net: sctp: implement rfc6458, 5.3.5. SCTP_RCVINFO cmsg support

This patch implements section 5.3.5. of RFC6458, that is, support
for 'SCTP Receive Information Structure' (SCTP_RCVINFO) which is
placed into ancillary data cmsghdr structure for each recvmsg()
call.

This option can be enabled/disabled via setsockopt(2) on SOL_SCTP
level by setting an int value with 1/0 for SCTP_RECVRCVINFO in user
space applications as per RFC6458, section 8.1.29.

The sctp_rcvinfo structure is defined as per RFC as below ...

  struct sctp_rcvinfo {
    uint16_t rcv_sid;
    uint16_t rcv_ssn;
    uint16_t rcv_flags;
    <-- 2 bytes hole  -->
    uint32_t rcv_ppid;
    uint32_t rcv_tsn;
    uint32_t rcv_cumtsn;
    uint32_t rcv_context;
    sctp_assoc_t rcv_assoc_id;
  };

... and provided under cmsg_level IPPROTO_SCTP, cmsg_type
SCTP_RCVINFO, while cmsg_data[] contains struct sctp_rcvinfo.
An sctp_rcvinfo item always corresponds to the data in msg_iov.

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>

2 files changed, 7 insertions, 1 deletions

diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index 7af9a0f5d8ce..11d5df015370 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -207,7 +207,9 @@ struct sctp_sock {
         struct sctp_paddrparams paddrparam;
         struct sctp_event_subscribe subscribe;
         struct sctp_assocparams assocparams;
+
         int user_frag;
+
         __u32 autoclose;
         __u8 nodelay;
         __u8 disable_fragments;
@@ -215,6 +217,7 @@ struct sctp_sock {
         __u8 frag_interleave;
         __u32 adaptation_ind;
         __u32 pd_point;
+        __u8 recvrcvinfo;
 
         atomic_t pd_mode;
         /* Receive to here while partial delivery is in effect. */
diff --git a/include/net/sctp/ulpevent.h b/include/net/sctp/ulpevent.h
index daacb32b55b5..e8095f973e94 100644
--- a/include/net/sctp/ulpevent.h
+++ b/include/net/sctp/ulpevent.h
@@ -129,7 +129,10 @@ struct sctp_ulpevent *sctp_ulpevent_make_sender_dry_event(
         const struct sctp_association *asoc, gfp_t gfp);
 
 void sctp_ulpevent_read_sndrcvinfo(const struct sctp_ulpevent *event,
-        struct msghdr *);
+                                   struct msghdr *);
+void sctp_ulpevent_read_rcvinfo(const struct sctp_ulpevent *event,
+                                struct msghdr *);
+
 __u16 sctp_ulpevent_get_notification_type(const struct sctp_ulpevent *event);
 
 /* Is this event type enabled? */