Add support for TCP timestamps

src/include/gpxe/tcp.h

 	uint16_t urg;		/* Urgent pointer */
 };
 
-/**
- * TCP MSS option
+/** @defgroup tcpopts TCP options
+ * @{
  */
+
+/** End of TCP options list */
+#define TCP_OPTION_END 0
+
+/** TCP option pad */
+#define TCP_OPTION_NOP 1
+
+/** Generic TCP option */
+struct tcp_option {
+	uint8_t kind;
+	uint8_t length;
+} __attribute__ (( packed ));
+
+/** TCP MSS option */
 struct tcp_mss_option {
 	uint8_t kind;
 	uint8_t length;
 	uint16_t mss;
-};
+} __attribute__ (( packed ));
 
 /** Code for the TCP MSS option */
 #define TCP_OPTION_MSS 2
 
+/** TCP timestamp option */
+struct tcp_timestamp_option {
+	uint8_t kind;
+	uint8_t length;
+	uint32_t tsval;
+	uint32_t tsecr;
+} __attribute__ (( packed ));
+
+/** Padded TCP timestamp option (used for sending) */
+struct tcp_timestamp_padded_option {
+	uint8_t nop[2];
+	struct tcp_timestamp_option tsopt;
+} __attribute__ (( packed ));
+
+/** Code for the TCP timestamp option */
+#define TCP_OPTION_TS 8
+
+/** Parsed TCP options */
+struct tcp_options {
+	/** MSS option, if present */
+	const struct tcp_mss_option *mssopt;
+	/** Timestampe option, if present */
+	const struct tcp_timestamp_option *tsopt;
+};
+
+/** @} */
+
 /*
  * TCP flags
  */

src/net/tcp.c

 	 * Equivalent to RCV.NXT in RFC 793 terminology.
 	 */
 	uint32_t rcv_ack;
+	/** Most recent received timestamp
+	 *
+	 * Equivalent to TS.Recent in RFC 1323 terminology.
+	 */
+	uint32_t ts_recent;
+	/** Timestamps enabled */
+	int timestamps;
 
 	/** Transmit queue */
 	struct list_head queue;
 	struct io_buffer *iobuf;
 	struct tcp_header *tcphdr;
 	struct tcp_mss_option *mssopt;
+	struct tcp_timestamp_padded_option *tsopt;
 	void *payload;
 	unsigned int flags;
 	size_t len = 0;
 		mssopt->length = sizeof ( *mssopt );
 		mssopt->mss = htons ( TCP_MSS );
 	}
+	if ( ( flags & TCP_SYN ) || tcp->timestamps ) {
+		tsopt = iob_push ( iobuf, sizeof ( *tsopt ) );
+		memset ( tsopt->nop, TCP_OPTION_NOP, sizeof ( tsopt->nop ) );
+		tsopt->tsopt.kind = TCP_OPTION_TS;
+		tsopt->tsopt.length = sizeof ( tsopt->tsopt );
+		tsopt->tsopt.tsval = ntohl ( currticks() );
+		tsopt->tsopt.tsecr = ntohl ( tcp->ts_recent );
+	}
 	tcphdr = iob_push ( iobuf, sizeof ( *tcphdr ) );
 	memset ( tcphdr, 0, sizeof ( *tcphdr ) );
 	tcphdr->src = tcp->local_port;
 	return NULL;
 }
 
+/**
+ * Parse TCP received options
+ *
+ * @v tcp		TCP connection
+ * @v data		Raw options data
+ * @v len		Raw options length
+ * @v options		Options structure to fill in
+ */
+static void tcp_rx_opts ( struct tcp_connection *tcp, const void *data,
+			  size_t len, struct tcp_options *options ) {
+	const void *end = ( data + len );
+	const struct tcp_option *option;
+	unsigned int kind;
+
+	memset ( options, 0, sizeof ( *options ) );
+	while ( data < end ) {
+		option = data;
+		kind = option->kind;
+		if ( kind == TCP_OPTION_END )
+			return;
+		if ( kind == TCP_OPTION_NOP ) {
+			data++;
+			continue;
+		}
+		switch ( kind ) {
+		case TCP_OPTION_MSS:
+			options->mssopt = data;
+			break;
+		case TCP_OPTION_TS:
+			options->tsopt = data;
+			break;
+		default:
+			DBGC ( tcp, "TCP %p received unknown option %d\n",
+			       tcp, kind );
+			break;
+		}
+		data += option->length;
+	}
+}
+
 /**
  * Handle TCP received SYN
  *
  * @v tcp		TCP connection
  * @v seq		SEQ value (in host-endian order)
+ * @v options		TCP options
  * @ret rc		Return status code
  */
-static int tcp_rx_syn ( struct tcp_connection *tcp, uint32_t seq ) {
+static int tcp_rx_syn ( struct tcp_connection *tcp, uint32_t seq,
+			struct tcp_options *options ) {
 
 	/* Synchronise sequence numbers on first SYN */
-	if ( ! ( tcp->tcp_state & TCP_STATE_RCVD ( TCP_SYN ) ) )
+	if ( ! ( tcp->tcp_state & TCP_STATE_RCVD ( TCP_SYN ) ) ) {
 		tcp->rcv_ack = seq;
+		if ( options->tsopt )
+			tcp->timestamps = 1;
+	}
 
 	/* Ignore duplicate SYN */
 	if ( ( tcp->rcv_ack - seq ) > 0 )
 		    uint16_t pshdr_csum ) {
 	struct tcp_header *tcphdr = iobuf->data;
 	struct tcp_connection *tcp;
+	struct tcp_options options;
 	unsigned int hlen;
 	uint16_t csum;
 	uint32_t start_seq;
 	ack = ntohl ( tcphdr->ack );
 	win = ntohs ( tcphdr->win );
 	flags = tcphdr->flags;
+	tcp_rx_opts ( tcp, ( ( ( void * ) tcphdr ) + sizeof ( *tcphdr ) ),
+		      ( hlen - sizeof ( *tcphdr ) ), &options );
 	iob_pull ( iobuf, hlen );
 	len = iob_len ( iobuf );
 
 
 	/* Handle SYN, if present */
 	if ( flags & TCP_SYN ) {
-		tcp_rx_syn ( tcp, seq );
+		tcp_rx_syn ( tcp, seq, &options );
 		seq++;
 	}
 
 		seq++;
 	}
 
+	/* Update timestamp, if present and applicable */
+	if ( ( seq == tcp->rcv_ack ) && options.tsopt )
+		tcp->ts_recent = ntohl ( options.tsopt->tsval );
+
 	/* Dump out any state change as a result of the received packet */
 	tcp_dump_state ( tcp );