1.\" Copyright (c) 1983, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" From: @(#)send.2 8.2 (Berkeley) 2/21/94 29.\" $FreeBSD$ 30.\" 31.Dd December 15, 2006 32.Dt SCTP_SENDMSG 3 33.Os 34.Sh NAME 35.Nm sctp_sendmsg , 36.Nm sctp_sendmsgx 37.Nd send a message from an SCTP socket 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.In sys/types.h 42.In sys/socket.h 43.In netinet/sctp.h 44.Ft ssize_t 45.Fo sctp_sendmsg 46.Fa "int s" "const void *msg" "size_t len" "const struct sockaddr *to" 47.Fa "socklen_t tolen" "uint32_t ppid" "uint32_t flags" "uint16_t stream_no" 48.Fa "uint32_t timetolive" "uint32_t context" 49.Fc 50.Ft ssize_t 51.Fo sctp_sendmsgx 52.Fa "int s" "const void *msg" "size_t len" "const struct sockaddr *to" 53.Fa "int addrcnt" "uint32_t ppid" "uint32_t flags" "uint16_t stream_no" 54.Fa "uint32_t timetolive" "uint32_t context" 55.Fc 56.Sh DESCRIPTION 57The 58.Fn sctp_sendmsg 59system call 60is used to transmit a message to another SCTP endpoint. 61The 62.Fn sctp_sendmsg 63may be used at any time. 64If the socket is a one-to-many type (SOCK_SEQPACKET) 65socket then an attempt to send to an address that no association exists to will 66implicitly create a new association. 67Data sent in such an instance will result in 68the data being sent on the third leg of the SCTP four-way handshake. 69Note that if 70the socket is a one-to-one type (SOCK_STREAM) socket then an association must 71be in existence (by use of the 72.Xr connect 2 73system call). 74Calling 75.Fn sctp_sendmsg 76or 77.Fn sctp_sendmsgx 78on a non-connected one-to-one socket will result in 79.Va errno 80being set to 81.Er ENOTCONN , 82-1 being returned, and the message not being transmitted. 83.Pp 84The address of the target is given by 85.Fa to 86with 87.Fa tolen 88specifying its size. 89The length of the message 90.Fa msg 91is given by 92.Fa len . 93If the message is too long to pass atomically through the 94underlying protocol, 95.Va errno 96is set to 97.Er EMSGSIZE , 98-1 is returned, and 99the message is not transmitted. 100.Pp 101No indication of failure to deliver is implicit in a 102.Xr sctp_sendmsg 3 103call. 104Locally detected errors are indicated by a return value of -1. 105.Pp 106If no space is available at the socket to hold 107the message to be transmitted, then 108.Xr sctp_sendmsg 3 109normally blocks, unless the socket has been placed in 110non-blocking I/O mode. 111The 112.Xr select 2 113system call may be used to determine when it is possible to 114send more data on one-to-one type (SOCK_STREAM) sockets. 115.Pp 116The 117.Fa ppid 118argument is an opaque 32 bit value that is passed transparently 119through the stack to the peer endpoint. 120It will be available on 121reception of a message (see 122.Xr sctp_recvmsg 3 ) . 123Note that the stack passes this value without regard to byte 124order. 125.Pp 126The 127.Fa flags 128argument may include one or more of the following: 129.Bd -literal 130#define SCTP_EOF 0x0100 /* Start a shutdown procedures */ 131#define SCTP_ABORT 0x0200 /* Send an ABORT to peer */ 132#define SCTP_UNORDERED 0x0400 /* Message is un-ordered */ 133#define SCTP_ADDR_OVER 0x0800 /* Override the primary-address */ 134#define SCTP_SENDALL 0x1000 /* Send this on all associations */ 135 /* for the endpoint */ 136/* The lower byte is an enumeration of PR-SCTP policies */ 137#define SCTP_PR_SCTP_TTL 0x0001 /* Time based PR-SCTP */ 138#define SCTP_PR_SCTP_BUF 0x0002 /* Buffer based PR-SCTP */ 139#define SCTP_PR_SCTP_RTX 0x0003 /* Number of retransmissions based PR-SCTP */ 140.Ed 141.Pp 142The flag 143.Dv SCTP_EOF 144is used to instruct the SCTP stack to queue this message 145and then start a graceful shutdown of the association. 146All 147remaining data in queue will be sent after which the association 148will be shut down. 149.Pp 150.Dv SCTP_ABORT 151is used to immediately terminate an association. 152An abort 153is sent to the peer and the local TCB is destroyed. 154.Pp 155.Dv SCTP_UNORDERED 156is used to specify that the message being sent has no 157specific order and should be delivered to the peer application 158as soon as possible. 159When this flag is absent messages 160are delivered in order within the stream they are sent, but without 161respect to order to peer streams. 162.Pp 163The flag 164.Dv SCTP_ADDR_OVER 165is used to specify that an specific address should be used. 166Normally 167SCTP will use only one of a multi-homed peers addresses as the primary 168address to send to. 169By default, no matter what the 170.Fa to 171argument is, this primary address is used to send data. 172By specifying 173this flag, the user is asking the stack to ignore the primary address 174and instead use the specified address not only as a lookup mechanism 175to find the association but also as the actual address to send to. 176.Pp 177For a one-to-many type (SOCK_SEQPACKET) socket the flag 178.Dv SCTP_SENDALL 179can be used as a convenient way to make one send call and have 180all associations that are under the socket get a copy of the message. 181Note that this mechanism is quite efficient and makes only one actual 182copy of the data which is shared by all the associations for sending. 183.Pp 184The remaining flags are used for the partial reliability extension (RFC3758) 185and will only be effective if the peer endpoint supports this extension. 186This option specifies what local policy the local endpoint should use 187in skipping data. 188If none of these options are set, then data is 189never skipped over. 190.Pp 191.Dv SCTP_PR_SCTP_TTL 192is used to indicate that a time based lifetime is being applied 193to the data. 194The 195.Fa timetolive 196argument is then a number of milliseconds for which the data is 197attempted to be transmitted. 198If that many milliseconds elapse 199and the peer has not acknowledged the data, the data will be 200skipped and no longer transmitted. 201Note that this policy does 202not even assure that the data will ever be sent. 203In times of a congestion 204with large amounts of data being queued, the 205.Fa timetolive 206may expire before the first transmission is ever made. 207.Pp 208The 209.Dv SCTP_PR_SCTP_BUF 210based policy transforms the 211.Fa timetolive 212field into a total number of bytes allowed on the outbound 213send queue. 214If that number or more bytes are in queue, then 215other buffer based sends are looked to be removed and 216skipped. 217Note that this policy may also result in the data 218never being sent if no buffer based sends are in queue and 219the maximum specified by 220.Fa timetolive 221bytes is in queue. 222.Pp 223The 224.Dv SCTP_PR_SCTP_RTX 225policy transforms the 226.Fa timetolive 227into a number of retransmissions to allow. 228This policy 229always assures that at a minimum one send attempt is 230made of the data. 231After which no more than 232.Fa timetolive 233retransmissions will be made before the data is skipped. 234.Pp 235.Fa stream_no 236is the SCTP stream that you wish to send the 237message on. 238Streams in SCTP are reliable (or partially reliable) flows of ordered 239messages. 240The 241.Fa context 242field is used only in the event the message cannot be sent. 243This is an opaque 244value that the stack retains and will give to the user when a failed send 245is given if that notification is enabled (see 246.Xr sctp 4 ) . 247Normally a user process can use this value to index some application 248specific data structure when a send cannot be fulfilled. 249.Fn sctp_sendmsgx 250is identical to 251.Fn sctp_sendmsg 252with the exception that it takes an array of sockaddr structures in the 253argument 254.Fa to 255and adds the additional argument 256.Fa addrcnt 257which specifies how many addresses are in the array. 258This allows a 259caller to implicitly set up an association passing multiple addresses 260as if 261.Fn sctp_connectx 262had been called to set up the association. 263.Sh RETURN VALUES 264The call returns the number of characters sent, or -1 265if an error occurred. 266.Sh ERRORS 267The 268.Fn sctp_sendmsg 269system call 270fails if: 271.Bl -tag -width Er 272.It Bq Er EBADF 273An invalid descriptor was specified. 274.It Bq Er ENOTSOCK 275The argument 276.Fa s 277is not a socket. 278.It Bq Er EFAULT 279An invalid user space address was specified for an argument. 280.It Bq Er EMSGSIZE 281The socket requires that message be sent atomically, 282and the size of the message to be sent made this impossible. 283.It Bq Er EAGAIN 284The socket is marked non-blocking and the requested operation 285would block. 286.It Bq Er ENOBUFS 287The system was unable to allocate an internal buffer. 288The operation may succeed when buffers become available. 289.It Bq Er ENOBUFS 290The output queue for a network interface was full. 291This generally indicates that the interface has stopped sending, 292but may be caused by transient congestion. 293.It Bq Er EHOSTUNREACH 294The remote host was unreachable. 295.It Bq Er ENOTCONN 296On a one-to-one style socket no association exists. 297.It Bq Er ECONNRESET 298An abort was received by the stack while the user was 299attempting to send data to the peer. 300.It Bq Er ENOENT 301On a one-to-many style socket no address is specified 302so that the association cannot be located or the 303.Dv SCTP_ABORT 304flag was specified on a non-existing association. 305.It Bq Er EPIPE 306The socket is unable to send anymore data 307.Dv ( SBS_CANTSENDMORE 308has been set on the socket). 309This typically means that the socket 310is not connected and is a one-to-one style socket. 311.El 312.Sh SEE ALSO 313.Xr connect 2 , 314.Xr getsockopt 2 , 315.Xr recv 2 , 316.Xr select 2 , 317.Xr sendmsg 2 , 318.Xr socket 2 , 319.Xr write 2 , 320.Xr sctp_connectx 3 , 321.Xr sctp 4 322.Sh BUGS 323Because in the one-to-many style socket 324.Fn sctp_sendmsg 325or 326.Fn sctp_sendmsgx 327may have multiple associations under one endpoint, a 328select on write will only work for a one-to-one style 329socket. 330