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Diffstat (limited to 'lib/libc/sys/accept.2')
-rw-r--r-- | lib/libc/sys/accept.2 | 186 |
1 files changed, 186 insertions, 0 deletions
diff --git a/lib/libc/sys/accept.2 b/lib/libc/sys/accept.2 new file mode 100644 index 0000000..df6c0b1 --- /dev/null +++ b/lib/libc/sys/accept.2 @@ -0,0 +1,186 @@ +.\" Copyright (c) 1983, 1990, 1991, 1993 +.\" The Regents of the University of California. 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. +.\" 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. +.\" +.\" @(#)accept.2 8.2 (Berkeley) 12/11/93 +.\" $FreeBSD$ +.\" +.Dd December 11, 1993 +.Dt ACCEPT 2 +.Os +.Sh NAME +.Nm accept +.Nd accept a connection on a socket +.Sh LIBRARY +.Lb libc +.Sh SYNOPSIS +.In sys/types.h +.In sys/socket.h +.Ft int +.Fn accept "int s" "struct sockaddr * restrict addr" "socklen_t * restrict addrlen" +.Sh DESCRIPTION +The argument +.Fa s +is a socket that has been created with +.Xr socket 2 , +bound to an address with +.Xr bind 2 , +and is listening for connections after a +.Xr listen 2 . +The +.Fn accept +system call extracts the first connection request on the +queue of pending connections, creates a new socket, +and allocates a new file descriptor for the socket which +inherits the state of the +.Dv O_NONBLOCK +property from the original socket +.Fa s . +.Pp +If no pending connections are +present on the queue, and the original socket +is not marked as non-blocking, +.Fn accept +blocks the caller until a connection is present. +If the original socket +is marked non-blocking and no pending +connections are present on the queue, +.Fn accept +returns an error as described below. +The accepted socket +may not be used +to accept more connections. +The original socket +.Fa s +remains open. +.Pp +The argument +.Fa addr +is a result argument that is filled-in with +the address of the connecting entity, +as known to the communications layer. +The exact format of the +.Fa addr +argument is determined by the domain in which the communication +is occurring. +A null pointer may be specified for +.Fa addr +if the address information is not desired; +in this case, +.Fa addrlen +is not used and should also be null. +Otherwise, the +.Fa addrlen +argument +is a value-result argument; it should initially contain the +amount of space pointed to by +.Fa addr ; +on return it will contain the actual length (in bytes) of the +address returned. +This call +is used with connection-based socket types, currently with +.Dv SOCK_STREAM . +.Pp +It is possible to +.Xr select 2 +a socket for the purposes of doing an +.Fn accept +by selecting it for read. +.Pp +For certain protocols which require an explicit confirmation, +such as +.Tn ISO +or +.Tn DATAKIT , +.Fn accept +can be thought of +as merely dequeueing the next connection +request and not implying confirmation. +Confirmation can be implied by a normal read or write on the new +file descriptor, and rejection can be implied by closing the +new socket. +.Pp +For some applications, performance may be enhanced by using an +.Xr accept_filter 9 +to pre-process incoming connections. +.Pp +Portable programs should not rely on the +.Dv O_NONBLOCK +property being inherited. +.Sh RETURN VALUES +The call returns \-1 on error. +If it succeeds, it returns a non-negative +integer that is a descriptor for the accepted socket. +.Sh ERRORS +The +.Fn accept +system call will fail if: +.Bl -tag -width Er +.It Bq Er EBADF +The descriptor is invalid. +.It Bq Er EINTR +The +.Fn accept +operation was interrupted. +.It Bq Er EMFILE +The per-process descriptor table is full. +.It Bq Er ENFILE +The system file table is full. +.It Bq Er ENOTSOCK +The descriptor references a file, not a socket. +.It Bq Er EINVAL +.Xr listen 2 +has not been called on the socket descriptor. +.It Bq Er EINVAL +The +.Fa addrlen +argument is negative. +.It Bq Er EFAULT +The +.Fa addr +argument is not in a writable part of the +user address space. +.It Bq Er EWOULDBLOCK +The socket is marked non-blocking and no connections +are present to be accepted. +.It Bq Er ECONNABORTED +A connection arrived, but it was closed while waiting +on the listen queue. +.El +.Sh SEE ALSO +.Xr bind 2 , +.Xr connect 2 , +.Xr getpeername 2 , +.Xr getsockname 2 , +.Xr listen 2 , +.Xr select 2 , +.Xr socket 2 , +.Xr accept_filter 9 +.Sh HISTORY +The +.Fn accept +system call appeared in +.Bx 4.2 . |