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Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" $FreeBSD$ 33.\" 34.Dd December 15, 2006 35.Dt SCTP_SEND 3 36.Os 37.Sh NAME 38.Nm sctp_send , 39.Nm sctp_sendx 40.Nd send a message from an SCTP socket 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.In sys/types.h 45.In sys/socket.h 46.In netinet/sctp.h 47.Ft ssize_t 48.Fo sctp_send 49.Fa "int sd" "const void *msg" "size_t len" 50.Fa "const struct sctp_sndrcvinfo *sinfo" "int flags" 51.Fc 52.Ft ssize_t 53.Fo sctp_sendx 54.Fa "int sd" "const void *msg" "size_t len" "struct sockaddr *addrs" 55.Fa "int addrcnt" "const struct sctp_sndrcvinfo *sinfo" "int flags" 56.Fc 57.Sh DESCRIPTION 58The 59.Fn sctp_send 60system call 61is used to transmit a message to another SCTP endpoint. 62.Fn sctp_send 63may be used to send data to an existing association for both 64one-to-many (SOCK_SEQPACKET) and one-to-one (SOCK_STREAM) socket types. 65The length of the message 66.Fa msg 67is given by 68.Fa len . 69If the message is too long to pass atomically through the 70underlying protocol, 71.Va errno 72is set to 73.Er EMSGSIZE , 74-1 is returned, and 75the message is not transmitted. 76.Pp 77No indication of failure to deliver is implicit in a 78.Fn sctp_send 79Locally detected errors are indicated by a return value of -1. 80.Pp 81If no messages space is available at the socket to hold 82the message to be transmitted, then 83.Fn sctp_send 84normally blocks, unless the socket has been placed in 85non-blocking I/O mode. 86The 87.Xr select 2 88system call may be used to determine when it is possible to 89send more data on one-to-one type (SOCK_STREAM) sockets. 90.Pp 91The 92.Fa sinfo 93structure is used to control various SCTP features 94and has the following format: 95.Bd -literal 96struct sctp_sndrcvinfo { 97 u_int16_t sinfo_stream; /* Stream sending to */ 98 u_int16_t sinfo_ssn; /* valid for recv only */ 99 u_int16_t sinfo_flags; /* flags to control sending */ 100 u_int32_t sinfo_ppid; /* ppid field */ 101 u_int32_t sinfo_context; /* context field */ 102 u_int32_t sinfo_timetolive; /* timetolive for PR-SCTP */ 103 u_int32_t sinfo_tsn; /* valid for recv only */ 104 u_int32_t sinfo_cumtsn; /* valid for recv only */ 105 sctp_assoc_t sinfo_assoc_id; /* The association id */ 106}; 107.Ed 108.Pp 109The 110.Fa sinfo->sinfo_ppid 111argument is an opaque 32 bit value that is passed transparently 112through the stack to the peer endpoint. It will be available on 113reception of a message (see 114.Xr sctp_recvmsg 2 115). 116Note that the stack passes this value without regard to byte 117order. 118.Pp 119The 120.Fa sinfo->sinfo_flags 121argument may include one or more of the following: 122.Bd -literal 123#define SCTP_EOF 0x0100 /* Start a shutdown procedures */ 124#define SCTP_ABORT 0x0200 /* Send an ABORT to peer */ 125#define SCTP_UNORDERED 0x0400 /* Message is un-ordered */ 126#define SCTP_ADDR_OVER 0x0800 /* Override the primary-address */ 127#define SCTP_SENDALL 0x1000 /* Send this on all associations */ 128 /* for the endpoint */ 129/* The lower byte is an enumeration of PR-SCTP policies */ 130#define SCTP_PR_SCTP_TTL 0x0001 /* Time based PR-SCTP */ 131#define SCTP_PR_SCTP_BUF 0x0002 /* Buffer based PR-SCTP */ 132#define SCTP_PR_SCTP_RTX 0x0003 /* Number of retransmissions based PR-SCTP */ 133.Ed 134.Pp 135The flag 136.Dv SCTP_EOF 137is used to instruct the SCTP stack to queue this message 138and then start a graceful shutdown of the association. 139All 140remaining data in queue will be sent after which the association 141will be shut down. 142.Pp 143.Dv SCTP_ABORT 144is used to immediately terminate an association. 145An abort 146is sent to the peer and the local TCB is destroyed. 147.Pp 148.Dv SCTP_UNORDERED 149is used to specify that the message being sent has no 150specific order and should be delivered to the peer application 151as soon as possible. 152When this flag is absent messages 153are delivered in order within the stream they are sent, but without 154respect to order to peer streams. 155.Pp 156The flag 157.Dv SCTP_ADDR_OVER 158is used to specify that a specific address should be used. 159Normally 160SCTP will use only one of a multi-homed peers addresses as the primary 161address to send to. 162By default, no matter what the 163.Fa to 164argument is, this primary address is used to send data. 165By specifying 166this flag, the user is asking the stack to ignore the primary address 167and instead use the specified address not only as a lookup mechanism 168to find the association but also as the actual address to send to. 169.Pp 170For a one-to-many type (SOCK_SEQPACKET) socket the flag 171.Dv SCTP_SENDALL 172can be used as a convenient way to make one send call and have 173all associations that are under the socket get a copy of the message. 174Note that this mechanism is quite efficent and makes only one actual 175copy of the data which is shared by all the associations for sending. 176.Pp 177The remaining flags are used for the partial reliabilty extension (RFC3758) 178and will only be effective if the peer endpoint supports this extension. 179This option specifies what local policy the local endpoint should use 180in skipping data. 181If none of these options are set, then data is 182never skipped over. 183.Pp 184.Dv SCTP_PR_SCTP_TTL 185Is used to indicate that a time based lifetime is being applied 186to the data. 187The 188.Fa sinfo->sinfo_timetolive 189argument is then a number of milliseconds for which the data is 190attempted to be transmitted. 191If that many milliseconds ellapse 192and the peer has not acknowledged the data, the data will be 193skipped and no longer transmitted. 194Note that this policy does 195not even assure that the data will ever be sent. 196In times of a congestion 197with large amounts of data being queued, the 198.Fa sinfo->sinfo_timetolive 199may expire before the first transmission is ever made. 200.Pp 201The 202.Dv SCTP_PR_SCTP_BUF 203based policy transforms the 204.Fa sinfo->sinfo_timetolive 205field into a total number of bytes allowed on the outbound 206send queue. 207If that number or more bytes are in queue, then 208other buffer-based sends are looked to be removed and 209skipped. Note that this policy may also result in the data 210never being sent if no buffer based sends are in queue and 211the maximum specified by 212.Fa timetolive 213bytes is in queue. 214.Pp 215The 216.Dv SCTP_PR_SCTP_RTX 217policy transforms the 218.Fa sinfo->sinfo_timetolive 219into a number of retransmissions to allow. 220This policy 221always assures that at a minimum one send attempt is 222made of the data. 223After which no more than 224.Fa sinfo->sinfo_timetolive 225retransmissions will be made before the data is skipped. 226.Pp 227.Fa sinfo->sinfo_stream 228is the SCTP stream that you wish to send the 229message on. 230Streams in SCTP are reliable (or partially reliable) flows of ordered 231messages. 232.Pp 233The 234.Fa sinfo->sinfo_assoc_id 235field is used to 236select the association to send to on an one-to-many socket. 237For a one-to-one socket, this field is ignored. 238.Pp 239.Fa sinfo->sinfo_context 240field is used only in the event the message cannot be sent. 241This is an opaque 242value that the stack retains and will give to the user when a failed send 243is given if that notification is enabled (see 244.Xr sctp 4 245). 246Normally a user process can use this value to index some application 247specific data structure when a send cannot be fulfilled. 248.Pp 249The 250.Fa flags 251argument holds the same meaning and values as those found in 252.Xr sendmsg 2 253but is generally ignored by SCTP. 254.Pp 255The fields 256.Fa sinfo->sinfo_ssn , 257.Fa sinfo->sinfo_tsn , 258and 259.Fa sinfo->sinfo_cumtsn 260are used only when receiving messages and are thus ignored by 261.Fn sctp_send . 262The function 263.Fn sctp_sendx 264has the same properties as 265.Fn sctp_send 266with the additional arguments of an array of sockaddr structures 267passed in. 268With the 269.Fa addrs 270argument being given as an array of addresses to be sent to and 271the 272.Fa addrcnt 273argument indicating how many socket addresses are in the passed 274in array. 275Note that all of the addresses will only be used 276when an implicit association is being set up. 277This allows the 278user the equivilant behavior as doing a 279.Fn sctp_connectx 280followed by a 281.Fn sctp_send 282to the association. 283Note that if the 284.Fa sinfo->sinfo_assoc_id 285field is 0, then the first address will be used to look up 286the association in place of the association id. 287If both 288an address and an association id are specified, the association 289id has priority. 290.Sh RETURN VALUES 291The call returns the number of characters sent, or -1 292if an error occurred. 293.Sh ERRORS 294The 295.Fn sctp_send 296system call 297fail if: 298.Bl -tag -width Er 299.It Bq Er EBADF 300An invalid descriptor was specified. 301.It Bq Er ENOTSOCK 302The argument 303.Fa s 304is not a socket. 305.It Bq Er EFAULT 306An invalid user space address was specified for an argument. 307.It Bq Er EMSGSIZE 308The socket requires that message be sent atomically, 309and the size of the message to be sent made this impossible. 310.It Bq Er EAGAIN 311The socket is marked non-blocking and the requested operation 312would block. 313.It Bq Er ENOBUFS 314The system was unable to allocate an internal buffer. 315The operation may succeed when buffers become available. 316.It Bq Er ENOBUFS 317The output queue for a network interface was full. 318This generally indicates that the interface has stopped sending, 319but may be caused by transient congestion. 320.It Bq Er EHOSTUNREACH 321The remote host was unreachable. 322.It Bq Er ENOTCON 323On a one-to-one style socket no association exists. 324.It Bq Er ECONNRESET 325An abort was received by the stack while the user was 326attempting to send data to the peer. 327.It Bq Er ENOENT 328On a one-to-many style socket no address is specified 329so that the association cannot be located or the 330SCTP_ABORT flag was specified on a non-existing association. 331.It Bq Er EPIPE 332The socket is unable to send anymore data 333.Dv ( SBS_CANTSENDMORE 334has been set on the socket). 335This typically means that the socket 336is not connected and is a one-to-one style socket. 337.El 338.Sh SEE ALSO 339.Xr getsockopt 2 , 340.Xr recv 2 , 341.Xr select 2 , 342.Xr sendmsg 2 , 343.Xr socket 2 , 344.Xr write 2 345.Xr sctp_connectx 3 , 346.Xr sctp_recvmsg 3 , 347.Xr sctp_sendmsg 3 , 348.Xr sctp 4 349.Sh BUGS 350Because 351.Fn sctp_send 352may have multiple associations under one endpoint, a 353select on write will only work for a one-to-one style 354socket. 355