net: add wireless TX status socket option

The 802.1X EAPOL handshake hostapd does requires
knowing whether the frame was ack'ed by the peer.
Currently, we fudge this pretty badly by not even
transmitting the frame as a normal data frame but
injecting it with radiotap and getting the status
out of radiotap monitor as well. This is rather
complex, confuses users (mon.wlan0 presence) and
doesn't work with all hardware.

To get rid of that hack, introduce a real wifi TX
status option for data frame transmissions.

This works similar to the existing TX timestamping
in that it reflects the SKB back to the socket's
error queue with a SCM_WIFI_STATUS cmsg that has
an int indicating ACK status (0/1).

Since it is possible that at some point we will
want to have TX timestamping and wifi status in a
single errqueue SKB (there's little point in not
doing that), redefine SO_EE_ORIGIN_TIMESTAMPING
to SO_EE_ORIGIN_TXSTATUS which can collect more
than just the timestamp; keep the old constant
as an alias of course. Currently the internal APIs
don't make that possible, but it wouldn't be hard
to split them up in a way that makes it possible.

Thanks to Neil Horman for helping me figure out
the functions that add the control messages.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

3 files changed, 47 insertions, 0 deletions

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index ca4db40..2f6babd 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3168,6 +3168,26 @@ void skb_tstamp_tx(struct sk_buff *orig_skb,
 }
 EXPORT_SYMBOL_GPL(skb_tstamp_tx);
 
+void skb_complete_wifi_ack(struct sk_buff *skb, bool acked)
+{
+	struct sock *sk = skb->sk;
+	struct sock_exterr_skb *serr;
+	int err;
+
+	skb->wifi_acked_valid = 1;
+	skb->wifi_acked = acked;
+
+	serr = SKB_EXT_ERR(skb);
+	memset(serr, 0, sizeof(*serr));
+	serr->ee.ee_errno = ENOMSG;
+	serr->ee.ee_origin = SO_EE_ORIGIN_TXSTATUS;
+
+	err = sock_queue_err_skb(sk, skb);
+	if (err)
+		kfree_skb(skb);
+}
+EXPORT_SYMBOL_GPL(skb_complete_wifi_ack);
+
 
 /**
  * skb_partial_csum_set - set up and verify partial csum values for packet
diff --git a/net/core/sock.c b/net/core/sock.c
index 4ed7b1d..cbdf51c 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -740,6 +740,11 @@ set_rcvbuf:
 	case SO_RXQ_OVFL:
 		sock_valbool_flag(sk, SOCK_RXQ_OVFL, valbool);
 		break;
+
+	case SO_WIFI_STATUS:
+		sock_valbool_flag(sk, SOCK_WIFI_STATUS, valbool);
+		break;
+
 	default:
 		ret = -ENOPROTOOPT;
 		break;
@@ -961,6 +966,10 @@ int sock_getsockopt(struct socket *sock, int level, int optname,
 		v.val = !!sock_flag(sk, SOCK_RXQ_OVFL);
 		break;
 
+	case SO_WIFI_STATUS:
+		v.val = !!sock_flag(sk, SOCK_WIFI_STATUS);
+		break;
+
 	default:
 		return -ENOPROTOOPT;
 	}
diff --git a/net/socket.c b/net/socket.c
index 2877647..425ef42 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -538,6 +538,8 @@ int sock_tx_timestamp(struct sock *sk, __u8 *tx_flags)
 		*tx_flags |= SKBTX_HW_TSTAMP;
 	if (sock_flag(sk, SOCK_TIMESTAMPING_TX_SOFTWARE))
 		*tx_flags |= SKBTX_SW_TSTAMP;
+	if (sock_flag(sk, SOCK_WIFI_STATUS))
+		*tx_flags |= SKBTX_WIFI_STATUS;
 	return 0;
 }
 EXPORT_SYMBOL(sock_tx_timestamp);
@@ -674,6 +676,22 @@ void __sock_recv_timestamp(struct msghdr *msg, struct sock *sk,
 }
 EXPORT_SYMBOL_GPL(__sock_recv_timestamp);
 
+void __sock_recv_wifi_status(struct msghdr *msg, struct sock *sk,
+	struct sk_buff *skb)
+{
+	int ack;
+
+	if (!sock_flag(sk, SOCK_WIFI_STATUS))
+		return;
+	if (!skb->wifi_acked_valid)
+		return;
+
+	ack = skb->wifi_acked;
+
+	put_cmsg(msg, SOL_SOCKET, SCM_WIFI_STATUS, sizeof(ack), &ack);
+}
+EXPORT_SYMBOL_GPL(__sock_recv_wifi_status);
+
 static inline void sock_recv_drops(struct msghdr *msg, struct sock *sk,
 				   struct sk_buff *skb)
 {