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