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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.Dd December 15, 2006 29.Dt SCTP_SEND 3 30.Os 31.Sh NAME 32.Nm sctp_send , 33.Nm sctp_sendx 34.Nd send a message from an SCTP socket 35.Sh LIBRARY 36.Lb libc 37.Sh SYNOPSIS 38.In sys/types.h 39.In sys/socket.h 40.In netinet/sctp.h 41.Ft ssize_t 42.Fo sctp_send 43.Fa "int sd" "const void *msg" "size_t len" 44.Fa "const struct sctp_sndrcvinfo *sinfo" "int flags" 45.Fc 46.Ft ssize_t 47.Fo sctp_sendx 48.Fa "int sd" "const void *msg" "size_t len" "struct sockaddr *addrs" 49.Fa "int addrcnt" "const struct sctp_sndrcvinfo *sinfo" "int flags" 50.Fc 51.Sh DESCRIPTION 52The 53.Fn sctp_send 54system call 55is used to transmit a message to another SCTP endpoint. 56.Fn sctp_send 57may be used to send data to an existing association for both 58one-to-many (SOCK_SEQPACKET) and one-to-one (SOCK_STREAM) socket types. 59The length of the message 60.Fa msg 61is given by 62.Fa len . 63If the message is too long to pass atomically through the 64underlying protocol, 65.Va errno 66is set to 67.Er EMSGSIZE , 68-1 is returned, and 69the message is not transmitted. 70.Pp 71No indication of failure to deliver is implicit in a 72.Fn sctp_send . 73Locally detected errors are indicated by a return value of -1. 74.Pp 75If no space is available at the socket to hold 76the message to be transmitted, then 77.Fn sctp_send 78normally blocks, unless the socket has been placed in 79non-blocking I/O mode. 80The 81.Xr select 2 82system call may be used to determine when it is possible to 83send more data on one-to-one type (SOCK_STREAM) sockets. 84.Pp 85The 86.Fa sinfo 87structure is used to control various SCTP features 88and has the following format: 89.Bd -literal 90struct sctp_sndrcvinfo { 91 uint16_t sinfo_stream; /* Stream sending to */ 92 uint16_t sinfo_ssn; /* valid for recv only */ 93 uint16_t sinfo_flags; /* flags to control sending */ 94 uint32_t sinfo_ppid; /* ppid field */ 95 uint32_t sinfo_context; /* context field */ 96 uint32_t sinfo_timetolive; /* timetolive for PR-SCTP */ 97 uint32_t sinfo_tsn; /* valid for recv only */ 98 uint32_t sinfo_cumtsn; /* valid for recv only */ 99 sctp_assoc_t sinfo_assoc_id; /* The association id */ 100}; 101.Ed 102.Pp 103The 104.Fa sinfo->sinfo_ppid 105argument is an opaque 32 bit value that is passed transparently 106through the stack to the peer endpoint. 107It will be available on reception of a message (see 108.Xr sctp_recvmsg 3 ) . 109Note that the stack passes this value without regard to byte 110order. 111.Pp 112The 113.Fa sinfo->sinfo_flags 114argument may include one or more of the following: 115.Bd -literal 116#define SCTP_EOF 0x0100 /* Start a shutdown procedures */ 117#define SCTP_ABORT 0x0200 /* Send an ABORT to peer */ 118#define SCTP_UNORDERED 0x0400 /* Message is un-ordered */ 119#define SCTP_ADDR_OVER 0x0800 /* Override the primary-address */ 120#define SCTP_SENDALL 0x1000 /* Send this on all associations */ 121 /* for the endpoint */ 122/* The lower byte is an enumeration of PR-SCTP policies */ 123#define SCTP_PR_SCTP_TTL 0x0001 /* Time based PR-SCTP */ 124#define SCTP_PR_SCTP_BUF 0x0002 /* Buffer based PR-SCTP */ 125#define SCTP_PR_SCTP_RTX 0x0003 /* Number of retransmissions based PR-SCTP */ 126.Ed 127.Pp 128The flag 129.Dv SCTP_EOF 130is used to instruct the SCTP stack to queue this message 131and then start a graceful shutdown of the association. 132All 133remaining data in queue will be sent after which the association 134will be shut down. 135.Pp 136.Dv SCTP_ABORT 137is used to immediately terminate an association. 138An abort 139is sent to the peer and the local TCB is destroyed. 140.Pp 141.Dv SCTP_UNORDERED 142is used to specify that the message being sent has no 143specific order and should be delivered to the peer application 144as soon as possible. 145When this flag is absent messages 146are delivered in order within the stream they are sent, but without 147respect to order to peer streams. 148.Pp 149The flag 150.Dv SCTP_ADDR_OVER 151is used to specify that a specific address should be used. 152Normally 153SCTP will use only one of a multi-homed peers addresses as the primary 154address to send to. 155By default, no matter what the 156.Fa to 157argument is, this primary address is used to send data. 158By specifying 159this flag, the user is asking the stack to ignore the primary address 160and instead use the specified address not only as a lookup mechanism 161to find the association but also as the actual address to send to. 162.Pp 163For a one-to-many type (SOCK_SEQPACKET) socket the flag 164.Dv SCTP_SENDALL 165can be used as a convenient way to make one send call and have 166all associations that are under the socket get a copy of the message. 167Note that this mechanism is quite efficient and makes only one actual 168copy of the data which is shared by all the associations for sending. 169.Pp 170The remaining flags are used for the partial reliability extension (RFC3758) 171and will only be effective if the peer endpoint supports this extension. 172This option specifies what local policy the local endpoint should use 173in skipping data. 174If none of these options are set, then data is 175never skipped over. 176.Pp 177.Dv SCTP_PR_SCTP_TTL 178is used to indicate that a time based lifetime is being applied 179to the data. 180The 181.Fa sinfo->sinfo_timetolive 182argument is then a number of milliseconds for which the data is 183attempted to be transmitted. 184If that many milliseconds elapse 185and the peer has not acknowledged the data, the data will be 186skipped and no longer transmitted. 187Note that this policy does 188not even assure that the data will ever be sent. 189In times of a congestion 190with large amounts of data being queued, the 191.Fa sinfo->sinfo_timetolive 192may expire before the first transmission is ever made. 193.Pp 194The 195.Dv SCTP_PR_SCTP_BUF 196based policy transforms the 197.Fa sinfo->sinfo_timetolive 198field into a total number of bytes allowed on the outbound 199send queue. 200If that number or more bytes are in queue, then 201other buffer-based sends are looked to be removed and 202skipped. 203Note that this policy may also result in the data 204never being sent if no buffer based sends are in queue and 205the maximum specified by 206.Fa timetolive 207bytes is in queue. 208.Pp 209The 210.Dv SCTP_PR_SCTP_RTX 211policy transforms the 212.Fa sinfo->sinfo_timetolive 213into a number of retransmissions to allow. 214This policy 215always assures that at a minimum one send attempt is 216made of the data. 217After which no more than 218.Fa sinfo->sinfo_timetolive 219retransmissions will be made before the data is skipped. 220.Pp 221.Fa sinfo->sinfo_stream 222is the SCTP stream that you wish to send the 223message on. 224Streams in SCTP are reliable (or partially reliable) flows of ordered 225messages. 226.Pp 227The 228.Fa sinfo->sinfo_assoc_id 229field is used to 230select the association to send to on a one-to-many socket. 231For a one-to-one socket, this field is ignored. 232.Pp 233The 234.Fa sinfo->sinfo_context 235field is used only in the event the message cannot be sent. 236This is an opaque 237value that the stack retains and will give to the user when a failed send 238is given if that notification is enabled (see 239.Xr sctp 4 ) . 240Normally a user process can use this value to index some application 241specific data structure when a send cannot be fulfilled. 242.Pp 243The 244.Fa flags 245argument holds the same meaning and values as those found in 246.Xr sendmsg 2 247but is generally ignored by SCTP. 248.Pp 249The fields 250.Fa sinfo->sinfo_ssn , 251.Fa sinfo->sinfo_tsn , 252and 253.Fa sinfo->sinfo_cumtsn 254are used only when receiving messages and are thus ignored by 255.Fn sctp_send . 256The function 257.Fn sctp_sendx 258has the same properties as 259.Fn sctp_send 260with the additional arguments of an array of sockaddr structures 261passed in. 262With the 263.Fa addrs 264argument being given as an array of addresses to be sent to and 265the 266.Fa addrcnt 267argument indicating how many socket addresses are in the passed 268in array. 269Note that all of the addresses will only be used 270when an implicit association is being set up. 271This allows the 272user the equivalent behavior as doing a 273.Fn sctp_connectx 274followed by a 275.Fn sctp_send 276to the association. 277Note that if the 278.Fa sinfo->sinfo_assoc_id 279field is 0, then the first address will be used to look up 280the association in place of the association id. 281If both 282an address and an association id are specified, the association 283id has priority. 284.Sh RETURN VALUES 285The call returns the number of characters sent, or -1 286if an error occurred. 287.Sh ERRORS 288The 289.Fn sctp_send 290system call 291fails if: 292.Bl -tag -width Er 293.It Bq Er EBADF 294An invalid descriptor was specified. 295.It Bq Er ENOTSOCK 296The argument 297.Fa s 298is not a socket. 299.It Bq Er EFAULT 300An invalid user space address was specified for an argument. 301.It Bq Er EMSGSIZE 302The socket requires that message be sent atomically, 303and the size of the message to be sent made this impossible. 304.It Bq Er EAGAIN 305The socket is marked non-blocking and the requested operation 306would block. 307.It Bq Er ENOBUFS 308The system was unable to allocate an internal buffer. 309The operation may succeed when buffers become available. 310.It Bq Er ENOBUFS 311The output queue for a network interface was full. 312This generally indicates that the interface has stopped sending, 313but may be caused by transient congestion. 314.It Bq Er EHOSTUNREACH 315The remote host was unreachable. 316.It Bq Er ENOTCONN 317On a one-to-one style socket no association exists. 318.It Bq Er ECONNRESET 319An abort was received by the stack while the user was 320attempting to send data to the peer. 321.It Bq Er ENOENT 322On a one-to-many style socket no address is specified 323so that the association cannot be located or the 324SCTP_ABORT flag was specified on a non-existing association. 325.It Bq Er EPIPE 326The socket is unable to send anymore data 327.Dv ( SBS_CANTSENDMORE 328has been set on the socket). 329This typically means that the socket 330is not connected and is a one-to-one style socket. 331.El 332.Sh SEE ALSO 333.Xr getsockopt 2 , 334.Xr recv 2 , 335.Xr select 2 , 336.Xr sendmsg 2 , 337.Xr socket 2 , 338.Xr write 2 , 339.Xr sctp_connectx 3 , 340.Xr sctp_recvmsg 3 , 341.Xr sctp_sendmsg 3 , 342.Xr sctp 4 343.Sh BUGS 344Because 345.Fn sctp_send 346may have multiple associations under one endpoint, a 347select on write will only work for a one-to-one style 348socket. 349