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ntp: use NTP instead of echo for presend

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Switch to NTP for presend as the echo service (RFC 862) is rarely
enabled. When presend is active, send an NTP client packet to the
server/peer and ignore the reply.

This also fixes presend with separate client sockets. The destination
port can't be changed on connected sockets, so the echo packet was sent
to the NTP port instead of the echo port.
This commit is contained in:
Miroslav Lichvar
2014-08-15 15:45:48 +02:00
parent ff4abc69c3
commit cd5105b1db
4 changed files with 18 additions and 32 deletions
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18
ntp_core.c
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@@ -85,8 +85,8 @@ struct NCR_Instance_Record {
received packets) */
int presend_minpoll; /* If the current polling interval is
at least this, an echo datagram
will be send some time before every
at least this, an extra client packet
will be send some time before normal
transmit. This ensures that both
us and the server/peer have an ARP
entry for each other ready, which
@@ -191,7 +191,7 @@ struct NCR_Instance_Record {
#define IBURST_GOOD_SAMPLES 4
#define IBURST_TOTAL_SAMPLES SOURCE_REACH_BITS
/* Time to wait after sending echo to 'warm up' link */
/* Time to wait after sending packet to 'warm up' link */
#define WARM_UP_DELAY 4.0
/* The NTP protocol version that we support */
@@ -820,7 +820,7 @@ transmit_timeout(void *arg)
}
/* Check whether we need to 'warm up' the link to the other end by
sending an echo exchange to ensure both ends' ARP caches are
sending an NTP exchange to ensure both ends' ARP caches are
primed. On loaded systems this might also help ensure that bits
of the program are paged in properly before we start. */
@@ -828,8 +828,11 @@ transmit_timeout(void *arg)
(inst->presend_minpoll <= inst->local_poll) &&
!inst->presend_done) {
/* Send */
NIO_SendEcho(&inst->remote_addr, &inst->local_addr);
/* Send a client packet, don't store the local tx values
as the reply will be ignored */
transmit_packet(MODE_CLIENT, inst->local_poll, NTP_VERSION, 0, 0,
&inst->remote_orig, &inst->local_rx, NULL, NULL,
&inst->remote_addr, &inst->local_addr);
inst->presend_done = 1;
@@ -1483,6 +1486,9 @@ NCR_ProcessKnown
break;
case MODE_SERVER:
/* Ignore presend reply */
if (inst->presend_done)
break;
switch(inst->mode) {
case MODE_ACTIVE: