Merge branch 'dropcount'

Eyal Birger says:

====================
net: move skb->dropcount to skb->cb[]

Commit 977750076d98 ("af_packet: add interframe drop cmsg (v6)")
unionized skb->mark and skb->dropcount in order to allow recording
of the socket drop count while maintaining struct sk_buff size.

skb->dropcount was introduced since there was no available room
in skb->cb[] in packet sockets. However, its introduction led to
the inability to export skb->mark to userspace.

It was considered to alias skb->priority instead of skb->mark.
However, that would lead to the inabilty to export skb->priority
to userspace if desired. Such change may also lead to hard-to-find
issues as skb->priority is assumed to be alias free, and, as noted
by Shmulik Ladkani, is not 'naturally orthogonal' with other skb
fields.

This patch series follows the suggestions made by Eric Dumazet moving
the dropcount metric to skb->cb[], eliminating this problem
at the expense of 4 bytes less in skb->cb[] for protocol families
using it.

The patch series include compactization of bluetooth and packet
use of skb->cb[] as well as the infrastructure for placing dropcount
in skb->cb[].
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

18 files changed, 79 insertions, 48 deletions

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index d898b32..bba1330 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -492,7 +492,6 @@ static inline u32 skb_mstamp_us_delta(const struct skb_mstamp *t1,
   *	@napi_id: id of the NAPI struct this skb came from
  *	@secmark: security marking
  *	@mark: Generic packet mark
- *	@dropcount: total number of sk_receive_queue overflows
  *	@vlan_proto: vlan encapsulation protocol
  *	@vlan_tci: vlan tag control information
  *	@inner_protocol: Protocol (encapsulation)
@@ -641,7 +640,6 @@ struct sk_buff {
 #endif
 	union {
 		__u32		mark;
-		__u32		dropcount;
 		__u32		reserved_tailroom;
 	};
 
diff --git a/include/net/bluetooth/bluetooth.h b/include/net/bluetooth/bluetooth.h
index e00455a..4500bf8 100644
--- a/include/net/bluetooth/bluetooth.h
+++ b/include/net/bluetooth/bluetooth.h
@@ -275,21 +275,17 @@ struct hci_dev;
 
 typedef void (*hci_req_complete_t)(struct hci_dev *hdev, u8 status, u16 opcode);
 
-struct hci_req_ctrl {
-	bool			start;
-	u8			event;
-	hci_req_complete_t	complete;
-};
-
 struct bt_skb_cb {
 	__u8 pkt_type;
-	__u8 incoming;
+	__u8 force_active;
 	__u16 opcode;
 	__u16 expect;
-	__u8 force_active;
+	__u8 incoming:1;
+	__u8 req_start:1;
+	u8 req_event;
+	hci_req_complete_t req_complete;
 	struct l2cap_chan *chan;
 	struct l2cap_ctrl control;
-	struct hci_req_ctrl req;
 	bdaddr_t bdaddr;
 	__le16 psm;
 };
diff --git a/include/net/sock.h b/include/net/sock.h
index ab186b1..38369d3 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -2078,6 +2078,29 @@ static inline int sock_intr_errno(long timeo)
 	return timeo == MAX_SCHEDULE_TIMEOUT ? -ERESTARTSYS : -EINTR;
 }
 
+struct sock_skb_cb {
+	u32 dropcount;
+};
+
+/* Store sock_skb_cb at the end of skb->cb[] so protocol families
+ * using skb->cb[] would keep using it directly and utilize its
+ * alignement guarantee.
+ */
+#define SOCK_SKB_CB_OFFSET ((FIELD_SIZEOF(struct sk_buff, cb) - \
+			    sizeof(struct sock_skb_cb)))
+
+#define SOCK_SKB_CB(__skb) ((struct sock_skb_cb *)((__skb)->cb + \
+			    SOCK_SKB_CB_OFFSET))
+
+#define sock_skb_cb_check_size(size) \
+	BUILD_BUG_ON((size) > SOCK_SKB_CB_OFFSET)
+
+static inline void
+sock_skb_set_dropcount(const struct sock *sk, struct sk_buff *skb)
+{
+	SOCK_SKB_CB(skb)->dropcount = atomic_read(&sk->sk_drops);
+}
+
 void __sock_recv_timestamp(struct msghdr *msg, struct sock *sk,
 			   struct sk_buff *skb);
 void __sock_recv_wifi_status(struct msghdr *msg, struct sock *sk,
diff --git a/net/bluetooth/af_bluetooth.c b/net/bluetooth/af_bluetooth.c
index ce22e0c..4b904c9 100644
--- a/net/bluetooth/af_bluetooth.c
+++ b/net/bluetooth/af_bluetooth.c
@@ -711,10 +711,9 @@ EXPORT_SYMBOL_GPL(bt_debugfs);
 
 static int __init bt_init(void)
 {
-	struct sk_buff *skb;
 	int err;
 
-	BUILD_BUG_ON(sizeof(struct bt_skb_cb) > sizeof(skb->cb));
+	sock_skb_cb_check_size(sizeof(struct bt_skb_cb));
 
 	BT_INFO("Core ver %s", VERSION);
 
diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index 3322d3f..80f40e8 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -3517,7 +3517,7 @@ int hci_send_cmd(struct hci_dev *hdev, __u16 opcode, __u32 plen,
 	/* Stand-alone HCI commands must be flagged as
 	 * single-command requests.
 	 */
-	bt_cb(skb)->req.start = true;
+	bt_cb(skb)->req_start = 1;
 
 	skb_queue_tail(&hdev->cmd_q, skb);
 	queue_work(hdev->workqueue, &hdev->cmd_work);
@@ -4195,7 +4195,7 @@ static bool hci_req_is_complete(struct hci_dev *hdev)
 	if (!skb)
 		return true;
 
-	return bt_cb(skb)->req.start;
+	return bt_cb(skb)->req_start;
 }
 
 static void hci_resend_last(struct hci_dev *hdev)
@@ -4255,14 +4255,14 @@ void hci_req_cmd_complete(struct hci_dev *hdev, u16 opcode, u8 status)
 	 * command queue (hdev->cmd_q).
 	 */
 	if (hdev->sent_cmd) {
-		req_complete = bt_cb(hdev->sent_cmd)->req.complete;
+		req_complete = bt_cb(hdev->sent_cmd)->req_complete;
 
 		if (req_complete) {
 			/* We must set the complete callback to NULL to
 			 * avoid calling the callback more than once if
 			 * this function gets called again.
 			 */
-			bt_cb(hdev->sent_cmd)->req.complete = NULL;
+			bt_cb(hdev->sent_cmd)->req_complete = NULL;
 
 			goto call_complete;
 		}
@@ -4271,12 +4271,12 @@ void hci_req_cmd_complete(struct hci_dev *hdev, u16 opcode, u8 status)
 	/* Remove all pending commands belonging to this request */
 	spin_lock_irqsave(&hdev->cmd_q.lock, flags);
 	while ((skb = __skb_dequeue(&hdev->cmd_q))) {
-		if (bt_cb(skb)->req.start) {
+		if (bt_cb(skb)->req_start) {
 			__skb_queue_head(&hdev->cmd_q, skb);
 			break;
 		}
 
-		req_complete = bt_cb(skb)->req.complete;
+		req_complete = bt_cb(skb)->req_complete;
 		kfree_skb(skb);
 	}
 	spin_unlock_irqrestore(&hdev->cmd_q.lock, flags);
diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index a3fb094..8e8c433 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -3106,7 +3106,7 @@ static void hci_cmd_status_evt(struct hci_dev *hdev, struct sk_buff *skb)
 		cancel_delayed_work(&hdev->cmd_timer);
 
 	if (ev->status ||
-	    (hdev->sent_cmd && !bt_cb(hdev->sent_cmd)->req.event))
+	    (hdev->sent_cmd && !bt_cb(hdev->sent_cmd)->req_event))
 		hci_req_cmd_complete(hdev, opcode, ev->status);
 
 	if (ev->ncmd && !test_bit(HCI_RESET, &hdev->flags)) {
@@ -5039,7 +5039,7 @@ void hci_event_packet(struct hci_dev *hdev, struct sk_buff *skb)
 
 	skb_pull(skb, HCI_EVENT_HDR_SIZE);
 
-	if (hdev->sent_cmd && bt_cb(hdev->sent_cmd)->req.event == event) {
+	if (hdev->sent_cmd && bt_cb(hdev->sent_cmd)->req_event == event) {
 		struct hci_command_hdr *cmd_hdr = (void *) hdev->sent_cmd->data;
 		u16 opcode = __le16_to_cpu(cmd_hdr->opcode);
 
diff --git a/net/bluetooth/hci_request.c b/net/bluetooth/hci_request.c
index b59f92c..f857e76 100644
--- a/net/bluetooth/hci_request.c
+++ b/net/bluetooth/hci_request.c
@@ -55,7 +55,7 @@ int hci_req_run(struct hci_request *req, hci_req_complete_t complete)
 		return -ENODATA;
 
 	skb = skb_peek_tail(&req->cmd_q);
-	bt_cb(skb)->req.complete = complete;
+	bt_cb(skb)->req_complete = complete;
 
 	spin_lock_irqsave(&hdev->cmd_q.lock, flags);
 	skb_queue_splice_tail(&req->cmd_q, &hdev->cmd_q);
@@ -116,9 +116,9 @@ void hci_req_add_ev(struct hci_request *req, u16 opcode, u32 plen,
 	}
 
 	if (skb_queue_empty(&req->cmd_q))
-		bt_cb(skb)->req.start = true;
+		bt_cb(skb)->req_start = 1;
 
-	bt_cb(skb)->req.event = event;
+	bt_cb(skb)->req_event = event;
 
 	skb_queue_tail(&req->cmd_q, skb);
 }
diff --git a/net/bluetooth/hci_sock.c b/net/bluetooth/hci_sock.c
index 1d65c5b..37198fb 100644
--- a/net/bluetooth/hci_sock.c
+++ b/net/bluetooth/hci_sock.c
@@ -965,7 +965,7 @@ static int hci_sock_sendmsg(struct kiocb *iocb, struct socket *sock,
 			/* Stand-alone HCI commands must be flagged as
 			 * single-command requests.
 			 */
-			bt_cb(skb)->req.start = true;
+			bt_cb(skb)->req_start = 1;
 
 			skb_queue_tail(&hdev->cmd_q, skb);
 			queue_work(hdev->workqueue, &hdev->cmd_work);
diff --git a/net/can/bcm.c b/net/can/bcm.c
index ee9ffd9..d559f92 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -328,7 +328,7 @@ static void bcm_send_to_user(struct bcm_op *op, struct bcm_msg_head *head,
 	 *  containing the interface index.
 	 */
 
-	BUILD_BUG_ON(sizeof(skb->cb) < sizeof(struct sockaddr_can));
+	sock_skb_cb_check_size(sizeof(struct sockaddr_can));
 	addr = (struct sockaddr_can *)skb->cb;
 	memset(addr, 0, sizeof(*addr));
 	addr->can_family  = AF_CAN;
diff --git a/net/can/raw.c b/net/can/raw.c
index 00c13ef..94601b7 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -95,8 +95,8 @@ struct raw_sock {
  */
 static inline unsigned int *raw_flags(struct sk_buff *skb)
 {
-	BUILD_BUG_ON(sizeof(skb->cb) <= (sizeof(struct sockaddr_can) +
-					 sizeof(unsigned int)));
+	sock_skb_cb_check_size(sizeof(struct sockaddr_can) +
+			       sizeof(unsigned int));
 
 	/* return pointer after struct sockaddr_can */
 	return (unsigned int *)(&((struct sockaddr_can *)skb->cb)[1]);
@@ -135,7 +135,7 @@ static void raw_rcv(struct sk_buff *oskb, void *data)
 	 *  containing the interface index.
 	 */
 
-	BUILD_BUG_ON(sizeof(skb->cb) < sizeof(struct sockaddr_can));
+	sock_skb_cb_check_size(sizeof(struct sockaddr_can));
 	addr = (struct sockaddr_can *)skb->cb;
 	memset(addr, 0, sizeof(*addr));
 	addr->can_family  = AF_CAN;
diff --git a/net/core/sock.c b/net/core/sock.c
index 93c8b20..9c74fc8 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -466,7 +466,7 @@ int sock_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 	skb_dst_force(skb);
 
 	spin_lock_irqsave(&list->lock, flags);
-	skb->dropcount = atomic_read(&sk->sk_drops);
+	sock_skb_set_dropcount(sk, skb);
 	__skb_queue_tail(list, skb);
 	spin_unlock_irqrestore(&list->lock, flags);
 
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index d2e49ba..4ce954c 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1675,7 +1675,7 @@ static int __init inet_init(void)
 	struct list_head *r;
 	int rc = -EINVAL;
 
-	BUILD_BUG_ON(sizeof(struct inet_skb_parm) > FIELD_SIZEOF(struct sk_buff, cb));
+	sock_skb_cb_check_size(sizeof(struct inet_skb_parm));
 
 	rc = proto_register(&tcp_prot, 1);
 	if (rc)
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 9d72a0f..4b57ea8 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3005,12 +3005,11 @@ static void __init tcp_init_mem(void)
 
 void __init tcp_init(void)
 {
-	struct sk_buff *skb = NULL;
 	unsigned long limit;
 	int max_rshare, max_wshare, cnt;
 	unsigned int i;
 
-	BUILD_BUG_ON(sizeof(struct tcp_skb_cb) > sizeof(skb->cb));
+	sock_skb_cb_check_size(sizeof(struct tcp_skb_cb));
 
 	percpu_counter_init(&tcp_sockets_allocated, 0, GFP_KERNEL);
 	percpu_counter_init(&tcp_orphan_count, 0, GFP_KERNEL);
diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index e8c4400..6bafcc2 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -824,7 +824,7 @@ static int __init inet6_init(void)
 	struct list_head *r;
 	int err = 0;
 
-	BUILD_BUG_ON(sizeof(struct inet6_skb_parm) > FIELD_SIZEOF(struct sk_buff, cb));
+	sock_skb_cb_check_size(sizeof(struct inet6_skb_parm));
 
 	/* Register the socket-side information for inet6_create.  */
 	for (r = &inetsw6[0]; r < &inetsw6[SOCK_MAX]; ++r)
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 9c28cec..9db8369 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -216,10 +216,16 @@ static void prb_fill_vlan_info(struct tpacket_kbdq_core *,
 static void packet_flush_mclist(struct sock *sk);
 
 struct packet_skb_cb {
-	unsigned int origlen;
 	union {
 		struct sockaddr_pkt pkt;
-		struct sockaddr_ll ll;
+		union {
+			/* Trick: alias skb original length with
+			 * ll.sll_family and ll.protocol in order
+			 * to save room.
+			 */
+			unsigned int origlen;
+			struct sockaddr_ll ll;
+		};
 	} sa;
 };
 
@@ -1810,13 +1816,10 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
 		skb = nskb;
 	}
 
-	BUILD_BUG_ON(sizeof(*PACKET_SKB_CB(skb)) + MAX_ADDR_LEN - 8 >
-		     sizeof(skb->cb));
+	sock_skb_cb_check_size(sizeof(*PACKET_SKB_CB(skb)) + MAX_ADDR_LEN - 8);
 
 	sll = &PACKET_SKB_CB(skb)->sa.ll;
-	sll->sll_family = AF_PACKET;
 	sll->sll_hatype = dev->type;
-	sll->sll_protocol = skb->protocol;
 	sll->sll_pkttype = skb->pkt_type;
 	if (unlikely(po->origdev))
 		sll->sll_ifindex = orig_dev->ifindex;
@@ -1825,7 +1828,10 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
 
 	sll->sll_halen = dev_parse_header(skb, sll->sll_addr);
 
-	PACKET_SKB_CB(skb)->origlen = skb->len;
+	/* sll->sll_family and sll->sll_protocol are set in packet_recvmsg().
+	 * Use their space for storing the original skb length.
+	 */
+	PACKET_SKB_CB(skb)->sa.origlen = skb->len;
 
 	if (pskb_trim(skb, snaplen))
 		goto drop_n_acct;
@@ -1839,7 +1845,7 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
 
 	spin_lock(&sk->sk_receive_queue.lock);
 	po->stats.stats1.tp_packets++;
-	skb->dropcount = atomic_read(&sk->sk_drops);
+	sock_skb_set_dropcount(sk, skb);
 	__skb_queue_tail(&sk->sk_receive_queue, skb);
 	spin_unlock(&sk->sk_receive_queue.lock);
 	sk->sk_data_ready(sk);
@@ -2883,6 +2889,7 @@ static int packet_recvmsg(struct kiocb *iocb, struct socket *sock,
 	struct sk_buff *skb;
 	int copied, err;
 	int vnet_hdr_len = 0;
+	unsigned int origlen = 0;
 
 	err = -EINVAL;
 	if (flags & ~(MSG_PEEK|MSG_DONTWAIT|MSG_TRUNC|MSG_CMSG_COMPAT|MSG_ERRQUEUE))
@@ -2982,6 +2989,15 @@ static int packet_recvmsg(struct kiocb *iocb, struct socket *sock,
 	if (err)
 		goto out_free;
 
+	if (sock->type != SOCK_PACKET) {
+		struct sockaddr_ll *sll = &PACKET_SKB_CB(skb)->sa.ll;
+
+		/* Original length was stored in sockaddr_ll fields */
+		origlen = PACKET_SKB_CB(skb)->sa.origlen;
+		sll->sll_family = AF_PACKET;
+		sll->sll_protocol = skb->protocol;
+	}
+
 	sock_recv_ts_and_drops(msg, sk, skb);
 
 	if (msg->msg_name) {
@@ -2993,6 +3009,7 @@ static int packet_recvmsg(struct kiocb *iocb, struct socket *sock,
 			msg->msg_namelen = sizeof(struct sockaddr_pkt);
 		} else {
 			struct sockaddr_ll *sll = &PACKET_SKB_CB(skb)->sa.ll;
+
 			msg->msg_namelen = sll->sll_halen +
 				offsetof(struct sockaddr_ll, sll_addr);
 		}
@@ -3006,7 +3023,7 @@ static int packet_recvmsg(struct kiocb *iocb, struct socket *sock,
 		aux.tp_status = TP_STATUS_USER;
 		if (skb->ip_summed == CHECKSUM_PARTIAL)
 			aux.tp_status |= TP_STATUS_CSUMNOTREADY;
-		aux.tp_len = PACKET_SKB_CB(skb)->origlen;
+		aux.tp_len = origlen;
 		aux.tp_snaplen = skb->len;
 		aux.tp_mac = 0;
 		aux.tp_net = skb_network_offset(skb);
diff --git a/net/rxrpc/ar-recvmsg.c b/net/rxrpc/ar-recvmsg.c
index 4575485..d58ba70 100644
--- a/net/rxrpc/ar-recvmsg.c
+++ b/net/rxrpc/ar-recvmsg.c
@@ -150,7 +150,7 @@ int rxrpc_recvmsg(struct kiocb *iocb, struct socket *sock,
 				       &call->conn->trans->peer->srx, len);
 				msg->msg_namelen = len;
 			}
-			sock_recv_ts_and_drops(msg, &rx->sk, skb);
+			sock_recv_timestamp(msg, &rx->sk, skb);
 		}
 
 		/* receive the message */
diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
index 8f34b27..53b7acd 100644
--- a/net/sctp/protocol.c
+++ b/net/sctp/protocol.c
@@ -1322,8 +1322,7 @@ static __init int sctp_init(void)
 	int max_share;
 	int order;
 
-	BUILD_BUG_ON(sizeof(struct sctp_ulpevent) >
-		     sizeof(((struct sk_buff *) 0)->cb));
+	sock_skb_cb_check_size(sizeof(struct sctp_ulpevent));
 
 	/* Allocate bind_bucket and chunk caches. */
 	status = -ENOBUFS;
diff --git a/net/socket.c b/net/socket.c
index bbedbfc..b78cf60 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -731,9 +731,9 @@ EXPORT_SYMBOL_GPL(__sock_recv_wifi_status);
 static inline void sock_recv_drops(struct msghdr *msg, struct sock *sk,
 				   struct sk_buff *skb)
 {
-	if (sock_flag(sk, SOCK_RXQ_OVFL) && skb && skb->dropcount)
+	if (sock_flag(sk, SOCK_RXQ_OVFL) && skb && SOCK_SKB_CB(skb)->dropcount)
 		put_cmsg(msg, SOL_SOCKET, SO_RXQ_OVFL,
-			sizeof(__u32), &skb->dropcount);
+			sizeof(__u32), &SOCK_SKB_CB(skb)->dropcount);
 }
 
 void __sock_recv_ts_and_drops(struct msghdr *msg, struct sock *sk,