ntp: add extension field to provide network correction

To be able to verify PTP corrections, the client will need to know both
the correction of the request received by the server and the correction
of the response. Add a new experimental NTP extension field that the
clients will use to request the correction and servers return the
value.

diff --git a/ntp.h b/ntp.h
index 1ef36834504aa40b206ea147c076ac4f81e16a3b..165adbc210eda1168083dcc9f820b67bc87a6cff 100644 (file)
--- a/ntp.h
+++ b/ntp.h
@@ -116,8 +116,10 @@ typedef struct {
 /* Non-authentication extension fields and corresponding internal flags */
 
 #define NTP_EF_EXP_MONO_ROOT            0xF323
+#define NTP_EF_EXP_NET_CORRECTION       0xF324
 
 #define NTP_EF_FLAG_EXP_MONO_ROOT       0x1
+#define NTP_EF_FLAG_EXP_NET_CORRECTION  0x2
 
 /* Pre-NTPv5 experimental extension field */
 typedef struct {
@@ -130,6 +132,15 @@ typedef struct {
 
 #define NTP_EF_EXP_MONO_ROOT_MAGIC      0xF5BEDD9AU
 
+/* Experimental extension field to provide PTP corrections */
+typedef struct {
+  uint32_t magic;
+  NTP_int64 correction;
+  uint32_t reserved[3];
+} NTP_EFExpNetCorrection;
+
+#define NTP_EF_EXP_NET_CORRECTION_MAGIC 0x07AC2CEBU
+
 /* Authentication extension fields */
 
 #define NTP_EF_NTS_UNIQUE_IDENTIFIER    0x0104

diff --git a/ntp_core.c b/ntp_core.c
index fae5e7b19be77efe763b8b31fc12341e2ee7fba8..7b0a39999832ae40878116550785ad74a9de3a3d 100644 (file)
--- a/ntp_core.c
+++ b/ntp_core.c
@@ -375,6 +375,7 @@ do_size_checks(void)
   assert(offsetof(NTP_Packet, transmit_ts)     == 40);
 
   assert(sizeof (NTP_EFExpMonoRoot) == 24);
+  assert(sizeof (NTP_EFExpNetCorrection) == 24);
 }
 
 /* ================================================== */
@@ -1595,6 +1596,11 @@ parse_packet(NTP_Packet *packet, int length, NTP_PacketInfo *info)
                       NTP_EF_EXP_MONO_ROOT_MAGIC))
           info->ext_field_flags |= NTP_EF_FLAG_EXP_MONO_ROOT;
         break;
+      case NTP_EF_EXP_NET_CORRECTION:
+        if (is_exp_ef(ef_body, ef_body_length, sizeof (NTP_EFExpNetCorrection),
+                      NTP_EF_EXP_NET_CORRECTION_MAGIC))
+          info->ext_field_flags |= NTP_EF_FLAG_EXP_NET_CORRECTION;
+        break;
       default:
         DEBUG_LOG("Unknown extension field type=%x", (unsigned int)ef_type);
     }