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rxrpc: Add keepalive for a call 

We need to transmit a packet every so often to act as a keepalive for the
peer (which has a timeout from the last time it received a packet) and also
to prevent any intervening firewalls from closing the route.

Do this by resetting a timer every time we transmit a packet.  If the timer
ever expires, we transmit a PING ACK packet and thereby also elicit a PING
RESPONSE ACK from the other side - which prevents our last-rx timeout from
expiring.

The timer is set to 1/6 of the last-rx timeout so that we can detect the
other side going away if it misses 6 replies in a row.

This is particularly necessary for servers where the processing of the
service function may take a significant amount of time.

Signed-off-by: David Howells <dhowells@redhat.com>
This commit is contained in:
David Howells 2017-11-24 10:18:42 +00:00
parent bd1fdf8cfd
commit 415f44e432
4 changed files with 40 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
include/trace/events/rxrpc.h
View File

@ -141,6 +141,7 @@ enum rxrpc_timer_trace {
rxrpc_timer_exp_ack,
rxrpc_timer_exp_hard,
rxrpc_timer_exp_idle,
rxrpc_timer_exp_keepalive,
rxrpc_timer_exp_lost_ack,
rxrpc_timer_exp_normal,
rxrpc_timer_exp_ping,
@ -152,6 +153,7 @@ enum rxrpc_timer_trace {
rxrpc_timer_set_for_ack,
rxrpc_timer_set_for_hard,
rxrpc_timer_set_for_idle,
rxrpc_timer_set_for_keepalive,
rxrpc_timer_set_for_lost_ack,
rxrpc_timer_set_for_normal,
rxrpc_timer_set_for_ping,
@ -162,6 +164,7 @@ enum rxrpc_timer_trace {
enum rxrpc_propose_ack_trace {
rxrpc_propose_ack_client_tx_end,
rxrpc_propose_ack_input_data,
rxrpc_propose_ack_ping_for_keepalive,
rxrpc_propose_ack_ping_for_lost_ack,
rxrpc_propose_ack_ping_for_lost_reply,
rxrpc_propose_ack_ping_for_params,
@ -311,6 +314,7 @@ enum rxrpc_congest_change {
EM(rxrpc_timer_exp_ack, "ExpAck") \
EM(rxrpc_timer_exp_hard, "ExpHrd") \
EM(rxrpc_timer_exp_idle, "ExpIdl") \
EM(rxrpc_timer_exp_keepalive, "ExpKA ") \
EM(rxrpc_timer_exp_lost_ack, "ExpLoA") \
EM(rxrpc_timer_exp_normal, "ExpNml") \
EM(rxrpc_timer_exp_ping, "ExpPng") \
@ -321,6 +325,7 @@ enum rxrpc_congest_change {
EM(rxrpc_timer_set_for_ack, "SetAck") \
EM(rxrpc_timer_set_for_hard, "SetHrd") \
EM(rxrpc_timer_set_for_idle, "SetIdl") \
EM(rxrpc_timer_set_for_keepalive, "KeepAl") \
EM(rxrpc_timer_set_for_lost_ack, "SetLoA") \
EM(rxrpc_timer_set_for_normal, "SetNml") \
EM(rxrpc_timer_set_for_ping, "SetPng") \
@ -330,6 +335,7 @@ enum rxrpc_congest_change {
#define rxrpc_propose_ack_traces \
EM(rxrpc_propose_ack_client_tx_end, "ClTxEnd") \
EM(rxrpc_propose_ack_input_data, "DataIn ") \
EM(rxrpc_propose_ack_ping_for_keepalive, "KeepAlv") \
EM(rxrpc_propose_ack_ping_for_lost_ack, "LostAck") \
EM(rxrpc_propose_ack_ping_for_lost_reply, "LostRpl") \
EM(rxrpc_propose_ack_ping_for_params, "Params ") \

1
net/rxrpc/ar-internal.h
View File

@ -519,6 +519,7 @@ struct rxrpc_call {
unsigned long ack_lost_at; /* When ACK is figured as lost */
unsigned long resend_at; /* When next resend needs to happen */
unsigned long ping_at; /* When next to send a ping */
unsigned long keepalive_at; /* When next to send a keepalive ping */
unsigned long expect_rx_by; /* When we expect to get a packet by */
unsigned long expect_req_by; /* When we expect to get a request DATA packet by */
unsigned long expect_term_by; /* When we expect call termination by */

10
net/rxrpc/call_event.c
View File

@ -366,6 +366,15 @@ recheck_state:
set_bit(RXRPC_CALL_EV_ACK_LOST, &call->events);
}
t = READ_ONCE(call->keepalive_at);
if (time_after_eq(now, t)) {
trace_rxrpc_timer(call, rxrpc_timer_exp_keepalive, now);
cmpxchg(&call->keepalive_at, t, now + MAX_JIFFY_OFFSET);
rxrpc_propose_ACK(call, RXRPC_ACK_PING, 0, 0, true, true,
rxrpc_propose_ack_ping_for_keepalive);
set_bit(RXRPC_CALL_EV_PING, &call->events);
}
t = READ_ONCE(call->ping_at);
if (time_after_eq(now, t)) {
trace_rxrpc_timer(call, rxrpc_timer_exp_ping, now);
@ -423,6 +432,7 @@ recheck_state:
set(call->ack_at);
set(call->ack_lost_at);
set(call->resend_at);
set(call->keepalive_at);
set(call->ping_at);
now = jiffies;

23
net/rxrpc/output.c
View File

@ -32,6 +32,24 @@ struct rxrpc_abort_buffer {
__be32 abort_code;
};
/*
* Arrange for a keepalive ping a certain time after we last transmitted. This
* lets the far side know we're still interested in this call and helps keep
* the route through any intervening firewall open.
*
* Receiving a response to the ping will prevent the ->expect_rx_by timer from
* expiring.
*/
static void rxrpc_set_keepalive(struct rxrpc_call *call)
{
unsigned long now = jiffies, keepalive_at = call->next_rx_timo / 6;
keepalive_at += now;
WRITE_ONCE(call->keepalive_at, keepalive_at);
rxrpc_reduce_call_timer(call, keepalive_at, now,
rxrpc_timer_set_for_keepalive);
}
/*
* Fill out an ACK packet.
*/
@ -205,6 +223,8 @@ int rxrpc_send_ack_packet(struct rxrpc_call *call, bool ping,
call->ackr_seen = top;
spin_unlock_bh(&call->lock);
}
rxrpc_set_keepalive(call);
}
out:
@ -388,6 +408,9 @@ done:
}
}
}
rxrpc_set_keepalive(call);
_leave(" = %d [%u]", ret, call->peer->maxdata);
return ret;