[v14,1/2] net: Add TCP protocol

From: "Ying-Chun Liu (PaulLiu)" <paul.liu@linaro.org>

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

The current standard is TCP with selective acknowledgment.

Signed-off-by: Duncan Hare <DH@Synoia.com>
Signed-off-by: Duncan Hare <DuncanCHare@yahoo.com>
Signed-off-by: Ying-Chun Liu (PaulLiu) <paul.liu@linaro.org>
Cc: Christian Gmeiner <christian.gmeiner@gmail.com>
Cc: Joe Hershberger <joe.hershberger@ni.com>
Cc: Ramon Fried <rfried.dev@gmail.com>
---
v13: Fix some issues which is reviewed by Christian
v14: Add options to enable/disable SACK.
---
 include/net.h     |   8 +-
 include/net/tcp.h | 222 +++++++++++++++
 net/Kconfig       |  12 +
 net/Makefile      |   1 +
 net/net.c         |  30 ++
 net/tcp.c         | 709 ++++++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 981 insertions(+), 1 deletion(-)
 create mode 100644 include/net/tcp.h
 create mode 100644 net/tcp.c

>Hi Ying,
>You woke up an old can, Can you elaborate on the changes you did to
>the original patchset ?
>I'm reviewing this instead of Joe, so I want to get some context.
>
>I would appreciate it if you could separate the SACK support to a
>separate patch, preferably option based.
>The TCP stack is complicated enough and will require a lot of
>tinkering / bug fixing in the future. It's best if we could turn
>on/off specific RFC which are not originally part of the TCP protocol.
>
>Thanks,
>Ramon

Hi Ramon,

Please review this patch again.

I've added an option to disable/enable SACK.
However it is harder to separate the SACK support as a separate commit.
I continue the old one which was together with SACK already.

Thanks a lot,
Paul

On 4/21/22 18:54, Ying-Chun Liu wrote:
> From: "Ying-Chun Liu (PaulLiu)" <paul.liu@linaro.org>
> 
> Currently file transfers are done using tftp or NFS both
> over udp. This requires a request to be sent from client
> (u-boot) to the boot server.
> 
> The current standard is TCP with selective acknowledgment.
> 
> Signed-off-by: Duncan Hare <DH@Synoia.com>
> Signed-off-by: Duncan Hare <DuncanCHare@yahoo.com>
> Signed-off-by: Ying-Chun Liu (PaulLiu) <paul.liu@linaro.org>
> Cc: Christian Gmeiner <christian.gmeiner@gmail.com>
> Cc: Joe Hershberger <joe.hershberger@ni.com>
> Cc: Ramon Fried <rfried.dev@gmail.com>
> ---
> v13: Fix some issues which is reviewed by Christian
> v14: Add options to enable/disable SACK.
> ---
>   include/net.h     |   8 +-
>   include/net/tcp.h | 222 +++++++++++++++
>   net/Kconfig       |  12 +
>   net/Makefile      |   1 +
>   net/net.c         |  30 ++
>   net/tcp.c         | 709 ++++++++++++++++++++++++++++++++++++++++++++++
>   6 files changed, 981 insertions(+), 1 deletion(-)
>   create mode 100644 include/net/tcp.h
>   create mode 100644 net/tcp.c
> 
> diff --git a/include/net.h b/include/net.h
> index 675bf4171b..220eba2e21 100644
> --- a/include/net.h
> +++ b/include/net.h
> @@ -365,6 +365,7 @@ struct vlan_ethernet_hdr {
>   #define PROT_NCSI	0x88f8		/* NC-SI control packets        */
>   
>   #define IPPROTO_ICMP	 1	/* Internet Control Message Protocol	*/
> +#define IPPROTO_TCP	 6	/* Transmission Control Protocol	*/

here is tab followed by space. I know it is on ICMP but no reason to c&p the 
same issue. Just use tab for indentation.


>   #define IPPROTO_UDP	17	/* User Datagram Protocol		*/
>   
>   /*
> @@ -687,7 +688,7 @@ static inline void net_send_packet(uchar *pkt, int len)
>   }
>   
>   /*

Why not to switch it to kernel-doc format and let it also check.

> - * Transmit "net_tx_packet" as UDP packet, performing ARP request if needed
> + * Transmit "net_tx_packet" as UDP or TCP packet, send ARP request if needed
>    *  (ether will be populated)
>    *
>    * @param ether Raw packet buffer
> @@ -695,10 +696,15 @@ static inline void net_send_packet(uchar *pkt, int len)
>    * @param dport Destination UDP port
>    * @param sport Source UDP port
>    * @param payload_len Length of data after the UDP header
> + * @param action TCP action to be performed
> + * @param tcp_seq_num TCP sequence number of this transmission
> + * @param tcp_ack_num TCP stream acknolegement number
>    */
>   int net_send_ip_packet(uchar *ether, struct in_addr dest, int dport, int sport,
>   		       int payload_len, int proto, u8 action, u32 tcp_seq_num,
>   		       u32 tcp_ack_num);
> +int net_send_tcp_packet(int payload_len, int dport, int sport, u8 action,
> +			u32 tcp_seq_num, u32 tcp_ack_num);

new function should require also kernel-doc documentation.

>   int net_send_udp_packet(uchar *ether, struct in_addr dest, int dport,
>   			int sport, int payload_len);
>   
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> new file mode 100644
> index 0000000000..417a6d0f4e
> --- /dev/null
> +++ b/include/net/tcp.h

[u-boot](debian-sent3)$ ./scripts/kernel-doc -v -man include/net/tcp.h > /dev/null
include/net/tcp.h:1: warning: no structured comments found

Do you really have nothing to document?


> @@ -0,0 +1,222 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * TCP Support with SACK for file transfer.
> + *
> + * Copyright 2017 Duncan Hare, All rights reserved.
> + */
> +
> +#define TCP_ACTIVITY 127		/* Number of packets received   */
> +					/* before console progress mark */
> +
> +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	*/

I would move all comments directly to kernel-doc documentation. The same for 
others below.

> +} __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		/* Timestamp 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
> + */

Is this still valid?

> +
> +#define TCP_MSS		1460		/* Max segment size		*/
> +#define TCP_SCALE	0x01		/* Scale			*/
> +
> +struct tcp_mss {			/* TCP Max Segment size		*/
> +	u8	kind;			/* Field ID			*/
> +	u8	len;			/* Field length			*/
> +	u16	mss;			/* Segment size value		*/
> +} __packed;
> +
> +struct tcp_scale {			/* TCP Windows Scale		*/
> +	u8	kind;			/* Field ID			*/
> +	u8	len;			/* Filed length			*/
> +	u8	scale;			/* windows shift value used for */
> +					/* networks with many hops	*/
> +					/* Typically 4 or more hops	*/
> +} __packed;
> +
> +struct tcp_sack_p {			/* SACK permitted		*/
> +	u8	kind;			/* Field Id			*/
> +	u8	len;			/* Field length			*/
> +} __packed;
> +
> +struct sack_edges {
> +	u32	l;			/* Left edge of stream		*/
> +	u32	r;			/* right edge of stream		*/
> +} __packed;
> +
> +#define TCP_SACK_SIZE (sizeof(struct sack_edges))
> +
> +/*
> + * A TCP stream has holes when packets are missing or disordered.
> + * A hill is the inverse of a hole, and is data received.
> + * TCP received hills (a sequence of data), and inferrs Holes
> + * from the "hills" or packets received.
> + */
> +
> +#define TCP_SACK_HILLS	4
> +
> +struct tcp_sack_v {
> +	u8	kind;			/* Field ID		        */
> +	u8	len;			/* Field Length			*/
> +	struct	sack_edges hill[TCP_SACK_HILLS]; /* L & R window edges	*/
> +} __packed;
> +
> +struct tcp_t_opt {			/* TCP time stamps option	*/
> +	u8	kind;			/* Field id			*/
> +	u8	len;			/* Field length			*/
> +	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 TCP/IP 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 connection
> + */
> +
> +enum TCP_STATE {

what's the reason for using uper case. When I look at other enums they are 
normally lower case.

> +	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 */
> +};
> +
> +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
> + */

kernel-doc please.

> +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 ef0aa161f7..73e4bcb88e 100644
> --- a/net/Kconfig
> +++ b/net/Kconfig
> @@ -159,6 +159,18 @@ config BOOTP_SERVERIP
>   	  variable, not the BOOTP server. This affects the operation of both
>   	  bootp and tftp.
>   
> +config PROT_TCP
> +	bool "TCP stack"
> +	help
> +	  Enable a generic tcp framework that allows defining a custom
> +	  handler for tcp protocol.
> +
> +config PROT_TCP_SACK
> +	bool "TCP SACK support"

here should be at least dependency on PROT_TCP. If you don't have it and select 
PROT_TCP_SACK but not PROT_TCP you get build issue when 2/2 is applied.

> +	help
> +	  TCP protocol with SACK. Selecting this will provide the fastest

you have good opportunity to describe what SACK is. Based on this description 
you are telling to users to study what SACK is and if make sense to enable it.
Any guindance where this should be selected would be also useful.

> +	  file transfer possible.
> +
>   endif   # if NET
>   
>   config SYS_RX_ETH_BUFFER
> diff --git a/net/Makefile b/net/Makefile
> index fb3eba840f..f68ad94767 100644
> --- a/net/Makefile
> +++ b/net/Makefile
> @@ -29,6 +29,7 @@ obj-$(CONFIG_CMD_TFTPBOOT) += tftp.o
>   obj-$(CONFIG_UDP_FUNCTION_FASTBOOT)  += fastboot.o
>   obj-$(CONFIG_CMD_WOL)  += wol.o
>   obj-$(CONFIG_PROT_UDP) += udp.o
> +obj-$(CONFIG_PROT_TCP) += tcp.o
>   
>   # Disable this warning as it is triggered by:
>   # sprintf(buf, index ? "foo%d" : "foo", index)
> diff --git a/net/net.c b/net/net.c
> index 072a82d8f9..28d9fbd227 100644
> --- a/net/net.c
> +++ b/net/net.c
> @@ -116,6 +116,7 @@
>   #if defined(CONFIG_CMD_WOL)
>   #include "wol.h"
>   #endif
> +#include <net/tcp.h>
>   
>   /** BOOTP EXTENTIONS **/
>   
> @@ -386,6 +387,8 @@ int net_init(void)
>   
>   		/* Only need to setup buffer pointers once. */
>   		first_call = 0;
> +		if (IS_ENABLED(CONFIG_PROT_TCP))
> +			tcp_set_tcp_state(TCP_CLOSED);
>   	}
>   
>   	return net_init_loop();
> @@ -816,6 +819,16 @@ int net_send_udp_packet(uchar *ether, struct in_addr dest, int dport, int sport,
>   				  IPPROTO_UDP, 0, 0, 0);
>   }
>   
> +#if defined(CONFIG_PROT_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, u8 action, u32 tcp_seq_num,
>   		       u32 tcp_ack_num)
> @@ -847,6 +860,14 @@ int net_send_ip_packet(uchar *ether, struct in_addr dest, int dport, int sport,
>   				   payload_len);
>   		pkt_hdr_size = eth_hdr_size + IP_UDP_HDR_SIZE;
>   		break;
> +#if defined(CONFIG_PROT_TCP)
> +	case IPPROTO_TCP:
> +		pkt_hdr_size = eth_hdr_size +
> +		tcp_set_tcp_header(pkt + eth_hdr_size, dport, sport,

indentation is weird.

> +				   payload_len, action, tcp_seq_num,
> +				   tcp_ack_num);
> +	break;
> +#endif
>   	default:
>   		return -EINVAL;
>   	}
> @@ -1253,6 +1274,15 @@ 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_PROT_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..ebd349c3e8
> --- /dev/null
> +++ b/net/tcp.c
> @@ -0,0 +1,709 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright 2017 Duncan Hare, all rights reserved.
> + */
> +
> +/*
> + * General Desription:
> + *
> + * TCP support for the wget command, for fast file downloading.
> + *
> + * HTTP/TCP Receiver:
> + *
> + *      Prerequisites:  - 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 <env_internal.h>
> +#include <errno.h>
> +#include <net.h>
> +#include <net/tcp.h>
> +
> +/*
> + * TCP sliding window  control used by us to request re-TX
> + */
> +
> +static struct tcp_sack_v tcp_lost;

this is only valid when PROT_TCP_SACK is enabled. You should find a way how to 
handle this.

> +
> +/* 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;

All of these should be static.


> +
> +/*
> + * 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;

The same for these. They should be static and any description what they are used 
for would be also useful.

> +
> +/* TCP connection state */
> +static enum TCP_STATE tcp_state;
> +
> +/*
> + * 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.
> + */
> +
> +/* 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;
> +}
> +

documentation would be helpful.

> +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;

0x00 is just 0

> +
> +	net_copy_ip((void *)&b->ph.p_src, &src);
> +	net_copy_ip((void *)&b->ph.p_dst, &dest);
> +	b->ph.rsvd	= 0x00;

here too. And remove this indentation in front of =.


> +	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;

here is also attempt for indentation which is not even aligned with the code 
below. Just remove that indentation completely and you don't need to worrry 
about it.

> +
> +	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 = TCP_1_NOP;
> +	b->sack.sack_v.len  = 0x00;
> +
> +#if defined(CONFIG_PROT_TCP_SACK)

Reported by checkpatch. No reason to use if defined here.

> +	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;

another indentation.

> +		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.
> +	 */

this comment is also valid for your

> +
> +	b->sack.hdr.tcp_hlen = (((TCP_HDR_SIZE + TCP_TSOPT_SIZE
> +				+ tcp_lost.len + 3)  >> 2) << 4);

This is at least second time I see >> 2) << 4 and one more below. Why not to 
create any macro for it or macro for that values.

> +
> +#else
> +	b->sack.sack_v.kind = 0x00;
> +	b->sack.hdr.tcp_hlen = (((TCP_HDR_SIZE + TCP_TSOPT_SIZE
> +				+ 3)  >> 2) << 4);

Does it make sense to create macro for this?
CP_HDR_SIZE + TCP_TSOPT_SIZE + 3


> +#endif
> +	/*
> +	 * 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;

And another shift. Is it the same 2 as above? Use macros.

> +}
> +
> +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;
> +#if defined(CONFIG_PROT_TCP_SACK)

another checkpatch warning here.


> +	b->ip.sack_p.kind       = TCP_P_SACK;
> +	b->ip.sack_p.len        = TCP_OPT_LEN_2;
> +#else
> +	b->ip.sack_p.kind       = TCP_1_NOP;
> +	b->ip.sack_p.len        = TCP_1_NOP;
> +#endif
> +	b->ip.t_opt.kind        = TCP_O_TS;
> +	b->ip.t_opt.len         = TCP_OPT_LEN_A;
> +	loc_timestamp           = get_ticks();
> +	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;

single line and no indenatation please.

> +
> +/*
> + * Header: 5 32 bit words. 4 bits TCP header Length, 4 bits reserved options
> + */

this should be aligned with the code.

> +	b->ip.hdr.tcp_flags	= action;
> +	pkt_hdr_len		= IP_TCP_HDR_SIZE;
> +	b->ip.hdr.tcp_hlen      = 0x50;

no indenatation please. and 0x50 looks like magic value - macro for it please.

> +
> +	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 SYNs */
> +			action    = TCP_FIN;

remove indenatation

> +			tcp_state = TCP_FIN_WAIT_1;
> +		} else {
> +			tcp_state = TCP_SYN_SENT;
> +		}
> +	break;

indent with the code. The same for breaks below.

> +	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):

this looks quite weird. Please fix it.

> +		if (tcp_state == TCP_CLOSE_WAIT)
> +			tcp_state = TCP_CLOSING;

newline

> +		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 */

Checkpatch reports this as an error.

CHECK: Prefer 'fallthrough;' over fallthrough comment
#271: FILE: net/tcp.c:271:
+					/* 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;

indentation.

> +
> +	/*
> +	 * 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);

 >>double space - please remove.

> +
> +	b->ip.hdr.tcp_xsum	= 0x0000;
> +	b->ip.hdr.tcp_ugr	= 0x0000;

indentation.

> +
> +	b->ip.hdr.tcp_xsum = tcp_set_pseudo_header(pkt, net_ip, net_server_ip,
> +						   tcp_len, pkt_len);
> +
> +	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)
> + */
> +
> +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;

please squashed some of them together. So many lines for nothing.

> +	enum pkt_state expect = PKT;
> +

no reason for newline here.

> +	u32 seq   = tcp_seq_num - tcp_seq_init;
> +	u32 hol_l = tcp_ack_edge - tcp_seq_init;
> +	u32 hol_r = 0;

any reason to mix unsigned int with u32. Just use the same typ.

> +
> +	/* Place new seq number in correct place in receive array */
> +
remove this newline.

> +	if (prev_len == 0)
> +		prev_len = len;

newline

> +	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 calculation, calculation breaks.
> + */

not aligned comment with the code.

> +		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++)  {

alignment should be different.

> +		switch (expect) {
> +		case NOPKT:
> +			switch (edge_a[sack_in].st) {
> +			case NOPKT:
> +				debug_cond(DEBUG_INT_STATE, "N");
> +			break;

indent it with the code.

> +			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;

ditto.

> +			}
> +		break;

ditto and the same below.

> +		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;
> +/*
> + *	NOPs are options with a zero length, and thus are special.
> + *	All other options have length fields.
> + */

indent with the code.

> +
> +	for (p = o; p < (o + o_len); p = p + p[1]) {
> +		if (p[1] != 0) {
> +			switch (p[0]) {
> +			case TCP_O_END:
> +				return; /* Finished processing options */

useless comment

> +			case TCP_O_MSS:
> +			case TCP_O_SCL:
> +			case TCP_P_SACK:
> +			case TCP_V_SACK:
> +				break; /* Continue to process options */
> +			case TCP_O_TS:
> +				tsopt = (struct tcp_t_opt *)p;
> +				rmt_timestamp = tsopt->t_snd;
> +				return;
> +			break;

indentation.

> +			} /* End switch, process optional NOPs */

we see that this is end of switch. Just remove it and put it to next line.

> +
> +			if (p[0] == TCP_O_NOP)
> +				p++;
> +		} else {
> +			return; /* Finished processing options */

It will be much better if you remove one level of indenation and simply do

if (!p[1])
	return;

switch (p[0]) {
....




> +		}
> +	}
> +}
> +
> +u8 tcp_state_machine(u8 tcp_flags, u32 *tcp_seq_num, int payload_len)

static?

> +{
> +	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;

indentation - fix the whole file. I see it below too. Fix it everywhere.

> +	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;

does order matter here? Or is it
if
else if
else if?

> +		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;

another double space here.

> +			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)

else if (tcp_ack) {
...

> +				action = TCP_DATA;
> +		}
> +		break;
> +	case TCP_ESTABLISHED:
> +		debug_cond(DEBUG_INT_STATE,
> +			   "TCP_ESTABLISHED %x\n", tcp_flags);

this doesn't look longer than 80 chars.

> +		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)

else if {

> +				action = TCP_DATA;
> +		}
> +		if (tcp_push)
> +			action = action | TCP_PUSH;
> +		if (tcp_syn)
> +			action = TCP_ACK + TCP_RST;

here is another pattern as above and below it is the same. Does order matter 
here because you are rewriting action. Is it correct?


> +		break;
> +	case TCP_CLOSE_WAIT:
> +		debug_cond(DEBUG_INT_STATE, "TCP_CLOSE_WAIT (%x)\n", tcp_flags);
> +		action = TCP_DATA;			/* Wait for app	*/

is comment valid?


> +		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;

pack it a little bit.

> +
> +	/*
> +	 * Verify IP header
> +	 */

single line comment.

> +	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");

hmm - interesting description.

> +
> +	b->ip.hdr.ip_src = net_server_ip;
> +	b->ip.hdr.ip_dst = net_ip;
> +	b->ip.hdr.ip_sum = 0x0000;

for me 0x0000 is just 0.

> +	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
> +	 */

single line.

> +	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);

another >> 2 - macro please.

> +	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);
> +
> +	/* Packets are not ordered. Send to app as received. */
> +
> +	tcp_action  = tcp_state_machine(b->ip.hdr.tcp_flags,

double space - check the whole file.

> +					&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 Ack & Seq 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);
> +	}
> +}

M