.\" Copyright (c) 1983, 1990, 1991 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.
.\" 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.
.\"
.\"     $Id: recv.2,v 1.8 2001/08/15 18:00:48 hanataka Exp $
.\"
.\" Modified Sat Jul 24 00:22:20 1993 by Rik Faith <faith@cs.unc.edu>
.\" Modified Tue Oct 22 17:45:19 1996 by Eric S. Raymond <esr@thyrsus.com>
.\" Modified 1998,1999 by Andi Kleen
.\" 2001-06-19 corrected SO_EE_OFFENDER, bug report by James Hawtin
.\"
.\" Japanese Version Copyright (c) 1996 Akira Yoshiyama
.\"         all rights reserved.
.\" Translated 1996-07-18, Akira Yoshiyama <yosshy@jedi.seg.kobe-u.ac.jp>
.\" Modified 1997-12-14, HANATAKA Shinya <hanataka@abyss.rim.or.jp>
.\" Modified 1999-08-14, HANATAKA Shinya <hanataka@abyss.rim.or.jp>
.\" Updated & Modified 2000-10-12, HAYAKAWA Hitoshi <cz8cb01@linux.or.jp>
.\"        and NAKANO Takeo <nakano@apm.seikei.ac.jp>
.\" Updated & Modified 2001-02-09, NAKANO Takeo
.\" Updated 2003-10-11, Kentaro Shirakata <argrath@ub32.org>
.\" Updated 2005-03-14, Akihiro MOTOKI <amotoki@dd.iij4u.or.jp>
.\" Updated 2006-04-15, Akihiro MOTOKI, Catch up to LDP v2.29
.\" Updated 2007-10-12, Akihiro MOTOKI, LDP v2.66
.\" Updated 2008-08-06, Akihiro MOTOKI, LDP v3.05
.\" Updated 2009-04-13, Akihiro MOTOKI, LDP v3.20
.\"
.\"WORD:	ancillary data		ǡ
.\"WORD:	ancillary message	å
.\"WORD:	invalid			
.\"
.TH RECV 2 2008-12-03 "Linux" "Linux Programmer's Manual"
.SH ̾
recv, recvfrom, recvmsg \- åȤå
.SH 
.\" .B #include <sys/uio.h>
.\" .br
.nf
.B #include <sys/types.h>
.br
.B #include <sys/socket.h>
.sp
.BI "ssize_t recv(int " sockfd ", void *" buf ", size_t " len ", int " flags );
.sp
.BI "ssize_t recvfrom(int " sockfd ", void *" buf ", size_t " len ", int " flags ,
.BI "                 struct sockaddr *" src_addr ", socklen_t *" addrlen );
.sp
.BI "ssize_t recvmsg(int " sockfd ", struct msghdr *" msg ", int " flags );
.fi
.SH 
.BR recvfrom ()

.BR recvmsg ()
ϡåȤåΤ˻Ѥ롣
ޤåȤΥǡˤȤȤǤ
ΤȤåȤ³ظ (connection-oriened) ǤäƤʤƤ褤
.PP
.I src_addr
 NULL ʳǡؤΥץȥ뤫ɥ쥹ʬ硢
.I src_addr
ˤϤɥ쥹롣
.I src_addr
 NULL ξ硢
.I src_addr
ˤϲʤξ硢
.I addrlen
ϻѤ줺ΰ NULL ˤƤ٤Ǥ롣
.\" (Unix ɥᥤȥ󥿡ͥåȥɥᥤΤɤΥǡॽåȤǤ
.\" .I src_addr
.\" ɥ쥹롣ޤUnix ɥᥤΥȥ꡼ॽåȤǤ
.\" Ʊͤ󥿡ͥåȥɥᥤΥȥ꡼ॽåȤǤ
.\" .I src_addr
.\" ˥ɥ쥹ʤ)
.\" [嵭 AF_UNIX  AF_INET åȤ˴ؤϥͥ 2.4.18 Ǥ
.\" ưƱǤ롣 (MTK, 22 Jul 02)]

.I addrlen
ξѤΰǤ롣ƤӽФˤϡƤӽФ
.I src_addr
˳ƤХåե礭ǽƤ٤Ǥ롣
֤äƤˤϡɥ쥹μºݤ礭ѹ롣
Ϥ줿Хåե᤮ˤϡ֤륢ɥ쥹
ڤͤ롣ξˤϡ
.I addrlen
ǤϡƤӽФϤ줿ͤ礭֤ͤ롣
.PP
.BR recv ()
̾
.I ³Ѥߤ (connected)
å
.RB ( connect (2)
򻲾) ˤĤƤΤ߻Ѥ졢
.I src_addr
 NULL ꤷ
.BR recvfrom ()
Ǥ롣
.PP
λĤΥ롼Ϥ⡢ˤϥåĹ֤
åĹ᤮ƻꤵ줿Хåեڤʤäˤϡ
ååȤμˤäƤ;ʬΥХȤΤƤ
⤷ʤ
.PP
åȤ˼å¸ߤʤä硢
ѤΥϥå夹ޤԤġ
åȤ (non-blocking)
ꤵƤ
.RB ( fcntl (2)
򻲾)  \-1 ֤ѿ
.I errno

.B EAGAIN

.B EWOULDBLOCK
ꤹ롣
μѤΥϡǡΥ׵ᤷ
ãޤԤĤΤǤϤʤ餫Υǡ
(ǡκ祵׵ᤷǤ)
.PP
.BR select (2)

.BR poll (2)
ȤäơΥǡϤȽǤǤ롣
.PP
.BR recv ()

.I flags
ˤϡʲͤ 1İʾ塢ӥåñ̤
.I OR ()
äΤꤹ:
.TP
.BR MSG_CMSG_CLOEXEC " (" recvmsg "() Τ; Linux 2.6.23)"
.RB ( unix (7)
Ƥ)
.B SCM_RIGHTS
Ȥä Unix ɥᥤΥեǥץͳǼ
եǥץˤĤ close-on-exec ե饰򥻥åȤ롣
Υե饰ϡ
.BR open (2)

.B O_CLOEXEC
ե饰ƱͳͭѤǤ롣
.TP
.BR MSG_DONTWAIT " (Linux 2.2 ʹ)"
 (non-blocking) ͭˤ롣
ߤ褦ʾ˥顼
.B EAGAIN

.B EWOULDBLOCK
ǸƤӽФԤ
.RB ( fcntl (2)

.B F_SETFL

.B O_NONBLOCK
ե饰ꤹ뤳ȤˤäƤͭˤǤ)
.TP
.BR MSG_ERRQUEUE " (Linux 2.2 ʹ)"
Υե饰ꤹȡ
塼줿顼򥽥åȤΥ顼塼褦ˤʤ롣
Υ顼åȤ߹ޤϤ졢
åμ̤ϥץȥ˰¸
(IPv4 ξ
.BR IP_RECVERR )
桼ϽʬʥΥХåեѰդʤФʤʤ
å˴ؤܺ٤ʾ
.BR cmsg (3)

.BR ip (7)
򻲾ȤΤȡ
顼θȤʤäꥸʥѥåȤΥڥɤϡ
.I msg_iovec
ͳ̾ΥǡȤϤ롣
顼򵯤ǡΥꥸʥΰ襢ɥ쥹ϡ
.I msg_name
ͳǻȤǤ롣
.IP
ʥ顼ξϥɥ쥹Ϥʤ
(
.I cmsghdr

.I cmsg_len
СǥåǤ)
顼ξ
.B MSG_ERRQUIE

.I msghdr
˥åȤ롣
顼Ϥ줿ˤϡ塼äƤ뼡Υ顼˴𤤤ơ
ԤΥåȡ顼졢ΥåκݤϤ롣

.IP
Υ顼
.I sock_extended_err
¤Τ󶡤:
.in +4n
.nf

#define SO_EE_ORIGIN_NONE    0
#define SO_EE_ORIGIN_LOCAL   1
#define SO_EE_ORIGIN_ICMP    2
#define SO_EE_ORIGIN_ICMP6   3

struct sock_extended_err
{
    uint32_t ee_errno;   /* error number */
    uint8_t  ee_origin;  /* where the error originated */
    uint8_t  ee_type;    /* type */
    uint8_t  ee_code;    /* code */
    uint8_t  ee_pad;     /* padding */
    uint32_t ee_info;    /* additional information */
    uint32_t ee_data;    /* other data */
    /* More data may follow */
};

struct sockaddr *SO_EE_OFFENDER(struct sock_extended_err *);
.fi
.in
.IP
.I ee_errno
ˤϥ塼줿顼
.I errno
äƤ롣
.I ee_origin
ˤϥ顼ȯΥꥸ󡦥 (origin code) äƤ롣
¾Υեɤϥץȥ¸Ǥ롣
.B SO_EE_OFFENDER
ޥϡŪʥå˼äơ
顼ȯͥåȥ֥ȤΥɥ쥹ؤΥݥ󥿤֤
ɥ쥹ξˤϡ
.I sockaddr

.I sa_family
С
.B AF_UNSPEC
ˤʤäƤ롣
.I sockaddr
¾ΥեɤǤ롣
顼ȯѥåȤΥڥɤ̾ΥǡȤϤ롣
.IP
ǤΥ顼ξˤϥɥ쥹Ϥʤ (
.I cmsghdr

.I cmsg_len
СǥåǤ)
顼ä硢
.B MSG_ERRQUEUE

.I msghdr
ꤵ롣
顼Ϥ줿ˤϡ
ԤˤʤäƤåȡ顼塼äƤ
Υ顼˴Ťƺ졢ΥåκݤϤ롣
.TP
.B MSG_OOB
Υե饰ϡ̾Υǡȥ꡼ǤϼǤʤ
Ӱ賰 (out-of-band) ǡμ׵᤹롣
ץȥˤäƤϡ
̾Υǡ塼Ƭ®ãǡ֤Τ뤬
Τ褦ʥץȥǤϤΥե饰ϻѤǤʤ
.TP
.B MSG_PEEK
Υե饰ꤹȡ
塼κǽΥǡ֤Ȥ塼ǡʤ
äơθǤ⤦ټƤӽФȡƱǡ֤뤳Ȥˤʤ롣
.TP
.BR MSG_TRUNC " (Linux 2.2 ʹ)"
raw å
.RB ( AF_PACKET )
Internet datagram  å (Linux 2.4.27/2.6.8 ʹ)
netlink (Linux 2.6.22 ʹ) åȤξ硢
ѥåȤǡĹϤХåեĹäˤ⡢
ѥåȤǡμºݤĹ֤
Unix ɥᥤ󥽥å
.RB ( unix (7))
åȤˤĤƤϼƤʤ

Internet ȥ꡼ॽåȤǤѤˤĤƤ
.BR tcp (7)
򻲾ȡ
.TP
.BR MSG_WAITALL " (Linux 2.2 ʹ)"
Υե饰ϡ׵ᤷ̤äѤΥǡ夹ޤǡ
 (block) 褦׵᤹롣
âʥꡢ顼 (disconnect) ȯꡢ
˼ǡۤʤ뷿äꤷˤϡ
׵ᤷ̤ǡʤƤ֤뤳Ȥ롣
.PP
.BR recvmsg ()
ϡľϤο򸺤餹
.I msghdr
¤ΤѤ롣ι¤Τ
.I <sys/socket.h>
ǰʲΤ褦Ƥ:
.in +4n
.nf

struct iovec {                    /* Scatter/gather array items */
    void  *iov_base;              /* Starting address */
    size_t iov_len;               /* Number of bytes to transfer */
};

struct msghdr {
    void         *msg_name;       /* optional address */
    socklen_t     msg_namelen;    /* size of address */
    struct iovec *msg_iov;        /* scatter/gather array */
    size_t        msg_iovlen;     /* # elements in msg_iov */
    void         *msg_control;    /* ancillary data, see below */
    socklen_t     msg_controllen; /* ancillary data buffer len */
    int           msg_flags;      /* flags on received message */
};
.fi
.in
.PP
.I msg_name

.I msg_namelen
ϡåȤ³ƤʤΥɥ쥹ꤹ롣
̾ɬפʤˤ
.I msg_name
 NULL ݥ󥿤ꤹ롣
.I msg_iov

.I msg_iovlen
եɤ
.BR readv (2)
˵ҤƤ褦ʬ/ѤΥ٥ȥ (scatter-gather locations)
ꤹ롣
.I msg_control
եɤ
.I msg_controllen
Ĺ¾Υץȥå
ǡΤΥХåեؤΥݥ󥿤Ǥ롣
.BR recvmsg ()
Ƥֺݤˤϡ
.I msg_controllen

.I msg_control
ΥХåեĹƤɬפ롣
뤬֤ä硢åĹäƤ롣
.PP
åηϰʲ̤:
.in +4n
.nf

struct cmsghdr {
    socklen_t     cmsg_len;     /* data byte count, including hdr */
    int           cmsg_level;   /* originating protocol */
    int           cmsg_type;    /* protocol-specific type */
/* followed by
    unsigned char cmsg_data[]; */
};
.fi
.in
.PP
ǡϡ
.BR cmsg (3)
줿ޥͳǤΤߥ٤Ǥ롣
.PP
򤢤ȡ Linux ϤǡΥᥫ˥
Unix åȾǤγĥ顼 IP ץ
ե롦ǥץμϤѤƤ롣
.PP
msghdr 
.I msg_flags
եɤ
.BR recvmsg ()
Υ꥿ꤵ롣ˤϤĤΥե饰롣
.TP
.B MSG_EOR
ϥ쥳ɤν (end-of-record) 򼨤
֤줿ǡʥ쥳ɤǤ뤳Ȥ򼨤 (Ūˤ
.B SOCK_SEQPACKET
ΥåȤǻѤ)
.TP
.B MSG_TRUNC
ǡबͿ줿Хåե礭äˡ
ǡΤϤ߽ФʬΤƤ줿Ȥ򼨤
.TP
.B MSG_CTRUNC
ǡΤΥХåե­ˡ
ǡΰΤƤ줿Ȥ򼨤
.TP
.B MSG_OOB
®ãǡӰ賰ǡȤ򼨤
.TP
.B MSG_ERRQUEUE
ǡϼʤä
åȤΥ顼塼ĥ顼Ȥ򼨤
.SH ֤
ΥϼХȿ֤
顼ξ \-1 ֤
³褬åȥ¹Ԥϡ֤ͤ 0 Ȥʤ롣
.SH 顼
ϥåؤȯŪʥ顼Ǥ롣
¾Υ顼ؤΥץȥ롦⥸塼졢
֤뤫⤷ʤ
Υޥ˥奢򻲾Ȥ뤳ȡ
.TP
.BR EAGAIN " ޤ " EWOULDBLOCK
.\" Actually EAGAIN on Linux
åȤ (non-blocking) ꤵƤ
ߤ褦ʾˤʤä
˻ڤ (timeout) ꤵƤ
ǡ˻ڤˤʤä
POSIX.1-2001 ϡξˤɤΥ顼֤ȤǧƤꡢ
 2 ĤƱͤĤȤƤʤ
äơܿɬפʥץꥱǤϡξβǽ
ǧ٤Ǥ롣
.TP
.B EBADF

.I sockfd
ʥǥץǤ롣
.TP
.B ECONNREFUSED
⡼ȤΥۥȤǥͥåȥ³ݤ줿
(褯ͳȤƤϡ׵ᤷӥưƤʤʤɤ)
.TP
.B EFAULT
ХåեؤΥݥ󥿤ץΥɥ쥹ֳؤƤ롣
.TP
.B EINTR
ǡˡʥ뤬Ƴޤ줿
.BR signal (7)
ȡ
.TP
.B EINVAL
ʰϤ줿
.\" e.g., msg_namelen < 0 for recvmsg() or addrlen < 0 for recvfrom()
.TP
.B ENOMEM
.BR recvmsg ()
ΤΥ꤬ݤǤʤä
.TP
.B ENOTCONN
åȤ³ظץȥ뤬ƤƤꡢ
ޤ³Ƥʤ
.RB ( connect (2)

.BR accept (2)
򻲾ȤΤ)
.TP
.B ENOTSOCK

.I sockfd
åȤ򻲾ȤƤʤ
.SH 
4.4BSD (δؿ 4.2BSD Ǹ줿), POSIX.1-2001
.LP
POSIX.1-2001 Ǥϡ
.BR MSG_OOB ,
.BR MSG_PEEK ,
.B MSG_WAITALL
ե饰ܤƤ롣
.SH 
嵭Υץȥפ glibc2 ˤäƤ롣
Single Unix Specification ǤƱͤ
֤ͤη \fIssize_t\fP ȤʤäƤ
( 4.x BSD  libc4  libc5  \fIint\fP ѤƤ)
.I flags
 4.x BSD Ǥ \fIint\fP libc4  libc5 Ǥ \fIunsigned int\fP Ǥ롣
.I len
 4.x BSD Ǥ \fIint\fP  libc4  libc5 Ǥ \fIsize_t\fP Ǥ롣
.I addrlen
 4.x BSD, libc4, libc5 Ǥ \fIint\ *\fP Ǥ롣
ߤ \fIsocklen_t\ *\fP  POSIX ȯƤ줿
.BR accept (2)
⻲Ȥ뤳ȡ

POSIX.1-2001 Ǥϡ¤
.I msghdr
Υե
.I msg_controllen

.I socklen_t
Ǥ٤ȤƤ뤬
ߤ glibc (glibc 2.4) Ǥ
.I size_t
Ǥ롣
.\" glibc bug raised 12 Mar 2006
.\" http://sourceware.org/bugzilla/show_bug.cgi?id=2448
.\" The problem is an underlying kernel issue: the size of the
.\" __kernel_size_t type used to type this field varies
.\" across architectures, but socklen_t is always 32 bits.
.SH 
.BR recvfrom ()
㤬
.BR getaddrinfo (3)
˵ܤƤ롣
.SH Ϣ
.BR fcntl (2),
.BR getsockopt (2),
.BR read (2),
.BR select (2),
.BR shutdown (2),
.BR socket (2),
.BR cmsg (3),
.BR sockatmark (3),
.BR socket (7)