[U-Boot,v10,2/3] Adding TCP

Message ID 20180414234336.26636-3-DH@synoia.com
State New
Delegated to: Joe Hershberger
Headers show
Series
  • Why netboot:
Related show

Commit Message

Duncan Hare April 14, 2018, 11:43 p.m.
From: Duncan Hare <DuncanCHare@yahoo.com>

All the code is new, and not copied from any source.

Series-changes
The previous patch was using an old version of net/Kconfig,
which prevented requesting options for a bootp/dhcp request.

A similar issue fixed with a cmd/Kconfig.
Items in include/net.h fixed.

Signed-off-by: Duncan Hare <DH@Synoia.com>
Signed-off-by: Duncan Hare <DuncanCHare@yahoo.com>
---

Why TCP:

Currently file transfer are done using tftp or NFS both
over udp. This requires a request to be sent from client
(u-boot) to the boot server.

For a 4 Mbyte kernel, with a 1k block size this requires
4,000 request for a block.

Using a large block size, one greater than the Ethernet
maximum frame size limitation, would require fragmentation,
which u-boot supports. However missing fragment recovery
requires timeout detection and re-transmission requests
for missing fragments.

In networks with large latency, for example: the internet,
UDP is vwey slow. What is a 30 second transfer on a local
boot server and LAN increase to over 3 minutes, because of
all the requests/response traffic.

This was anticipated in the evolution of the IP protocols
and TCP was developed and then enhanced for high latency high
bandwidth networks.

The current standard is TCP with selective acknowledgment.

Routine tcp_print_buffer() is used to print portions of
non zero terminated buffers. If there is an existing routine
please let me know. I'm from the world of length fields
not zero terminated strings (zOS).


Changes in v10: None

 include/net.h     |   8 +-
 include/net/tcp.h | 218 ++++++++++++++++
 net/Kconfig       |   5 +
 net/Makefile      |   2 +-
 net/net.c         |  51 +++-
 net/tcp.c         | 749 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 1023 insertions(+), 10 deletions(-)
 create mode 100644 include/net/tcp.h
 create mode 100644 net/tcp.c

Patch

diff --git a/include/net.h b/include/net.h
index 7e5f5a6a5b..e29d804a23 100644
--- a/include/net.h
+++ b/include/net.h
@@ -548,7 +548,7 @@  extern int		net_restart_wrap;	/* Tried all network devices */
 
 enum proto_t {
 	BOOTP, RARP, ARP, TFTPGET, DHCP, PING, DNS, NFS, CDP, NETCONS, SNTP,
-	TFTPSRV, TFTPPUT, LINKLOCAL
+	TFTPSRV, TFTPPUT, LINKLOCAL, WGET
 };
 
 extern char	net_boot_file_name[1024];/* Boot File name */
@@ -681,11 +681,15 @@  static inline void net_send_packet(uchar *pkt, int len)
  * @param payload_len Length of data after the UDP header
  */
 int net_send_ip_packet(uchar *ether, struct in_addr dest, int dport, int sport,
-		       int payload_len, int proto);
+		       int payload_len, int proto, u8 action, u32 tcp_seq_num,
+		       u32 tcp_ack_num);
 
 int net_send_udp_packet(uchar *ether, struct in_addr dest, int dport,
 			int sport, int payload_len);
 
+int net_send_tcp_packet(int payload_len, int dport, int sport, u8 action,
+			u32 tcp_seq_num, u32 tcp_ack_num);
+
 /* Processes a received packet */
 void net_process_received_packet(uchar *in_packet, int len);
 
diff --git a/include/net/tcp.h b/include/net/tcp.h
new file mode 100644
index 0000000000..81f263351e
--- /dev/null
+++ b/include/net/tcp.h
@@ -0,0 +1,218 @@ 
+/*
+ *	TCP Support for file transfer.
+ *
+ *	Copyright 2017 Duncan Hare, All rights reserved.
+ *
+ *      SPDX-License-Identifier:        GPL-2.0
+ */
+
+#define TCP_ACTIVITY 127		/* Activity on downloading      */
+
+struct ip_tcp_hdr {
+	u8		ip_hl_v;	/* header length and version	*/
+	u8		ip_tos;		/* type of service		*/
+	u16		ip_len;		/* total length			*/
+	u16		ip_id;		/* identification		*/
+	u16		ip_off;		/* fragment offset field	*/
+	u8		ip_ttl;		/* time to live			*/
+	u8		ip_p;		/* protocol			*/
+	u16		ip_sum;		/* checksum			*/
+	struct in_addr	ip_src;		/* Source IP address		*/
+	struct in_addr	ip_dst;		/* Destination IP address	*/
+	u16		tcp_src;	/* TCP source port		*/
+	u16		tcp_dst;	/* TCP destination port		*/
+	u32		tcp_seq;	/* TCP sequence number		*/
+	u32		tcp_ack;	/* TCP Acknowledgment number	*/
+	u8		tcp_hlen;	/* 4 bits TCP header Length/4	*/
+					/* 4 bits Reserved		*/
+					/* 2 more bits reserved		*/
+	u8		tcp_flags;	/* see defines			*/
+	u16		tcp_win;	/* TCP windows size		*/
+	u16		tcp_xsum;	/* Checksum			*/
+	u16		tcp_ugr;	/* Pointer to urgent data	*/
+} __packed;
+
+#define IP_TCP_HDR_SIZE		(sizeof(struct ip_tcp_hdr))
+#define TCP_HDR_SIZE		(IP_TCP_HDR_SIZE  - IP_HDR_SIZE)
+
+#define TCP_DATA	0x00	/* Data Packet - internal use only	*/
+#define TCP_FIN		0x01	/* Finish flag				*/
+#define TCP_SYN		0x02	/* Synch (start) flag			*/
+#define TCP_RST		0x04	/* reset flag				*/
+#define TCP_PUSH	0x08	/* Push - Notify app			*/
+#define TCP_ACK		0x10	/* Acknowledgment of data received	*/
+#define TCP_URG		0x20	/* Urgent				*/
+#define TCP_ECE		0x40	/* Congestion control			*/
+#define TCP_CWR		0x80	/* Congestion Control			*/
+
+/*
+ * TCP header options, Seq, MSS, and SACK
+ */
+
+#define TCP_SACK 32			/* Number of packets analyzed   */
+					/* on leading edge of stream    */
+
+#define TCP_O_END	0x00		/* End of option list		*/
+#define TCP_1_NOP	0x01		/* Single padding NOP		*/
+#define TCP_O_NOP	0x01010101	/* NOPs pad to 32 bit boundary	*/
+#define TCP_O_MSS	0x02		/* MSS Size option		*/
+#define TCP_O_SCL	0x03		/* Window Scale option		*/
+#define TCP_P_SACK	0x04		/* SACK permitted		*/
+#define TCP_V_SACK	0x05		/* SACK values			*/
+#define TCP_O_TS	0x08		/* Timestanp option		*/
+#define TCP_OPT_LEN_2	0x02
+#define TCP_OPT_LEN_3	0x03
+#define TCP_OPT_LEN_4	0x04
+#define TCP_OPT_LEN_6	0x06
+#define TCP_OPT_LEN_8	0x08
+#define TCP_OPT_LEN_A	0x0a		/* Timestamp Length		*/
+
+/*
+ * Please review the warning in net.c about these two parameters.
+ * They are part of a promise of RX buffer size to the sending TCP
+ */
+
+#define TCP_MSS		1460		/* Max segment size - 1460	*/
+#define TCP_SCALE	0x01		/* Scale 1			*/
+
+struct tcp_mss {			/* TCP Mex Segment size		*/
+	u8	kind;			/* 0x02				*/
+	u8	len;			/* 0x04				*/
+	u16	mss;			/* 1460 - Max segment size	*/
+} __packed;
+
+struct tcp_scale {			/* TCP Windows Scale		*/
+	u8	kind;			/* 0x03				*/
+	u8	len;			/* 0x03				*/
+	u8	scale;			/* win shift fat fast networks	*/
+} __packed;
+
+struct tcp_sack_p {			/* SACK permitted		*/
+	u8	kind;			/* 0x04				*/
+	u8	len;			/* Length			*/
+} __packed;
+
+struct sack_edges {
+	u32	l;
+	u32	r;
+} __packed;
+
+#define TCP_SACK_SIZE (sizeof(struct sack_edges))
+
+#define TCP_SACK_HILLS	4
+
+struct tcp_sack_v {
+	u8	kind;			/* 0x05			        */
+	u8	len;				 /* Length		*/
+	struct	sack_edges hill[TCP_SACK_HILLS]; /* L & R widow edges	*/
+} __packed;
+
+struct tcp_t_opt {			/* TCP time stamps option	*/
+	u8	kind;			/* 0x08				*/
+	u8	len;			/* 0x0a				*/
+	u32	t_snd;			/* Sender timestamp		*/
+	u32	t_rcv;			/* Receiver timestamp		*/
+} __packed;
+
+#define TCP_TSOPT_SIZE	(sizeof(struct tcp_t_opt))
+
+/*
+ * ip tcp  structure with options
+ */
+
+struct ip_tcp_hdr_o {
+	struct	ip_tcp_hdr	hdr;
+	struct	tcp_mss		mss;
+	struct	tcp_scale	scale;
+	struct	tcp_sack_p	sack_p;
+	struct	tcp_t_opt	t_opt;
+	u8	end;
+} __packed;
+
+#define IP_TCP_O_SIZE		(sizeof(struct ip_tcp_hdr_o))
+
+struct ip_tcp_hdr_s {
+	struct	ip_tcp_hdr	hdr;
+	struct	tcp_t_opt	t_opt;
+	struct	tcp_sack_v	sack_v;
+	u8	end;
+} __packed;
+
+#define IP_TCP_SACK_SIZE	(sizeof(struct ip_tcp_hdr_s))
+
+/*
+ * TCP pseudo header definitions
+ */
+#define PSEUDO_PAD_SIZE	8
+
+struct pseudo_hdr {
+	u8 padding[PSEUDO_PAD_SIZE];	/* pseudo hdr size = ip_tcp hdr size */
+	struct in_addr p_src;
+	struct in_addr p_dst;
+	u8      rsvd;
+	u8      p;
+	u16     len;
+} __packed;
+
+#define PSEUDO_HDR_SIZE	(sizeof(struct pseudo_hdr)) - PSEUDO_PAD_SIZE
+
+/*
+ * union for building IP/TCP packet.
+ * build Pseudo header in packed buffer first, calculate TCP checksum
+ * then build IP header in packed  buffer.
+ */
+
+union tcp_build_pkt {
+	struct pseudo_hdr ph;
+	struct ip_tcp_hdr_o ip;
+	struct ip_tcp_hdr_s sack;
+	uchar  raw[1600];
+} __packed;
+
+/*
+ * TCP STATE MACHINE STATES FOR SOCKET
+ */
+
+enum TCP_STATE {
+	TCP_CLOSED,		/* Need to send SYN to connect		  */
+	TCP_SYN_SENT,		/* Trying to connect, waiting for SYN ACK */
+	TCP_ESTABLISHED,	/* both server & client have a connection */
+	TCP_CLOSE_WAIT,		/* Rec FIN, passed to app for FIN, ACK rsp*/
+	TCP_CLOSING,		/* Rec FIN, sent FIN, ACK waiting for ACK */
+	TCP_FIN_WAIT_1,		/* Sent FIN waiting for response	  */
+	TCP_FIN_WAIT_2		/* Rec ACK from FIN sent, waiting for FIN */
+};
+
+int tcp_find_in_buffer(uchar raw[], int payload_len, uchar field[],
+		       int field_len);
+void tcp_print_buffer(uchar raw[], int pkt_len, int payload_len,
+		      int hdr_len, bool hide);
+enum TCP_STATE tcp_get_tcp_state(void);
+void tcp_set_tcp_state(enum TCP_STATE new_state);
+int tcp_set_tcp_header(uchar *pkt, int dport, int sport, int payload_len,
+		       u8 action, u32 tcp_seq_num, u32 tcp_ack_num);
+
+/*
+ * An incoming packet handler.
+ * @param pkt    pointer to the application packet
+ * @param dport  destination UDP port
+ * @param sip    source IP address
+ * @param sport  source UDP port
+ * @param len    packet length
+ */
+typedef void rxhand_tcp(uchar *pkt, unsigned int dport,
+			struct in_addr sip, unsigned int sport,
+			unsigned int len);
+void tcp_set_tcp_handler(rxhand_tcp *f);
+
+void rxhand_tcp_f(union tcp_build_pkt *b, unsigned int len);
+
+/*
+ * An incoming TCP packet handler for the TCP protocol.
+ * There is also a dynamic function pointer for TCP based commands to
+ * receive incoming traffic after the TCP protocol code has done its work.
+ */
+
+void rxhand_action(u8 tcp_action, int payload_len, u32 tcp_seq_num,
+		   u32 tcp_ack_num, unsigned int pkt_len,
+		   union tcp_build_pkt *b);
diff --git a/net/Kconfig b/net/Kconfig
index 143c4416cd..cc6dd83fc4 100644
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -33,6 +33,11 @@  config NET_TFTP_VARS
 	  If unset, timeout and maximum are hard-defined as 1 second
 	  and 10 timouts per TFTP transfer.
 
+config TCP
+	bool "Include Subset TCP stack for wget"
+	help
+	  TCP protocol support for wget.
+
 config BOOTP_BOOTPATH
 	bool "Enable BOOTP BOOTPATH"
 	depends on CMD_NET
diff --git a/net/Makefile b/net/Makefile
index ae54eee5af..25729ebeeb 100644
--- a/net/Makefile
+++ b/net/Makefile
@@ -25,7 +25,7 @@  obj-$(CONFIG_CMD_PING) += ping.o
 obj-$(CONFIG_CMD_RARP) += rarp.o
 obj-$(CONFIG_CMD_SNTP) += sntp.o
 obj-$(CONFIG_CMD_NET)  += tftp.o
-
+obj-$(CONFIG_TCP)      += tcp.o
 # Disable this warning as it is triggered by:
 # sprintf(buf, index ? "foo%d" : "foo", index)
 # and this is intentional usage.
diff --git a/net/net.c b/net/net.c
index df4e7317e7..7adc4b472c 100644
--- a/net/net.c
+++ b/net/net.c
@@ -107,6 +107,9 @@ 
 #if defined(CONFIG_CMD_SNTP)
 #include "sntp.h"
 #endif
+#if defined(CONFIG_TCP)
+#include <net/tcp.h>
+#endif
 
 DECLARE_GLOBAL_DATA_PTR;
 
@@ -382,6 +385,9 @@  void net_init(void)
 
 		/* Only need to setup buffer pointers once. */
 		first_call = 0;
+#if defined(CONFIG_TCP)
+		tcp_set_tcp_state(TCP_CLOSED);
+#endif
 	}
 
 	net_init_loop();
@@ -781,11 +787,22 @@  int net_send_udp_packet(uchar *ether, struct in_addr dest, int dport, int sport,
 			int payload_len)
 {
 	return net_send_ip_packet(ether, dest, dport, sport, payload_len,
-				  IPPROTO_UDP);
+				  IPPROTO_UDP, 0, 0, 0);
+}
+
+#if defined(CONFIG_TCP)
+int net_send_tcp_packet(int payload_len, int dport, int sport, u8 action,
+			u32 tcp_seq_num, u32 tcp_ack_num)
+{
+	return net_send_ip_packet(net_server_ethaddr, net_server_ip, dport,
+				  sport, payload_len, IPPROTO_TCP, action,
+				  tcp_seq_num, tcp_ack_num);
 }
+#endif
 
 int net_send_ip_packet(uchar *ether, struct in_addr dest, int dport, int sport,
-		       int payload_len, int proto)
+		       int payload_len, int proto, u8 action, u32 tcp_seq_num,
+		       u32 tcp_ack_num)
 {
 	uchar *pkt;
 	int eth_hdr_size;
@@ -794,6 +811,13 @@  int net_send_ip_packet(uchar *ether, struct in_addr dest, int dport, int sport,
 		debug_cond(DEBUG_DEV_PKT,
 			   "UDP Send  (to=%pI4, from=%pI4, len=%d)\n",
 			   &dest, &net_ip, payload_len);
+#if defined(CONFIG_TCP)
+
+	} else {
+		debug_cond(DEBUG_DEV_PKT,
+			   "TCP Send  (%pI4, %pI4, len=%d, A=%x)\n",
+			   &dest, &net_ip, payload_len, action);
+#endif
 	}
 
 	/* make sure the net_tx_packet is initialized (net_init() was called) */
@@ -812,15 +836,19 @@  int net_send_ip_packet(uchar *ether, struct in_addr dest, int dport, int sport,
 	pkt = (uchar *)net_tx_packet;
 
 	eth_hdr_size = net_set_ether(pkt, ether, PROT_IP);
-	switch (proto) {
-	case IPPROTO_UDP:
+	if (proto == IPPROTO_UDP) {
 		net_set_udp_header(pkt + eth_hdr_size, dest,
 				   dport, sport, payload_len);
 		pkt_hdr_size = eth_hdr_size + IP_UDP_HDR_SIZE;
-	break;
-	default:
-		return -1;
+
+#if defined(CONFIG_TCP)
+	} else {
+		pkt_hdr_size = eth_hdr_size +
+		tcp_set_tcp_header(pkt + eth_hdr_size, dport, sport,
+				   payload_len, action,
+				   tcp_seq_num, tcp_ack_num);
 	}
+#endif
 
 	/* if MAC address was not discovered yet, do an ARP request */
 	if (memcmp(ether, net_null_ethaddr, 6) == 0) {
@@ -1225,6 +1253,15 @@  void net_process_received_packet(uchar *in_packet, int len)
 		if (ip->ip_p == IPPROTO_ICMP) {
 			receive_icmp(ip, len, src_ip, et);
 			return;
+#if defined(CONFIG_TCP)
+		} else if (ip->ip_p == IPPROTO_TCP) {
+			debug_cond(DEBUG_DEV_PKT,
+				   "TCP PH (to=%pI4, from=%pI4, len=%d)\n",
+				   &dst_ip, &src_ip, len);
+
+				rxhand_tcp_f((union tcp_build_pkt *)ip, len);
+			return;
+#endif
 		} else if (ip->ip_p != IPPROTO_UDP) {	/* Only UDP packets */
 			return;
 		}
diff --git a/net/tcp.c b/net/tcp.c
new file mode 100644
index 0000000000..9f4fc9fc20
--- /dev/null
+++ b/net/tcp.c
@@ -0,0 +1,749 @@ 
+/*
+ *	Copyright 2017 Duncan Hare, all rights reserved.
+ *	SPDX-License-Identifier:        GPL-2.0
+ */
+
+/*
+ * General Desription:
+ *
+ * TCP support for the wget command, for fast file downloading.
+ *
+ * HTTP/TCP Receiver:
+ *
+ *      Prequeisites:   - own ethernet address
+ *                      - own IP address
+ *                      - Server IP address
+ *                      - Server with TCP
+ *                      - TCP application (eg wget)
+ *      Next Step       HTTPS?
+ */
+#include <common.h>
+#include <command.h>
+#include <console.h>
+#include <environment.h>
+#include <errno.h>
+#include <net.h>
+#include <net/tcp.h>
+#if defined(CONFIG_CMD_WGET)
+#include <net/wget.h>
+#endif
+
+/*
+ * TCP sliding window  control
+ * used by us to request re-TX
+ */
+
+static struct tcp_sack_v tcp_lost;
+
+/* TCP option timestamp */
+static u32 loc_timestamp;
+static u32 rmt_timestamp;
+
+u32 tcp_seq_init;
+u32 tcp_ack_edge;
+u32 tcp_seq_max;
+
+int tcp_activity_count;
+
+/*
+ * Search for TCP_SACK and review the
+ * comments before the code section
+ * TCP_SACK is the number of packets
+ * at the front of the stream
+ */
+
+enum pkt_state {PKT, NOPKT};
+struct sack_r {
+	struct sack_edges se;
+	enum   pkt_state st;
+};
+
+struct sack_r edge_a[TCP_SACK];
+unsigned int sack_idx;
+unsigned int prev_len;
+
+/* TCP connection state */
+static enum TCP_STATE tcp_state;
+
+/*
+ * An incoming TCP packet handler for the TCP protocol.
+ * There is also a dymanic function pointer for TCP based commads to
+ * receive incoming traffic after the TCP protocol code has done its work.
+ */
+
+/* Current TCP RX packet handler */
+static rxhand_tcp *tcp_packet_handler;
+
+enum TCP_STATE tcp_get_tcp_state(void)
+{
+	return tcp_state;
+}
+
+void tcp_set_tcp_state(enum TCP_STATE new_state)
+{
+	tcp_state = new_state;
+}
+
+void tcp_print_buffer(uchar raw[], int pkt_len, int payload_len,
+		      int hdr_len, bool hide)
+{
+	int i;
+
+	for (i = pkt_len - payload_len; i < pkt_len; i++) {
+		if (i <= hdr_len)
+			printf("%02X", raw[i]);
+		else if ((raw[i] > 0x19) && (raw[i] < 0x7f))
+			putc(raw[i]);
+		else if (hide == 0)
+			putc(raw[i]);
+		else
+			printf("%02X", raw[i]);
+	}
+	printf("%s", "\n");
+}
+
+int tcp_find_in_buffer(uchar raw[], int payload_len, uchar field[],
+		       int field_len)
+{
+	int i, j;
+
+	for (i = 0; i < payload_len; i++) {
+		if (raw[i] == field[0]) {
+			for (j = 1; j < field_len; j++) {
+				if (raw[i + j] != field[j])
+					break;
+			if (j == field_len)
+				return i;
+			}
+		}
+	}
+	return 0;
+}
+
+static void dummy_handler(uchar *pkt, unsigned int dport,
+			  struct in_addr sip, unsigned int sport,
+			  unsigned int len)
+{
+}
+
+void tcp_set_tcp_handler(rxhand_tcp *f)
+{
+	debug_cond(DEBUG_INT_STATE, "--- net_loop TCP handler set (%p)\n", f);
+	if (!f)
+		tcp_packet_handler = dummy_handler;
+	else
+		tcp_packet_handler = f;
+}
+
+u16 tcp_set_pseudo_header(uchar *pkt, struct in_addr src, struct in_addr dest,
+			  int tcp_len, int pkt_len)
+{
+	union tcp_build_pkt *b = (union tcp_build_pkt *)pkt;
+	int checksum_len;
+
+	/*
+	 * Pseudo header
+	 *
+	 * Zero the byte after the last byte so that the header checksum
+	 * will always work.
+	 */
+
+	pkt[pkt_len] = 0x00;
+
+	net_copy_ip((void *)&b->ph.p_src, &src);
+	net_copy_ip((void *)&b->ph.p_dst, &dest);
+	b->ph.rsvd	= 0x00;
+	b->ph.p		= IPPROTO_TCP;
+	b->ph.len	= htons(tcp_len);
+	checksum_len	= tcp_len + PSEUDO_HDR_SIZE;
+
+	debug_cond(DEBUG_DEV_PKT,
+		   "TCP Pesudo  Header  (to=%pI4, from=%pI4, Len=%d)\n",
+		   &b->ph.p_dst, &b->ph.p_src, checksum_len);
+
+	return compute_ip_checksum(pkt + PSEUDO_PAD_SIZE, checksum_len);
+}
+
+int net_set_ack_options(union tcp_build_pkt *b)
+{
+	b->sack.hdr.tcp_hlen  = (TCP_HDR_SIZE >> 2) << 4;
+
+	b->sack.t_opt.kind		= TCP_O_TS;
+	b->sack.t_opt.len		= TCP_OPT_LEN_A;
+	b->sack.t_opt.t_snd		= htons(loc_timestamp);
+	b->sack.t_opt.t_rcv		= rmt_timestamp;
+	b->sack.sack_v.kind             = 0x01;
+	b->sack.sack_v.len		= 0x00;
+
+	if (tcp_lost.len > TCP_OPT_LEN_2) {
+		debug_cond(DEBUG_DEV_PKT, "TCP ack opt lost.len %x\n",
+			   tcp_lost.len);
+		b->sack.sack_v.len              = tcp_lost.len;
+		b->sack.sack_v.kind		= TCP_V_SACK;
+		b->sack.sack_v.hill[0].l = htonl(tcp_lost.hill[0].l);
+		b->sack.sack_v.hill[0].r = htonl(tcp_lost.hill[0].r);
+
+		/*
+		 * These SACK structures are initialized with NOPs to
+		 * provide TCP header alignment padding. There are 4
+		 * SACK structures used for both header padding and
+		 * internally.
+		 */
+
+		b->sack.sack_v.hill[1].l = htonl(tcp_lost.hill[1].l);
+		b->sack.sack_v.hill[1].r = htonl(tcp_lost.hill[1].r);
+		b->sack.sack_v.hill[2].l = htonl(tcp_lost.hill[2].l);
+		b->sack.sack_v.hill[2].r = htonl(tcp_lost.hill[2].r);
+		b->sack.sack_v.hill[3].l = TCP_O_NOP;
+		b->sack.sack_v.hill[3].r = TCP_O_NOP;
+	}
+
+	/*
+	 * TCP lengths are stored as a rounded up number of 32 bit words
+	 * Add 3 to length round up, rounded, then divided into the length
+	 * in 32 bit words.
+	 */
+
+	b->sack.hdr.tcp_hlen = (((TCP_HDR_SIZE + TCP_TSOPT_SIZE
+				+ tcp_lost.len + 3)  >> 2) << 4);
+
+	/*
+	 * This returns the actual rounded up length of the
+	 * TCP header to add to the total packet length
+	 */
+
+	return b->sack.hdr.tcp_hlen >> 2;
+}
+
+void net_set_syn_options(union tcp_build_pkt *b)
+{
+	tcp_lost.len		= 0;
+	b->ip.hdr.tcp_hlen      = 0xa0;
+
+	b->ip.mss.kind          = TCP_O_MSS;
+	b->ip.mss.len           = TCP_OPT_LEN_4;
+	b->ip.mss.mss           = htons(TCP_MSS);
+	b->ip.scale.kind        = TCP_O_SCL;
+	b->ip.scale.scale       = TCP_SCALE;
+	b->ip.scale.len         = TCP_OPT_LEN_3;
+	b->ip.sack_p.kind       = TCP_P_SACK;
+	b->ip.sack_p.len        = TCP_OPT_LEN_2;
+	b->ip.t_opt.kind        = TCP_O_TS;
+	b->ip.t_opt.len         = TCP_OPT_LEN_A;
+	loc_timestamp           = get_ticks() % 3072;
+	rmt_timestamp           = 0x00000000;
+	b->ip.t_opt.t_snd       = 0;
+	b->ip.t_opt.t_rcv       = 0x00000000;
+	b->ip.end               = TCP_O_END;
+}
+
+int tcp_set_tcp_header(uchar *pkt, int dport, int sport, int payload_len,
+		       u8 action, u32 tcp_seq_num, u32 tcp_ack_num)
+{
+	union tcp_build_pkt *b = (union tcp_build_pkt *)pkt;
+	int	pkt_hdr_len;
+	int	pkt_len;
+	int	tcp_len;
+
+	b->ip.hdr.tcp_flags	= action;
+	pkt_hdr_len		= IP_TCP_HDR_SIZE;
+	b->ip.hdr.tcp_hlen      = 0x50;		/* Header is 5 32 bit words  */
+						/* 4 bits TCP header Length/4*/
+						/* 4 bits Reserved           */
+						/* For options		     */
+	switch (action) {
+	case TCP_SYN:
+		debug_cond(DEBUG_DEV_PKT,
+			   "TCP Hdr:SYN (%pI4, %pI4, sq=%d, ak=%d)\n",
+			   &net_server_ip, &net_ip,
+			   tcp_seq_num, tcp_ack_num);
+		tcp_activity_count = 0;
+		net_set_syn_options(b);
+		tcp_seq_num = 0;
+		tcp_ack_num = 0;
+		pkt_hdr_len = IP_TCP_O_SIZE;
+		if (tcp_state == TCP_SYN_SENT) {  /* Too many sins */
+			action    = TCP_FIN;
+			tcp_state = TCP_FIN_WAIT_1;
+		} else {
+			tcp_state = TCP_SYN_SENT;
+		}
+	break;
+	case TCP_ACK:
+		pkt_hdr_len         = IP_HDR_SIZE +
+				      net_set_ack_options(b);
+		b->ip.hdr.tcp_flags = action;
+		debug_cond(DEBUG_DEV_PKT,
+			   "TCP Hdr:ACK (%pI4, %pI4, s=%d, a=%d, A=%x)\n",
+			   &net_server_ip, &net_ip, tcp_seq_num, tcp_ack_num,
+			   action);
+	break;
+	case TCP_FIN:
+		debug_cond(DEBUG_DEV_PKT,
+			   "TCP Hdr:FIN  (%pI4, %pI4, s=%d, a=%d)\n",
+			   &net_server_ip, &net_ip, tcp_seq_num, tcp_ack_num);
+		payload_len = 0;
+		pkt_hdr_len = IP_TCP_HDR_SIZE;
+		tcp_state   = TCP_FIN_WAIT_1;
+
+	break;
+
+	/* Notify connection closing */
+
+	case (TCP_FIN | TCP_ACK):
+	case ((TCP_FIN | TCP_ACK) | TCP_PUSH):
+		if (tcp_state == TCP_CLOSE_WAIT)
+			tcp_state = TCP_CLOSING;
+		tcp_ack_edge++;
+		debug_cond(DEBUG_DEV_PKT,
+			   "TCP Hdr:FIN ACK PSH(%pI4, %pI4, s=%d, a=%d, A=%x)\n",
+			   &net_server_ip, &net_ip,
+			   tcp_seq_num, tcp_ack_edge, action);
+					/* FALLTHRU */
+	default:
+		pkt_hdr_len         = IP_HDR_SIZE +
+				      net_set_ack_options(b);
+		b->ip.hdr.tcp_flags = action | TCP_PUSH | TCP_ACK;
+		debug_cond(DEBUG_DEV_PKT,
+			   "TCP Hdr:dft  (%pI4, %pI4, s=%d, a=%d, A=%x)\n",
+			   &net_server_ip, &net_ip,
+			   tcp_seq_num, tcp_ack_num, action);
+	}
+
+	pkt_len	= pkt_hdr_len + payload_len;
+	tcp_len	= pkt_len - IP_HDR_SIZE;
+
+	/* TCP Header */
+	b->ip.hdr.tcp_ack       = htonl(tcp_ack_edge);
+	b->ip.hdr.tcp_src	= htons(sport);
+	b->ip.hdr.tcp_dst	= htons(dport);
+	b->ip.hdr.tcp_seq	= htonl(tcp_seq_num);
+	tcp_seq_num		= tcp_seq_num + payload_len;
+
+	/*
+	 * TCP window size - TCP header variable tcp_win.
+	 * Change tcp_win only if you have an understanding of network
+	 * overrun, congestion, TCP segment sizes, TCP windows, TCP scale,
+	 * queuing theory  and packet buffering. If there are too few buffers,
+	 * there will be data loss, recovery may work or the sending TCP,
+	 * the server, could abort the stream transmission.
+	 * MSS is governed by maximum Ethernet frame length.
+	 * The number of buffers is governed by the desire to have a queue of
+	 * full buffers to be processed at the destination to maximize
+	 * throughput. Temporary memory use for the boot phase on modern
+	 * SOCs is may not be considered a constraint to buffer space, if
+	 * it is, then the u-boot tftp or nfs kernel netboot should be
+	 * considered.
+	 */
+
+	b->ip.hdr.tcp_win	= htons(PKTBUFSRX * TCP_MSS >>  TCP_SCALE);
+
+	b->ip.hdr.tcp_xsum	= 0x0000;
+	b->ip.hdr.tcp_ugr	= 0x0000;
+
+	b->ip.hdr.tcp_xsum = tcp_set_pseudo_header(pkt, net_ip, net_server_ip,
+						   tcp_len, pkt_len);
+
+	/*
+	 * IP Header
+	 */
+
+	net_set_ip_header((uchar *)&b->ip, net_server_ip, net_ip,
+			  pkt_len, IPPROTO_TCP);
+
+	return pkt_hdr_len;
+}
+
+/*
+ * Selective Acknowledgment (Essential for fast stream transfer)
+ *
+ * Before modifying this section of code, which the author found difficult
+ * to write, please be familiar with the SACK (Selective Acknowledgment) RFCs.
+ */
+
+void tcp_hole(u32 tcp_seq_num, u32 len, u32 tcp_seq_max)
+{
+	unsigned int idx_sack;
+	unsigned int sack_end = TCP_SACK - 1;
+	unsigned int sack_in;
+	unsigned int hill = 0;
+	enum pkt_state expect = PKT;
+
+	u32 seq   = tcp_seq_num - tcp_seq_init;
+	u32 hol_l = tcp_ack_edge - tcp_seq_init;
+	u32 hol_r = 0;
+
+	/* Place seq number in correct place */
+
+	if (prev_len == 0)
+		prev_len = len;
+	idx_sack = sack_idx + ((tcp_seq_num - tcp_ack_edge) / prev_len);
+	if (idx_sack < TCP_SACK) {
+		edge_a[idx_sack].se.l = tcp_seq_num;
+		edge_a[idx_sack].se.r = tcp_seq_num + len;
+		edge_a[idx_sack].st   = PKT;
+
+		/* The fin (last) packet is not the same length as data packets,
+		 * and if it's length is recorded and used for array index
+		 * the array index calculations break.
+		 */
+		if (prev_len < len)
+			prev_len = len;
+	}
+
+	debug_cond(DEBUG_DEV_PKT,
+		   "TCP 1 seq %d, edg %d, len %d, sack_idx %d, sack_end %d\n",
+		    seq, hol_l, len, sack_idx, sack_end);
+
+	/* Right edge of contiguous stream, is the left edge of first hill */
+
+	hol_l = tcp_seq_num - tcp_seq_init;
+	hol_r = hol_l + len;
+
+	tcp_lost.len = TCP_OPT_LEN_2;
+
+	debug_cond(DEBUG_DEV_PKT,
+		   "TCP 1 in %d, seq %d, pkt_l %d, pkt_r %d, sack_idx %d, sack_end %d\n",
+		   idx_sack, seq, hol_l, hol_r, sack_idx, sack_end);
+
+	for (sack_in = sack_idx; sack_in < sack_end && hill < TCP_SACK_HILLS;
+		 sack_in++)  {
+		switch (expect) {
+		case NOPKT:
+			switch (edge_a[sack_in].st) {
+			case NOPKT:
+				debug_cond(DEBUG_INT_STATE, "N");
+			break;
+			case PKT:
+				debug_cond(DEBUG_INT_STATE, "n");
+					tcp_lost.hill[hill].l =
+						edge_a[sack_in].se.l;
+					tcp_lost.hill[hill].r =
+						edge_a[sack_in].se.r;
+				expect = PKT;
+			break;
+			}
+		break;
+		case PKT:
+			switch (edge_a[sack_in].st) {
+			case NOPKT:
+				debug_cond(DEBUG_INT_STATE, "p");
+				if ((sack_in > sack_idx) &&
+				    (hill < TCP_SACK_HILLS)) {
+					hill++;
+					tcp_lost.len += TCP_OPT_LEN_8;
+				}
+				expect = NOPKT;
+			break;
+			case PKT:
+				debug_cond(DEBUG_INT_STATE, "P");
+
+				if (tcp_ack_edge == edge_a[sack_in].se.l) {
+					tcp_ack_edge = edge_a[sack_in].se.r;
+					edge_a[sack_in].st = NOPKT;
+					sack_idx++;
+				} else {
+					if (hill < TCP_SACK_HILLS)
+						tcp_lost.hill[hill].r =
+							edge_a[sack_in].se.r;
+				if (sack_in == sack_end - 1)
+					tcp_lost.hill[hill].r =
+						edge_a[sack_in].se.r;
+				}
+			break;
+			}
+		break;
+		}
+	}
+	debug_cond(DEBUG_INT_STATE, "\n");
+	if (tcp_lost.len <= TCP_OPT_LEN_2)
+		sack_idx = 0;
+}
+
+void tcp_parse_options(uchar *o, int o_len)
+{
+	struct tcp_t_opt  *tsopt;
+	uchar *p = o;
+
+	for (p = o; p < (o + o_len); p = p + p[1]) {
+		if (p[1] != 0) {
+			switch (p[0]) {
+			case TCP_O_END:
+				return;
+			case TCP_O_MSS:
+			break;
+			case TCP_O_SCL:
+			break;
+			case TCP_P_SACK:
+			break;
+			case TCP_V_SACK:
+			break;
+			case TCP_O_TS:
+				tsopt = (struct tcp_t_opt *)p;
+				rmt_timestamp = tsopt->t_snd;
+				return;
+			break;
+			}
+			if (p[0] == TCP_O_NOP)
+				p++;
+		} else {
+			return;
+		}
+	}
+}
+
+u8 tcp_state_machine(u8 tcp_flags, u32 *tcp_seq_num, int payload_len)
+{
+	u8  tcp_fin  = tcp_flags & TCP_FIN;
+	u8  tcp_syn  = tcp_flags & TCP_SYN;
+	u8  tcp_rst  = tcp_flags & TCP_RST;
+	u8  tcp_push = tcp_flags & TCP_PUSH;
+	u8  tcp_ack  = tcp_flags & TCP_ACK;
+	u8  action   = TCP_DATA;
+	int i;
+
+	/*
+	 * tcp_flags are examined to determine TX action in a given state
+	 * tcp_push is interpreted to mean "inform the app"
+	 * urg, ece, cer and nonce flags are not supported.
+	 *
+	 * exe and crw are use to signal and confirm knowledge of congestion.
+	 * This TCP only sends a file request and acks. If it generates
+	 * congestion, the network is broken.
+	 */
+
+	debug_cond(DEBUG_INT_STATE, "TCP STATE ENTRY %x\n", action);
+	if (tcp_rst) {
+		action    = TCP_DATA;
+		tcp_state = TCP_CLOSED;
+		net_set_state(NETLOOP_FAIL);
+		debug_cond(DEBUG_INT_STATE, "TCP Reset %x\n", tcp_flags);
+		return TCP_RST;
+	}
+
+	switch  (tcp_state) {
+	case TCP_CLOSED:
+	debug_cond(DEBUG_INT_STATE, "TCP CLOSED %x\n", tcp_flags);
+		if (tcp_fin)
+			action = TCP_DATA;
+		if (tcp_syn)
+			action = TCP_RST;
+		if (tcp_ack)
+			action = TCP_DATA;
+	break;
+	case TCP_SYN_SENT:
+		debug_cond(DEBUG_INT_STATE, "TCP_SYN_SENT %x, %d\n",
+			   tcp_flags, *tcp_seq_num);
+		if (tcp_fin) {
+			action = action | TCP_PUSH;
+			tcp_state = TCP_CLOSE_WAIT;
+		}
+		if (tcp_syn) {
+			action = action |  TCP_ACK | TCP_PUSH;
+			if (tcp_ack) {
+				tcp_seq_init          = *tcp_seq_num;
+				*tcp_seq_num          = *tcp_seq_num + 1;
+				tcp_seq_max           = *tcp_seq_num;
+				tcp_ack_edge          = *tcp_seq_num;
+				sack_idx              = 0;
+				edge_a[sack_idx].se.l = *tcp_seq_num;
+				edge_a[sack_idx].se.r = *tcp_seq_num;
+				prev_len              = 0;
+				tcp_state             = TCP_ESTABLISHED;
+				for (i = 0; i < TCP_SACK; i++)
+					edge_a[i].st   = NOPKT;
+			}
+		} else {
+			if (tcp_ack)
+				action = TCP_DATA;
+		}
+	break;
+	case TCP_ESTABLISHED:
+		debug_cond(DEBUG_INT_STATE,
+			   "TCP_ESTABLISHED %x\n", tcp_flags);
+		if (*tcp_seq_num > tcp_seq_max)
+			tcp_seq_max = *tcp_seq_num;
+		if (payload_len > 0) {
+			tcp_hole(*tcp_seq_num, payload_len, tcp_seq_max);
+			tcp_fin = TCP_DATA;  /* cause standalone FIN */
+		}
+
+		if ((tcp_fin) && (tcp_lost.len <= TCP_OPT_LEN_2)) {
+			action    = action | TCP_FIN | TCP_PUSH | TCP_ACK;
+			tcp_state =  TCP_CLOSE_WAIT;
+		} else {
+			if (tcp_ack)
+				action = TCP_DATA;
+		}
+		if (tcp_push)
+			action = action | TCP_PUSH;
+		if (tcp_syn)
+			action = TCP_ACK + TCP_RST;
+	break;
+	case TCP_CLOSE_WAIT:
+		debug_cond(DEBUG_INT_STATE, "TCP_CLOSE_WAIT (%x)\n", tcp_flags);
+		action = TCP_DATA;			/* Wait for app	*/
+	break;
+	case TCP_FIN_WAIT_2:
+		debug_cond(DEBUG_INT_STATE, "TCP_FIN_WAIT_2 (%x)\n", tcp_flags);
+		if (tcp_fin)
+			action =  TCP_DATA;
+		if (tcp_syn)
+			action =  TCP_DATA;
+		if (tcp_ack) {
+			action =  TCP_PUSH | TCP_ACK;
+			tcp_state = TCP_CLOSED;
+			puts("\n");
+		}
+	break;
+	case TCP_FIN_WAIT_1:
+		debug_cond(DEBUG_INT_STATE, "TCP_FIN_WAIT_1 (%x)\n", tcp_flags);
+		if (tcp_fin) {
+			action = TCP_ACK | TCP_FIN;
+			 tcp_state = TCP_FIN_WAIT_2;
+		}
+		if (tcp_syn)
+			action =  TCP_RST;
+		if (tcp_ack) {
+			tcp_state = TCP_CLOSED;
+			tcp_seq_num = tcp_seq_num + 1;
+		}
+	break;
+	case TCP_CLOSING:
+		debug_cond(DEBUG_INT_STATE, "TCP_CLOSING (%x)\n", tcp_flags);
+		if (tcp_fin)
+			action = TCP_DATA;
+		if (tcp_syn)
+			action = TCP_RST;
+		if (tcp_ack) {
+			action = TCP_PUSH;
+			tcp_state = TCP_CLOSED;
+			puts("\n");
+		}
+	break;
+	}
+	return action;
+}
+
+void rxhand_tcp_f(union tcp_build_pkt *b, unsigned int pkt_len)
+{
+	int tcp_len     = pkt_len - IP_HDR_SIZE;
+	u16 tcp_rx_xsum = b->ip.hdr.ip_sum;
+	u8  tcp_action  = TCP_DATA;
+	u32 tcp_seq_num;
+	u32 tcp_ack_num;
+	struct in_addr action_and_state;
+
+	int tcp_hdr_len;
+	int payload_len;
+
+	/*
+	 * Verify IP header
+	 */
+		debug_cond(DEBUG_DEV_PKT,
+			   "TCP RX in RX Sum (to=%pI4, from=%pI4, len=%d)\n",
+			   &b->ip.hdr.ip_src, &b->ip.hdr.ip_dst, pkt_len);
+
+		debug_cond(DEBUG_DEV_PKT,
+			   "In__________________________________________\n");
+
+	b->ip.hdr.ip_src	= net_server_ip;
+	b->ip.hdr.ip_dst	= net_ip;
+	b->ip.hdr.ip_sum	= 0x0000;
+	if (tcp_rx_xsum != compute_ip_checksum(b, IP_HDR_SIZE)) {
+		debug_cond(DEBUG_DEV_PKT,
+			   "TCP RX IP xSum Error (%pI4, =%pI4, len=%d)\n",
+			   &net_ip, &net_server_ip, pkt_len);
+		return;
+	}
+
+	/*
+	 * Build Pseudo header and Verify TCP header
+	 */
+	tcp_rx_xsum = b->ip.hdr.tcp_xsum;
+	b->ip.hdr.tcp_xsum = 0x0000;
+	if (tcp_rx_xsum != tcp_set_pseudo_header((uchar *)b, b->ip.hdr.ip_src,
+						 b->ip.hdr.ip_dst, tcp_len,
+						 pkt_len)) {
+		debug_cond(DEBUG_DEV_PKT,
+			   "TCP RX TCP xSum Error (%pI4, %pI4, len=%d)\n",
+			   &net_ip, &net_server_ip, tcp_len);
+		return;
+	}
+
+	tcp_hdr_len = (b->ip.hdr.tcp_hlen >> 2);
+	payload_len = tcp_len - tcp_hdr_len;
+
+	if (tcp_hdr_len > TCP_HDR_SIZE)
+		tcp_parse_options((uchar *)b + IP_TCP_HDR_SIZE,
+				  tcp_hdr_len - TCP_HDR_SIZE);
+	/*
+	 * Incoming sequence and ack numbers are server's view of the numbers.
+	 * The app must swap the numbers when responding.
+	 */
+
+	tcp_seq_num = ntohl(b->ip.hdr.tcp_seq);
+	tcp_ack_num = ntohl(b->ip.hdr.tcp_ack);
+
+	/*
+	 * Sent first packet send from server as first to app
+	 * Other packets could be ordered, but are currently not ordered.
+	 */
+
+	tcp_action  = tcp_state_machine(b->ip.hdr.tcp_flags,
+					&tcp_seq_num, payload_len);
+
+	/*
+	 * State altering command to be sent.
+	 * The packet sequence and ack numbers are in the tcp_seq_num
+	 * and tcp_ack_num variables. The current packet, its position
+	 * in the data stream, is the in the range of those variables.
+	 *
+	 * In the "application push" invocation, the TCP header with all
+	 * its information is pointed to by the packet pointer.
+	 *
+	 * in the typedef
+	 *      void rxhand_tcp(uchar *pkt, unsigned int dport,
+	 *                      struct in_addr sip, unsigned int sport,
+	 *                      unsigned int len);
+	 * *pkt is the pointer to the payload
+	 * dport is used for tcp_seg_num
+	 * action_and_state.s_addr is used for TCP state
+	 * sport is used for tcp_ack_num (which is unused by the app)
+	 * pkt_ length is the payload length.
+	 *
+	 * TCP_PUSH from the state machine with a payload length of 0 is a
+	 * connect or disconnect event
+	 */
+
+	tcp_activity_count++;
+	if (tcp_activity_count > TCP_ACTIVITY) {
+		puts("| ");
+		tcp_activity_count = 0;
+	}
+
+	if ((tcp_action & TCP_PUSH) || (payload_len > 0)) {
+		debug_cond(DEBUG_DEV_PKT,
+			   "TCP Notify (action=%x, Seq=%d,Ack=%d,Pay%d)\n",
+			   tcp_action, tcp_seq_num, tcp_ack_num, payload_len);
+
+		action_and_state.s_addr = tcp_action;
+		(*tcp_packet_handler) ((uchar *)b + pkt_len - payload_len,
+				       tcp_seq_num, action_and_state,
+				       tcp_ack_num, payload_len);
+
+	} else if (tcp_action != TCP_DATA) {
+		debug_cond(DEBUG_DEV_PKT,
+			   "TCP Action (action=%x,Seq=%d,Ack=%d,Pay=%d)\n",
+			   tcp_action, tcp_seq_num, tcp_ack_num, payload_len);
+
+	/*
+	 * Warning: Incoming Seq & Ack  sequence numbers are transposed here
+	 * to outgoing Seq & Ack sequence numbers
+	 */
+		net_send_tcp_packet(0, ntohs(b->ip.hdr.tcp_src),
+				    ntohs(b->ip.hdr.tcp_dst),
+				    (tcp_action & (~TCP_PUSH)),
+				    tcp_seq_num, tcp_ack_num);
+	}
+}