net: add option to enable error queue packets waking select

Currently, when a socket receives something on the error queue it only wakes up
the socket on select if it is in the "read" list, that is the socket has
something to read. It is useful also to wake the socket if it is in the error
list, which would enable software to wait on error queue packets without waking
up for regular data on the socket. The main use case is for receiving
timestamped transmit packets which return the timestamp to the socket via the
error queue. This enables an application to select on the socket for the error
queue only instead of for the regular traffic.

-v2-
* Added the SO_SELECT_ERR_QUEUE socket option to every architechture specific file
* Modified every socket poll function that checks error queue

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Cc: Jeffrey Kirsher <jeffrey.t.kirsher@intel.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Matthew Vick <matthew.vick@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

7 files changed, 22 insertions, 6 deletions

diff --git a/net/bluetooth/af_bluetooth.c b/net/bluetooth/af_bluetooth.c
index d3ee69b35a78..409902f892ff 100644
--- a/net/bluetooth/af_bluetooth.c
+++ b/net/bluetooth/af_bluetooth.c
@@ -422,7 +422,8 @@ unsigned int bt_sock_poll(struct file *file, struct socket *sock,
 		return bt_accept_poll(sk);
 
 	if (sk->sk_err || !skb_queue_empty(&sk->sk_error_queue))
-		mask |= POLLERR;
+		mask |= POLLERR |
+			sock_flag(sk, SOCK_SELECT_ERR_QUEUE) ? POLLPRI : 0;
 
 	if (sk->sk_shutdown & RCV_SHUTDOWN)
 		mask |= POLLRDHUP | POLLIN | POLLRDNORM;
diff --git a/net/core/datagram.c b/net/core/datagram.c
index 368f9c3f9dc6..36da5b663514 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -749,7 +749,9 @@ unsigned int datagram_poll(struct file *file, struct socket *sock,
 
 	/* exceptional events? */
 	if (sk->sk_err || !skb_queue_empty(&sk->sk_error_queue))
-		mask |= POLLERR;
+		mask |= POLLERR |
+			sock_flag(sk, SOCK_SELECT_ERR_QUEUE) ? POLLPRI : 0;
+
 	if (sk->sk_shutdown & RCV_SHUTDOWN)
 		mask |= POLLRDHUP | POLLIN | POLLRDNORM;
 	if (sk->sk_shutdown == SHUTDOWN_MASK)
diff --git a/net/core/sock.c b/net/core/sock.c
index a19e728d5fb6..2ff5f3619a8d 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -907,6 +907,10 @@ set_rcvbuf:
 		sock_valbool_flag(sk, SOCK_NOFCS, valbool);
 		break;
 
+	case SO_SELECT_ERR_QUEUE:
+		sock_valbool_flag(sk, SOCK_SELECT_ERR_QUEUE, valbool);
+		break;
+
 	default:
 		ret = -ENOPROTOOPT;
 		break;
@@ -1160,6 +1164,10 @@ int sock_getsockopt(struct socket *sock, int level, int optname,
 		v.val = sock_flag(sk, SOCK_FILTER_LOCKED);
 		break;
 
+	case SO_SELECT_ERR_QUEUE:
+		v.val = sock_flag(sk, SOCK_SELECT_ERR_QUEUE);
+		break;
+
 	default:
 		return -ENOPROTOOPT;
 	}
diff --git a/net/iucv/af_iucv.c b/net/iucv/af_iucv.c
index a7d11ffe4284..f0550a38f295 100644
--- a/net/iucv/af_iucv.c
+++ b/net/iucv/af_iucv.c
@@ -1461,7 +1461,8 @@ unsigned int iucv_sock_poll(struct file *file, struct socket *sock,
 		return iucv_accept_poll(sk);
 
 	if (sk->sk_err || !skb_queue_empty(&sk->sk_error_queue))
-		mask |= POLLERR;
+		mask |= POLLERR |
+			sock_flag(sk, SOCK_SELECT_ERR_QUEUE) ? POLLPRI : 0;
 
 	if (sk->sk_shutdown & RCV_SHUTDOWN)
 		mask |= POLLRDHUP;
diff --git a/net/nfc/llcp/sock.c b/net/nfc/llcp/sock.c
index f1b377e247fe..2d55e8a45958 100644
--- a/net/nfc/llcp/sock.c
+++ b/net/nfc/llcp/sock.c
@@ -521,7 +521,8 @@ static unsigned int llcp_sock_poll(struct file *file, struct socket *sock,
 		return llcp_accept_poll(sk);
 
 	if (sk->sk_err || !skb_queue_empty(&sk->sk_error_queue))
-		mask |= POLLERR;
+		mask |= POLLERR |
+			sock_flag(sk, SOCK_SELECT_ERR_QUEUE) ? POLLPRI : 0;
 
 	if (!skb_queue_empty(&sk->sk_receive_queue))
 		mask |= POLLIN | POLLRDNORM;
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index b9070736b8d9..dd21ae3013d8 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -6185,7 +6185,8 @@ unsigned int sctp_poll(struct file *file, struct socket *sock, poll_table *wait)
 
 	/* Is there any exceptional events?  */
 	if (sk->sk_err || !skb_queue_empty(&sk->sk_error_queue))
-		mask |= POLLERR;
+		mask |= POLLERR |
+			sock_flag(sk, SOCK_SELECT_ERR_QUEUE) ? POLLPRI : 0;
 	if (sk->sk_shutdown & RCV_SHUTDOWN)
 		mask |= POLLRDHUP | POLLIN | POLLRDNORM;
 	if (sk->sk_shutdown == SHUTDOWN_MASK)
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 971282b6f6a3..fb7a63ff71a5 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -2196,7 +2196,9 @@ static unsigned int unix_dgram_poll(struct file *file, struct socket *sock,
 
 	/* exceptional events? */
 	if (sk->sk_err || !skb_queue_empty(&sk->sk_error_queue))
-		mask |= POLLERR;
+		mask |= POLLERR |
+			sock_flag(sk, SOCK_SELECT_ERR_QUEUE) ? POLLPRI : 0;
+
 	if (sk->sk_shutdown & RCV_SHUTDOWN)
 		mask |= POLLRDHUP | POLLIN | POLLRDNORM;
 	if (sk->sk_shutdown == SHUTDOWN_MASK)