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src/net/neighbour.c
581 строка
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Michael Brown
[neighbour] Discard deferred packets before discarding complete entries
21 май 2026, 15:01
21 май 2026, 15:01
2d82369
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/* * Copyright (C) 2013 Michael Brown <mbrown@fensystems.co.uk>. * * 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 ); FILE_SECBOOT ( PERMITTED ); #include <stdint.h> #include <stdlib.h> #include <string.h> #include <errno.h> #include <ipxe/iobuf.h> #include <ipxe/retry.h> #include <ipxe/timer.h> #include <ipxe/malloc.h> #include <ipxe/pending.h> #include <ipxe/neighbour.h> #include <config/fault.h> /** @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 ) /** Neighbour discovery maximum burst count for delayed transmissions * * When using delay injection, timer quantisation can cause a large * number of delayed packets to be scheduled at the same time. This * can quickly exhaust available transmit descriptors, leading to * packets that are dropped completely (not just delayed). * * Limit the number of delayed packets that we will attempt to * transmit at once, to allow time for transmit completions to occur. */ #define NEIGHBOUR_DELAY_MAX_BURST 2 /** The neighbour cache */ struct list_head neighbours = LIST_HEAD_INIT ( neighbours ); /** Pending operation for delayed transmissions */ static struct pending_operation neighbour_delayed; 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 ); set_timer_limits ( &neighbour->timer, NEIGHBOUR_MIN_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 ); } /** * Transmit deferred packets * * @v neighbour Neighbour cache entry */ static void neighbour_tx_queue ( struct neighbour *neighbour ) { struct net_device *netdev = neighbour->netdev; struct net_protocol *net_protocol = neighbour->net_protocol; const void *ll_dest = neighbour->ll_dest; struct neighbour_delay *delay; struct io_buffer *iobuf; unsigned long elapsed; unsigned long threshold; unsigned int count = 0; int rc; /* 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){ /* Handle delay injection */ if ( NEIGHBOUR_DELAY_MS ) { /* Determine elapsed time since transmission attempt */ delay = iobuf->data; elapsed = ( currticks() - delay->start ); threshold = ( NEIGHBOUR_DELAY_MS * TICKS_PER_MS ); /* Defer transmission if not yet scheduled */ if ( elapsed < threshold ) { start_timer_fixed ( &neighbour->timer, ( threshold - elapsed ) ); break; } /* Defer transmission if maximum burst count reached */ if ( ++count >= NEIGHBOUR_DELAY_MAX_BURST ) { start_timer_nodelay ( &neighbour->timer ); break; } /* Strip pseudo-header */ iob_pull ( iobuf, sizeof ( *delay ) ); /* Remove pending operation */ pending_put ( &neighbour_delayed ); } /* Transmit deferred packet */ 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 ); } /** * Drop a deferred packet * * @v neighbour Neighbour cache entry * @v rc Reason for drop * @ret dropped Number of deferred packets dropped */ static unsigned int neighbour_drop ( struct neighbour *neighbour, int rc ) { struct net_device *netdev = neighbour->netdev; struct net_protocol *net_protocol = neighbour->net_protocol; struct io_buffer *iobuf; /* Get oldest deferred packet, if any */ iobuf = list_first_entry ( &neighbour->tx_queue, struct io_buffer, list ); if ( ! iobuf ) return 0; /* Drop deferred packet */ DBGC2 ( neighbour, "NEIGHBOUR %s %s %s dropping deferred packet: %s\n", netdev->name, net_protocol->name, net_protocol->ntoa ( neighbour->net_dest ), strerror ( rc ) ); list_del ( &iobuf->list ); if ( NEIGHBOUR_DELAY_MS ) pending_put ( &neighbour_delayed ); netdev_tx_err ( neighbour->netdev, iobuf, rc ); return 1; } /** * 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; /* 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 ) ); /* Mark discovery as complete */ neighbour->discovery = NULL; /* Transmit any deferred packets */ neighbour_tx_queue ( neighbour ); } /** * 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; /* Take ownership from cache */ list_del ( &neighbour->list ); /* Stop timer */ stop_timer ( &neighbour->timer ); /* Drop any deferred packets */ while ( neighbour_drop ( neighbour, rc ) ) {} assert ( list_empty ( &neighbour->tx_queue ) ); /* Drop remaining reference */ DBGC ( neighbour, "NEIGHBOUR %s %s %s destroyed: %s\n", netdev->name, net_protocol->name, net_protocol->ntoa ( neighbour->net_dest ), strerror ( rc ) ); 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 the timer is being (ab)used for delay injection, then * transmit the deferred packet queue. */ if ( NEIGHBOUR_DELAY_MS && ( ! neighbour->discovery ) ) { neighbour_tx_queue ( neighbour ); return; } /* 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 * @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 ) { struct neighbour *neighbour; struct neighbour_delay *delay; int rc; /* 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 discovery is still in progress or if delay injection is * in use, then queue for later transmission. */ if ( NEIGHBOUR_DELAY_MS || neighbour->discovery ) { /* Add to deferred packet queue */ 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 ); /* Handle delay injection, if applicable */ if ( NEIGHBOUR_DELAY_MS ) { /* Record original transmission time */ delay = iob_push ( iobuf, sizeof ( *delay ) ); delay->start = currticks(); /* Add pending operation */ pending_get ( &neighbour_delayed ); /* Process deferred packet queue, if possible */ if ( ! neighbour->discovery ) neighbour_tx_queue ( neighbour ); } return 0; } /* Otherwise, transmit immediately */ if ( ( rc = net_tx ( iobuf, netdev, net_protocol, neighbour->ll_dest, netdev->ll_addr ) ) != 0 ) { return rc; } return 0; } /** * 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 * @v priv Private data */ static void neighbour_flush ( struct net_device *netdev, void *priv __unused ) { 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 deferred packets from neighbour cache entries * * @ret discarded Number of cached items discarded */ static unsigned int neighbour_queue_discard ( void ) { struct neighbour *neighbour; unsigned int discarded = 0; /* Try to discard one deferred packet from each cache entry */ list_for_each_entry ( neighbour, &neighbours, list ) discarded += neighbour_drop ( neighbour, -ENOBUFS ); return discarded; } /** Neighbour cache deferred packet discarder */ struct cache_discarder neighbour_queue_discarder __cache_discarder ( CACHE_NORMAL ) = { .discard = neighbour_queue_discard, }; /** * Discard some complete neighbour cache entries * * @ret discarded Number of cached items discarded */ static unsigned int neighbour_discard ( void ) { struct neighbour *neighbour; /* Identify oldest cache entry, if any */ neighbour = list_last_entry ( &neighbours, struct neighbour, list ); if ( ! neighbour ) return 0; /* Sanity check: all deferred packets must already have been dropped */ assert ( list_empty ( &neighbour->tx_queue ) ); /* Destroy the cache entry */ neighbour_destroy ( neighbour, -ENOBUFS ); return 1; } /** * 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, };