From: Miroslav Lichvar <mlichvar@redhat.com>
Date: Tue, 14 Dec 2021 09:04:39 +0000 (+0100)
Subject: ntp: avoid unnecessary source lookups
X-Git-Tag: 4.2~6
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f2ba20f2932e3fcd76f5bd5d0d53248a560e51ef;p=thirdparty%2Fchrony.git

ntp: avoid unnecessary source lookups

Avoid searching the hash table of sources when a packet in the client
mode is received. It cannot be a response from our source. Analogously,
avoid source lookups for transmitted packets in the server mode. This
doesn't change anything for packets in symmetric modes, which can be
requests and responses at the same time.

This slightly improves the maximum packet rate handled as a server.
---

diff --git a/ntp_sources.c b/ntp_sources.c
index 852602ab..3cbb2ae7 100644
--- a/ntp_sources.c
+++ b/ntp_sources.c
@@ -1100,8 +1100,10 @@ NSR_ProcessRx(NTP_Remote_Address *remote_addr, NTP_Local_Address *local_addr,
 
   assert(initialised);
 
-  /* Must match IP address AND port number */
-  if (find_slot2(remote_addr, &slot) == 2) {
+  /* Avoid unnecessary lookup if the packet cannot be a response from our
+     source.  Otherwise, it must match both IP address and port number. */
+  if (NTP_LVM_TO_MODE(message->lvm) != MODE_CLIENT &&
+      find_slot2(remote_addr, &slot) == 2) {
     record = get_record(slot);
 
     if (!NCR_ProcessRxKnown(record->data, local_addr, rx_ts, message, length))
@@ -1137,8 +1139,10 @@ NSR_ProcessTx(NTP_Remote_Address *remote_addr, NTP_Local_Address *local_addr,
   SourceRecord *record;
   int slot;
 
-  /* Must match IP address AND port number */
-  if (find_slot2(remote_addr, &slot) == 2) {
+  /* Avoid unnecessary lookup if the packet cannot be a request to our
+     source.  Otherwise, it must match both IP address and port number. */
+  if (NTP_LVM_TO_MODE(message->lvm) != MODE_SERVER &&
+      find_slot2(remote_addr, &slot) == 2) {
     record = get_record(slot);
     NCR_ProcessTxKnown(record->data, local_addr, tx_ts, message, length);
   } else {
diff --git a/test/unit/ntp_sources.c b/test/unit/ntp_sources.c
index e8b74206..ea3910ff 100644
--- a/test/unit/ntp_sources.c
+++ b/test/unit/ntp_sources.c
@@ -110,7 +110,7 @@ change_remote_address(NCR_Instance inst, NTP_Remote_Address *remote_addr, int nt
 void
 test_unit(void)
 {
-  char source_line[] = "127.0.0.1 offline", conf[] = "port 0", name[64], msg[1];
+  char source_line[] = "127.0.0.1 offline", conf[] = "port 0", name[64];
   int i, j, k, slot, found, pool, prev_n;
   uint32_t hash = 0, conf_id;
   NTP_Remote_Address addrs[256], addr;
@@ -120,6 +120,7 @@ test_unit(void)
   RPT_ActivityReport report;
   CPS_NTP_Source source;
   NSR_Status status;
+  NTP_Packet msg;
 
   CNF_Initialise(0, 0);
   CNF_ParseLine(NULL, 1, conf);
@@ -272,12 +273,14 @@ test_unit(void)
 
         switch (random() % 5) {
           case 0:
+            msg.lvm = NTP_LVM(0, NTP_VERSION, random() % 2 ? MODE_CLIENT : MODE_SERVER);
             NSR_ProcessTx(get_record(slot)->remote_addr, &local_addr,
-                          &local_ts, (NTP_Packet *)msg, 0);
+                          &local_ts, &msg, 0);
             break;
           case 1:
+            msg.lvm = NTP_LVM(0, NTP_VERSION, random() % 2 ? MODE_CLIENT : MODE_SERVER);
             NSR_ProcessRx(get_record(slot)->remote_addr, &local_addr,
-                          &local_ts, (NTP_Packet *)msg, 0);
+                          &local_ts, &msg, 0);
             break;
           case 2:
             NSR_HandleBadSource(&get_record(slot)->remote_addr->ip_addr);