rxrpc: Calculate serial skew on packet reception
Calculate the serial number skew in the data_ready handler when a packet
has been received and a connection looked up. The skew is cached in the
sk_buff's priority field.
The connection highest received serial number is updated at this time also.
This can be done without locks or atomic instructions because, at this
point, the code is serialised by the socket.
This generates more accurate skew data because if the packet is offloaded
to a work queue before this is determined, more packets may come in,
bumping the highest serial number and thereby increasing the apparent skew.
This also removes some unnecessary atomic ops.
Signed-off-by: David Howells <dhowells@redhat.com>
diff --git a/net/rxrpc/input.c b/net/rxrpc/input.c
index 70bb778..34f7431 100644
--- a/net/rxrpc/input.c
+++ b/net/rxrpc/input.c
@@ -125,6 +125,7 @@
bool terminal;
int ret, ackbit, ack;
u32 serial;
+ u16 skew;
u8 flags;
_enter("{%u,%u},,{%u}", call->rx_data_post, call->rx_first_oos, seq);
@@ -133,6 +134,7 @@
ASSERTCMP(sp->call, ==, NULL);
flags = sp->hdr.flags;
serial = sp->hdr.serial;
+ skew = skb->priority;
spin_lock(&call->lock);
@@ -231,7 +233,7 @@
spin_unlock(&call->lock);
atomic_inc(&call->ackr_not_idle);
- rxrpc_propose_ACK(call, RXRPC_ACK_DELAY, serial, false);
+ rxrpc_propose_ACK(call, RXRPC_ACK_DELAY, skew, serial, false);
_leave(" = 0 [posted]");
return 0;
@@ -244,7 +246,7 @@
discard_and_ack:
_debug("discard and ACK packet %p", skb);
- __rxrpc_propose_ACK(call, ack, serial, true);
+ __rxrpc_propose_ACK(call, ack, skew, serial, true);
discard:
spin_unlock(&call->lock);
rxrpc_free_skb(skb);
@@ -252,7 +254,7 @@
return 0;
enqueue_and_ack:
- __rxrpc_propose_ACK(call, ack, serial, true);
+ __rxrpc_propose_ACK(call, ack, skew, serial, true);
enqueue_packet:
_net("defer skb %p", skb);
spin_unlock(&call->lock);
@@ -304,7 +306,7 @@
{
struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
__be32 wtmp;
- u32 hi_serial, abort_code;
+ u32 abort_code;
_enter("%p,%p", call, skb);
@@ -321,18 +323,12 @@
}
#endif
- /* track the latest serial number on this connection for ACK packet
- * information */
- hi_serial = atomic_read(&call->conn->hi_serial);
- while (sp->hdr.serial > hi_serial)
- hi_serial = atomic_cmpxchg(&call->conn->hi_serial, hi_serial,
- sp->hdr.serial);
-
/* request ACK generation for any ACK or DATA packet that requests
* it */
if (sp->hdr.flags & RXRPC_REQUEST_ACK) {
_proto("ACK Requested on %%%u", sp->hdr.serial);
- rxrpc_propose_ACK(call, RXRPC_ACK_REQUESTED, sp->hdr.serial, false);
+ rxrpc_propose_ACK(call, RXRPC_ACK_REQUESTED,
+ skb->priority, sp->hdr.serial, false);
}
switch (sp->hdr.type) {
@@ -637,7 +633,7 @@
struct rxrpc_skb_priv *sp;
struct rxrpc_local *local = sk->sk_user_data;
struct sk_buff *skb;
- int ret;
+ int ret, skew;
_enter("%p", sk);
@@ -700,8 +696,21 @@
rcu_read_lock();
conn = rxrpc_find_connection_rcu(local, skb);
- if (!conn)
+ if (!conn) {
+ skb->priority = 0;
goto cant_route_call;
+ }
+
+ /* Note the serial number skew here */
+ skew = (int)sp->hdr.serial - (int)conn->hi_serial;
+ if (skew >= 0) {
+ if (skew > 0)
+ conn->hi_serial = sp->hdr.serial;
+ skb->priority = 0;
+ } else {
+ skew = -skew;
+ skb->priority = min(skew, 65535);
+ }
if (sp->hdr.callNumber == 0) {
/* Connection-level packet */