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ntp: limit number of pool sources

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A new option can be now used in the pool directive: maxsources sets the
maximum number of sources that can be used from the pool, the default
value is 4.

On start, when the pool name is resolved, chronyd will add up to 16
sources, one for each resolved address. When the number of sources from
which at least one valid reply was received reaches maxsources, the
other sources will be removed.
This commit is contained in:
Miroslav Lichvar
2014-11-26 16:40:33 +01:00
parent f2c80cae44
commit 308bcae257
7 changed files with 93 additions and 10 deletions
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57
ntp_sources.c
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@@ -51,6 +51,9 @@ typedef struct {
NCR_Instance data; /* Data for the protocol engine for this source */
int pool; /* Number of the pool from which was this source
added or INVALID_POOL */
int tentative; /* Flag indicating there was no valid response
yet and the source may be removed if other
sources from the pool respond first */
} SourceRecord;
/* Hash table of SourceRecord, the size should be a power of two */
@@ -98,6 +101,10 @@ static NSR_SourceResolvingEndHandler resolving_end_handler = NULL;
struct SourcePool {
char *name;
int port;
/* Number of sources added from this pool (ignoring tentative sources) */
int sources;
/* Maximum number of sources */
int max_sources;
};
/* Array of SourcePool */
@@ -317,6 +324,7 @@ add_source(NTP_Remote_Address *remote_addr, NTP_Source_Type type, SourceParamete
record->data = NCR_GetInstance(remote_addr, type, params);
record->remote_addr = NCR_GetRemoteAddress(record->data);
record->pool = pool;
record->tentative = pool != INVALID_POOL ? 1 : 0;
if (auto_start_sources)
NCR_StartInstance(record->data);
@@ -512,6 +520,8 @@ NSR_AddSourceByName(char *name, int port, int pool, NTP_Source_Type type, Source
sp = (struct SourcePool *)ARR_GetNewElement(pools);
sp->name = Strdup(name);
sp->port = port;
sp->sources = 0;
sp->max_sources = params->max_sources;
us->new_source.pool = ARR_GetSize(pools) - 1;
us->new_source.max_new_sources = MAX_POOL_SOURCES;
}
@@ -682,19 +692,62 @@ NSR_HandleBadSource(IPAddr *address)
/* ================================================== */
static void remove_tentative_pool_sources(int pool)
{
SourceRecord *record;
unsigned int i, removed;
for (i = removed = 0; i < ARR_GetSize(records); i++) {
record = get_record(i);
if (!record->remote_addr || record->pool != pool || !record->tentative)
continue;
DEBUG_LOG(LOGF_NtpSources, "removing tentative source %s",
UTI_IPToString(&record->remote_addr->ip_addr));
clean_source_record(record);
removed++;
}
if (removed)
rehash_records();
}
/* This routine is called by ntp_io when a new packet arrives off the network,
possibly with an authentication tail */
void
NSR_ProcessReceive(NTP_Packet *message, struct timeval *now, double now_err, NTP_Remote_Address *remote_addr, NTP_Local_Address *local_addr, int length)
{
SourceRecord *record;
struct SourcePool *pool;
int slot, found;
assert(initialised);
find_slot(remote_addr, &slot, &found);
if (found == 2) { /* Must match IP address AND port number */
NCR_ProcessKnown(message, now, now_err, get_record(slot)->data,
local_addr, length);
record = get_record(slot);
if (!NCR_ProcessKnown(message, now, now_err, record->data, local_addr, length))
return;
if (record->tentative) {
/* First reply from a pool source */
record->tentative = 0;
assert(record->pool != INVALID_POOL);
pool = (struct SourcePool *)ARR_GetElement(pools, record->pool);
pool->sources++;
DEBUG_LOG(LOGF_NtpSources, "pool %s has %d confirmed sources",
pool->name, pool->sources);
/* If the number of sources reached the configured maximum, remove
the tentative sources added from this pool */
if (pool->sources >= pool->max_sources)
remove_tentative_pool_sources(record->pool);
}
} else {
NCR_ProcessUnknown(message, now, now_err, remote_addr, local_addr, length);
}