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Some updates on "gratuitious ARP" from RFC3220. Cleanup of some code and comments.

STABLE-2_1_x
likewise 22 years ago
parent
4e2260c74c
commit
4eadc22a36
3 changed files with 48 additions and 73 deletions
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  1. 8
      src/core/netif.c
  2. 30
      src/include/lwip/netif.h
  3. 83
      src/netif/etharp.c

8
src/core/netif.c
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@ -198,6 +198,14 @@ netif_set_ipaddr(struct netif *netif, struct ip_addr *ipaddr)
}
#endif
ip_addr_set(&(netif->ip_addr), ipaddr);
#if 0 /* only allowed for Ethernet interfaces TODO: how can we check? */
/** For Ethernet network interfaces, we would like to send a
* "gratuitous ARP"; this is an ARP packet sent by a node in order
* to spontaneously cause other nodes to update an entry in their
* ARP cache. From RFC 3220 "IP Mobility Support for IPv4" section 4.6.
*/
etharp_query(netif, ipaddr, NULL);
#endif
LWIP_DEBUGF(NETIF_DEBUG | DBG_TRACE | DBG_STATE | 3, ("netif: IP address of interface %c%c set to %u.%u.%u.%u\n",
netif->name[0], netif->name[1],
(unsigned int)(ntohl(netif->ip_addr.addr) >> 24 & 0xff),

30
src/include/lwip/netif.h
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@ -52,7 +52,8 @@
/** whether the network interface is 'up'. this is
* a software flag used to control whether this network
* interface is enabled and processes traffic */
* interface is enabled and processes traffic.
* TODO: who should act on this flag, lwIP stack or driver?? */
#define NETIF_FLAG_UP 0x1U
/** if set, the netif has broadcast capability */
#define NETIF_FLAG_BROADCAST 0x2U
@ -61,35 +62,36 @@
/** if set, the interface is configured using DHCP */
#define NETIF_FLAG_DHCP 0x08U
/** if set, the interface has an active link
* (set by the interface) */
* (set by the network interface driver) */
#define NETIF_FLAG_LINK_UP 0x10U
/** generic data structure used for all lwIP network interfaces */
/** Generic data structure used for all lwIP network interfaces.
* The following fields should be filled in by the initialization
* function for the device driver: hwaddr_len, hwaddr[], mtu, flags */
struct netif {
/** pointer to next in linked list */
struct netif *next;
/** The following fields should be filled in by the
initialization function for the device driver. */
/** IP address configuration in network byte order */
struct ip_addr ip_addr;
struct ip_addr netmask;
struct ip_addr gw;
/** This function is called by the network device driver
to pass a packet up the TCP/IP stack. */
* to pass a packet up the TCP/IP stack. */
err_t (* input)(struct pbuf *p, struct netif *inp);
/** This function is called by the IP module when it wants
to send a packet on the interface. This function typically
first resolves the hardware address, then sends the packet. */
* to send a packet on the interface. This function typically
* first resolves the hardware address, then sends the packet. */
err_t (* output)(struct netif *netif, struct pbuf *p,
struct ip_addr *ipaddr);
/** This function is called by the ARP module when it wants
to send a packet on the interface. This function outputs
the pbuf as-is on the link medium. */
* to send a packet on the interface. This function outputs
* the pbuf as-is on the link medium. */
err_t (* linkoutput)(struct netif *netif, struct pbuf *p);
/** This field can be set by the device driver and could point
to state information for the device. */
* to state information for the device. */
void *state;
#if LWIP_DHCP
/** the DHCP client state information for this netif */
@ -101,12 +103,12 @@ struct netif {
unsigned char hwaddr[NETIF_MAX_HWADDR_LEN];
/** maximum transfer unit (in bytes) */
u16_t mtu;
/** flags (see NETIF_FLAG_ above) */
u8_t flags;
/** descriptive abbreviation */
char name[2];
/** number of this interface */
u8_t num;
/** NETIF_FLAG_* */
u8_t flags;
};
/** The list of network interfaces. */

83
src/netif/etharp.c
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@ -6,8 +6,10 @@
* to a physical address when sending a packet, and the second part answers
* requests from other machines for our physical address.
*
* This implementation complies with RFC 826 (Ethernet ARP) and supports
* Gratuitious ARP from RFC3220 (IP Mobility Support for IPv4) section 4.6.
* This implementation complies with RFC 826 (Ethernet ARP). It supports
* Gratuitious ARP from RFC3220 (IP Mobility Support for IPv4) section 4.6
* if an interface calls etharp_query(our_netif, its_ip_addr, NULL) upon
* address change.
*/
/*
@ -40,49 +42,8 @@
*
* This file is part of the lwIP TCP/IP stack.
*
* Author: Adam Dunkels <adam@sics.se>
*
*/
/**
* TODO:
* - pbufs should be sent from the queue once an ARP entry state
* goes from PENDING to STABLE.
* - Non-PENDING entries MUST NOT have queued packets.
*/
/*
* TODO:
*
RFC 3220 4.6 IP Mobility Support for IPv4 January 2002
- A Gratuitous ARP [45] is an ARP packet sent by a node in order
to spontaneously cause other nodes to update an entry in their
ARP cache. A gratuitous ARP MAY use either an ARP Request or
an ARP Reply packet. In either case, the ARP Sender Protocol
Address and ARP Target Protocol Address are both set to the IP
address of the cache entry to be updated, and the ARP Sender
Hardware Address is set to the link-layer address to which this
cache entry should be updated. When using an ARP Reply packet,
the Target Hardware Address is also set to the link-layer
address to which this cache entry should be updated (this field
is not used in an ARP Request packet).
In either case, for a gratuitous ARP, the ARP packet MUST be
transmitted as a local broadcast packet on the local link. As
specified in [36], any node receiving any ARP packet (Request
or Reply) MUST update its local ARP cache with the Sender
Protocol and Hardware Addresses in the ARP packet, if the
receiving node has an entry for that IP address already in its
ARP cache. This requirement in the ARP protocol applies even
for ARP Request packets, and for ARP Reply packets that do not
match any ARP Request transmitted by the receiving node [36].
*
My suggestion would be to send a ARP request for our newly obtained
address upon configuration of an Ethernet interface.
*/
#include "lwip/opt.h"
#include "lwip/inet.h"
#include "netif/etharp.h"
@ -242,13 +203,13 @@ find_arp_entry(void)
return ERR_MEM;
}
/* clean up the recycled stable entry */
/* clean up the oldest stable entry (to be recycled) */
if (arp_table[i].state == ETHARP_STATE_STABLE) {
#if ARP_QUEUEING
/* and empty the packet queue */
if (arp_table[i].p != NULL) {
/* remove all queued packets */
LWIP_DEBUGF(ETHARP_DEBUG, ("find_arp_entry: freeing entry %u, packet queue %p.\n", i, (void *)(arp_table[i].p)));
/* remove all queued packets */
pbuf_free(arp_table[i].p);
arp_table[i].p = NULL;
}
@ -292,12 +253,11 @@ update_arp_entry(struct netif *netif, struct ip_addr *ipaddr, struct eth_addr *e
LWIP_DEBUGF(ETHARP_DEBUG | DBG_TRACE, ("update_arp_entry: will not add 0.0.0.0 to ARP cache\n"));
return NULL;
}
/* Walk through the ARP mapping table and try to find an entry to
update. If none is found, the IP -> MAC address mapping is
inserted in the ARP table. */
/* Walk through the ARP mapping table and try to find an entry to update.
* If none is found, a new IP -> MAC address mapping is inserted. */
for (i = 0; i < ARP_TABLE_SIZE; ++i) {
/* Check if the source IP address of the incoming packet matches
the IP address in this ARP table entry. */
* the IP address in this ARP table entry. */
if (arp_table[i].state != ETHARP_STATE_EMPTY &&
ip_addr_cmp(ipaddr, &arp_table[i].ipaddr)) {
/* pending entry? */
@ -307,12 +267,8 @@ update_arp_entry(struct netif *netif, struct ip_addr *ipaddr, struct eth_addr *e
arp_table[i].state = ETHARP_STATE_STABLE;
/* fall-through to next if */
}
/* stable entry? (possibly just marked to become stable) */
/* stable entry? (possibly just marked stable) */
if (arp_table[i].state == ETHARP_STATE_STABLE) {
#if ARP_QUEUEING
struct pbuf *p;
struct eth_hdr *ethhdr;
#endif
LWIP_DEBUGF(ETHARP_DEBUG | DBG_TRACE, ("update_arp_entry: updating stable entry %u\n", i));
/* An old entry found, update this and return. */
for (k = 0; k < netif->hwaddr_len; ++k) {
@ -324,11 +280,13 @@ update_arp_entry(struct netif *netif, struct ip_addr *ipaddr, struct eth_addr *e
#if ARP_QUEUEING
while (arp_table[i].p != NULL) {
/* get the first packet on the queue (if any) */
p = arp_table[i].p;
struct pbuf *p = arp_table[i].p;
/* Ethernet header */
struct eth_hdr *ethhdr = p->payload;;
/* remember (and reference) remainder of queue */
/* note: this will also terminate the p pbuf chain */
arp_table[i].p = pbuf_dequeue(p);
/* fill-in Ethernet header */
ethhdr = p->payload;
for (k = 0; k < netif->hwaddr_len; ++k) {
ethhdr->dest.addr[k] = ethaddr->addr[k];
ethhdr->src.addr[k] = netif->hwaddr[k];
@ -521,7 +479,7 @@ etharp_arp_input(struct netif *netif, struct eth_addr *ethaddr, struct pbuf *p)
}
break;
case ARP_REPLY:
/* ARP reply. We insert or update the ARP table later. */
/* ARP reply. We already updated the ARP cache earlier. */
LWIP_DEBUGF(ETHARP_DEBUG | DBG_TRACE, ("etharp_arp_input: incoming ARP reply\n"));
#if (LWIP_DHCP && DHCP_DOES_ARP_CHECK)
/* DHCP wants to know about ARP replies to our wanna-have-address */
@ -696,20 +654,24 @@ err_t etharp_query(struct netif *netif, struct ip_addr *ipaddr, struct pbuf *q)
err_t result = ERR_OK;
s8_t i;
u8_t perform_arp_request = 1;
/* prevent 'unused argument' warning if ARP_QUEUEING == 0 */
/* prevent 'unused argument' compiler warning if ARP_QUEUEING == 0 */
(void)q;
srcaddr = (struct eth_addr *)netif->hwaddr;
/* bail out if this IP address is pending */
for (i = 0; i < ARP_TABLE_SIZE; ++i) {
/* valid ARP cache entry with matching IP address? */
if (arp_table[i].state != ETHARP_STATE_EMPTY &&
ip_addr_cmp(ipaddr, &arp_table[i].ipaddr)) {
/* pending entry? */
if (arp_table[i].state == ETHARP_STATE_PENDING) {
LWIP_DEBUGF(ETHARP_DEBUG | DBG_TRACE | DBG_STATE, ("etharp_query: requested IP already pending as entry %u\n", i));
/* break out of for-loop, user may wish to queue a packet on a pending entry */
/* TODO: we will issue a new ARP request, which should not occur too often */
/* we might want to run a faster timer on ARP to limit this */
/* { i != ARP_TABLE_SIZE } */
break;
}
/* stable entry? */
else if (arp_table[i].state == ETHARP_STATE_STABLE) {
LWIP_DEBUGF(ETHARP_DEBUG | DBG_TRACE | DBG_STATE, ("etharp_query: requested IP already stable as entry %u\n", i));
/* User wishes to queue a packet on a stable entry (or does she want to send
@ -720,6 +682,7 @@ err_t etharp_query(struct netif *netif, struct ip_addr *ipaddr, struct pbuf *q)
* immediately. I chose to implement the former approach.
*/
perform_arp_request = (q?1:0);
/* { i != ARP_TABLE_SIZE } */
break;
}
}
@ -739,9 +702,11 @@ err_t etharp_query(struct netif *netif, struct ip_addr *ipaddr, struct pbuf *q)
ip_addr_set(&arp_table[i].ipaddr, ipaddr);
}
/* { i is now valid } */
#if ARP_QUEUEING /* queue packet (even on a stable entry, see above) */
#if ARP_QUEUEING /* queue the given q packet */
/* copy any PBUF_REF referenced payloads into PBUF_RAM */
/* (the caller assumes the referenced payload can be freed) */
q = pbuf_take(q);
/* queue packet (even on a stable entry, see above) */
pbuf_queue(arp_table[i].p, q);
#endif
/* ARP request? */

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