net: sctp: implement rfc6458, 5.3.6. SCTP_NXTINFO cmsg support
This patch implements section 5.3.6. of RFC6458, that is, support
for 'SCTP Next Receive Information Structure' (SCTP_NXTINFO) which
is placed into ancillary data cmsghdr structure for each recvmsg()
call, if this information is already available when delivering the
current message.
This option can be enabled/disabled via setsockopt(2) on SOL_SCTP
level by setting an int value with 1/0 for SCTP_RECVNXTINFO in
user space applications as per RFC6458, section 8.1.30.
The sctp_nxtinfo structure is defined as per RFC as below ...
struct sctp_nxtinfo {
uint16_t nxt_sid;
uint16_t nxt_flags;
uint32_t nxt_ppid;
uint32_t nxt_length;
sctp_assoc_t nxt_assoc_id;
};
... and provided under cmsg_level IPPROTO_SCTP, cmsg_type
SCTP_NXTINFO, while cmsg_data[] contains struct sctp_nxtinfo.
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>
diff --git a/net/sctp/ulpevent.c b/net/sctp/ulpevent.c
index b31f365..e049298 100644
--- a/net/sctp/ulpevent.c
+++ b/net/sctp/ulpevent.c
@@ -911,6 +911,44 @@
sizeof(rinfo), &rinfo);
}
+/* RFC6458, Section 5.3.6. SCTP Next Receive Information Structure
+ * (SCTP_NXTINFO)
+ */
+static void __sctp_ulpevent_read_nxtinfo(const struct sctp_ulpevent *event,
+ struct msghdr *msghdr,
+ const struct sk_buff *skb)
+{
+ struct sctp_nxtinfo nxtinfo;
+
+ memset(&nxtinfo, 0, sizeof(nxtinfo));
+ nxtinfo.nxt_sid = event->stream;
+ nxtinfo.nxt_ppid = event->ppid;
+ nxtinfo.nxt_flags = event->flags;
+ if (sctp_ulpevent_is_notification(event))
+ nxtinfo.nxt_flags |= SCTP_NOTIFICATION;
+ nxtinfo.nxt_length = skb->len;
+ nxtinfo.nxt_assoc_id = sctp_assoc2id(event->asoc);
+
+ put_cmsg(msghdr, IPPROTO_SCTP, SCTP_NXTINFO,
+ sizeof(nxtinfo), &nxtinfo);
+}
+
+void sctp_ulpevent_read_nxtinfo(const struct sctp_ulpevent *event,
+ struct msghdr *msghdr,
+ struct sock *sk)
+{
+ struct sk_buff *skb;
+ int err;
+
+ skb = sctp_skb_recv_datagram(sk, MSG_PEEK, 1, &err);
+ if (skb != NULL) {
+ __sctp_ulpevent_read_nxtinfo(sctp_skb2event(skb),
+ msghdr, skb);
+ /* Just release refcount here. */
+ kfree_skb(skb);
+ }
+}
+
/* Do accounting for bytes received and hold a reference to the association
* for each skb.
*/