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[arp] Increase robustness of ARP discarder 

Take ownership from the ARP cache at the start of arp_destroy(), to
ensure that no code path can lead to arp_destroy() being re-entered.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
pull/598/head
Michael Brown 2012-10-19 23:03:38 +01:00
parent a4d1250810
commit 885384faf3
1 changed files with 10 additions and 7 deletions
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17
src/net/arp.c
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@ -180,13 +180,16 @@ static void arp_destroy ( struct arp_entry *arp, int rc ) {
struct net_device *netdev = arp->netdev; struct net_device *netdev = arp->netdev;
struct net_protocol *net_protocol = arp->net_protocol; struct net_protocol *net_protocol = arp->net_protocol;
struct io_buffer *iobuf; struct io_buffer *iobuf;
struct io_buffer *tmp;
/* Take ownership from cache */
list_del ( &arp->list );
/* Stop timer */ /* Stop timer */
stop_timer ( &arp->timer ); stop_timer ( &arp->timer );
/* Discard any outstanding I/O buffers */ /* Discard any outstanding I/O buffers */
list_for_each_entry_safe ( iobuf, tmp, &arp->tx_queue, list ) { while ( ( iobuf = list_first_entry ( &arp->tx_queue, struct io_buffer,
list ) ) != NULL ) {
DBGC2 ( arp, "ARP %p %s %s %s discarding deferred packet: " DBGC2 ( arp, "ARP %p %s %s %s discarding deferred packet: "
"%s\n", arp, netdev->name, net_protocol->name, "%s\n", arp, netdev->name, net_protocol->name,
net_protocol->ntoa ( arp->net_dest ), strerror ( rc ) ); net_protocol->ntoa ( arp->net_dest ), strerror ( rc ) );
@ -198,8 +201,7 @@ static void arp_destroy ( struct arp_entry *arp, int rc ) {
net_protocol->name, net_protocol->ntoa ( arp->net_dest ), net_protocol->name, net_protocol->ntoa ( arp->net_dest ),
strerror ( rc ) ); strerror ( rc ) );
/* Remove from cache and drop reference */ /* Drop remaining reference */
list_del ( &arp->list );
ref_put ( &arp->refcnt ); ref_put ( &arp->refcnt );
} }
@ -518,12 +520,13 @@ static unsigned int arp_discard ( void ) {
struct arp_entry *arp; struct arp_entry *arp;
/* Drop oldest cache entry, if any */ /* Drop oldest cache entry, if any */
list_for_each_entry_reverse ( arp, &arp_entries, list ) { arp = list_last_entry ( &arp_entries, struct arp_entry, list );
if ( arp ) {
arp_destroy ( arp, -ENOBUFS ); arp_destroy ( arp, -ENOBUFS );
return 1; return 1;
} } else {
return 0; return 0;
}
} }
/** ARP cache discarder /** ARP cache discarder