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ntp: add pre-NTPv5 experimental extension field

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Add an experimental extension field for some features that were proposed
for NTPv5. Higher-resolution root delay and dispersion (using 28-bit
fraction) are added. A monotonic receive timestamp will allow a
frequency transfer between the server and client. The client will be
able to separate the server's time corrections from frequency
corrections by tracking the offset between the real-time and monotonic
receive timestamps.

The field has a type of 0xF323 from the new experimental range proposed
by the NTP working group. Include a magic 32-bit value in the field to
avoid interoperability issues if a different implementation choses the
same type for its own experimental field. The value will be changed on
incompatible changes to avoid issues between two different chrony
versions.
This commit is contained in:
Miroslav Lichvar 2021-11-10 14:52:04 +01:00
parent 125d7a5c32
commit a97ca73704
2 changed files with 22 additions and 0 deletions
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17
ntp.h
View file

@ -113,6 +113,23 @@ typedef struct {
#define NTP_REFID_LOCAL 0x7F7F0101UL /* 127.127.1.1 */
#define NTP_REFID_SMOOTH 0x7F7F01FFUL /* 127.127.1.255 */
/* Non-authentication extension fields and corresponding internal flags */
#define NTP_EF_EXP1 0xF323
#define NTP_EF_FLAG_EXP1 0x1
/* Pre-NTPv5 experimental extension field */
typedef struct {
uint32_t magic;
NTP_int32 root_delay;
NTP_int32 root_dispersion;
NTP_int64 mono_receive_ts;
uint32_t mono_epoch;
} NTP_ExtFieldExp1;
#define NTP_EF_EXP1_MAGIC 0xF5BEDD9AU
/* Authentication extension fields */
#define NTP_EF_NTS_UNIQUE_IDENTIFIER 0x0104

5
ntp_core.c
View file

@ -1406,6 +1406,11 @@ parse_packet(NTP_Packet *packet, int length, NTP_PacketInfo *info)
case NTP_EF_NTS_AUTH_AND_EEF:
info->auth.mode = NTP_AUTH_NTS;
break;
case NTP_EF_EXP1:
if (ef_body_length == sizeof (NTP_ExtFieldExp1) &&
ntohl(((NTP_ExtFieldExp1 *)ef_body)->magic) == NTP_EF_EXP1_MAGIC)
info->ext_field_flags |= NTP_EF_FLAG_EXP1;
break;
default:
DEBUG_LOG("Unknown extension field type=%x", (unsigned int)ef_type);
}