sctp: add support for some msg_control options from RFC6458

This patchset is to add support for 3 msg_control options described in RFC6458:

5.3.7. SCTP PR-SCTP Information Structure (SCTP_PRINFO) 5.3.9. SCTP Destination IPv4 Address Structure (SCTP_DSTADDRV4) 5.3.10. SCTP Destination IPv6 Address Structure (SCTP_DSTADDRV6)

one send flag described in RFC6458:

SCTP_SENDALL: This flag, if set, will cause a one-to-many style socket to send the message to all associations that are currently established on this socket. For the one-to- one style socket, this flag has no effect.

Note there is another msg_control option:

5.3.8. SCTP AUTH Information Structure (SCTP_AUTHINFO)

It's a little complicated, I will post it in another patchset after this.

Xin Long (3):
sctp: add support for PR-SCTP Information for sendmsg
sctp: add support for SCTP_DSTADDRV4/6 Information for sendmsg
sctp: add support for snd flag SCTP_SENDALL process in sendmsg

 include/net/sctp/structs.h |   2 +
 include/uapi/linux/sctp.h  |  23 ++++++++
 net/sctp/socket.c          | 143 +++++++++++++++++++++++++++++++++++++++++++--
 3 files changed, 163 insertions(+), 5 deletions(-)

2.1.0