/* * Copyright (C) 2013 Michael Brown . * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License as * published by the Free Software Foundation; either version 2 of the * License, or any later version. * * This program is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA * 02110-1301, USA. * * You can also choose to distribute this program under the terms of * the Unmodified Binary Distribution Licence (as given in the file * COPYING.UBDL), provided that you have satisfied its requirements. */ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL ); #include #include #include #include #include #include #include #include #include /** @file * * Neighbour discovery * * This file implements the abstract functions of neighbour discovery, * independent of the underlying network protocol (e.g. ARP or NDP). * */ /** Neighbour discovery minimum timeout */ #define NEIGHBOUR_MIN_TIMEOUT ( TICKS_PER_SEC / 8 ) /** Neighbour discovery maximum timeout */ #define NEIGHBOUR_MAX_TIMEOUT ( TICKS_PER_SEC * 3 ) /** The neighbour cache */ struct list_head neighbours = LIST_HEAD_INIT ( neighbours ); static void neighbour_expired ( struct retry_timer *timer, int over ); /** * Free neighbour cache entry * * @v refcnt Reference count */ static void neighbour_free ( struct refcnt *refcnt ) { struct neighbour *neighbour = container_of ( refcnt, struct neighbour, refcnt ); /* Sanity check */ assert ( list_empty ( &neighbour->tx_queue ) ); /* Drop reference to network device */ netdev_put ( neighbour->netdev ); /* Free neighbour */ free ( neighbour ); } /** * Create neighbour cache entry * * @v netdev Network device * @v net_protocol Network-layer protocol * @v net_dest Destination network-layer address * @ret neighbour Neighbour cache entry, or NULL if allocation failed */ static struct neighbour * neighbour_create ( struct net_device *netdev, struct net_protocol *net_protocol, const void *net_dest ) { struct neighbour *neighbour; /* Allocate and initialise entry */ neighbour = zalloc ( sizeof ( *neighbour ) ); if ( ! neighbour ) return NULL; ref_init ( &neighbour->refcnt, neighbour_free ); neighbour->netdev = netdev_get ( netdev ); neighbour->net_protocol = net_protocol; memcpy ( neighbour->net_dest, net_dest, net_protocol->net_addr_len ); timer_init ( &neighbour->timer, neighbour_expired, &neighbour->refcnt ); neighbour->timer.min_timeout = NEIGHBOUR_MIN_TIMEOUT; neighbour->timer.max_timeout = NEIGHBOUR_MAX_TIMEOUT; INIT_LIST_HEAD ( &neighbour->tx_queue ); /* Transfer ownership to cache */ list_add ( &neighbour->list, &neighbours ); DBGC ( neighbour, "NEIGHBOUR %s %s %s created\n", netdev->name, net_protocol->name, net_protocol->ntoa ( net_dest ) ); return neighbour; } /** * Find neighbour cache entry * * @v netdev Network device * @v net_protocol Network-layer protocol * @v net_dest Destination network-layer address * @ret neighbour Neighbour cache entry, or NULL if not found */ static struct neighbour * neighbour_find ( struct net_device *netdev, struct net_protocol *net_protocol, const void *net_dest ) { struct neighbour *neighbour; list_for_each_entry ( neighbour, &neighbours, list ) { if ( ( neighbour->netdev == netdev ) && ( neighbour->net_protocol == net_protocol ) && ( memcmp ( neighbour->net_dest, net_dest, net_protocol->net_addr_len ) == 0 ) ) { /* Move to start of cache */ list_del ( &neighbour->list ); list_add ( &neighbour->list, &neighbours ); return neighbour; } } return NULL; } /** * Start neighbour discovery * * @v neighbour Neighbour cache entry * @v discovery Neighbour discovery protocol * @v net_source Source network-layer address */ static void neighbour_discover ( struct neighbour *neighbour, struct neighbour_discovery *discovery, const void *net_source ) { struct net_device *netdev = neighbour->netdev; struct net_protocol *net_protocol = neighbour->net_protocol; /* Record discovery protocol and source network-layer address */ neighbour->discovery = discovery; memcpy ( neighbour->net_source, net_source, net_protocol->net_addr_len ); /* Start timer to trigger neighbour discovery */ start_timer_nodelay ( &neighbour->timer ); DBGC ( neighbour, "NEIGHBOUR %s %s %s discovering via %s\n", netdev->name, net_protocol->name, net_protocol->ntoa ( neighbour->net_dest ), neighbour->discovery->name ); } /** * Complete neighbour discovery * * @v neighbour Neighbour cache entry * @v ll_dest Destination link-layer address */ static void neighbour_discovered ( struct neighbour *neighbour, const void *ll_dest ) { struct net_device *netdev = neighbour->netdev; struct ll_protocol *ll_protocol = netdev->ll_protocol; struct net_protocol *net_protocol = neighbour->net_protocol; struct io_buffer *iobuf; int rc; /* Fill in link-layer address */ memcpy ( neighbour->ll_dest, ll_dest, ll_protocol->ll_addr_len ); DBGC ( neighbour, "NEIGHBOUR %s %s %s is %s %s\n", netdev->name, net_protocol->name, net_protocol->ntoa ( neighbour->net_dest ), ll_protocol->name, ll_protocol->ntoa ( neighbour->ll_dest ) ); /* Stop retransmission timer */ stop_timer ( &neighbour->timer ); /* Transmit any packets in queue. Take out a temporary * reference on the entry to prevent it from going out of * scope during the call to net_tx(). */ ref_get ( &neighbour->refcnt ); while ( ( iobuf = list_first_entry ( &neighbour->tx_queue, struct io_buffer, list )) != NULL){ DBGC2 ( neighbour, "NEIGHBOUR %s %s %s transmitting deferred " "packet\n", netdev->name, net_protocol->name, net_protocol->ntoa ( neighbour->net_dest ) ); list_del ( &iobuf->list ); if ( ( rc = net_tx ( iobuf, netdev, net_protocol, ll_dest, netdev->ll_addr ) ) != 0 ) { DBGC ( neighbour, "NEIGHBOUR %s %s %s could not " "transmit deferred packet: %s\n", netdev->name, net_protocol->name, net_protocol->ntoa ( neighbour->net_dest ), strerror ( rc ) ); /* Ignore error and continue */ } } ref_put ( &neighbour->refcnt ); } /** * Destroy neighbour cache entry * * @v neighbour Neighbour cache entry * @v rc Reason for destruction */ static void neighbour_destroy ( struct neighbour *neighbour, int rc ) { struct net_device *netdev = neighbour->netdev; struct net_protocol *net_protocol = neighbour->net_protocol; struct io_buffer *iobuf; /* Take ownership from cache */ list_del ( &neighbour->list ); /* Stop timer */ stop_timer ( &neighbour->timer ); /* Discard any outstanding I/O buffers */ while ( ( iobuf = list_first_entry ( &neighbour->tx_queue, struct io_buffer, list )) != NULL){ DBGC2 ( neighbour, "NEIGHBOUR %s %s %s discarding deferred " "packet: %s\n", netdev->name, net_protocol->name, net_protocol->ntoa ( neighbour->net_dest ), strerror ( rc ) ); list_del ( &iobuf->list ); netdev_tx_err ( neighbour->netdev, iobuf, rc ); } DBGC ( neighbour, "NEIGHBOUR %s %s %s destroyed: %s\n", netdev->name, net_protocol->name, net_protocol->ntoa ( neighbour->net_dest ), strerror ( rc ) ); /* Drop remaining reference */ ref_put ( &neighbour->refcnt ); } /** * Handle neighbour timer expiry * * @v timer Retry timer * @v fail Failure indicator */ static void neighbour_expired ( struct retry_timer *timer, int fail ) { struct neighbour *neighbour = container_of ( timer, struct neighbour, timer ); struct net_device *netdev = neighbour->netdev; struct net_protocol *net_protocol = neighbour->net_protocol; struct neighbour_discovery *discovery = neighbour->discovery; const void *net_dest = neighbour->net_dest; const void *net_source = neighbour->net_source; int rc; /* If we have failed, destroy the cache entry */ if ( fail ) { neighbour_destroy ( neighbour, -ETIMEDOUT ); return; } /* Restart the timer */ start_timer ( &neighbour->timer ); /* Transmit neighbour request */ if ( ( rc = discovery->tx_request ( netdev, net_protocol, net_dest, net_source ) ) != 0 ) { DBGC ( neighbour, "NEIGHBOUR %s %s %s could not transmit %s " "request: %s\n", netdev->name, net_protocol->name, net_protocol->ntoa ( neighbour->net_dest ), neighbour->discovery->name, strerror ( rc ) ); /* Retransmit when timer expires */ return; } } /** * Transmit packet, determining link-layer address via neighbour discovery * * @v iobuf I/O buffer * @v netdev Network device * @v discovery Neighbour discovery protocol * @v net_protocol Network-layer protocol * @v net_dest Destination network-layer address * @v net_source Source network-layer address * @v ll_source Source link-layer address * @ret rc Return status code */ int neighbour_tx ( struct io_buffer *iobuf, struct net_device *netdev, struct net_protocol *net_protocol, const void *net_dest, struct neighbour_discovery *discovery, const void *net_source, const void *ll_source ) { struct neighbour *neighbour; /* Find or create neighbour cache entry */ neighbour = neighbour_find ( netdev, net_protocol, net_dest ); if ( ! neighbour ) { neighbour = neighbour_create ( netdev, net_protocol, net_dest ); if ( ! neighbour ) return -ENOMEM; neighbour_discover ( neighbour, discovery, net_source ); } /* If a link-layer address is available then transmit * immediately, otherwise queue for later transmission. */ if ( neighbour_has_ll_dest ( neighbour ) ) { return net_tx ( iobuf, netdev, net_protocol, neighbour->ll_dest, ll_source ); } else { DBGC2 ( neighbour, "NEIGHBOUR %s %s %s deferring packet\n", netdev->name, net_protocol->name, net_protocol->ntoa ( net_dest ) ); list_add_tail ( &iobuf->list, &neighbour->tx_queue ); return -EAGAIN; } } /** * Update existing neighbour cache entry * * @v netdev Network device * @v net_protocol Network-layer protocol * @v net_dest Destination network-layer address * @v ll_dest Destination link-layer address * @ret rc Return status code */ int neighbour_update ( struct net_device *netdev, struct net_protocol *net_protocol, const void *net_dest, const void *ll_dest ) { struct neighbour *neighbour; /* Find neighbour cache entry */ neighbour = neighbour_find ( netdev, net_protocol, net_dest ); if ( ! neighbour ) return -ENOENT; /* Set destination address */ neighbour_discovered ( neighbour, ll_dest ); return 0; } /** * Define neighbour cache entry * * @v netdev Network device * @v net_protocol Network-layer protocol * @v net_dest Destination network-layer address * @v ll_dest Destination link-layer address, if known * @ret rc Return status code */ int neighbour_define ( struct net_device *netdev, struct net_protocol *net_protocol, const void *net_dest, const void *ll_dest ) { struct neighbour *neighbour; /* Find or create neighbour cache entry */ neighbour = neighbour_find ( netdev, net_protocol, net_dest ); if ( ! neighbour ) { neighbour = neighbour_create ( netdev, net_protocol, net_dest ); if ( ! neighbour ) return -ENOMEM; } /* Set destination address */ neighbour_discovered ( neighbour, ll_dest ); return 0; } /** * Update neighbour cache on network device state change or removal * * @v netdev Network device */ static void neighbour_flush ( struct net_device *netdev ) { struct neighbour *neighbour; struct neighbour *tmp; /* Remove all neighbour cache entries when a network device is closed */ if ( ! netdev_is_open ( netdev ) ) { list_for_each_entry_safe ( neighbour, tmp, &neighbours, list ) neighbour_destroy ( neighbour, -ENODEV ); } } /** Neighbour driver (for net device notifications) */ struct net_driver neighbour_net_driver __net_driver = { .name = "Neighbour", .notify = neighbour_flush, .remove = neighbour_flush, }; /** * Discard some cached neighbour entries * * @ret discarded Number of cached items discarded */ static unsigned int neighbour_discard ( void ) { struct neighbour *neighbour; /* Drop oldest cache entry, if any */ neighbour = list_last_entry ( &neighbours, struct neighbour, list ); if ( neighbour ) { neighbour_destroy ( neighbour, -ENOBUFS ); return 1; } else { return 0; } } /** * Neighbour cache discarder * * Neighbour cache entries are deemed to have a high replacement cost, * since flushing an active neighbour cache entry midway through a TCP * transfer will cause substantial disruption. */ struct cache_discarder neighbour_discarder __cache_discarder (CACHE_EXPENSIVE)={ .discard = neighbour_discard, };