aef221ac80
Reviewed by: silby
232 lines
6.0 KiB
Groff
232 lines
6.0 KiB
Groff
.\" Copyright (c) 2003, David G. Lawrence
|
|
.\" 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 unmodified, this list of conditions, and the following
|
|
.\" disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd November 5, 1998
|
|
.Dt SENDFILE 2
|
|
.Os
|
|
.Sh NAME
|
|
.Nm sendfile
|
|
.Nd send a file to a socket
|
|
.Sh LIBRARY
|
|
.Lb libc
|
|
.Sh SYNOPSIS
|
|
.In sys/types.h
|
|
.In sys/socket.h
|
|
.In sys/uio.h
|
|
.Ft int
|
|
.Fn sendfile "int fd" "int s" "off_t offset" "size_t nbytes" "struct sf_hdtr *hdtr" "off_t *sbytes" "int flags"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn sendfile
|
|
system call
|
|
sends a regular file specified by descriptor
|
|
.Fa fd
|
|
out a stream socket specified by descriptor
|
|
.Fa s .
|
|
.Pp
|
|
The
|
|
.Fa offset
|
|
argument specifies where to begin in the file.
|
|
The
|
|
.Fa nbytes
|
|
argument specifies how many bytes of the file should be sent, with 0 having the special
|
|
meaning of send until the end of file has been reached.
|
|
.Pp
|
|
An optional header and/or trailer can be sent before and after the file data by specifying
|
|
a pointer to a struct sf_hdtr, which has the following structure:
|
|
.Pp
|
|
.Bd -literal -offset indent -compact
|
|
struct sf_hdtr {
|
|
struct iovec *headers; /* pointer to header iovecs */
|
|
int hdr_cnt; /* number of header iovecs */
|
|
struct iovec *trailers; /* pointer to trailer iovecs */
|
|
int trl_cnt; /* number of trailer iovecs */
|
|
};
|
|
.Ed
|
|
.Pp
|
|
The
|
|
.Fa headers
|
|
and
|
|
.Fa trailers
|
|
pointers, if non-NULL, point to arrays of struct iovec structures.
|
|
See the
|
|
.Fn writev
|
|
system call for information on the iovec structure.
|
|
The number of iovecs in these
|
|
arrays is specified by
|
|
.Fa hdr_cnt
|
|
and
|
|
.Fa trl_cnt .
|
|
.Pp
|
|
If non-NULL, the system will write the total number of bytes sent on the socket to the
|
|
variable pointed to by
|
|
.Fa sbytes .
|
|
.Pp
|
|
The
|
|
.Fa flags
|
|
argument is currently undefined and should be specified as 0.
|
|
.Pp
|
|
When using a socket marked for non-blocking I/O,
|
|
.Fn sendfile
|
|
may send fewer bytes than requested.
|
|
In this case, the number of bytes successfully
|
|
written is returned in
|
|
.Fa *sbytes
|
|
(if specified),
|
|
and the error
|
|
.Er EAGAIN
|
|
is returned.
|
|
.Sh IMPLEMENTATION NOTES
|
|
The
|
|
.Fx
|
|
implementation of
|
|
.Fn sendfile
|
|
is "zero-copy", meaning that it has been optimized so that copying of the file data is avoided.
|
|
.Sh TUNING
|
|
Internally, this system call uses a special
|
|
.Xr sendfile 2
|
|
buffer
|
|
.Pq Vt "struct sf_buf"
|
|
to handle sending file data to the client.
|
|
If the sending socket is
|
|
blocking, and there are not enough sendfile buffers available,
|
|
.Xr sendfile 2
|
|
will block and report a state of
|
|
.Dq Li sfbufa .
|
|
If the sending socket is non-blocking and there are not enough
|
|
sendfile buffers available, the call will block and wait for the
|
|
necessary buffers to become available before finishing the call.
|
|
.Pp
|
|
The number of
|
|
.Vt sf_buf Ns 's
|
|
allocated should be proportional to the number of nmbclusters used to
|
|
send data to a client via
|
|
.Xr sendfile 2 .
|
|
Tune accordingly to avoid blocking!
|
|
Busy installations that make extensive use of
|
|
.Xr sendfile 2
|
|
may want to increase these values to be inline with their
|
|
.Va kern.ipc.nmbclusters
|
|
(see
|
|
.Xr tuning 7
|
|
for details).
|
|
.Pp
|
|
The number of
|
|
.Xr sendfile 2
|
|
buffers in use is determined at boot time by either the
|
|
.Va kern.ipc.nsfbufs
|
|
.Xr loader.conf 5
|
|
variable or the
|
|
.Dv NSFBUFS
|
|
kernel configuration tunable.
|
|
The number of sendfile buffers scales with
|
|
.Va kern.maxusers .
|
|
.Va kern.ipc.nsfbufsused
|
|
and
|
|
.Va kern.ipc.nsfbufspeak
|
|
read-only sysctl variables show current and peak
|
|
.Xr sendfile 2
|
|
buffers usage respectively.
|
|
These values may also be viewed through
|
|
.Nm netstat Fl m .
|
|
.Sh RETURN VALUES
|
|
.Rv -std sendfile
|
|
.Sh ERRORS
|
|
.Bl -tag -width Er
|
|
.It Bq Er EBADF
|
|
The
|
|
.Fa fd
|
|
argument
|
|
is not a valid file descriptor.
|
|
.It Bq Er EBADF
|
|
The
|
|
.Fa s
|
|
argument
|
|
is not a valid socket descriptor.
|
|
.It Bq Er ENOTSOCK
|
|
The
|
|
.Fa s
|
|
argument
|
|
is not a socket.
|
|
.It Bq Er EINVAL
|
|
The
|
|
.Fa fd
|
|
argument
|
|
is not a regular file.
|
|
.It Bq Er EINVAL
|
|
The
|
|
.Fa s
|
|
argument
|
|
is not a SOCK_STREAM type socket.
|
|
.It Bq Er EINVAL
|
|
The
|
|
.Fa offset
|
|
argument
|
|
is negative or out of range.
|
|
.It Bq Er ENOTCONN
|
|
The
|
|
.Fa s
|
|
argument
|
|
points to an unconnected socket.
|
|
.It Bq Er EPIPE
|
|
The socket peer has closed the connection.
|
|
.It Bq Er EIO
|
|
An error occurred while reading from
|
|
.Fa fd .
|
|
.It Bq Er EFAULT
|
|
An invalid address was specified for an argument.
|
|
.It Bq Er EINTR
|
|
A signal interrupted sendfile before it could be completed. If specified, the number
|
|
of bytes successfully sent will be returned in
|
|
.Fa *sbytes .
|
|
.It Bq Er EAGAIN
|
|
The socket is marked for non-blocking I/O and not all data was sent due to the socket buffer being filled.
|
|
If specified, the number of bytes successfully sent will be returned in
|
|
.Fa *sbytes .
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr netstat 1 ,
|
|
.Xr open 2 ,
|
|
.Xr send 2 ,
|
|
.Xr socket 2 ,
|
|
.Xr writev 2 ,
|
|
.Xr tuning 7
|
|
.Sh HISTORY
|
|
The
|
|
.Fn sendfile
|
|
system call
|
|
first appeared in
|
|
.Fx 3.0 .
|
|
This manual page first appeared in
|
|
.Fx 3.1 .
|
|
.Sh AUTHORS
|
|
The
|
|
.Fn sendfile
|
|
system call
|
|
and this manual page were written by
|
|
.An David G. Lawrence Aq dg@dglawrence.com .
|