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[src/trunk]: src/sys Make DAD destructions (MP-)safe with callout_stop
details: https://anonhg.NetBSD.org/src/rev/a0eb40cb454c
branches: trunk
changeset: 829071:a0eb40cb454c
user: ozaki-r <ozaki-r%NetBSD.org@localhost>
date: Tue Jan 16 08:13:47 2018 +0000
description:
Make DAD destructions (MP-)safe with callout_stop
arp_dad_stoptimer and nd6_dad_stoptimer can be called with or without
softnet_lock held and unfortunately we have no easy way to statically know which.
So it is hard to use callout_halt there.
To address the situation, we use callout_stop to make the code safe. The new
approach copes with the issue by delegating the destruction of a callout to
callout itself, which allows us to not wait the callout to finish. This can be
done thanks to that DAD objects are separated from other data such as ifa.
The approach is suggested by riastradh@
Proposed on tech-kern@ and tech-net@
diffstat:
sys/netinet/if_arp.c | 58 +++++++++++++++++++++++-------------------
sys/netinet6/nd6_nbr.c | 68 +++++++++++++++++++++++++------------------------
2 files changed, 67 insertions(+), 59 deletions(-)
diffs (262 lines):
diff -r 2758a371103e -r a0eb40cb454c sys/netinet/if_arp.c
--- a/sys/netinet/if_arp.c Tue Jan 16 07:57:58 2018 +0000
+++ b/sys/netinet/if_arp.c Tue Jan 16 08:13:47 2018 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: if_arp.c,v 1.255 2017/11/17 07:37:12 ozaki-r Exp $ */
+/* $NetBSD: if_arp.c,v 1.256 2018/01/16 08:13:47 ozaki-r Exp $ */
/*-
* Copyright (c) 1998, 2000, 2008 The NetBSD Foundation, Inc.
@@ -68,7 +68,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: if_arp.c,v 1.255 2017/11/17 07:37:12 ozaki-r Exp $");
+__KERNEL_RCSID(0, "$NetBSD: if_arp.c,v 1.256 2018/01/16 08:13:47 ozaki-r Exp $");
#ifdef _KERNEL_OPT
#include "opt_ddb.h"
@@ -173,7 +173,8 @@
static void arp_drainstub(void);
-static void arp_dad_timer(struct ifaddr *);
+struct dadq;
+static void arp_dad_timer(struct dadq *);
static void arp_dad_start(struct ifaddr *);
static void arp_dad_stop(struct ifaddr *);
static void arp_dad_duplicated(struct ifaddr *, const char *);
@@ -1534,18 +1535,18 @@
{
callout_reset(&dp->dad_timer_ch, ticks,
- (void (*)(void *))arp_dad_timer, (void *)dp->dad_ifa);
+ (void (*)(void *))arp_dad_timer, dp);
}
static void
-arp_dad_stoptimer(struct dadq *dp)
+arp_dad_destroytimer(struct dadq *dp)
{
-#ifdef NET_MPSAFE
- callout_halt(&dp->dad_timer_ch, NULL);
-#else
- callout_halt(&dp->dad_timer_ch, softnet_lock);
-#endif
+ TAILQ_REMOVE(&dadq, dp, dad_list);
+ /* Request the timer to destroy dp. */
+ dp->dad_ifa = NULL;
+ callout_reset(&dp->dad_timer_ch, 0,
+ (void (*)(void *))arp_dad_timer, dp);
}
static void
@@ -1665,36 +1666,39 @@
}
/* Prevent the timer from running anymore. */
- TAILQ_REMOVE(&dadq, dp, dad_list);
+ arp_dad_destroytimer(dp);
+
mutex_exit(&arp_dad_lock);
- arp_dad_stoptimer(dp);
-
- kmem_intr_free(dp, sizeof(*dp));
ifafree(ifa);
}
static void
-arp_dad_timer(struct ifaddr *ifa)
+arp_dad_timer(struct dadq *dp)
{
- struct in_ifaddr *ia = (struct in_ifaddr *)ifa;
- struct dadq *dp;
+ struct ifaddr *ifa;
+ struct in_ifaddr *ia;
char ipbuf[INET_ADDRSTRLEN];
bool need_free = false;
SOFTNET_KERNEL_LOCK_UNLESS_NET_MPSAFE();
mutex_enter(&arp_dad_lock);
- /* Sanity check */
- if (ia == NULL) {
- log(LOG_ERR, "%s: called with null parameter\n", __func__);
+ ifa = dp->dad_ifa;
+ if (ifa == NULL) {
+ /* ifa is being deleted. DAD should be freed too. */
+ if (callout_pending(&dp->dad_timer_ch)) {
+ /*
+ * The callout is scheduled again, so we cannot destroy
+ * dp in this run.
+ */
+ goto done;
+ }
+ need_free = true;
goto done;
}
- dp = arp_dad_find(ifa);
- if (dp == NULL) {
- /* DAD seems to be stopping, so do nothing. */
- goto done;
- }
+
+ ia = (struct in_ifaddr *)ifa;
if (ia->ia4_flags & IN_IFF_DUPLICATED) {
log(LOG_ERR, "%s: called with duplicate address %s(%s)\n",
__func__, IN_PRINT(ipbuf, &ia->ia_addr.sin_addr),
@@ -1769,8 +1773,10 @@
mutex_exit(&arp_dad_lock);
if (need_free) {
+ callout_destroy(&dp->dad_timer_ch);
kmem_intr_free(dp, sizeof(*dp));
- ifafree(ifa);
+ if (ifa != NULL)
+ ifafree(ifa);
}
SOFTNET_KERNEL_UNLOCK_UNLESS_NET_MPSAFE();
diff -r 2758a371103e -r a0eb40cb454c sys/netinet6/nd6_nbr.c
--- a/sys/netinet6/nd6_nbr.c Tue Jan 16 07:57:58 2018 +0000
+++ b/sys/netinet6/nd6_nbr.c Tue Jan 16 08:13:47 2018 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: nd6_nbr.c,v 1.143 2018/01/16 07:56:55 ozaki-r Exp $ */
+/* $NetBSD: nd6_nbr.c,v 1.144 2018/01/16 08:13:47 ozaki-r Exp $ */
/* $KAME: nd6_nbr.c,v 1.61 2001/02/10 16:06:14 jinmei Exp $ */
/*
@@ -31,7 +31,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: nd6_nbr.c,v 1.143 2018/01/16 07:56:55 ozaki-r Exp $");
+__KERNEL_RCSID(0, "$NetBSD: nd6_nbr.c,v 1.144 2018/01/16 08:13:47 ozaki-r Exp $");
#ifdef _KERNEL_OPT
#include "opt_inet.h"
@@ -79,8 +79,8 @@
struct dadq;
static struct dadq *nd6_dad_find(struct ifaddr *);
static void nd6_dad_starttimer(struct dadq *, int);
-static void nd6_dad_stoptimer(struct dadq *);
-static void nd6_dad_timer(struct ifaddr *);
+static void nd6_dad_destroytimer(struct dadq *);
+static void nd6_dad_timer(struct dadq *);
static void nd6_dad_ns_output(struct dadq *, struct ifaddr *);
static void nd6_dad_ns_input(struct ifaddr *);
static void nd6_dad_na_input(struct ifaddr *);
@@ -1087,18 +1087,18 @@
{
callout_reset(&dp->dad_timer_ch, ticks,
- (void (*)(void *))nd6_dad_timer, (void *)dp->dad_ifa);
+ (void (*)(void *))nd6_dad_timer, dp);
}
static void
-nd6_dad_stoptimer(struct dadq *dp)
+nd6_dad_destroytimer(struct dadq *dp)
{
-#ifdef NET_MPSAFE
- callout_halt(&dp->dad_timer_ch, NULL);
-#else
- callout_halt(&dp->dad_timer_ch, softnet_lock);
-#endif
+ TAILQ_REMOVE(&dadq, dp, dad_list);
+ /* Request the timer to destroy dp. */
+ dp->dad_ifa = NULL;
+ callout_reset(&dp->dad_timer_ch, 0,
+ (void (*)(void *))nd6_dad_timer, dp);
}
/*
@@ -1210,20 +1210,18 @@
}
/* Prevent the timer from running anymore. */
- TAILQ_REMOVE(&dadq, dp, dad_list);
+ nd6_dad_destroytimer(dp);
+
mutex_exit(&nd6_dad_lock);
- nd6_dad_stoptimer(dp);
-
- kmem_intr_free(dp, sizeof(*dp));
ifafree(ifa);
}
static void
-nd6_dad_timer(struct ifaddr *ifa)
+nd6_dad_timer(struct dadq *dp)
{
- struct in6_ifaddr *ia = (struct in6_ifaddr *)ifa;
- struct dadq *dp;
+ struct ifaddr *ifa;
+ struct in6_ifaddr *ia;
int duplicate = 0;
char ip6buf[INET6_ADDRSTRLEN];
bool need_free = false;
@@ -1231,16 +1229,21 @@
SOFTNET_KERNEL_LOCK_UNLESS_NET_MPSAFE();
mutex_enter(&nd6_dad_lock);
- /* Sanity check */
- if (ia == NULL) {
- log(LOG_ERR, "nd6_dad_timer: called with null parameter\n");
+ ifa = dp->dad_ifa;
+ if (ifa == NULL) {
+ /* ifa is being deleted. DAD should be freed too. */
+ if (callout_pending(&dp->dad_timer_ch)) {
+ /*
+ * The callout is scheduled again, so we cannot destroy
+ * dp in this run.
+ */
+ goto done;
+ }
+ need_free = true;
goto done;
}
- dp = nd6_dad_find(ifa);
- if (dp == NULL) {
- /* DAD seems to be stopping, so do nothing. */
- goto done;
- }
+
+ ia = (struct in6_ifaddr *)ifa;
if (ia->ia6_flags & IN6_IFF_DUPLICATED) {
log(LOG_ERR, "nd6_dad_timer: called with duplicate address "
"%s(%s)\n",
@@ -1316,9 +1319,10 @@
mutex_exit(&nd6_dad_lock);
if (need_free) {
+ callout_destroy(&dp->dad_timer_ch);
kmem_intr_free(dp, sizeof(*dp));
- ifafree(ifa);
- ifa = NULL;
+ if (ifa != NULL)
+ ifafree(ifa);
}
if (duplicate)
@@ -1392,13 +1396,11 @@
}
}
- TAILQ_REMOVE(&dadq, dp, dad_list);
+ /* We are done with DAD, with duplicated address found. (failure) */
+ nd6_dad_destroytimer(dp);
+
mutex_exit(&nd6_dad_lock);
- /* We are done with DAD, with duplicated address found. (failure) */
- nd6_dad_stoptimer(dp);
-
- kmem_intr_free(dp, sizeof(*dp));
ifafree(ifa);
}
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