[PATCH] sctp: add support for busy polling to sctp protocol

[Neil Horman <nhorman@tuxdriver.com>]

The busy polling socket option adds support for sockets to busy wait on data
arriving on the napi queue from which they have most recently received a frame.
Currently only tcp and udp support this feature, but theres no reason sctp can't
do so as well.  Add it in so appliations can take advantage of it

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
CC: Vlad Yasevich <vyasevich@gmail.com>
CC: "David S. Miller" <davem@davemloft.net>
CC: Daniel Borkmann <dborkman@redhat.com>
CC: netdev@vger.kernel.org
---
 net/sctp/socket.c   | 5 +++++
 net/sctp/ulpqueue.c | 4 ++++
 2 files changed, 9 insertions(+)

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 981aaf8..9788e07 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -71,6 +71,7 @@
 #include <net/route.h>
 #include <net/ipv6.h>
 #include <net/inet_common.h>
+#include <net/busy_poll.h>
 
 #include <linux/socket.h> /* for sa_family_t */
 #include <linux/export.h>
@@ -6553,6 +6554,10 @@ static struct sk_buff *sctp_skb_recv_datagram(struct sock *sk, int flags,
 		if (sk->sk_shutdown & RCV_SHUTDOWN)
 			break;
 
+		if (sk_can_busy_loop(sk) &&
+		    sk_busy_loop(sk, noblock))
+			continue;
+
 		/* User doesn't want to wait.  */
 		error = -EAGAIN;
 		if (!timeo)
diff --git a/net/sctp/ulpqueue.c b/net/sctp/ulpqueue.c
index 5dc9411..a4df012 100644
--- a/net/sctp/ulpqueue.c
+++ b/net/sctp/ulpqueue.c
@@ -38,6 +38,7 @@
 #include <linux/types.h>
 #include <linux/skbuff.h>
 #include <net/sock.h>
+#include <net/busy_poll.h>
 #include <net/sctp/structs.h>
 #include <net/sctp/sctp.h>
 #include <net/sctp/sm.h>
@@ -204,6 +205,9 @@ int sctp_ulpq_tail_event(struct sctp_ulpq *ulpq, struct sctp_ulpevent *event)
 	if (sock_flag(sk, SOCK_DEAD) || (sk->sk_shutdown & RCV_SHUTDOWN))
 		goto out_free;
 
+	if (!sctp_ulpevent_is_notification(event))
+		sk_mark_napi_id(sk, skb);
+
 	/* Check if the user wishes to receive this event.  */
 	if (!sctp_ulpevent_is_enabled(event, &sctp_sk(sk)->subscribe))
 		goto out_free;
-- 
1.8.3.1