BSD 4_3_Net_2 release

[unix-history] / usr / src / lib / libc / sys / recv.2

diff --git a/usr/src/lib/libc/sys/recv.2 b/usr/src/lib/libc/sys/recv.2
index bc91007..7847ca3 100644 (file)
--- a/usr/src/lib/libc/sys/recv.2
+++ b/usr/src/lib/libc/sys/recv.2
@@ -1,164 +1,263 @@
-.\" Copyright (c) 1983 Regents of the University of California.
-.\" All rights reserved.  The Berkeley software License Agreement
-.\" specifies the terms and conditions for redistribution.
+.\" Copyright (c) 1983, 1990, 1991 The Regents of the University of California.
+.\" All rights reserved.

 .\"
 .\"

-.\"    @(#)recv.2      5.1 (Berkeley) %G%
+.\" 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.

 .\"
 .\"

-.TH RECV 2 "7 July 1983"
-.UC 5
-.SH NAME
-recv, recvfrom, recvmsg \- receive a message from a socket
-.SH SYNOPSIS
-.nf
-.ft B
-#include <sys/types.h>
-#include <sys/socket.h>
-.PP
-.ft B
-cc = recv(s, buf, len, flags)
-int cc, s;
-char *buf;
-int len, flags;
-.PP
-.ft B
-cc = recvfrom(s, buf, len, flags, from, fromlen)
-int cc, s;
-char *buf;
-int len, flags;
-struct sockaddr *from;
-int *fromlen;
-.PP
-.ft B
-cc = recvmsg(s, msg, flags)
-int cc, s;
-struct msghdr msg[];
-int flags;
-.ft R
-.SH DESCRIPTION
-.IR Recv ,
-.IR recvfrom ,
+.\" 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.
+.\"
+.\"     @(#)recv.2     6.11 (Berkeley) 5/1/91
+.\"
+.Dd May 1, 1991
+.Dt RECV 2
+.Os BSD 4.3r
+.Sh NAME
+.Nm recv ,
+.Nm recvfrom ,
+.Nm recvmsg
+.Nd receive a message from a socket
+.Sh SYNOPSIS
+.Fd #include <sys/types.h>
+.Fd #include <sys/socket.h>
+.Ft int
+.Fn recv "int s" "void *buf" "int len" "int flags"
+.Ft int
+.Fn recvfrom "int s" "void *buf" "int len" "int flags" "struct sockaddr *from" "int *fromlen"
+.Ft int
+.Fn recvmsg "int s" "struct msghdr *msg" "int flags"
+.Sh DESCRIPTION
+.Fn Recvfrom

 and
 and

-.IR recvmsg
-are used to receive messages from a socket.
-.PP
-The 
-.I recv
-call may be used only on a 
-.I connected
-socket (see
-.IR connect (2)),
-while 
-.I recvfrom
-and 
-.I recvmsg
-may be used to receive data on a socket whether
-it is in a connected state or not.
-.PP
+.Fn recvmsg
+are used to receive messages from a socket,
+and may be used to receive data on a socket whether or not
+it is connection-oriented.
+.Pp

 If
 If

-.I from
-is non-zero, the source address of the message is filled in.
-.I Fromlen
+.Fa from
+is non-nil, and the socket is not connection-oriented,
+the source address of the message is filled in.
+.Fa Fromlen

 is a value-result parameter, initialized to the size of
 the buffer associated with
 is a value-result parameter, initialized to the size of
 the buffer associated with

-.IR from ,
+.Fa from ,

 and modified on return to indicate the actual size of the
 address stored there.
 and modified on return to indicate the actual size of the
 address stored there.

-The length of the message is returned in
-.IR cc .
+.Pp
+The 
+.Fn recv
+call is normally used only on a 
+.Em connected
+socket (see
+.Xr connect 2 )
+and is identical to
+.Fn recvfrom
+with a nil
+.Fa from
+parameter.
+As it is redundant, it may not be supported in future releases.
+.Pp
+All three routines return the length of the message on successful
+completion.

 If a message is too long to fit in the supplied buffer,
 excess bytes may be discarded depending on the type of socket
 If a message is too long to fit in the supplied buffer,
 excess bytes may be discarded depending on the type of socket

-the message is received from; see
-.IR socket (2).
-.PP
+the message is received from (see
+.Xr socket 2 ) .
+.Pp

 If no messages are available at the socket, the
 receive call waits for a message to arrive, unless
 the socket is nonblocking (see
 If no messages are available at the socket, the
 receive call waits for a message to arrive, unless
 the socket is nonblocking (see

-.IR ioctl (2))
-in which case a
-.I cc
-of \-1 is returned with the external variable errno
-set to EWOULDBLOCK.
-.PP
+.Xr fcntl 2 )
+in which case the value
+-1 is returned and the external variable
+.Va errno
+set to
+.Er EWOULDBLOCK.
+The receive calls normally return any data available,
+up to the requested amount,
+rather than waiting for receipt of the full amount requested;
+this behavior is affected by the socket-level options
+.Dv SO_RCVLOWAT
+and
+.Dv SO_RCVTIMEO
+described in
+.Xr getsockopt 2 .
+.Pp

 The
 The

-.IR select (2)
-call may be used to determine when more data arrives.
-.PP
+.Xr select 2
+call may be used to determine when more data arrive.
+.Pp

 The
 The

-.I flags
-argument to a send call is formed by 
-.IR or 'ing
-one or more of the values,
-.PP
-.nf
-.RS
-.DT
-#define        MSG_PEEK        0x1     /* peek at incoming message */
-#define        MSG_OOB 0x2     /* process out-of-band data */
-.RE
-.fi
-.PP
+.Fa flags
+argument to a recv call is formed by 
+.Em or Ap ing
+one or more of the values:
+.Bl -column MSG_WAITALL -offset indent
+.It Dv MSG_OOB Ta process out-of-band data
+.It Dv MSG_PEEK Ta peek at incoming message
+.It Dv MSG_WAITALL Ta wait for full request or error
+.El

 The
 The

-.I recvmsg
+.Dv MSG_OOB
+flag requests receipt of out-of-band data
+that would not be received in the normal data stream.
+Some protocols place expedited data at the head of the normal
+data queue, and thus this flag cannot be used with such protocols.
+The MSG_PEEK flag causes the receive operation to return data
+from the beginning of the receive queue without removing that
+data from the queue.
+Thus, a subsequent receive call will return the same data.
+The MSG_WAITALL flag requests that the operation block until
+the full request is satisfied.
+However, the call may still return less data than requested
+if a signal is caught, an error or disconnect occurs,
+or the next data to be received is of a different type than that returned.
+.Pp
+The
+.Fn recvmsg

 call uses a 
 call uses a 

-.I msghdr
+.Fa msghdr

 structure to minimize the number of directly supplied parameters.
 This structure has the following form, as defined in
 structure to minimize the number of directly supplied parameters.
 This structure has the following form, as defined in

-.IR <sys/socket.h> :
-.PP
-.nf
-.RS
-.DT
+.Ao Pa sys/socket.h Ac :
+.Pp
+.Bd -literal

 struct msghdr {
 struct msghdr {

-       caddr_t msg_name;               /* optional address */
-       int     msg_namelen;            /* size of address */
-       struct  iov *msg_iov;           /* scatter/gather array */
-       int     msg_iovlen;             /* # elements in msg_iov */
-       caddr_t msg_accrights;          /* access rights sent/received */
-       int     msg_accrightslen;
+       caddr_t msg_name;       /* optional address */
+       u_int   msg_namelen;    /* size of address */
+       struct  iovec *msg_iov; /* scatter/gather array */
+       u_int   msg_iovlen;     /* # elements in msg_iov */
+       caddr_t msg_control;    /* ancillary data, see below */
+       u_int   msg_controllen; /* ancillary data buffer len */
+       int     msg_flags;      /* flags on received message */

 };
 };

-.RE
-.fi
-.PP
+.Ed
+.Pp

 Here
 Here

-.I msg_name
+.Fa msg_name

 and
 and

-.I msg_namelen
+.Fa msg_namelen

 specify the destination address if the socket is unconnected;
 specify the destination address if the socket is unconnected;

-.I msg_name
+.Fa msg_name

 may be given as a null pointer if no names are desired or required.
 may be given as a null pointer if no names are desired or required.

-The 
-.I msg_iov
+.Fa Msg_iov

 and
 and

-.I msg_iovlen
-describe the scatter gather locations, as described in
-.IR read (2).
-Access rights to be sent along with the message are specified
-in 
-.IR msg_accrights ,
+.Fa msg_iovlen
+describe scatter gather locations, as discussed in
+.Xr read 2 .
+.Fa Msg_control ,

 which has length
 which has length

-.IR msg_accrightslen .
-.SH "RETURN VALUE
-These calls return the number of bytes received, or \-1
+.Fa msg_controllen ,
+points to a buffer for other protocol control related messages
+or other miscellaneous ancillary data.
+The messages are of the form:
+.Bd -literal
+struct cmsghdr {
+       u_int   cmsg_len;       /* data byte count, including hdr */
+       int     cmsg_level;     /* originating protocol */
+       int     cmsg_type;      /* protocol-specific type */
+/* followed by
+       u_char  cmsg_data[]; */
+};
+.Ed
+As an example, one could use this to learn of changes in the data-stream
+in XNS/SPP, or in ISO, to obtain user-connection-request data by requesting
+a recvmsg with no data buffer provided immediately after an
+.Fn accept
+call.
+.Pp
+Open file descriptors are now passed as ancillary data for
+.Dv AF_UNIX
+domain sockets, with
+.Fa cmsg_level
+set to
+.Dv SOL_SOCKET
+and
+.Fa cmsg_type
+set to
+.Dv SCM_RIGHTS .
+.Pp
+The
+.Fa msg_flags
+field is set on return according to the message received.
+.Dv MSG_EOR
+indicates end-of-record;
+the data returned completed a record (generally used with sockets of type
+.Dv SOCK_SEQPACKET ) .
+.Dv MSG_TRUNC
+indicates that
+the trailing portion of a datagram was discarded because the datagram
+was larger than the buffer supplied.
+.Dv MSG_CTRUNC
+indicates that some
+control data were discarded due to lack of space in the buffer
+for ancillary data.
+.Dv MSG_OOB
+is returned to indicate that expedited or out-of-band data were received.
+.Pp
+.Sh RETURN VALUES
+These calls return the number of bytes received, or -1

 if an error occurred.
 if an error occurred.

-.SH ERRORS
+.Sh ERRORS

 The calls fail if:
 The calls fail if:

-.TP 20
-[EBADF]
-The argument \fIs\fP is an invalid descriptor.
-.TP 20
-[ENOTSOCK]
-The argument \fIs\fP is not a socket.
-.TP 20
-[EWOULDBLOCK]
-The socket is marked non-blocking and the receive operation
-would block.
-.TP 20
-[EINTR]
+.Bl -tag -width EWOULDBLOCKAA
+.It Bq Er EBADF
+The argument
+.Fa s
+is an invalid descriptor.
+.It Bq Er ENOTCONN
+The socket is assoicated with a connection-oriented protocol
+and has not been connected (see
+.Xr connect 2
+and
+.Xr accept 2 ).
+.It Bq Er ENOTSOCK
+The argument
+.Fa s
+does not refer to a socket.
+.It Bq Er EWOULDBLOCK
+The socket is marked non-blocking, and the receive operation
+would block, or
+a receive timeout had been set,
+and the timeout expired before data were received.
+.It Bq Er EINTR

 The receive was interrupted by delivery of a signal before
 The receive was interrupted by delivery of a signal before

-any data was available for the receive.
-.TP 20
-[EFAULT]
-The data was specified to be received into a non-existent
-or protected part of the process address space.
-.SH SEE ALSO
-read(2), send(2), socket(2)
+any data were available.
+.It Bq Er EFAULT
+The receive buffer pointer(s) point outside the process's
+address space.
+.El
+.Sh SEE ALSO
+.Xr fcntl 2 ,
+.Xr read 2 ,
+.Xr select 2 ,
+.Xr getsockopt 2 ,
+.Xr socket 2
+.Sh HISTORY
+The
+.Nm
+function call appeared in
+.Bx 4.2 .