uIP Address Resolution Protocol

Collaboration diagram for uIP Address Resolution Protocol:

Files
file	uip_arp.c
file	uip_arp.h

Classes
struct	arp_entry
struct	uip_eth_addr
struct	uip_eth_hdr
struct	uip_arp_hdr
struct	uip_ethip_hdr

Macros
#define	UIP_LOG(m)
#define	UIP_STAT(s)
#define	ARP_TRY_HARD   0x01
#define	ARP_MAXAGE   240
#define	ARP_MAXPENDING   2
#define	ARP_REQUEST   1
#define	ARP_REPLY   2
#define	ARP_HWTYPE_ETH   1
#define	ARPH_HWLEN(hdr)   (ntohs((hdr)->_hwlen_protolen) >> 8)
#define	ARPH_PROTOLEN(hdr)   (ntohs((hdr)->_hwlen_protolen) & 0xff)
#define	ARPH_HWLEN_SET(hdr, len)   (hdr)->_hwlen_protolen = htons(ARPH_PROTOLEN(hdr) | ((len) << 8))
#define	ARPH_PROTOLEN_SET(hdr, len)   (hdr)->_hwlen_protolen = htons((len) | (ARPH_HWLEN(hdr) << 8))
#define	UIP_ARP_TMRINTERVAL   5000
#define	UIP_ETHTYPE_ARP   0x0806
#define	UIP_ETHTYPE_IP   0x0800
#define	UIP_ETHTYPE_IP6   0x86dd
#define	PACK_STRUCT_STRUCT   __attribute__((packed))

Enumerations
enum	arp_state { ARP_STATE_EMPTY, ARP_STATE_PENDING, ARP_STATE_STABLE, ARP_STATE_EXPIRED }

Functions
void	uip_arp_init (void)
void	uip_arp_timer (void)
static s8_t	uip_arp_findentry (struct uip_ip_addr *ipaddr, u8_t flags)
static s8_t	uip_arp_update (struct uip_netif *netif, struct uip_ip_addr *ipaddr, struct uip_eth_addr *ethaddr, u8_t flags)
void	uip_arp_ipin (struct uip_netif *netif, struct uip_pbuf *p)
void	uip_arp_arpin (struct uip_netif *netif, struct uip_eth_addr *ethaddr, struct uip_pbuf *p)
s8_t	uip_arp_out (struct uip_netif *netif, struct uip_ip_addr *ipaddr, struct uip_pbuf *q)
s8_t	uip_arp_arpquery (struct uip_netif *netif, struct uip_ip_addr *ipaddr, struct uip_pbuf *q)
s8_t	uip_arp_arprequest (struct uip_netif *netif, struct uip_ip_addr *ipaddr)
	uip_eth_addr::PACK_STRUCT_FIELD (u8_t addr[6])
	uip_eth_hdr::PACK_STRUCT_FIELD (struct uip_eth_addr dest)
	uip_eth_hdr::PACK_STRUCT_FIELD (u16_t type)
	uip_arp_hdr::PACK_STRUCT_FIELD (struct uip_eth_hdr ethhdr)
	uip_arp_hdr::PACK_STRUCT_FIELD (u16_t hwtype)
	uip_arp_hdr::PACK_STRUCT_FIELD (struct uip_eth_addr shwaddr)
	uip_arp_hdr::PACK_STRUCT_FIELD (struct uip_ip_addr2 sipaddr)
	uip_ethip_hdr::PACK_STRUCT_FIELD (struct uip_eth_hdr ethhdr)
	uip_ethip_hdr::PACK_STRUCT_FIELD (struct uip_ip_hdr ip)

Variables
static const struct uip_eth_addr	ethbroadcast = {{0xff,0xff,0xff,0xff,0xff,0xff}}
static struct arp_entry	arp_table [UIP_ARPTAB_SIZE]
PACK_STRUCT_BEGIN struct uip_eth_addr	PACK_STRUCT_STRUCT
PACK_STRUCT_END struct uip_eth_addr	uip_ethaddr

Detailed Description

The Address Resolution Protocol ARP is used for mapping between IP addresses and link level addresses such as the Ethernet MAC addresses. ARP uses broadcast queries to ask for the link level address of a known IP address and the host which is configured with the IP address for which the query was meant, will respond with its link level address.

Note

This ARP implementation only supports Ethernet.

Macro Definition Documentation

ARP_HWTYPE_ETH

#define ARP_HWTYPE_ETH   1

ARP_MAXAGE

#define ARP_MAXAGE   240

ARP_MAXPENDING

#define ARP_MAXPENDING   2

ARP_REPLY

#define ARP_REPLY   2

ARP_REQUEST

#define ARP_REQUEST   1

ARP_TRY_HARD

#define ARP_TRY_HARD   0x01

ARPH_HWLEN

#define ARPH_HWLEN

(

hdr

)

(ntohs((hdr)->_hwlen_protolen) >> 8)

ARPH_HWLEN_SET

#define ARPH_HWLEN_SET	(		hdr,
			len
	)		(hdr)->_hwlen_protolen = htons(ARPH_PROTOLEN(hdr) | ((len) << 8))

ARPH_PROTOLEN

#define ARPH_PROTOLEN

(

hdr

)

(ntohs((hdr)->_hwlen_protolen) & 0xff)

ARPH_PROTOLEN_SET

#define ARPH_PROTOLEN_SET	(		hdr,
			len
	)		(hdr)->_hwlen_protolen = htons((len) | (ARPH_HWLEN(hdr) << 8))

PACK_STRUCT_STRUCT

PACK_STRUCT_END PACK_STRUCT_BEGIN struct uip_ip_hdr PACK_STRUCT_STRUCT   __attribute__((packed))

UIP_ARP_TMRINTERVAL

#define UIP_ARP_TMRINTERVAL   5000

UIP_ETHTYPE_ARP

#define UIP_ETHTYPE_ARP   0x0806

UIP_ETHTYPE_IP

#define UIP_ETHTYPE_IP   0x0800

UIP_ETHTYPE_IP6

#define UIP_ETHTYPE_IP6   0x86dd

UIP_LOG

#define UIP_LOG

(

m

)

UIP_STAT

#define UIP_STAT

(

s

)

Enumeration Type Documentation

arp_state

enum arp_state

Enumerator
ARP_STATE_EMPTY
ARP_STATE_PENDING
ARP_STATE_STABLE
ARP_STATE_EXPIRED

Function Documentation

PACK_STRUCT_FIELD() [1/9]

uip_eth_addr::PACK_STRUCT_FIELD

(

u8_t

addr[6]

)

PACK_STRUCT_FIELD() [2/9]

uip_eth_hdr::PACK_STRUCT_FIELD

(

struct uip_eth_addr

dest

)

PACK_STRUCT_FIELD() [3/9]

uip_eth_hdr::PACK_STRUCT_FIELD

(

u16_t

type

)

PACK_STRUCT_FIELD() [4/9]

uip_arp_hdr::PACK_STRUCT_FIELD

(

struct uip_eth_hdr

ethhdr

)

PACK_STRUCT_FIELD() [5/9]

uip_arp_hdr::PACK_STRUCT_FIELD

(

u16_t

hwtype

)

PACK_STRUCT_FIELD() [6/9]

uip_arp_hdr::PACK_STRUCT_FIELD

(

struct uip_eth_addr

shwaddr

)

PACK_STRUCT_FIELD() [7/9]

uip_arp_hdr::PACK_STRUCT_FIELD

(

struct uip_ip_addr2

sipaddr

)

PACK_STRUCT_FIELD() [8/9]

uip_ethip_hdr::PACK_STRUCT_FIELD

(

struct uip_eth_hdr

ethhdr

)

PACK_STRUCT_FIELD() [9/9]

uip_ethip_hdr::PACK_STRUCT_FIELD

(

struct uip_ip_hdr

ip

)

uip_arp_arpin()

void uip_arp_arpin	(	struct uip_netif *	netif,
		struct uip_eth_addr *	ethaddr,
		struct uip_pbuf *	p
	)

ARP processing for incoming ARP packets.

This function should be called by the device driver when an ARP packet has been received. The function will act differently depending on the ARP packet type: if it is a reply for a request that we previously sent out, the ARP cache will be filled in with the values from the ARP reply. If the incoming ARP packet is an ARP request for our IP address, an ARP reply packet is created and put into the uip_buf[] buffer.

When the function returns, the value of the global variable uip_len indicates whether the device driver should send out a packet or not. If uip_len is zero, no packet should be sent. If uip_len is non-zero, it contains the length of the outbound packet that is present in the uip_buf[] buffer.

This function expects an ARP packet with a prepended Ethernet header in the uip_buf[] buffer, and the length of the packet in the global variable uip_len.

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uip_arp_arpquery()

s8_t uip_arp_arpquery	(	struct uip_netif *	netif,
		struct uip_ip_addr *	ipaddr,
		struct uip_pbuf *	q
	)

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uip_arp_arprequest()

s8_t uip_arp_arprequest	(	struct uip_netif *	netif,
		struct uip_ip_addr *	ipaddr
	)

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uip_arp_findentry()

static s8_t uip_arp_findentry ( struct uip_ip_addr *  ipaddr, u8_t  flags  )

static

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uip_arp_init()

void uip_arp_init

(

void

)

Initialize the ARP module.

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uip_arp_ipin()

void uip_arp_ipin	(	struct uip_netif *	netif,
		struct uip_pbuf *	p
	)

ARP processing for incoming IP packets

This function should be called by the device driver when an IP packet has been received. The function will check if the address is in the ARP cache, and if so the ARP cache entry will be refreshed. If no ARP cache entry was found, a new one is created.

This function expects an IP packet with a prepended Ethernet header in the uip_buf[] buffer, and the length of the packet in the global variable uip_len.

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uip_arp_out()

s8_t uip_arp_out	(	struct uip_netif *	netif,
		struct uip_ip_addr *	ipaddr,
		struct uip_pbuf *	q
	)

Prepend Ethernet header to an outbound IP packet and see if we need to send out an ARP request.

This function should be called before sending out an IP packet. The function checks the destination IP address of the IP packet to see what Ethernet MAC address that should be used as a destination MAC address on the Ethernet.

If the destination IP address is in the local network (determined by logical ANDing of netmask and our IP address), the function checks the ARP cache to see if an entry for the destination IP address is found. If so, an Ethernet header is prepended and the function returns. If no ARP cache entry is found for the destination IP address, the packet in the uip_buf[] is replaced by an ARP request packet for the IP address. The IP packet is dropped and it is assumed that they higher level protocols (e.g., TCP) eventually will retransmit the dropped packet.

If the destination IP address is not on the local network, the IP address of the default router is used instead.

When the function returns, a packet is present in the uip_buf[] buffer, and the length of the packet is in the global variable uip_len.

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uip_arp_timer()

void uip_arp_timer

(

void

)

Periodic ARP processing function.

This function performs periodic timer processing in the ARP module and should be called at regular intervals. The recommended interval is 10 seconds between the calls.

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uip_arp_update()

static s8_t uip_arp_update ( struct uip_netif *  netif, struct uip_ip_addr *  ipaddr, struct uip_eth_addr *  ethaddr, u8_t  flags  )

static

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Variable Documentation

arp_table

struct arp_entry arp_table[UIP_ARPTAB_SIZE]

static

ethbroadcast

const struct uip_eth_addr ethbroadcast = {{0xff,0xff,0xff,0xff,0xff,0xff}}

static

PACK_STRUCT_STRUCT

PACK_STRUCT_END PACK_STRUCT_BEGIN struct uip_ethip_hdr PACK_STRUCT_STRUCT

uip_ethaddr

PACK_STRUCT_END struct uip_eth_addr uip_ethaddr