[ntp] Add simple NTP client

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/include/ipxe/errfile.h

@@ -265,6 +265,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define ERRFILE_peerblk			( ERRFILE_NET | 0x00460000 )
 #define ERRFILE_peermux			( ERRFILE_NET | 0x00470000 )
 #define ERRFILE_xsigo			( ERRFILE_NET | 0x00480000 )
+#define ERRFILE_ntp			( ERRFILE_NET | 0x00490000 )
 
 #define ERRFILE_image		      ( ERRFILE_IMAGE | 0x00000000 )
 #define ERRFILE_elf		      ( ERRFILE_IMAGE | 0x00010000 )

src/include/ipxe/ntp.h

@@ -0,0 +1,109 @@
+#ifndef _IPXE_NTP_H
+#define _IPXE_NTP_H
+
+/** @file
+ *
+ * Network Time Protocol
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <stdint.h>
+#include <ipxe/in.h>
+#include <ipxe/interface.h>
+
+/** NTP port */
+#define NTP_PORT 123
+
+/** An NTP short-format timestamp */
+struct ntp_short {
+	/** Seconds */
+	uint16_t seconds;
+	/** Fraction of a second */
+	uint16_t fraction;
+} __attribute__ (( packed ));
+
+/** An NTP timestamp */
+struct ntp_timestamp {
+	/** Seconds */
+	uint32_t seconds;
+	/** Fraction of a second */
+	uint32_t fraction;
+} __attribute__ (( packed ));
+
+/** An NTP reference identifier */
+union ntp_id {
+	/** Textual identifier */
+	char text[4];
+	/** IPv4 address */
+	struct in_addr in;
+	/** Opaque integer */
+	uint32_t opaque;
+};
+
+/** An NTP header */
+struct ntp_header {
+	/** Flags */
+	uint8_t flags;
+	/** Stratum */
+	uint8_t stratum;
+	/** Polling rate */
+	int8_t poll;
+	/** Precision */
+	int8_t precision;
+	/** Root delay */
+	struct ntp_short delay;
+	/** Root dispersion */
+	struct ntp_short dispersion;
+	/** Reference clock identifier */
+	union ntp_id id;
+	/** Reference timestamp */
+	struct ntp_timestamp reference;
+	/** Originate timestamp */
+	struct ntp_timestamp originate;
+	/** Receive timestamp */
+	struct ntp_timestamp receive;
+	/** Transmit timestamp */
+	struct ntp_timestamp transmit;
+} __attribute__ (( packed ));
+
+/** Leap second indicator: unknown */
+#define NTP_FL_LI_UNKNOWN 0xc0
+
+/** NTP version: 1 */
+#define NTP_FL_VN_1 0x20
+
+/** NTP mode: client */
+#define NTP_FL_MODE_CLIENT 0x03
+
+/** NTP mode: server */
+#define NTP_FL_MODE_SERVER 0x04
+
+/** NTP mode mask */
+#define NTP_FL_MODE_MASK 0x07
+
+/** NTP timestamp for start of Unix epoch */
+#define NTP_EPOCH 2208988800UL
+
+/** NTP fraction of a second magic value
+ *
+ * This is a policy decision.
+ */
+#define NTP_FRACTION_MAGIC 0x69505845UL
+
+/** NTP minimum retransmission timeout
+ *
+ * This is a policy decision.
+ */
+#define NTP_MIN_TIMEOUT ( 1 * TICKS_PER_SEC )
+
+/** NTP maximum retransmission timeout
+ *
+ * This is a policy decision.
+ */
+#define NTP_MAX_TIMEOUT ( 10 * TICKS_PER_SEC )
+
+extern int start_ntp ( struct interface *job, const char *hostname );
+
+#endif /* _IPXE_NTP_H */