_connect(struct connect_args *uap)
{
        struct sockaddr *sa;
        int error;

        error = getsockaddr(&sa, uap->name, uap->namelen);
        if (error)
                return (error);
        error = kern_connect(uap->s, 0, sa);
        FREE(sa, M_SONAME);

        return (error);
}

/*
 * connect_args(int s, int fflags, caddr_t name, int namelen)
 *
 * MPALMOSTSAFE
 */
int
sys_extconnect(struct extconnect_args *uap)
{
        struct sockaddr *sa;
        int error;
        int fflags = uap->flags & O_FMASK;

        error = getsockaddr(&sa, uap->name, uap->namelen);
        if (error)
                return (error);
        error = kern_connect(uap->s, fflags, sa);
        FREE(sa, M_SONAME);

        return (error);
}

int
kern_socketpair(int domain, int type, int protocol, int *sv)
{
        struct thread *td = curthread;
        struct filedesc *fdp;
        struct file *fp1, *fp2;
        struct socket *so1, *so2;
        int fd1, fd2, error;

        fdp = td->td_proc->p_fd;
        error = socreate(domain, &so1, type, protocol, td);
        if (error)
                return (error);
        error = socreate(domain, &so2, type, protocol, td);
        if (error)
                goto free1;
        error = falloc(td->td_lwp, &fp1, &fd1);
        if (error)
                goto free2;
        sv[0] = fd1;
        fp1->f_data = so1;
        error = falloc(td->td_lwp, &fp2, &fd2);
        if (error)
                goto free3;
        fp2->f_data = so2;
        sv[1] = fd2;
        error = soconnect2(so1, so2);
        if (error)
                goto free4;
        if (type == SOCK_DGRAM) {
                /*
                 * Datagram socket connection is asymmetric.
                 */
                 error = soconnect2(so2, so1);
                 if (error)
                        goto free4;
        }
        fp1->f_type = fp2->f_type = DTYPE_SOCKET;
        fp1->f_flag = fp2->f_flag = FREAD|FWRITE;
        fp1->f_ops = fp2->f_ops = &socketops;
        fsetfd(fdp, fp1, fd1);
        fsetfd(fdp, fp2, fd2);
        fdrop(fp1);
        fdrop(fp2);
        return (error);
free4:
        fsetfd(fdp, NULL, fd2);
        fdrop(fp2);
free3:
        fsetfd(fdp, NULL, fd1);
        fdrop(fp1);
free2:
        (void)soclose(so2, 0);
free1:
        (void)soclose(so1, 0);
        return (error);
}

/*
 * socketpair(int domain, int type, int protocol, int *rsv)
 *
 * MPALMOSTSAFE
 */
int
sys_socketpair(struct socketpair_args *uap)
{
        int error, sockv[2];

        error = kern_socketpair(uap->domain, uap->type, uap->protocol, sockv);

        if (error == 0)
                error = copyout(sockv, uap->rsv, sizeof(sockv));
        return (error);
}

int
kern_sendmsg(int s, struct sockaddr *sa, struct uio *auio,
             struct mbuf *control, int flags, size_t *res)
{
        struct thread *td = curthread;
        struct lwp *lp = td->td_lwp;
        struct proc *p = td->td_proc;
        struct file *fp;
        size_t len;
        int error;
        struct socket *so;
#ifdef KTRACE
        struct iovec *ktriov = NULL;
        struct uio ktruio;
#endif

        error = holdsock(p->p_fd, s, &fp);
        if (error)
                return (error);
#ifdef KTRACE
        if (KTRPOINT(td, KTR_GENIO)) {
                int iovlen = auio->uio_iovcnt * sizeof (struct iovec);

                MALLOC(ktriov, struct iovec *, iovlen, M_TEMP, M_WAITOK);
                bcopy((caddr_t)auio->uio_iov, (caddr_t)ktriov, iovlen);
                ktruio = *auio;
        }
#endif
        len = auio->uio_resid;
        so = (struct socket *)fp->f_data;
        if ((flags & (MSG_FNONBLOCKING|MSG_FBLOCKING)) == 0) {
                if (fp->f_flag & FNONBLOCK)
                        flags |= MSG_FNONBLOCKING;
        }
        error = so_pru_sosend(so, sa, auio, NULL, control, flags, td);
        if (error) {
                if (auio->uio_resid != len && (error == ERESTART ||
                    error == EINTR || error == EWOULDBLOCK))
                        error = 0;
                if (error == EPIPE && !(flags & MSG_NOSIGNAL))
                        lwpsignal(p, lp, SIGPIPE);
        }
#ifdef KTRACE
        if (ktriov != NULL) {
                if (error == 0) {
                        ktruio.uio_iov = ktriov;
                        ktruio.uio_resid = len - auio->uio_resid;
                        ktrgenio(lp, s, UIO_WRITE, &ktruio, error);
                }
                FREE(ktriov, M_TEMP);
        }
#endif
        if (error == 0)
                *res  = len - auio->uio_resid;
        fdrop(fp);
        return (error);
}

/*
 * sendto_args(int s, caddr_t buf, size_t len, int flags, caddr_t to, int tolen)
 *
 * MPALMOSTSAFE
 */
int
sys_sendto(struct sendto_args *uap)
{
        struct thread *td = curthread;
        struct uio auio;
        struct iovec aiov;
        struct sockaddr *sa = NULL;
        int error;

        if (uap->to) {
                error = getsockaddr(&sa, uap->to, uap->tolen);
                if (error)
                        return (error);
        }
        aiov.iov_base = uap->buf;
        aiov.iov_len = uap->len;
        auio.uio_iov = &aiov;
        auio.uio_iovcnt = 1;
        auio.uio_offset = 0;
        auio.uio_resid = uap->len;
        auio.uio_segflg = UIO_USERSPACE;
        auio.uio_rw = UIO_WRITE;
        auio.uio_td = td;

        error = kern_sendmsg(uap->s, sa, &auio, NULL, uap->flags,
                             &uap->sysmsg_szresult);

        if (sa)
                FREE(sa, M_SONAME);
        return (error);
}

/*
 * sendmsg_args(int s, caddr_t msg, int flags)
 *
 * MPALMOSTSAFE
 */
int
sys_sendmsg(struct sendmsg_args *uap)
{
        struct thread *td = curthread;
        struct msghdr msg;
        struct uio auio;
        struct iovec aiov[UIO_SMALLIOV], *iov = NULL;
        struct sockaddr *sa = NULL;
        struct mbuf *control = NULL;
        int error;

        error = copyin(uap->msg, (caddr_t)&msg, sizeof(msg));
        if (error)
                return (error);

        /*
         * Conditionally copyin msg.msg_name.
         */
        if (msg.msg_name) {
                error = getsockaddr(&sa, msg.msg_name, msg.msg_namelen);
                if (error)
                        return (error);
        }

        /*
         * Populate auio.
         */
        error = iovec_copyin(msg.msg_iov, &iov, aiov, msg.msg_iovlen,
                             &auio.uio_resid);
        if (error)
                goto cleanup2;
        auio.uio_iov = iov;
        auio.uio_iovcnt = msg.msg_iovlen;
        auio.uio_offset = 0;
        auio.uio_segflg = UIO_USERSPACE;
        auio.uio_rw = UIO_WRITE;
        auio.uio_td = td;

        /*
         * Conditionally copyin msg.msg_control.
         */
        if (msg.msg_control) {
                if (msg.msg_controllen < sizeof(struct cmsghdr) ||
                    msg.msg_controllen > MLEN) {
                        error = EINVAL;
                        goto cleanup;
                }
                control = m_get(MB_WAIT, MT_CONTROL);
                if (control == NULL) {
                        error = ENOBUFS;
                        goto cleanup;
                }
                control->m_len = msg.msg_controllen;
                error = copyin(msg.msg_control, mtod(control, caddr_t),
                               msg.msg_controllen);
                if (error) {
                        m_free(control);
                        goto cleanup;
                }
        }

        error = kern_sendmsg(uap->s, sa, &auio, control, uap->flags,
                             &uap->sysmsg_szresult);

cleanup:
        iovec_free(&iov, aiov);
cleanup2:
        if (sa)
                FREE(sa, M_SONAME);
        return (error);
}

/*
 * kern_recvmsg() takes a handle to sa and control.  If the handle is non-
 * null, it returns a dynamically allocated struct sockaddr and an mbuf.
 * Don't forget to FREE() and m_free() these if they are returned.
 */
int
kern_recvmsg(int s, struct sockaddr **sa, struct uio *auio,
             struct mbuf **control, int *flags, size_t *res)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct file *fp;
        size_t len;
        int error;
        int lflags;
        struct socket *so;
#ifdef KTRACE
        struct iovec *ktriov = NULL;
        struct uio ktruio;
#endif

        error = holdsock(p->p_fd, s, &fp);
        if (error)
                return (error);
#ifdef KTRACE
        if (KTRPOINT(td, KTR_GENIO)) {
                int iovlen = auio->uio_iovcnt * sizeof (struct iovec);

                MALLOC(ktriov, struct iovec *, iovlen, M_TEMP, M_WAITOK);
                bcopy(auio->uio_iov, ktriov, iovlen);
                ktruio = *auio;
        }
#endif
        len = auio->uio_resid;
        so = (struct socket *)fp->f_data;

        if (flags == NULL || (*flags & (MSG_FNONBLOCKING|MSG_FBLOCKING)) == 0) {
                if (fp->f_flag & FNONBLOCK) {
                        if (flags) {
                                *flags |= MSG_FNONBLOCKING;
                        } else {
                                lflags = MSG_FNONBLOCKING;
                                flags = &lflags;
                        }
                }
        }

        error = so_pru_soreceive(so, sa, auio, NULL, control, flags);
        if (error) {
                if (auio->uio_resid != len && (error == ERESTART ||
                    error == EINTR || error == EWOULDBLOCK))
                        error = 0;
        }
#ifdef KTRACE
        if (ktriov != NULL) {
                if (error == 0) {
                        ktruio.uio_iov = ktriov;
                        ktruio.uio_resid = len - auio->uio_resid;
                        ktrgenio(td->td_lwp, s, UIO_READ, &ktruio, error);
                }
                FREE(ktriov, M_TEMP);
        }
#endif
        if (error == 0)
                *res = len - auio->uio_resid;
        fdrop(fp);
        return (error);
}

/*
 * recvfrom_args(int s, caddr_t buf, size_t len, int flags, 
 *                      caddr_t from, int *fromlenaddr)
 *
 * MPALMOSTSAFE
 */
int
sys_recvfrom(struct recvfrom_args *uap)
{
        struct thread *td = curthread;
        struct uio auio;
        struct iovec aiov;
        struct sockaddr *sa = NULL;
        int error, fromlen;

        if (uap->from && uap->fromlenaddr) {
                error = copyin(uap->fromlenaddr, &fromlen, sizeof(fromlen));
                if (error)
                        return (error);
                if (fromlen < 0)
                        return (EINVAL);
        } else {
                fromlen = 0;
        }
        aiov.iov_base = uap->buf;
        aiov.iov_len = uap->len;
        auio.uio_iov = &aiov;
        auio.uio_iovcnt = 1;
        auio.uio_offset = 0;
        auio.uio_resid = uap->len;
        auio.uio_segflg = UIO_USERSPACE;
        auio.uio_rw = UIO_READ;
        auio.uio_td = td;

        error = kern_recvmsg(uap->s, uap->from ? &sa : NULL, &auio, NULL,
                             &uap->flags, &uap->sysmsg_szresult);

        if (error == 0 && uap->from) {
                /* note: sa may still be NULL */
                if (sa) {
                        fromlen = MIN(fromlen, sa->sa_len);
                        error = copyout(sa, uap->from, fromlen);
                } else {
                        fromlen = 0;
                }
                if (error == 0) {
                        error = copyout(&fromlen, uap->fromlenaddr,
                                        sizeof(fromlen));
                }
        }
        if (sa)
                FREE(sa, M_SONAME);

        return (error);
}

/*
 * recvmsg_args(int s, struct msghdr *msg, int flags)
 *
 * MPALMOSTSAFE
 */
int
sys_recvmsg(struct recvmsg_args *uap)
{
        struct thread *td = curthread;
        struct msghdr msg;
        struct uio auio;
        struct iovec aiov[UIO_SMALLIOV], *iov = NULL;
        struct mbuf *m, *control = NULL;
        struct sockaddr *sa = NULL;
        caddr_t ctlbuf;
        socklen_t *ufromlenp, *ucontrollenp;
        int error, fromlen, controllen, len, flags, *uflagsp;

        /*
         * This copyin handles everything except the iovec.
         */
        error = copyin(uap->msg, &msg, sizeof(msg));
        if (error)
                return (error);

        if (msg.msg_name && msg.msg_namelen < 0)
                return (EINVAL);
        if (msg.msg_control && msg.msg_controllen < 0)
                return (EINVAL);

        ufromlenp = (socklen_t *)((caddr_t)uap->msg + offsetof(struct msghdr,
                    msg_namelen));
        ucontrollenp = (socklen_t *)((caddr_t)uap->msg + offsetof(struct msghdr,
                       msg_controllen));
        uflagsp = (int *)((caddr_t)uap->msg + offsetof(struct msghdr,
                                                        msg_flags));

        /*
         * Populate auio.
         */
        error = iovec_copyin(msg.msg_iov, &iov, aiov, msg.msg_iovlen,
                             &auio.uio_resid);
        if (error)
                return (error);
        auio.uio_iov = iov;
        auio.uio_iovcnt = msg.msg_iovlen;
        auio.uio_offset = 0;
        auio.uio_segflg = UIO_USERSPACE;
        auio.uio_rw = UIO_READ;
        auio.uio_td = td;

        flags = uap->flags;

        error = kern_recvmsg(uap->s,
                             (msg.msg_name ? &sa : NULL), &auio,
                             (msg.msg_control ? &control : NULL), &flags,
                             &uap->sysmsg_szresult);

        /*
         * Conditionally copyout the name and populate the namelen field.
         */
        if (error == 0 && msg.msg_name) {
                /* note: sa may still be NULL */
                if (sa != NULL) {
                        fromlen = MIN(msg.msg_namelen, sa->sa_len);
                        error = copyout(sa, msg.msg_name, fromlen);
                } else {
                        fromlen = 0;
                }
                if (error == 0)
                        error = copyout(&fromlen, ufromlenp,
                            sizeof(*ufromlenp));
        }

        /*
         * Copyout msg.msg_control and msg.msg_controllen.
         */
        if (error == 0 && msg.msg_control) {
                len = msg.msg_controllen;
                m = control;
                ctlbuf = (caddr_t)msg.msg_control;

                while(m && len > 0) {
                        unsigned int tocopy;

                        if (len >= m->m_len) {
                                tocopy = m->m_len;
                        } else {
                                msg.msg_flags |= MSG_CTRUNC;
                                tocopy = len;
                        }

                        error = copyout(mtod(m, caddr_t), ctlbuf, tocopy);
                        if (error)
                                goto cleanup;

                        ctlbuf += tocopy;
                        len -= tocopy;
                        m = m->m_next;
                }
                controllen = ctlbuf - (caddr_t)msg.msg_control;
                error = copyout(&controllen, ucontrollenp,
                    sizeof(*ucontrollenp));
        }

        if (error == 0)
                error = copyout(&flags, uflagsp, sizeof(*uflagsp));

cleanup:
        if (sa)
                FREE(sa, M_SONAME);
        iovec_free(&iov, aiov);
        if (control)
                m_freem(control);
        return (error);
}

/*
 * If sopt->sopt_td == NULL, then sopt->sopt_val is treated as an
 * in kernel pointer instead of a userland pointer.  This allows us
 * to manipulate socket options in the emulation code.
 */
int
kern_setsockopt(int s, struct sockopt *sopt)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct file *fp;
        int error;

        if (sopt->sopt_val == NULL && sopt->sopt_valsize != 0)
                return (EFAULT);
        if (sopt->sopt_val != NULL && sopt->sopt_valsize == 0)
                return (EINVAL);
        if (sopt->sopt_valsize < 0)
                return (EINVAL);

        error = holdsock(p->p_fd, s, &fp);
        if (error)
                return (error);

        error = sosetopt((struct socket *)fp->f_data, sopt);
        fdrop(fp);
        return (error);
}

/*
 * setsockopt_args(int s, int level, int name, caddr_t val, int valsize)
 *
 * MPALMOSTSAFE
 */
int
sys_setsockopt(struct setsockopt_args *uap)
{
        struct thread *td = curthread;
        struct sockopt sopt;
        int error;

        sopt.sopt_level = uap->level;
        sopt.sopt_name = uap->name;
        sopt.sopt_valsize = uap->valsize;
        sopt.sopt_td = td;
        sopt.sopt_val = NULL;

        if (sopt.sopt_valsize < 0 || sopt.sopt_valsize > SOMAXOPT_SIZE)
                return (EINVAL);
        if (uap->val) {
                sopt.sopt_val = kmalloc(sopt.sopt_valsize, M_TEMP, M_WAITOK);
                error = copyin(uap->val, sopt.sopt_val, sopt.sopt_valsize);
                if (error)
                        goto out;
        }

        error = kern_setsockopt(uap->s, &sopt);
out:
        if (uap->val)
                kfree(sopt.sopt_val, M_TEMP);
        return(error);
}

/*
 * If sopt->sopt_td == NULL, then sopt->sopt_val is treated as an
 * in kernel pointer instead of a userland pointer.  This allows us
 * to manipulate socket options in the emulation code.
 */
int
kern_getsockopt(int s, struct sockopt *sopt)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct file *fp;
        int error;

        if (sopt->sopt_val == NULL && sopt->sopt_valsize != 0)
                return (EFAULT);
        if (sopt->sopt_val != NULL && sopt->sopt_valsize == 0)
                return (EINVAL);
        if (sopt->sopt_valsize < 0 || sopt->sopt_valsize > SOMAXOPT_SIZE)
                return (EINVAL);

        error = holdsock(p->p_fd, s, &fp);
        if (error)
                return (error);

        error = sogetopt((struct socket *)fp->f_data, sopt);
        fdrop(fp);
        return (error);
}

/*
 * getsockopt_args(int s, int level, int name, caddr_t val, int *avalsize)
 *
 * MPALMOSTSAFE
 */
int
sys_getsockopt(struct getsockopt_args *uap)
{
        struct thread *td = curthread;
        struct  sockopt sopt;
        int     error, valsize;

        if (uap->val) {
                error = copyin(uap->avalsize, &valsize, sizeof(valsize));
                if (error)
                        return (error);
        } else {
                valsize = 0;
        }

        sopt.sopt_level = uap->level;
        sopt.sopt_name = uap->name;
        sopt.sopt_valsize = valsize;
        sopt.sopt_td = td;
        sopt.sopt_val = NULL;

        if (sopt.sopt_valsize < 0 || sopt.sopt_valsize > SOMAXOPT_SIZE)
                return (EINVAL);
        if (uap->val) {
                sopt.sopt_val = kmalloc(sopt.sopt_valsize, M_TEMP, M_WAITOK);
                error = copyin(uap->val, sopt.sopt_val, sopt.sopt_valsize);
                if (error)
                        goto out;
        }

        error = kern_getsockopt(uap->s, &sopt);
        if (error)
                goto out;
        valsize = sopt.sopt_valsize;
        error = copyout(&valsize, uap->avalsize, sizeof(valsize));
        if (error)
                goto out;
        if (uap->val)
                error = copyout(sopt.sopt_val, uap->val, sopt.sopt_valsize);
out:
        if (uap->val)
                kfree(sopt.sopt_val, M_TEMP);
        return (error);
}

/*
 * The second argument to kern_getsockname() is a handle to a struct sockaddr.
 * This allows kern_getsockname() to return a pointer to an allocated struct
 * sockaddr which must be freed later with FREE().  The caller must
 * initialize *name to NULL.
 */
int
kern_getsockname(int s, struct sockaddr **name, int *namelen)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct file *fp;
        struct socket *so;
        struct sockaddr *sa = NULL;
        int error;

        error = holdsock(p->p_fd, s, &fp);
        if (error)
                return (error);
        if (*namelen < 0) {
                fdrop(fp);
                return (EINVAL);
        }
        so = (struct socket *)fp->f_data;
        error = so_pru_sockaddr(so, &sa);
        if (error == 0) {
                if (sa == NULL) {
                        *namelen = 0;
                } else {
                        *namelen = MIN(*namelen, sa->sa_len);
                        *name = sa;
                }
        }

        fdrop(fp);
        return (error);
}

/*
 * getsockname_args(int fdes, caddr_t asa, int *alen)
 *
 * Get socket name.
 *
 * MPALMOSTSAFE
 */
int
sys_getsockname(struct getsockname_args *uap)
{
        struct sockaddr *sa = NULL;
        int error, sa_len;

        error = copyin(uap->alen, &sa_len, sizeof(sa_len));
        if (error)
                return (error);

        error = kern_getsockname(uap->fdes, &sa, &sa_len);

        if (error == 0)
                error = copyout(sa, uap->asa, sa_len);
        if (error == 0)
                error = copyout(&sa_len, uap->alen, sizeof(*uap->alen));
        if (sa)
                FREE(sa, M_SONAME);
        return (error);
}

/*
 * The second argument to kern_getpeername() is a handle to a struct sockaddr.
 * This allows kern_getpeername() to return a pointer to an allocated struct
 * sockaddr which must be freed later with FREE().  The caller must
 * initialize *name to NULL.
 */
int
kern_getpeername(int s, struct sockaddr **name, int *namelen)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct file *fp;
        struct socket *so;
        struct sockaddr *sa = NULL;
        int error;

        error = holdsock(p->p_fd, s, &fp);
        if (error)
                return (error);
        if (*namelen < 0) {
                fdrop(fp);
                return (EINVAL);
        }
        so = (struct socket *)fp->f_data;
        if ((so->so_state & (SS_ISCONNECTED|SS_ISCONFIRMING)) == 0) {
                fdrop(fp);
                return (ENOTCONN);
        }
        error = so_pru_peeraddr(so, &sa);
        if (error == 0) {
                if (sa == NULL) {
                        *namelen = 0;
                } else {
                        *namelen = MIN(*namelen, sa->sa_len);
                        *name = sa;
                }
        }

        fdrop(fp);
        return (error);
}

/*
 * getpeername_args(int fdes, caddr_t asa, int *alen)
 *
 * Get name of peer for connected socket.
 *
 * MPALMOSTSAFE
 */
int
sys_getpeername(struct getpeername_args *uap)
{
        struct sockaddr *sa = NULL;
        int error, sa_len;

        error = copyin(uap->alen, &sa_len, sizeof(sa_len));
        if (error)
                return (error);

        error = kern_getpeername(uap->fdes, &sa, &sa_len);

        if (error == 0)
                error = copyout(sa, uap->asa, sa_len);
        if (error == 0)
                error = copyout(&sa_len, uap->alen, sizeof(*uap->alen));
        if (sa)
                FREE(sa, M_SONAME);
        return (error);
}

int
getsockaddr(struct sockaddr **namp, caddr_t uaddr, size_t len)
{
        struct sockaddr *sa;
        int error;

        *namp = NULL;
        if (len > SOCK_MAXADDRLEN)
                return ENAMETOOLONG;
        if (len < offsetof(struct sockaddr, sa_data[0]))
                return EDOM;
        MALLOC(sa, struct sockaddr *, len, M_SONAME, M_WAITOK);
        error = copyin(uaddr, sa, len);
        if (error) {
                FREE(sa, M_SONAME);
        } else {
#if BYTE_ORDER != BIG_ENDIAN
                /*
                 * The bind(), connect(), and sendto() syscalls were not
                 * versioned for COMPAT_43.  Thus, this check must stay.
                 */
                if (sa->sa_family == 0 && sa->sa_len < AF_MAX)
                        sa->sa_family = sa->sa_len;
#endif
                sa->sa_len = len;
                *namp = sa;
        }
        return error;
}

/*
 * Detach a mapped page and release resources back to the system.
 * We must release our wiring and if the object is ripped out
 * from under the vm_page we become responsible for freeing the
 * page.
 *
 * MPSAFE
 */
static void
sf_buf_mfree(void *arg)
{
        struct sf_buf *sf = arg;
        vm_page_t m;

        m = sf_buf_page(sf);
        if (sf_buf_free(sf)) {
                /* sf invalid now */
                vm_page_unwire(m, 0);
                if (m->wire_count == 0 && m->object == NULL)
                        vm_page_try_to_free(m);
        }
}

/*
 * 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.
 *
 * In FreeBSD kern/uipc_syscalls.c,v 1.103, a bug was fixed that caused
 * the headers to count against the remaining bytes to be sent from
 * the file descriptor.  We may wish to implement a compatibility syscall
 * in the future.
 *
 * MPALMOSTSAFE
 */
int
sys_sendfile(struct sendfile_args *uap)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct file *fp;
        struct vnode *vp = NULL;
        struct sf_hdtr hdtr;
        struct iovec aiov[UIO_SMALLIOV], *iov = NULL;
        struct uio auio;
        struct mbuf *mheader = NULL;
        size_t hbytes = 0;
        size_t tbytes;
        off_t hdtr_size = 0;
        off_t sbytes;
        int error;

        KKASSERT(p);

        /*
         * Do argument checking. Must be a regular file in, stream
         * type and connected socket out, positive offset.
         */
        fp = holdfp(p->p_fd, uap->fd, FREAD);
        if (fp == NULL) {
                return (EBADF);
        }
        if (fp->f_type != DTYPE_VNODE) {
                fdrop(fp);
                return (EINVAL);
        }
        vp = (struct vnode *)fp->f_data;
        vref(vp);
        fdrop(fp);

        /*
         * If specified, get the pointer to the sf_hdtr struct for
         * any headers/trailers.
         */
        if (uap->hdtr) {
                error = copyin(uap->hdtr, &hdtr, sizeof(hdtr));
                if (error)
                        goto done;
                /*
                 * Send any headers.
                 */
                if (hdtr.headers) {
                        error = iovec_copyin(hdtr.headers, &iov, aiov,
                                             hdtr.hdr_cnt, &hbytes);
                        if (error)
                                goto done;
                        auio.uio_iov = iov;
                        auio.uio_iovcnt = hdtr.hdr_cnt;
                        auio.uio_offset = 0;
                        auio.uio_segflg = UIO_USERSPACE;
                        auio.uio_rw = UIO_WRITE;
                        auio.uio_td = td;
                        auio.uio_resid = hbytes;

                        mheader = m_uiomove(&auio);

                        iovec_free(&iov, aiov);
                        if (mheader == NULL)
                                goto done;
                }
        }

        error = kern_sendfile(vp, uap->s, uap->offset, uap->nbytes, mheader,
                              &sbytes, uap->flags);
        if (error)
                goto done;

        /*
         * Send trailers. Wimp out and use writev(2).
         */
        if (uap->hdtr != NULL && hdtr.trailers != NULL) {
                error = iovec_copyin(hdtr.trailers, &iov, aiov,
                                     hdtr.trl_cnt, &auio.uio_resid);
                if (error)
                        goto done;
                auio.uio_iov = iov;
                auio.uio_iovcnt = hdtr.trl_cnt;
                auio.uio_offset = 0;
                auio.uio_segflg = UIO_USERSPACE;
                auio.uio_rw = UIO_WRITE;
                auio.uio_td = td;

                error = kern_sendmsg(uap->s, NULL, &auio, NULL, 0, &tbytes);

                iovec_free(&iov, aiov);
                if (error)
                        goto done;
                hdtr_size += tbytes;    /* trailer bytes successfully sent */
        }

done:
        if (vp)
                vrele(vp);
        if (uap->sbytes != NULL) {
                sbytes += hdtr_size;
                copyout(&sbytes, uap->sbytes, sizeof(off_t));
        }
        return (error);
}

int
kern_sendfile(struct vnode *vp, int sfd, off_t offset, size_t nbytes,
              struct mbuf *mheader, off_t *sbytes, int flags)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct vm_object *obj;
        struct socket *so;
        struct file *fp;
        struct mbuf *m;
        struct sf_buf *sf;
        struct vm_page *pg;
        off_t off, xfsize;
        off_t hbytes = 0;
        int error = 0;

        if (vp->v_type != VREG) {
                error = EINVAL;
                goto done0;
        }
        if ((obj = vp->v_object) == NULL) {
                error = EINVAL;
                goto done0;
        }
        error = holdsock(p->p_fd, sfd, &fp);
        if (error)
                goto done0;
        so = (struct socket *)fp->f_data;
        if (so->so_type != SOCK_STREAM) {
                error = EINVAL;
                goto done;
        }
        if ((so->so_state & SS_ISCONNECTED) == 0) {
                error = ENOTCONN;
                goto done;
        }
        if (offset < 0) {
                error = EINVAL;
                goto done;
        }

        *sbytes = 0;
        /*
         * Protect against multiple writers to the socket.
         */
        ssb_lock(&so->so_snd, M_WAITOK);

        /*
         * Loop through the pages in 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.
         */
        for (off = offset; ; off += xfsize, *sbytes += xfsize + hbytes) {
                vm_pindex_t pindex;
                vm_offset_t pgoff;

                pindex = OFF_TO_IDX(off);
retry_lookup:
                /*
                 * Calculate the amount to transfer. Not to exceed a page,
                 * the EOF, or the passed in nbytes.
                 */
                xfsize = vp->v_filesize - off;
                if (xfsize > PAGE_SIZE)
                        xfsize = PAGE_SIZE;
                pgoff = (vm_offset_t)(off & PAGE_MASK);
                if (PAGE_SIZE - pgoff < xfsize)
                        xfsize = PAGE_SIZE - pgoff;
                if (nbytes && xfsize > (nbytes - *sbytes))
                        xfsize = nbytes - *sbytes;
                if (xfsize <= 0)
                        break;
                /*
                 * Optimize the non-blocking case by looking at the socket space
                 * before going to the extra work of constituting the sf_buf.
                 */
                if ((fp->f_flag & FNONBLOCK) && ssb_space(&so->so_snd) <= 0) {
                        if (so->so_state & SS_CANTSENDMORE)
                                error = EPIPE;
                        else
                                error = EAGAIN;
                        ssb_unlock(&so->so_snd);
                        goto done;
                }
                /*
                 * Attempt to look up the page.  
                 *
                 *      Allocate if not found, wait and loop if busy, then
                 *      wire the page.  critical section protection is
                 *      required to maintain the object association (an
                 *      interrupt can free the page) through to the
                 *      vm_page_wire() call.
                 */
                lwkt_gettoken(&vm_token);
                pg = vm_page_lookup(obj, pindex);
                if (pg == NULL) {
                        pg = vm_page_alloc(obj, pindex, VM_ALLOC_NORMAL);
                        if (pg == NULL) {
                                vm_wait(0);
                                lwkt_reltoken(&vm_token);
                                goto retry_lookup;
                        }
                        vm_page_wire(pg);
                        vm_page_wakeup(pg);
                } else if (vm_page_sleep_busy(pg, TRUE, "sfpbsy")) {
                        lwkt_reltoken(&vm_token);
                        goto retry_lookup;
                } else {
                        vm_page_wire(pg);
                }
                lwkt_reltoken(&vm_token);

                /*
                 * If page is not valid for what we need, initiate I/O
                 */

                if (!pg->valid || !vm_page_is_valid(pg, pgoff, xfsize)) {
                        struct uio auio;
                        struct iovec aiov;
                        int bsize;

                        /*
                         * Ensure that our page is still around when the I/O 
                         * completes.
                         */
                        vm_page_io_start(pg);

                        /*
                         * Get the page from backing store.
                         */
                        bsize = vp->v_mount->mnt_stat.f_iosize;
                        auio.uio_iov = &aiov;
                        auio.uio_iovcnt = 1;
                        aiov.iov_base = 0;
                        aiov.iov_len = MAXBSIZE;
                        auio.uio_resid = MAXBSIZE;
                        auio.uio_offset = trunc_page(off);
                        auio.uio_segflg = UIO_NOCOPY;
                        auio.uio_rw = UIO_READ;
                        auio.uio_td = td;
                        vn_lock(vp, LK_SHARED | LK_RETRY);
                        error = VOP_READ(vp, &auio, 
                                    IO_VMIO | ((MAXBSIZE / bsize) << 16),
                                    td->td_ucred);
                        vn_unlock(vp);
                        vm_page_flag_clear(pg, PG_ZERO);
                        vm_page_io_finish(pg);
                        if (error) {
                                crit_enter();
                                vm_page_unwire(pg, 0);
                                vm_page_try_to_free(pg);
                                crit_exit();
                                ssb_unlock(&so->so_snd);
                                goto done;
                        }
                }


                /*
                 * Get a sendfile buf. We usually wait as long as necessary,
                 * but this wait can be interrupted.
                 */
                if ((sf = sf_buf_alloc(pg)) == NULL) {
                        crit_enter();
                        vm_page_unwire(pg, 0);
                        vm_page_try_to_free(pg);
                        crit_exit();
                        ssb_unlock(&so->so_snd);
                        error = EINTR;
                        goto done;
                }

                /*
                 * Get an mbuf header and set it up as having external storage.
                 */
                MGETHDR(m, MB_WAIT, MT_DATA);
                if (m == NULL) {
                        error = ENOBUFS;
                        sf_buf_free(sf);
                        ssb_unlock(&so->so_snd);
                        goto done;
                }

                m->m_ext.ext_free = sf_buf_mfree;
                m->m_ext.ext_ref = sf_buf_ref;
                m->m_ext.ext_arg = sf;
                m->m_ext.ext_buf = (void *)sf_buf_kva(sf);
                m->m_ext.ext_size = PAGE_SIZE;
                m->m_data = (char *)sf_buf_kva(sf) + pgoff;
                m->m_flags |= M_EXT;
                m->m_pkthdr.len = m->m_len = xfsize;
                KKASSERT((m->m_flags & (M_EXT_CLUSTER)) == 0);

                if (mheader != NULL) {
                        hbytes = mheader->m_pkthdr.len;
                        mheader->m_pkthdr.len += m->m_pkthdr.len;
                        m_cat(mheader, m);
                        m = mheader;
                        mheader = NULL;
                } else
                        hbytes = 0;

                /*
                 * Add the buffer to the socket buffer chain.
                 */
                crit_enter();
retry_space:
                /*
                 * Make sure that the socket is still able to take more data.
                 * CANTSENDMORE being true usually means that the connection
                 * was closed. so_error is true when an error was sensed after
                 * a previous send.
                 * The state is checked after the page mapping and buffer
                 * allocation above since those operations may block and make
                 * any socket checks stale. From this point forward, nothing
                 * blocks before the pru_send (or more accurately, any blocking
                 * results in a loop back to here to re-check).
                 */
                if ((so->so_state & SS_CANTSENDMORE) || so->so_error) {
                        if (so->so_state & SS_CANTSENDMORE) {
                                error = EPIPE;
                        } else {
                                error = so->so_error;
                                so->so_error = 0;
                        }
                        m_freem(m);
                        ssb_unlock(&so->so_snd);
                        crit_exit();
                        goto done;
                }
                /*
                 * Wait for socket space to become available. We do this just
                 * after checking the connection state above in order to avoid
                 * a race condition with ssb_wait().
                 */
                if (ssb_space(&so->so_snd) < so->so_snd.ssb_lowat) {
                        if (fp->f_flag & FNONBLOCK) {
                                m_freem(m);
                                ssb_unlock(&so->so_snd);
                                crit_exit();
                                error = EAGAIN;
                                goto done;
                        }
                        error = ssb_wait(&so->so_snd);
                        /*
                         * An error from ssb_wait 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) {
                                m_freem(m);
                                ssb_unlock(&so->so_snd);
                                crit_exit();
                                goto done;
                        }
                        goto retry_space;
                }
                error = so_pru_send(so, 0, m, NULL, NULL, td);
                crit_exit();
                if (error) {
                        ssb_unlock(&so->so_snd);
                        goto done;
                }
        }
        if (mheader != NULL) {
                *sbytes += mheader->m_pkthdr.len;
                error = so_pru_send(so, 0, mheader, NULL, NULL, td);
                mheader = NULL;
        }
        ssb_unlock(&so->so_snd);

done:
        fdrop(fp);
done0:
        if (mheader != NULL)
                m_freem(mheader);
        return (error);
}

/*
 * MPALMOSTSAFE
 */
int
sys_sctp_peeloff(struct sctp_peeloff_args *uap)
{
#ifdef SCTP
        struct thread *td = curthread;
        struct filedesc *fdp = td->td_proc->p_fd;
        struct file *lfp = NULL;
        struct file *nfp = NULL;
        int error;
        struct socket *head, *so;
        caddr_t assoc_id;
        int fd;
        short fflag;            /* type must match fp->f_flag */

        assoc_id = uap->name;
        error = holdsock(td->td_proc->p_fd, uap->sd, &lfp);
        if (error)
                return (error);

        crit_enter();
        head = (struct socket *)lfp->f_data;
        error = sctp_can_peel_off(head, assoc_id);
        if (error) {
                crit_exit();
                goto done;
        }
        /*
         * At this point we know we do have a assoc to pull
         * we proceed to get the fd setup. This may block
         * but that is ok.
         */

        fflag = lfp->f_flag;
        error = falloc(td->td_lwp, &nfp, &fd);
        if (error) {
                /*
                 * Probably ran out of file descriptors. Put the
                 * unaccepted connection back onto the queue and
                 * do another wakeup so some other process might
                 * have a chance at it.
                 */
                crit_exit();
                goto done;
        }
        uap->sysmsg_iresult = fd;

        so = sctp_get_peeloff(head, assoc_id, &error);
        if (so == NULL) {
                /*
                 * Either someone else peeled it off OR
                 * we can't get a socket.
                 */
                goto noconnection;
        }
        soreference(so);                        /* reference needed */
        soclrstate(so, SS_NOFDREF | SS_COMP);   /* when clearing NOFDREF */
        so->so_head = NULL;
        if (head->so_sigio != NULL)
                fsetown(fgetown(&head->so_sigio), &so->so_sigio);

        nfp->f_type = DTYPE_SOCKET;
        nfp->f_flag = fflag;
        nfp->f_ops = &socketops;
        nfp->f_data = so;

noconnection:
        /*
         * Assign the file pointer to the reserved descriptor, or clear
         * the reserved descriptor if an error occured.
         */
        if (error)
                fsetfd(fdp, NULL, fd);
        else
                fsetfd(fdp, nfp, fd);
        crit_exit();
        /*
         * Release explicitly held references before returning.
         */
done:
        if (nfp != NULL)
                fdrop(nfp);
        fdrop(lfp);
        return (error);
#else /* SCTP */
        return(EOPNOTSUPP);
#endif /* SCTP */
}