Message-ID: <20091009193515.GA28196@hmsreliant.think-freely.org>
Date:	Fri, 9 Oct 2009 15:35:15 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	netdev@...r.kernel.org
Cc:	eric.dumazet@...il.com, davem@...emloft.net,
	socketcan@...tkopp.net, nhorman@...driver.com
Subject: Re: [PATCH] Generalize socket rx gap / receive queue overflow cmsg
	(v2)

Ok, take two of this patch, taking in Erics notes:

Change Notes:

1) Locking on dropcount cleaned up

2) Support for reading of dropcount moved to a lower level support function
(sock_recv_ts_and_drops, modeled after sock_recv_timestamp).  This should make
this work a good deal faster

3) Socket flags moved to sk->sk_flags structure in support of (2)

Works well for me.


========================================================================

Create a new socket level option to report number of queue overflows

Recently I augmented the AF_PACKET protocol to report the number of frames lost
on the socket receive queue between any two enqueued frames.  This value was
exported via a SOL_PACKET level cmsg.  AFter I completed that work it was
requested that this feature be generalized so that any datagram oriented socket
could make use of this option.  As such I've created this patch, It creates a
new SOL_SOCKET level option called SO_RXQ_OVFL, which when enabled exports a
SOL_SOCKET level cmsg that reports the nubmer of times the sk_receive_queue
overflowed between any two given frames.  It also augments the AF_PACKET
protocol to take advantage of this new feature (as it previously did not touch
sk->sk_drops, which this patch uses to record the overflow count).  Tested
successfully by me.

Notes:

1) Unlike my previous patch, this patch simply records the sk_drops value, which
is not a number of drops between packets, but rather a total number of drops.
Deltas must be computed in user space.

2) While this patch currently works with datagram oriented protocols, it will
also be accepted by non-datagram oriented protocols. I'm not sure if thats
agreeable to everyone, but my argument in favor of doing so is that, for those
protocols which aren't applicable to this option, sk_drops will always be zero,
and reporting no drops on a receive queue that isn't used for those
non-participating protocols seems reasonable to me.  This also saves us having
to code in a per-protocol opt in mechanism.

3) This applies cleanly to net-next assuming that commit
977750076d98c7ff6cbda51858bb5a5894a9d9ab (my af packet cmsg patch) is reverted

Signed-off-by: Neil Horman <nhorman@...driver.com>


 include/asm-generic/socket.h |    1 +
 include/linux/skbuff.h       |    6 ++++--
 include/net/sock.h           |   13 +++++++++++++
 net/atm/common.c             |    2 +-
 net/bluetooth/af_bluetooth.c |    2 +-
 net/bluetooth/rfcomm/sock.c  |    2 +-
 net/can/bcm.c                |    2 +-
 net/can/raw.c                |    2 +-
 net/core/sock.c              |   17 ++++++++++++++++-
 net/ieee802154/dgram.c       |    2 +-
 net/ieee802154/raw.c         |    2 +-
 net/ipv4/raw.c               |    2 +-
 net/ipv4/udp.c               |    2 +-
 net/ipv6/raw.c               |    2 +-
 net/ipv6/udp.c               |    2 +-
 net/key/af_key.c             |    2 +-
 net/packet/af_packet.c       |    7 +++----
 net/rxrpc/ar-recvmsg.c       |    2 +-
 net/sctp/socket.c            |    2 +-
 net/socket.c                 |    7 +++++++
 20 files changed, 58 insertions(+), 21 deletions(-)

diff --git a/include/asm-generic/socket.h b/include/asm-generic/socket.h
index 538991c..9a6115e 100644
--- a/include/asm-generic/socket.h
+++ b/include/asm-generic/socket.h
@@ -63,4 +63,5 @@
 #define SO_PROTOCOL		38
 #define SO_DOMAIN		39
 
+#define SO_RXQ_OVFL             40
 #endif /* __ASM_GENERIC_SOCKET_H */
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index df7b23a..8c866b5 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -389,8 +389,10 @@ struct sk_buff {
 #ifdef CONFIG_NETWORK_SECMARK
 	__u32			secmark;
 #endif
-
-	__u32			mark;
+	union {
+		__u32		mark;
+		__u32		dropcount;
+	};
 
 	__u16			vlan_tci;
 
diff --git a/include/net/sock.h b/include/net/sock.h
index 98398bd..ae48d99 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -505,6 +505,7 @@ enum sock_flags {
 	SOCK_TIMESTAMPING_RAW_HARDWARE, /* %SOF_TIMESTAMPING_RAW_HARDWARE */
 	SOCK_TIMESTAMPING_SYS_HARDWARE, /* %SOF_TIMESTAMPING_SYS_HARDWARE */
 	SOCK_FASYNC, /* fasync() active */
+	SOCK_RXQ_OVFL,
 };
 
 static inline void sock_copy_flags(struct sock *nsk, struct sock *osk)
@@ -1493,6 +1494,18 @@ sock_recv_timestamp(struct msghdr *msg, struct sock *sk, struct sk_buff *skb)
 		sk->sk_stamp = kt;
 }
 
+extern void __sock_recv_ts_and_drops(struct msghdr *msg, struct sock *sk,
+	struct sk_buff *skb);
+
+static __inline__ void
+sock_recv_ts_and_drops(struct msghdr *msg, struct sock *sk, struct sk_buff *skb)
+{
+	sock_recv_timestamp(msg, sk, skb);
+
+	if (sock_flag(sk, SOCK_RXQ_OVFL) && skb && skb->dropcount)
+		__sock_recv_ts_and_drops(msg, sk, skb);
+}
+
 /**
  * sock_tx_timestamp - checks whether the outgoing packet is to be time stamped
  * @msg:	outgoing packet
diff --git a/net/atm/common.c b/net/atm/common.c
index 950bd16..d61e051 100644
--- a/net/atm/common.c
+++ b/net/atm/common.c
@@ -496,7 +496,7 @@ int vcc_recvmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *msg,
 	error = skb_copy_datagram_iovec(skb, 0, msg->msg_iov, copied);
 	if (error)
 		return error;
-	sock_recv_timestamp(msg, sk, skb);
+	sock_recv_ts_and_drops(msg, sk, skb);
 	pr_debug("RcvM %d -= %d\n", atomic_read(&sk->sk_rmem_alloc), skb->truesize);
 	atm_return(vcc, skb->truesize);
 	skb_free_datagram(sk, skb);
diff --git a/net/bluetooth/af_bluetooth.c b/net/bluetooth/af_bluetooth.c
index 1f6e49c..399e59c 100644
--- a/net/bluetooth/af_bluetooth.c
+++ b/net/bluetooth/af_bluetooth.c
@@ -257,7 +257,7 @@ int bt_sock_recvmsg(struct kiocb *iocb, struct socket *sock,
 	skb_reset_transport_header(skb);
 	err = skb_copy_datagram_iovec(skb, 0, msg->msg_iov, copied);
 	if (err == 0)
-		sock_recv_timestamp(msg, sk, skb);
+		sock_recv_ts_and_drops(msg, sk, skb);
 
 	skb_free_datagram(sk, skb);
 
diff --git a/net/bluetooth/rfcomm/sock.c b/net/bluetooth/rfcomm/sock.c
index c707865..d3bfc1b 100644
--- a/net/bluetooth/rfcomm/sock.c
+++ b/net/bluetooth/rfcomm/sock.c
@@ -703,7 +703,7 @@ static int rfcomm_sock_recvmsg(struct kiocb *iocb, struct socket *sock,
 		copied += chunk;
 		size   -= chunk;
 
-		sock_recv_timestamp(msg, sk, skb);
+		sock_recv_ts_and_drops(msg, sk, skb);
 
 		if (!(flags & MSG_PEEK)) {
 			atomic_sub(chunk, &sk->sk_rmem_alloc);
diff --git a/net/can/bcm.c b/net/can/bcm.c
index 597da4f..2f47039 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -1534,7 +1534,7 @@ static int bcm_recvmsg(struct kiocb *iocb, struct socket *sock,
 		return err;
 	}
 
-	sock_recv_timestamp(msg, sk, skb);
+	sock_recv_ts_and_drops(msg, sk, skb);
 
 	if (msg->msg_name) {
 		msg->msg_namelen = sizeof(struct sockaddr_can);
diff --git a/net/can/raw.c b/net/can/raw.c
index b5e8979..962fc9f 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -702,7 +702,7 @@ static int raw_recvmsg(struct kiocb *iocb, struct socket *sock,
 		return err;
 	}
 
-	sock_recv_timestamp(msg, sk, skb);
+	sock_recv_ts_and_drops(msg, sk, skb);
 
 	if (msg->msg_name) {
 		msg->msg_namelen = sizeof(struct sockaddr_can);
diff --git a/net/core/sock.c b/net/core/sock.c
index 7626b6a..0897311 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -276,6 +276,8 @@ int sock_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 {
 	int err = 0;
 	int skb_len;
+	unsigned long flags;
+	struct sk_buff_head *list = &sk->sk_receive_queue;
 
 	/* Cast sk->rcvbuf to unsigned... It's pointless, but reduces
 	   number of warnings when compiling with -W --ANK
@@ -305,7 +307,10 @@ int sock_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 	 */
 	skb_len = skb->len;
 
-	skb_queue_tail(&sk->sk_receive_queue, skb);
+	spin_lock_irqsave(&list->lock, flags);
+	skb->dropcount = atomic_read(&sk->sk_drops);
+	__skb_queue_tail(list, skb);
+	spin_unlock_irqrestore(&list->lock, flags);
 
 	if (!sock_flag(sk, SOCK_DEAD))
 		sk->sk_data_ready(sk, skb_len);
@@ -702,6 +707,12 @@ set_rcvbuf:
 
 		/* We implement the SO_SNDLOWAT etc to
 		   not be settable (1003.1g 5.3) */
+	case SO_RXQ_OVFL:
+		if (valbool)
+			sock_set_flag(sk, SOCK_RXQ_OVFL);
+		else
+			sock_reset_flag(sk, SOCK_RXQ_OVFL);
+		break;
 	default:
 		ret = -ENOPROTOOPT;
 		break;
@@ -901,6 +912,10 @@ int sock_getsockopt(struct socket *sock, int level, int optname,
 		v.val = sk->sk_mark;
 		break;
 
+	case SO_RXQ_OVFL:
+		v.val = sock_flag(sk, SOCK_RXQ_OVFL);
+		break;
+
 	default:
 		return -ENOPROTOOPT;
 	}
diff --git a/net/ieee802154/dgram.c b/net/ieee802154/dgram.c
index a413b1b..25ad956 100644
--- a/net/ieee802154/dgram.c
+++ b/net/ieee802154/dgram.c
@@ -303,7 +303,7 @@ static int dgram_recvmsg(struct kiocb *iocb, struct sock *sk,
 	if (err)
 		goto done;
 
-	sock_recv_timestamp(msg, sk, skb);
+	sock_recv_ts_and_drops(msg, sk, skb);
 
 	if (flags & MSG_TRUNC)
 		copied = skb->len;
diff --git a/net/ieee802154/raw.c b/net/ieee802154/raw.c
index 30e74ee..769c8d1 100644
--- a/net/ieee802154/raw.c
+++ b/net/ieee802154/raw.c
@@ -191,7 +191,7 @@ static int raw_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 	if (err)
 		goto done;
 
-	sock_recv_timestamp(msg, sk, skb);
+	sock_recv_ts_and_drops(msg, sk, skb);
 
 	if (flags & MSG_TRUNC)
 		copied = skb->len;
diff --git a/net/ipv4/raw.c b/net/ipv4/raw.c
index 757c917..f18172b 100644
--- a/net/ipv4/raw.c
+++ b/net/ipv4/raw.c
@@ -682,7 +682,7 @@ static int raw_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 	if (err)
 		goto done;
 
-	sock_recv_timestamp(msg, sk, skb);
+	sock_recv_ts_and_drops(msg, sk, skb);
 
 	/* Copy the address. */
 	if (sin) {
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 6ec6a8a..bb96eee 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -951,7 +951,7 @@ try_again:
 		UDP_INC_STATS_USER(sock_net(sk),
 				UDP_MIB_INDATAGRAMS, is_udplite);
 
-	sock_recv_timestamp(msg, sk, skb);
+	sock_recv_ts_and_drops(msg, sk, skb);
 
 	/* Copy the address. */
 	if (sin) {
diff --git a/net/ipv6/raw.c b/net/ipv6/raw.c
index 4f24570..d8375bc 100644
--- a/net/ipv6/raw.c
+++ b/net/ipv6/raw.c
@@ -497,7 +497,7 @@ static int rawv6_recvmsg(struct kiocb *iocb, struct sock *sk,
 			sin6->sin6_scope_id = IP6CB(skb)->iif;
 	}
 
-	sock_recv_timestamp(msg, sk, skb);
+	sock_recv_ts_and_drops(msg, sk, skb);
 
 	if (np->rxopt.all)
 		datagram_recv_ctl(sk, msg, skb);
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index c6a303e..b51ee64 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -252,7 +252,7 @@ try_again:
 					UDP_MIB_INDATAGRAMS, is_udplite);
 	}
 
-	sock_recv_timestamp(msg, sk, skb);
+	sock_recv_ts_and_drops(msg, sk, skb);
 
 	/* Copy the address. */
 	if (msg->msg_name) {
diff --git a/net/key/af_key.c b/net/key/af_key.c
index c078ae6..472f659 100644
--- a/net/key/af_key.c
+++ b/net/key/af_key.c
@@ -3606,7 +3606,7 @@ static int pfkey_recvmsg(struct kiocb *kiocb,
 	if (err)
 		goto out_free;
 
-	sock_recv_timestamp(msg, sk, skb);
+	sock_recv_ts_and_drops(msg, sk, skb);
 
 	err = (flags & MSG_TRUNC) ? skb->len : copied;
 
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index f87ed48..bf3a295 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -627,15 +627,14 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
 
 	spin_lock(&sk->sk_receive_queue.lock);
 	po->stats.tp_packets++;
+	skb->dropcount = atomic_read(&sk->sk_drops);
 	__skb_queue_tail(&sk->sk_receive_queue, skb);
 	spin_unlock(&sk->sk_receive_queue.lock);
 	sk->sk_data_ready(sk, skb->len);
 	return 0;
 
 drop_n_acct:
-	spin_lock(&sk->sk_receive_queue.lock);
-	po->stats.tp_drops++;
-	spin_unlock(&sk->sk_receive_queue.lock);
+	po->stats.tp_drops = atomic_inc_return(&sk->sk_drops);
 
 drop_n_restore:
 	if (skb_head != skb->data && skb_shared(skb)) {
@@ -1478,7 +1477,7 @@ static int packet_recvmsg(struct kiocb *iocb, struct socket *sock,
 	if (err)
 		goto out_free;
 
-	sock_recv_timestamp(msg, sk, skb);
+	sock_recv_ts_and_drops(msg, sk, skb);
 
 	if (msg->msg_name)
 		memcpy(msg->msg_name, &PACKET_SKB_CB(skb)->sa,
diff --git a/net/rxrpc/ar-recvmsg.c b/net/rxrpc/ar-recvmsg.c
index a39bf97..60c2b94 100644
--- a/net/rxrpc/ar-recvmsg.c
+++ b/net/rxrpc/ar-recvmsg.c
@@ -146,7 +146,7 @@ int rxrpc_recvmsg(struct kiocb *iocb, struct socket *sock,
 				memcpy(msg->msg_name,
 				       &call->conn->trans->peer->srx,
 				       sizeof(call->conn->trans->peer->srx));
-			sock_recv_timestamp(msg, &rx->sk, skb);
+			sock_recv_ts_and_drops(msg, &rx->sk, skb);
 		}
 
 		/* receive the message */
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index c8d0575..0970e92 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -1958,7 +1958,7 @@ SCTP_STATIC int sctp_recvmsg(struct kiocb *iocb, struct sock *sk,
 	if (err)
 		goto out_free;
 
-	sock_recv_timestamp(msg, sk, skb);
+	sock_recv_ts_and_drops(msg, sk, skb);
 	if (sctp_ulpevent_is_notification(event)) {
 		msg->msg_flags |= MSG_NOTIFICATION;
 		sp->pf->event_msgname(event, msg->msg_name, addr_len);
diff --git a/net/socket.c b/net/socket.c
index d53ad11..c82146c 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -668,6 +668,13 @@ void __sock_recv_timestamp(struct msghdr *msg, struct sock *sk,
 
 EXPORT_SYMBOL_GPL(__sock_recv_timestamp);
 
+void __sock_recv_ts_and_drops(struct msghdr *msg, struct sock *sk,
+	struct sk_buff *skb)
+{
+	put_cmsg(msg, SOL_SOCKET, SO_RXQ_OVFL, sizeof(__u32), &skb->dropcount);
+}
+EXPORT_SYMBOL_GPL(__sock_recv_ts_and_drops);
+
 static inline int __sock_recvmsg(struct kiocb *iocb, struct socket *sock,
 				 struct msghdr *msg, size_t size, int flags)
 {
--
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