net: sctp: implement rfc6458, 8.1.31. SCTP_DEFAULT_SNDINFO support

This patch implements section 8.1.31. of RFC6458, which adds support
for setting/retrieving SCTP_DEFAULT_SNDINFO:

  Applications that wish to use the sendto() system call may wish
  to specify a default set of parameters that would normally be
  supplied through the inclusion of ancillary data. This socket
  option allows such an application to set the default sctp_sndinfo
  structure. The application that wishes to use this socket option
  simply passes the sctp_sndinfo structure (defined in Section 5.3.4)
  to this call. The input parameters accepted by this call include
  snd_sid, snd_flags, snd_ppid, and snd_context. The snd_flags
  parameter is composed of a bitwise OR of SCTP_UNORDERED, SCTP_EOF,
  and SCTP_SENDALL. The snd_assoc_id field specifies the association
  to which to apply the parameters. For a one-to-many style socket,
  any of the predefined constants are also allowed in this field.
  The field is ignored for one-to-one style sockets.

Joint work with Daniel Borkmann.

Signed-off-by: Geir Ola Vaagland <geirola@gmail.com>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/uapi/linux/sctp.h b/include/uapi/linux/sctp.h
index 222f82f..ce70fe6 100644
--- a/include/uapi/linux/sctp.h
+++ b/include/uapi/linux/sctp.h
@@ -97,6 +97,7 @@ typedef __s32 sctp_assoc_t;
 #define SCTP_PEER_ADDR_THLDS	31
 #define SCTP_RECVRCVINFO	32
 #define SCTP_RECVNXTINFO	33
+#define SCTP_DEFAULT_SNDINFO	34
 
 /* Internal Socket Options. Some of the sctp library functions are
  * implemented using these socket options.