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[neighbour] Generalise concept of neighbour discovery
Split the protocol-independent portions of arp.c into a separate file neighbour.c, to allow for sharing of functionality between IPv4+ARP and IPv6+NDP. Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown
479
src/net/neighbour.c
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479
src/net/neighbour.c
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@@ -0,0 +1,479 @@
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/*
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* Copyright (C) 2013 Michael Brown <mbrown@fensystems.co.uk>.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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* 02110-1301, USA.
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*/
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FILE_LICENCE ( GPL2_OR_LATER );
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#include <stdint.h>
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#include <stdlib.h>
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#include <string.h>
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#include <errno.h>
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#include <ipxe/refcnt.h>
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#include <ipxe/list.h>
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#include <ipxe/iobuf.h>
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#include <ipxe/retry.h>
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#include <ipxe/timer.h>
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#include <ipxe/malloc.h>
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#include <ipxe/neighbour.h>
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/** @file
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*
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* Neighbour discovery
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*
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* This file implements the abstract functions of neighbour discovery,
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* independent of the underlying network protocol (e.g. ARP or NDP).
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*
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*/
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/** A neighbour cache entry */
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struct neighbour {
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/** Reference count */
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struct refcnt refcnt;
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/** List of neighbour cache entries */
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struct list_head list;
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/** Network device */
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struct net_device *netdev;
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/** Network-layer protocol */
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struct net_protocol *net_protocol;
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/** Network-layer destination address */
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uint8_t net_dest[MAX_NET_ADDR_LEN];
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/** Link-layer destination address */
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uint8_t ll_dest[MAX_LL_ADDR_LEN];
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/** Neighbour discovery protocol (if any) */
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struct neighbour_discovery *discovery;
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/** Network-layer source address (if any) */
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uint8_t net_source[MAX_NET_ADDR_LEN];
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/** Retransmission timer */
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struct retry_timer timer;
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/** Pending I/O buffers */
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struct list_head tx_queue;
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};
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/** Neighbour discovery minimum timeout */
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#define NEIGHBOUR_MIN_TIMEOUT ( TICKS_PER_SEC / 8 )
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/** Neighbour discovery maximum timeout */
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#define NEIGHBOUR_MAX_TIMEOUT ( TICKS_PER_SEC * 3 )
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/** The neighbour cache */
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static LIST_HEAD ( neighbours );
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static void neighbour_expired ( struct retry_timer *timer, int over );
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/**
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* Free neighbour cache entry
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*
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* @v refcnt Reference count
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*/
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static void neighbour_free ( struct refcnt *refcnt ) {
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struct neighbour *neighbour =
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container_of ( refcnt, struct neighbour, refcnt );
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/* Sanity check */
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assert ( list_empty ( &neighbour->tx_queue ) );
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/* Drop reference to network device */
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netdev_put ( neighbour->netdev );
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/* Free neighbour */
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free ( neighbour );
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}
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/**
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* Test if neighbour cache entry has a valid link-layer address
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*
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* @v neighbour Neighbour cache entry
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* @ret has_ll_dest Neighbour cache entry has a valid link-layer address
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*/
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static inline __attribute__ (( always_inline )) int
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neighbour_has_ll_dest ( struct neighbour *neighbour ) {
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return ( ! timer_running ( &neighbour->timer ) );
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}
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/**
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* Create neighbour cache entry
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*
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* @v netdev Network device
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* @v net_protocol Network-layer protocol
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* @v net_dest Destination network-layer address
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* @ret neighbour Neighbour cache entry, or NULL if allocation failed
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*/
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static struct neighbour * neighbour_create ( struct net_device *netdev,
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struct net_protocol *net_protocol,
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const void *net_dest ) {
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struct neighbour *neighbour;
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/* Allocate and initialise entry */
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neighbour = zalloc ( sizeof ( *neighbour ) );
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if ( ! neighbour )
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return NULL;
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ref_init ( &neighbour->refcnt, neighbour_free );
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neighbour->netdev = netdev_get ( netdev );
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neighbour->net_protocol = net_protocol;
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memcpy ( neighbour->net_dest, net_dest,
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net_protocol->net_addr_len );
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timer_init ( &neighbour->timer, neighbour_expired, &neighbour->refcnt );
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neighbour->timer.min_timeout = NEIGHBOUR_MIN_TIMEOUT;
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neighbour->timer.max_timeout = NEIGHBOUR_MAX_TIMEOUT;
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INIT_LIST_HEAD ( &neighbour->tx_queue );
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/* Transfer ownership to cache */
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list_add ( &neighbour->list, &neighbours );
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DBGC ( neighbour, "NEIGHBOUR %s %s %s created\n", netdev->name,
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net_protocol->name, net_protocol->ntoa ( net_dest ) );
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return neighbour;
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}
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/**
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* Find neighbour cache entry
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*
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* @v netdev Network device
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* @v net_protocol Network-layer protocol
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* @v net_dest Destination network-layer address
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* @ret neighbour Neighbour cache entry, or NULL if not found
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*/
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static struct neighbour * neighbour_find ( struct net_device *netdev,
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struct net_protocol *net_protocol,
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const void *net_dest ) {
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struct neighbour *neighbour;
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list_for_each_entry ( neighbour, &neighbours, list ) {
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if ( ( neighbour->netdev == netdev ) &&
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( neighbour->net_protocol == net_protocol ) &&
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( memcmp ( neighbour->net_dest, net_dest,
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net_protocol->net_addr_len ) == 0 ) ) {
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/* Move to start of cache */
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list_del ( &neighbour->list );
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list_add ( &neighbour->list, &neighbours );
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return neighbour;
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}
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}
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return NULL;
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}
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/**
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* Start neighbour discovery
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*
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* @v neighbour Neighbour cache entry
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* @v discovery Neighbour discovery protocol
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* @v net_source Source network-layer address
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*/
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static void neighbour_discover ( struct neighbour *neighbour,
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struct neighbour_discovery *discovery,
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const void *net_source ) {
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struct net_device *netdev = neighbour->netdev;
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struct net_protocol *net_protocol = neighbour->net_protocol;
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/* Record discovery protocol and source network-layer address */
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neighbour->discovery = discovery;
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memcpy ( neighbour->net_source, net_source,
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net_protocol->net_addr_len );
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/* Start timer to trigger neighbour discovery */
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start_timer_nodelay ( &neighbour->timer );
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DBGC ( neighbour, "NEIGHBOUR %s %s %s discovering via %s\n",
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netdev->name, net_protocol->name,
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net_protocol->ntoa ( neighbour->net_dest ),
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neighbour->discovery->name );
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}
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/**
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* Complete neighbour discovery
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*
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* @v neighbour Neighbour cache entry
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* @v ll_dest Destination link-layer address
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*/
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static void neighbour_discovered ( struct neighbour *neighbour,
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const void *ll_dest ) {
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struct net_device *netdev = neighbour->netdev;
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struct ll_protocol *ll_protocol = netdev->ll_protocol;
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struct net_protocol *net_protocol = neighbour->net_protocol;
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struct io_buffer *iobuf;
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int rc;
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/* Fill in link-layer address */
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memcpy ( neighbour->ll_dest, ll_dest, ll_protocol->ll_addr_len );
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DBGC ( neighbour, "NEIGHBOUR %s %s %s is %s %s\n", netdev->name,
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net_protocol->name, net_protocol->ntoa ( neighbour->net_dest ),
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ll_protocol->name, ll_protocol->ntoa ( neighbour->ll_dest ) );
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/* Stop retransmission timer */
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stop_timer ( &neighbour->timer );
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/* Transmit any packets in queue. Take out a temporary
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* reference on the entry to prevent it from going out of
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* scope during the call to net_tx().
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*/
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ref_get ( &neighbour->refcnt );
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while ( ( iobuf = list_first_entry ( &neighbour->tx_queue,
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struct io_buffer, list )) != NULL){
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DBGC2 ( neighbour, "NEIGHBOUR %s %s %s transmitting deferred "
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"packet\n", netdev->name, net_protocol->name,
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net_protocol->ntoa ( neighbour->net_dest ) );
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list_del ( &iobuf->list );
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if ( ( rc = net_tx ( iobuf, netdev, net_protocol, ll_dest,
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netdev->ll_addr ) ) != 0 ) {
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DBGC ( neighbour, "NEIGHBOUR %s %s %s could not "
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"transmit deferred packet: %s\n",
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netdev->name, net_protocol->name,
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net_protocol->ntoa ( neighbour->net_dest ),
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strerror ( rc ) );
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/* Ignore error and continue */
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}
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}
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ref_put ( &neighbour->refcnt );
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}
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/**
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* Destroy neighbour cache entry
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*
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* @v neighbour Neighbour cache entry
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* @v rc Reason for destruction
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*/
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static void neighbour_destroy ( struct neighbour *neighbour, int rc ) {
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struct net_device *netdev = neighbour->netdev;
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struct net_protocol *net_protocol = neighbour->net_protocol;
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struct io_buffer *iobuf;
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/* Take ownership from cache */
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list_del ( &neighbour->list );
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/* Stop timer */
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stop_timer ( &neighbour->timer );
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/* Discard any outstanding I/O buffers */
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while ( ( iobuf = list_first_entry ( &neighbour->tx_queue,
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struct io_buffer, list )) != NULL){
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DBGC2 ( neighbour, "NEIGHBOUR %s %s %s discarding deferred "
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"packet: %s\n", netdev->name, net_protocol->name,
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net_protocol->ntoa ( neighbour->net_dest ),
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strerror ( rc ) );
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list_del ( &iobuf->list );
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netdev_tx_err ( neighbour->netdev, iobuf, rc );
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}
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DBGC ( neighbour, "NEIGHBOUR %s %s %s destroyed: %s\n", netdev->name,
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net_protocol->name, net_protocol->ntoa ( neighbour->net_dest ),
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strerror ( rc ) );
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/* Drop remaining reference */
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ref_put ( &neighbour->refcnt );
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}
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/**
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* Handle neighbour timer expiry
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*
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* @v timer Retry timer
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* @v fail Failure indicator
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*/
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static void neighbour_expired ( struct retry_timer *timer, int fail ) {
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struct neighbour *neighbour =
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container_of ( timer, struct neighbour, timer );
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struct net_device *netdev = neighbour->netdev;
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struct net_protocol *net_protocol = neighbour->net_protocol;
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struct neighbour_discovery *discovery =
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neighbour->discovery;
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const void *net_dest = neighbour->net_dest;
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const void *net_source = neighbour->net_source;
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int rc;
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/* If we have failed, destroy the cache entry */
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if ( fail ) {
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neighbour_destroy ( neighbour, -ETIMEDOUT );
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return;
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}
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/* Restart the timer */
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start_timer ( &neighbour->timer );
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/* Transmit neighbour request */
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if ( ( rc = discovery->tx_request ( netdev, net_protocol, net_dest,
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net_source ) ) != 0 ) {
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DBGC ( neighbour, "NEIGHBOUR %s %s %s could not transmit %s "
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"request: %s\n", netdev->name, net_protocol->name,
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net_protocol->ntoa ( neighbour->net_dest ),
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neighbour->discovery->name, strerror ( rc ) );
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/* Retransmit when timer expires */
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return;
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}
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}
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/**
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* Transmit packet, determining link-layer address via neighbour discovery
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*
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* @v iobuf I/O buffer
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* @v netdev Network device
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* @v discovery Neighbour discovery protocol
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* @v net_protocol Network-layer protocol
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* @v net_dest Destination network-layer address
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* @v net_source Source network-layer address
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* @v ll_source Source link-layer address
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* @ret rc Return status code
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*/
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int neighbour_tx ( struct io_buffer *iobuf, struct net_device *netdev,
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struct net_protocol *net_protocol, const void *net_dest,
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struct neighbour_discovery *discovery,
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const void *net_source, const void *ll_source ) {
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struct neighbour *neighbour;
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/* Find or create neighbour cache entry */
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neighbour = neighbour_find ( netdev, net_protocol, net_dest );
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if ( ! neighbour ) {
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neighbour = neighbour_create ( netdev, net_protocol, net_dest );
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if ( ! neighbour )
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return -ENOMEM;
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neighbour_discover ( neighbour, discovery, net_source );
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}
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/* If a link-layer address is available then transmit
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* immediately, otherwise queue for later transmission.
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*/
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if ( neighbour_has_ll_dest ( neighbour ) ) {
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return net_tx ( iobuf, netdev, net_protocol, neighbour->ll_dest,
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ll_source );
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} else {
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DBGC2 ( neighbour, "NEIGHBOUR %s %s %s deferring packet\n",
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netdev->name, net_protocol->name,
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net_protocol->ntoa ( net_dest ) );
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list_add_tail ( &iobuf->list, &neighbour->tx_queue );
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return -EAGAIN;
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}
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}
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/**
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* Update existing neighbour cache entry
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*
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* @v netdev Network device
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* @v net_protocol Network-layer protocol
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* @v net_dest Destination network-layer address
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* @v ll_dest Destination link-layer address
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* @ret rc Return status code
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*/
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int neighbour_update ( struct net_device *netdev,
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struct net_protocol *net_protocol,
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const void *net_dest, const void *ll_dest ) {
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struct neighbour *neighbour;
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/* Find neighbour cache entry */
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neighbour = neighbour_find ( netdev, net_protocol, net_dest );
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if ( ! neighbour )
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return -ENOENT;
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/* Set destination address */
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neighbour_discovered ( neighbour, ll_dest );
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return 0;
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}
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/**
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* Define neighbour cache entry
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*
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* @v netdev Network device
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* @v net_protocol Network-layer protocol
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* @v net_dest Destination network-layer address
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* @v ll_dest Destination link-layer address, if known
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* @ret rc Return status code
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*/
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int neighbour_define ( struct net_device *netdev,
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struct net_protocol *net_protocol,
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const void *net_dest, const void *ll_dest ) {
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struct neighbour *neighbour;
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/* Find or create neighbour cache entry */
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neighbour = neighbour_find ( netdev, net_protocol, net_dest );
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if ( ! neighbour ) {
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neighbour = neighbour_create ( netdev, net_protocol, net_dest );
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if ( ! neighbour )
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return -ENOMEM;
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}
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/* Set destination address */
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neighbour_discovered ( neighbour, ll_dest );
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return 0;
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}
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/**
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* Update neighbour cache on network device creation
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*
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* @v netdev Network device
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*/
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static int neighbour_probe ( struct net_device *netdev __unused ) {
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/* Nothing to do */
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return 0;
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}
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/**
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* Update neighbour cache on network device state change or removal
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*
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* @v netdev Network device
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*/
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static void neighbour_flush ( struct net_device *netdev ) {
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struct neighbour *neighbour;
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struct neighbour *tmp;
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/* Remove all neighbour cache entries when a network device is closed */
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if ( ! netdev_is_open ( netdev ) ) {
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list_for_each_entry_safe ( neighbour, tmp, &neighbours, list )
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neighbour_destroy ( neighbour, -ENODEV );
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}
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}
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/** Neighbour driver (for net device notifications) */
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struct net_driver neighbour_net_driver __net_driver = {
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.name = "Neighbour",
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.probe = neighbour_probe,
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.notify = neighbour_flush,
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.remove = neighbour_flush,
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};
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/**
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* Discard some cached neighbour entries
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*
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* @ret discarded Number of cached items discarded
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*/
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static unsigned int neighbour_discard ( void ) {
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struct neighbour *neighbour;
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/* Drop oldest cache entry, if any */
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neighbour = list_last_entry ( &neighbours, struct neighbour, list );
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if ( neighbour ) {
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neighbour_destroy ( neighbour, -ENOBUFS );
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return 1;
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} else {
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return 0;
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}
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}
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/**
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* Neighbour cache discarder
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*
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* Neighbour cache entries are deemed to have a high replacement cost,
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* since flushing an active neighbour cache entry midway through a TCP
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* transfer will cause substantial disruption.
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*/
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struct cache_discarder neighbour_discarder __cache_discarder (CACHE_EXPENSIVE)={
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.discard = neighbour_discard,
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};
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