From 415f44e43282a16ec0808c7ccfd401762e587437 Mon Sep 17 00:00:00 2001 From: David Howells Date: Fri, 24 Nov 2017 10:18:42 +0000 Subject: 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 --- net/rxrpc/ar-internal.h | 1 + net/rxrpc/call_event.c | 10 ++++++++++ net/rxrpc/output.c | 23 +++++++++++++++++++++++ 3 files changed, 34 insertions(+) (limited to 'net/rxrpc') diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h index 7e7b817c69f0..cdcbc798f921 100644 --- a/net/rxrpc/ar-internal.h +++ b/net/rxrpc/ar-internal.h @@ -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 */ diff --git a/net/rxrpc/call_event.c b/net/rxrpc/call_event.c index c65666b2f39e..bda952ffe6a6 100644 --- a/net/rxrpc/call_event.c +++ b/net/rxrpc/call_event.c @@ -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; diff --git a/net/rxrpc/output.c b/net/rxrpc/output.c index efe06edce189..42410e910aff 100644 --- a/net/rxrpc/output.c +++ b/net/rxrpc/output.c @@ -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; -- cgit v1.2.3