net.c

/*
 *	Copied from Linux Monitor (LiMon) - Networking.
 *
 *	Copyright 1994 - 2000 Neil Russell.
 *	(See License)
 *	Copyright 2000 Roland Borde
 *	Copyright 2000 Paolo Scaffardi
 *	Copyright 2000-2002 Wolfgang Denk, wd@denx.de
 *	SPDX-License-Identifier:	GPL-2.0
 */

/*
 * General Desription:
 *
 * The user interface supports commands for BOOTP, RARP, and TFTP.
 * Also, we support ARP internally. Depending on available data,
 * these interact as follows:
 *
 * BOOTP:
 *
 *	Prerequisites:	- own ethernet address
 *	We want:	- own IP address
 *			- TFTP server IP address
 *			- name of bootfile
 *	Next step:	ARP
 *
 * LINK_LOCAL:
 *
 *	Prerequisites:	- own ethernet address
 *	We want:	- own IP address
 *	Next step:	ARP
 *
 * RARP:
 *
 *	Prerequisites:	- own ethernet address
 *	We want:	- own IP address
 *			- TFTP server IP address
 *	Next step:	ARP
 *
 * ARP:
 *
 *	Prerequisites:	- own ethernet address
 *			- own IP address
 *			- TFTP server IP address
 *	We want:	- TFTP server ethernet address
 *	Next step:	TFTP
 *
 * DHCP:
 *
 *     Prerequisites:	- own ethernet address
 *     We want:		- IP, Netmask, ServerIP, Gateway IP
 *			- bootfilename, lease time
 *     Next step:	- TFTP
 *
 * TFTP:
 *
 *	Prerequisites:	- own ethernet address
 *			- own IP address
 *			- TFTP server IP address
 *			- TFTP server ethernet address
 *			- name of bootfile (if unknown, we use a default name
 *			  derived from our own IP address)
 *	We want:	- load the boot file
 *	Next step:	none
 *
 * NFS:
 *
 *	Prerequisites:	- own ethernet address
 *			- own IP address
 *			- name of bootfile (if unknown, we use a default name
 *			  derived from our own IP address)
 *	We want:	- load the boot file
 *	Next step:	none
 *
 * SNTP:
 *
 *	Prerequisites:	- own ethernet address
 *			- own IP address
 *	We want:	- network time
 *	Next step:	none
 */


#include <common.h>
#include <command.h>
#include <environment.h>
#include <errno.h>
#include <net.h>
#include <net/tftp.h>
#if defined(CONFIG_STATUS_LED)
#include <miiphy.h>
#include <status_led.h>
#endif
#include <watchdog.h>
#include <linux/compiler.h>
#include "arp.h"
#include "bootp.h"
#include "cdp.h"
#if defined(CONFIG_CMD_DNS)
#include "dns.h"
#endif
#include "link_local.h"
#include "nfs.h"
#include "ping.h"
#include "rarp.h"
#if defined(CONFIG_CMD_SNTP)
#include "sntp.h"
#endif

DECLARE_GLOBAL_DATA_PTR;

/** BOOTP EXTENTIONS **/

/* Our subnet mask (0=unknown) */
struct in_addr net_netmask;
/* Our gateways IP address */
struct in_addr net_gateway;
/* Our DNS IP address */
struct in_addr net_dns_server;
#if defined(CONFIG_BOOTP_DNS2)
/* Our 2nd DNS IP address */
struct in_addr net_dns_server2;
#endif

#ifdef CONFIG_MCAST_TFTP	/* Multicast TFTP */
struct in_addr net_mcast_addr;
#endif

/** END OF BOOTP EXTENTIONS **/

/* Our ethernet address */
u8 net_ethaddr[6];
/* Boot server enet address */
u8 net_server_ethaddr[6];
/* Our IP addr (0 = unknown) */
struct in_addr	net_ip;
/* Server IP addr (0 = unknown) */
struct in_addr	net_server_ip;
/* Current receive packet */
uchar *net_rx_packet;
/* Current rx packet length */
int		net_rx_packet_len;
/* IP packet ID */
static unsigned	net_ip_id;
/* Ethernet bcast address */
const u8 net_bcast_ethaddr[6] = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };
const u8 net_null_ethaddr[6];
#ifdef CONFIG_API
void (*push_packet)(void *, int len) = 0;
#endif
/* Network loop state */
enum net_loop_state net_state;
/* Tried all network devices */
int		net_restart_wrap;
/* Network loop restarted */
static int	net_restarted;
/* At least one device configured */
static int	net_dev_exists;

/* XXX in both little & big endian machines 0xFFFF == ntohs(-1) */
/* default is without VLAN */
ushort		net_our_vlan = 0xFFFF;
/* ditto */
ushort		net_native_vlan = 0xFFFF;

/* Boot File name */
char net_boot_file_name[1024];
/* The actual transferred size of the bootfile (in bytes) */
u32 net_boot_file_size;
/* Boot file size in blocks as reported by the DHCP server */
u32 net_boot_file_expected_size_in_blocks;

#if defined(CONFIG_CMD_SNTP)
/* NTP server IP address */
struct in_addr	net_ntp_server;
/* offset time from UTC */
int		net_ntp_time_offset;
#endif

static uchar net_pkt_buf[(PKTBUFSRX+1) * PKTSIZE_ALIGN + PKTALIGN];
/* Receive packets */
uchar *net_rx_packets[PKTBUFSRX];
/* Current UDP RX packet handler */
static rxhand_f *udp_packet_handler;
/* Current ARP RX packet handler */
static rxhand_f *arp_packet_handler;
#ifdef CONFIG_CMD_TFTPPUT
/* Current ICMP rx handler */
static rxhand_icmp_f *packet_icmp_handler;
#endif
/* Current timeout handler */
static thand_f *time_handler;
/* Time base value */
static ulong	time_start;
/* Current timeout value */
static ulong	time_delta;
/* THE transmit packet */
uchar *net_tx_packet;

static int net_check_prereq(enum proto_t protocol);

static int net_try_count;

int __maybe_unused net_busy_flag;

/**********************************************************************/

static int on_bootfile(const char *name, const char *value, enum env_op op,
	int flags)
{
	if (flags & H_PROGRAMMATIC)
		return 0;

	switch (op) {
	case env_op_create:
	case env_op_overwrite:
		copy_filename(net_boot_file_name, value,
			      sizeof(net_boot_file_name));
		break;
	default:
		break;
	}

	return 0;
}
U_BOOT_ENV_CALLBACK(bootfile, on_bootfile);

static int on_ipaddr(const char *name, const char *value, enum env_op op,
	int flags)
{
	if (flags & H_PROGRAMMATIC)
		return 0;

	net_ip = string_to_ip(value);

	return 0;
}
U_BOOT_ENV_CALLBACK(ipaddr, on_ipaddr);

static int on_gatewayip(const char *name, const char *value, enum env_op op,
	int flags)
{
	if (flags & H_PROGRAMMATIC)
		return 0;

	net_gateway = string_to_ip(value);

	return 0;
}
U_BOOT_ENV_CALLBACK(gatewayip, on_gatewayip);

static int on_netmask(const char *name, const char *value, enum env_op op,
	int flags)
{
	if (flags & H_PROGRAMMATIC)
		return 0;

	net_netmask = string_to_ip(value);

	return 0;
}
U_BOOT_ENV_CALLBACK(netmask, on_netmask);

static int on_serverip(const char *name, const char *value, enum env_op op,
	int flags)
{
	if (flags & H_PROGRAMMATIC)
		return 0;

	net_server_ip = string_to_ip(value);

	return 0;
}
U_BOOT_ENV_CALLBACK(serverip, on_serverip);

static int on_nvlan(const char *name, const char *value, enum env_op op,
	int flags)
{
	if (flags & H_PROGRAMMATIC)
		return 0;

	net_native_vlan = string_to_vlan(value);

	return 0;
}
U_BOOT_ENV_CALLBACK(nvlan, on_nvlan);

static int on_vlan(const char *name, const char *value, enum env_op op,
	int flags)
{
	if (flags & H_PROGRAMMATIC)
		return 0;

	net_our_vlan = string_to_vlan(value);

	return 0;
}
U_BOOT_ENV_CALLBACK(vlan, on_vlan);

#if defined(CONFIG_CMD_DNS)
static int on_dnsip(const char *name, const char *value, enum env_op op,
	int flags)
{
	if (flags & H_PROGRAMMATIC)
		return 0;

	net_dns_server = string_to_ip(value);

	return 0;
}
U_BOOT_ENV_CALLBACK(dnsip, on_dnsip);
#endif

/*
 * Check if autoload is enabled. If so, use either NFS or TFTP to download
 * the boot file.
 */
void net_auto_load(void)
{
#if defined(CONFIG_CMD_NFS)
	const char *s = getenv("autoload");

	if (s != NULL && strcmp(s, "NFS") == 0) {
		/*
		 * Use NFS to load the bootfile.
		 */
		nfs_start();
		return;
	}
#endif
	if (getenv_yesno("autoload") == 0) {
		/*
		 * Just use BOOTP/RARP to configure system;
		 * Do not use TFTP to load the bootfile.
		 */
		net_set_state(NETLOOP_SUCCESS);
		return;
	}
	tftp_start(TFTPGET);
}

static void net_init_loop(void)
{
	if (eth_get_dev())
		memcpy(net_ethaddr, eth_get_ethaddr(), 6);

	return;
}

static void net_clear_handlers(void)
{
	net_set_udp_handler(NULL);
	net_set_arp_handler(NULL);
	net_set_timeout_handler(0, NULL);
}

static void net_cleanup_loop(void)
{
	net_clear_handlers();
}

void net_init(void)
{
	static int first_call = 1;

	if (first_call) {
		/*
		 *	Setup packet buffers, aligned correctly.
		 */
		int i;

		net_tx_packet = &net_pkt_buf[0] + (PKTALIGN - 1);
		net_tx_packet -= (ulong)net_tx_packet % PKTALIGN;
		for (i = 0; i < PKTBUFSRX; i++) {
			net_rx_packets[i] = net_tx_packet +
				(i + 1) * PKTSIZE_ALIGN;
		}
		arp_init();
		net_clear_handlers();

		/* Only need to setup buffer pointers once. */
		first_call = 0;
	}

	net_init_loop();
}

/**********************************************************************/
/*
 *	Main network processing loop.
 */

int net_loop(enum proto_t protocol)
{
	int ret = -EINVAL;

	net_restarted = 0;
	net_dev_exists = 0;
	net_try_count = 1;
	debug_cond(DEBUG_INT_STATE, "--- net_loop Entry\n");

	bootstage_mark_name(BOOTSTAGE_ID_ETH_START, "eth_start");
	net_init();
	if (eth_is_on_demand_init() || protocol != NETCONS) {
		eth_halt();
		eth_set_current();
		ret = eth_init();
		if (ret < 0) {
			eth_halt();
			return ret;
		}
	} else {
		eth_init_state_only();
	}
restart:
#ifdef CONFIG_USB_KEYBOARD
	net_busy_flag = 0;
#endif
	net_set_state(NETLOOP_CONTINUE);

	/*
	 *	Start the ball rolling with the given start function.  From
	 *	here on, this code is a state machine driven by received
	 *	packets and timer events.
	 */
	debug_cond(DEBUG_INT_STATE, "--- net_loop Init\n");
	net_init_loop();

	switch (net_check_prereq(protocol)) {
	case 1:
		/* network not configured */
		eth_halt();
		return -ENODEV;

	case 2:
		/* network device not configured */
		break;

	case 0:
		net_dev_exists = 1;
		net_boot_file_size = 0;
		switch (protocol) {
		case TFTPGET:
#ifdef CONFIG_CMD_TFTPPUT
		case TFTPPUT:
#endif
			/* always use ARP to get server ethernet address */
			tftp_start(protocol);
			break;
#ifdef CONFIG_CMD_TFTPSRV
		case TFTPSRV:
			tftp_start_server();
			break;
#endif
#if defined(CONFIG_CMD_DHCP)
		case DHCP:
			bootp_reset();
			net_ip.s_addr = 0;
			dhcp_request();		/* Basically same as BOOTP */
			break;
#endif

		case BOOTP:
			bootp_reset();
			net_ip.s_addr = 0;
			bootp_request();
			break;

#if defined(CONFIG_CMD_RARP)
		case RARP:
			rarp_try = 0;
			net_ip.s_addr = 0;
			rarp_request();
			break;
#endif
#if defined(CONFIG_CMD_PING)
		case PING:
			ping_start();
			break;
#endif
#if defined(CONFIG_CMD_NFS)
		case NFS:
			nfs_start();
			break;
#endif
#if defined(CONFIG_CMD_CDP)
		case CDP:
			cdp_start();
			break;
#endif
#if defined(CONFIG_NETCONSOLE) && !(CONFIG_SPL_BUILD)
		case NETCONS:
			nc_start();
			break;
#endif
#if defined(CONFIG_CMD_SNTP)
		case SNTP:
			sntp_start();
			break;
#endif
#if defined(CONFIG_CMD_DNS)
		case DNS:
			dns_start();
			break;
#endif
#if defined(CONFIG_CMD_LINK_LOCAL)
		case LINKLOCAL:
			link_local_start();
			break;
#endif
		default:
			break;
		}

		break;
	}

#if defined(CONFIG_MII) || defined(CONFIG_CMD_MII)
#if	defined(CONFIG_SYS_FAULT_ECHO_LINK_DOWN)	&& \
	defined(CONFIG_STATUS_LED)			&& \
	defined(STATUS_LED_RED)
	/*
	 * Echo the inverted link state to the fault LED.
	 */
	if (miiphy_link(eth_get_dev()->name, CONFIG_SYS_FAULT_MII_ADDR))
		status_led_set(STATUS_LED_RED, STATUS_LED_OFF);
	else
		status_led_set(STATUS_LED_RED, STATUS_LED_ON);
#endif /* CONFIG_SYS_FAULT_ECHO_LINK_DOWN, ... */
#endif /* CONFIG_MII, ... */
#ifdef CONFIG_USB_KEYBOARD
	net_busy_flag = 1;
#endif

	/*
	 *	Main packet reception loop.  Loop receiving packets until
	 *	someone sets `net_state' to a state that terminates.
	 */
	for (;;) {
		WATCHDOG_RESET();
#ifdef CONFIG_SHOW_ACTIVITY
		show_activity(1);
#endif
		/*
		 *	Check the ethernet for a new packet.  The ethernet
		 *	receive routine will process it.
		 *	Most drivers return the most recent packet size, but not
		 *	errors that may have happened.
		 */
		eth_rx();

		/*
		 *	Abort if ctrl-c was pressed.
		 */
		if (ctrlc()) {
			/* cancel any ARP that may not have completed */
			net_arp_wait_packet_ip.s_addr = 0;

			net_cleanup_loop();
			eth_halt();
			/* Invalidate the last protocol */
			eth_set_last_protocol(BOOTP);

			puts("\nAbort\n");
			/* include a debug print as well incase the debug
			   messages are directed to stderr */
			debug_cond(DEBUG_INT_STATE, "--- net_loop Abort!\n");
			ret = -EINTR;
			goto done;
		}

		if (arp_timeout_check() > 0) {
		    time_start = get_timer(0);
		}

		/*
		 *	Check for a timeout, and run the timeout handler
		 *	if we have one.
		 */
		if (time_handler &&
		    ((get_timer(0) - time_start) > time_delta)) {
			thand_f *x;

#if defined(CONFIG_MII) || defined(CONFIG_CMD_MII)
#if	defined(CONFIG_SYS_FAULT_ECHO_LINK_DOWN)	&& \
	defined(CONFIG_STATUS_LED)			&& \
	defined(STATUS_LED_RED)
			/*
			 * Echo the inverted link state to the fault LED.
			 */
			if (miiphy_link(eth_get_dev()->name,
					CONFIG_SYS_FAULT_MII_ADDR))
				status_led_set(STATUS_LED_RED, STATUS_LED_OFF);
			else
				status_led_set(STATUS_LED_RED, STATUS_LED_ON);
#endif /* CONFIG_SYS_FAULT_ECHO_LINK_DOWN, ... */
#endif /* CONFIG_MII, ... */
			debug_cond(DEBUG_INT_STATE, "--- net_loop timeout\n");
			x = time_handler;
			time_handler = (thand_f *)0;
			(*x)();
		}

		if (net_state == NETLOOP_FAIL)
			ret = net_start_again();

		switch (net_state) {
		case NETLOOP_RESTART:
			net_restarted = 1;
			goto restart;

		case NETLOOP_SUCCESS:
			net_cleanup_loop();
			if (net_boot_file_size > 0) {
				printf("Bytes transferred = %d (%x hex)\n",
				       net_boot_file_size, net_boot_file_size);
				setenv_hex("filesize", net_boot_file_size);
				setenv_hex("fileaddr", load_addr);
			}
			if (protocol != NETCONS)
				eth_halt();
			else
				eth_halt_state_only();

			eth_set_last_protocol(protocol);

			ret = net_boot_file_size;
			debug_cond(DEBUG_INT_STATE, "--- net_loop Success!\n");
			goto done;

		case NETLOOP_FAIL:
			net_cleanup_loop();
			/* Invalidate the last protocol */
			eth_set_last_protocol(BOOTP);
			debug_cond(DEBUG_INT_STATE, "--- net_loop Fail!\n");
			goto done;

		case NETLOOP_CONTINUE:
			continue;
		}
	}

done:
#ifdef CONFIG_USB_KEYBOARD
	net_busy_flag = 0;
#endif
#ifdef CONFIG_CMD_TFTPPUT
	/* Clear out the handlers */
	net_set_udp_handler(NULL);
	net_set_icmp_handler(NULL);
#endif
	return ret;
}

/**********************************************************************/

static void start_again_timeout_handler(void)
{
	net_set_state(NETLOOP_RESTART);
}

int net_start_again(void)
{
	char *nretry;
	int retry_forever = 0;
	unsigned long retrycnt = 0;
	int ret;

	nretry = getenv("netretry");
	if (nretry) {
		if (!strcmp(nretry, "yes"))
			retry_forever = 1;
		else if (!strcmp(nretry, "no"))
			retrycnt = 0;
		else if (!strcmp(nretry, "once"))
			retrycnt = 1;
		else
			retrycnt = simple_strtoul(nretry, NULL, 0);
	} else {
		retrycnt = 0;
		retry_forever = 0;
	}

	if ((!retry_forever) && (net_try_count >= retrycnt)) {
		eth_halt();
		net_set_state(NETLOOP_FAIL);
		/*
		 * We don't provide a way for the protocol to return an error,
		 * but this is almost always the reason.
		 */
		return -ETIMEDOUT;
	}

	net_try_count++;

	eth_halt();
#if !defined(CONFIG_NET_DO_NOT_TRY_ANOTHER)
	eth_try_another(!net_restarted);
#endif
	ret = eth_init();
	if (net_restart_wrap) {
		net_restart_wrap = 0;
		if (net_dev_exists) {
			net_set_timeout_handler(10000UL,
						start_again_timeout_handler);
			net_set_udp_handler(NULL);
		} else {
			net_set_state(NETLOOP_FAIL);
		}
	} else {
		net_set_state(NETLOOP_RESTART);
	}
	return ret;
}

/**********************************************************************/
/*
 *	Miscelaneous bits.
 */

static void dummy_handler(uchar *pkt, unsigned dport,
			struct in_addr sip, unsigned sport,
			unsigned len)
{
}

rxhand_f *net_get_udp_handler(void)
{
	return udp_packet_handler;
}

void net_set_udp_handler(rxhand_f *f)
{
	debug_cond(DEBUG_INT_STATE, "--- net_loop UDP handler set (%p)\n", f);
	if (f == NULL)
		udp_packet_handler = dummy_handler;
	else
		udp_packet_handler = f;
}

rxhand_f *net_get_arp_handler(void)
{
	return arp_packet_handler;
}

void net_set_arp_handler(rxhand_f *f)
{
	debug_cond(DEBUG_INT_STATE, "--- net_loop ARP handler set (%p)\n", f);
	if (f == NULL)
		arp_packet_handler = dummy_handler;
	else
		arp_packet_handler = f;
}

#ifdef CONFIG_CMD_TFTPPUT
void net_set_icmp_handler(rxhand_icmp_f *f)
{
	packet_icmp_handler = f;
}
#endif

void net_set_timeout_handler(ulong iv, thand_f *f)
{
	if (iv == 0) {
		debug_cond(DEBUG_INT_STATE,
			   "--- net_loop timeout handler cancelled\n");
		time_handler = (thand_f *)0;
	} else {
		debug_cond(DEBUG_INT_STATE,
			   "--- net_loop timeout handler set (%p)\n", f);
		time_handler = f;
		time_start = get_timer(0);
		time_delta = iv * CONFIG_SYS_HZ / 1000;
	}
}

int net_send_udp_packet(uchar *ether, struct in_addr dest, int dport, int sport,
		int payload_len)
{
	uchar *pkt;
	int eth_hdr_size;
	int pkt_hdr_size;

	/* make sure the net_tx_packet is initialized (net_init() was called) */
	assert(net_tx_packet != NULL);
	if (net_tx_packet == NULL)
		return -1;

	/* convert to new style broadcast */
	if (dest.s_addr == 0)
		dest.s_addr = 0xFFFFFFFF;

	/* if broadcast, make the ether address a broadcast and don't do ARP */
	if (dest.s_addr == 0xFFFFFFFF)
		ether = (uchar *)net_bcast_ethaddr;

	pkt = (uchar *)net_tx_packet;

	eth_hdr_size = net_set_ether(pkt, ether, PROT_IP);
	pkt += eth_hdr_size;
	net_set_udp_header(pkt, dest, dport, sport, payload_len);
	pkt_hdr_size = eth_hdr_size + IP_UDP_HDR_SIZE;

	/* if MAC address was not discovered yet, do an ARP request */
	if (memcmp(ether, net_null_ethaddr, 6) == 0) {
		debug_cond(DEBUG_DEV_PKT, "sending ARP for %pI4\n", &dest);

		/* save the ip and eth addr for the packet to send after arp */
		net_arp_wait_packet_ip = dest;
		arp_wait_packet_ethaddr = ether;

		/* size of the waiting packet */
		arp_wait_tx_packet_size = pkt_hdr_size + payload_len;

		/* and do the ARP request */
		arp_wait_try = 1;
		arp_wait_timer_start = get_timer(0);
		arp_request();
		return 1;	/* waiting */
	} else {
		debug_cond(DEBUG_DEV_PKT, "sending UDP to %pI4/%pM\n",
			   &dest, ether);
		net_send_packet(net_tx_packet, pkt_hdr_size + payload_len);
		return 0;	/* transmitted */
	}
}

#ifdef CONFIG_IP_DEFRAG
/*
 * This function collects fragments in a single packet, according
 * to the algorithm in RFC815. It returns NULL or the pointer to
 * a complete packet, in static storage
 */
#ifndef CONFIG_NET_MAXDEFRAG
#define CONFIG_NET_MAXDEFRAG 16384
#endif
/*
 * MAXDEFRAG, above, is chosen in the config file and  is real data
 * so we need to add the NFS overhead, which is more than TFTP.
 * To use sizeof in the internal unnamed structures, we need a real
 * instance (can't do "sizeof(struct rpc_t.u.reply))", unfortunately).
 * The compiler doesn't complain nor allocates the actual structure
 */
static struct rpc_t rpc_specimen;
#define IP_PKTSIZE (CONFIG_NET_MAXDEFRAG + sizeof(rpc_specimen.u.reply))

#define IP_MAXUDP (IP_PKTSIZE - IP_HDR_SIZE)

/*
 * this is the packet being assembled, either data or frag control.
 * Fragments go by 8 bytes, so this union must be 8 bytes long
 */
struct hole {
	/* first_byte is address of this structure */
	u16 last_byte;	/* last byte in this hole + 1 (begin of next hole) */
	u16 next_hole;	/* index of next (in 8-b blocks), 0 == none */
	u16 prev_hole;	/* index of prev, 0 == none */
	u16 unused;
};

static struct ip_udp_hdr *__net_defragment(struct ip_udp_hdr *ip, int *lenp)
{
	static uchar pkt_buff[IP_PKTSIZE] __aligned(PKTALIGN);
	static u16 first_hole, total_len;
	struct hole *payload, *thisfrag, *h, *newh;
	struct ip_udp_hdr *localip = (struct ip_udp_hdr *)pkt_buff;
	uchar *indata = (uchar *)ip;
	int offset8, start, len, done = 0;
	u16 ip_off = ntohs(ip->ip_off);

	/* payload starts after IP header, this fragment is in there */
	payload = (struct hole *)(pkt_buff + IP_HDR_SIZE);
	offset8 =  (ip_off & IP_OFFS);
	thisfrag = payload + offset8;
	start = offset8 * 8;
	len = ntohs(ip->ip_len) - IP_HDR_SIZE;

	if (start + len > IP_MAXUDP) /* fragment extends too far */
		return NULL;

	if (!total_len || localip->ip_id != ip->ip_id) {
		/* new (or different) packet, reset structs */
		total_len = 0xffff;
		payload[0].last_byte = ~0;
		payload[0].next_hole = 0;
		payload[0].prev_hole = 0;
		first_hole = 0;
		/* any IP header will work, copy the first we received */
		memcpy(localip, ip, IP_HDR_SIZE);
	}

	/*
	 * What follows is the reassembly algorithm. We use the payload
	 * array as a linked list of hole descriptors, as each hole starts
	 * at a multiple of 8 bytes. However, last byte can be whatever value,
	 * so it is represented as byte count, not as 8-byte blocks.
	 */

	h = payload + first_hole;
	while (h->last_byte < start) {
		if (!h->next_hole) {
			/* no hole that far away */
			return NULL;
		}
		h = payload + h->next_hole;
	}

	/* last fragment may be 1..7 bytes, the "+7" forces acceptance */
	if (offset8 + ((len + 7) / 8) <= h - payload) {
		/* no overlap with holes (dup fragment?) */
		return NULL;
	}

	if (!(ip_off & IP_FLAGS_MFRAG)) {
		/* no more fragmentss: truncate this (last) hole */
		total_len = start + len;
		h->last_byte = start + len;
	}

	/*
	 * There is some overlap: fix the hole list. This code doesn't
	 * deal with a fragment that overlaps with two different holes
	 * (thus being a superset of a previously-received fragment).
	 */

	if ((h >= thisfrag) && (h->last_byte <= start + len)) {
		/* complete overlap with hole: remove hole */
		if (!h->prev_hole && !h->next_hole) {
			/* last remaining hole */
			done = 1;
		} else if (!h->prev_hole) {
			/* first hole */
			first_hole = h->next_hole;
			payload[h->next_hole].prev_hole = 0;
		} else if (!h->next_hole) {
			/* last hole */
			payload[h->prev_hole].next_hole = 0;
		} else {
			/* in the middle of the list */
			payload[h->next_hole].prev_hole = h->prev_hole;
			payload[h->prev_hole].next_hole = h->next_hole;
		}

	} else if (h->last_byte <= start + len) {
		/* overlaps with final part of the hole: shorten this hole */
		h->last_byte = start;

	} else if (h >= thisfrag) {
		/* overlaps with initial part of the hole: move this hole */
		newh = thisfrag + (len / 8);
		*newh = *h;
		h = newh;
		if (h->next_hole)
			payload[h->next_hole].prev_hole = (h - payload);
		if (h->prev_hole)
			payload[h->prev_hole].next_hole = (h - payload);
		else
			first_hole = (h - payload);

	} else {
		/* fragment sits in the middle: split the hole */
		newh = thisfrag + (len / 8);
		*newh = *h;
		h->last_byte = start;
		h->next_hole = (newh - payload);
		newh->prev_hole = (h - payload);
		if (newh->next_hole)
			payload[newh->next_hole].prev_hole = (newh - payload);
	}

	/* finally copy this fragment and possibly return whole packet */
	memcpy((uchar *)thisfrag, indata + IP_HDR_SIZE, len);
	if (!done)
		return NULL;

	localip->ip_len = htons(total_len);
	*lenp = total_len + IP_HDR_SIZE;
	return localip;
}

static inline struct ip_udp_hdr *net_defragment(struct ip_udp_hdr *ip,
	int *lenp)
{
	u16 ip_off = ntohs(ip->ip_off);
	if (!(ip_off & (IP_OFFS | IP_FLAGS_MFRAG)))
		return ip; /* not a fragment */
	return __net_defragment(ip, lenp);
}

#else /* !CONFIG_IP_DEFRAG */

static inline struct ip_udp_hdr *net_defragment(struct ip_udp_hdr *ip,
	int *lenp)
{
	u16 ip_off = ntohs(ip->ip_off);
	if (!(ip_off & (IP_OFFS | IP_FLAGS_MFRAG)))
		return ip; /* not a fragment */
	return NULL;
}
#endif