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Message-ID: <20121019192121.GB8315@kvack.org>
Date: Fri, 19 Oct 2012 15:21:21 -0400
From: Benjamin LaHaise <bcrl@...ck.org>
To: Willy Tarreau <w@....eu>
Cc: David Miller <davem@...emloft.net>, stable@...r.kernel.org,
netdev@...r.kernel.org
Subject: [PATCH 2/6] net: Document dst->obsolete better.
commit f5b0a8743601a4477419171f5046bd07d1c080a0
Author: David S. Miller <davem@...emloft.net>
Date: Thu Jul 19 12:31:33 2012 -0700
net: Document dst->obsolete better.
Add a big comment explaining how the field works, and use defines
instead of magic constants for the values assigned to it.
Suggested by Joe Perches.
Signed-off-by: David S. Miller <davem@...emloft.net>
This is a slightly modified backport of the above commit to cover additional
locationsi of dst.u.obsolete = -1.
Signed-off-by: Benjamin LaHaise <bcrl@...ck.org>
---
include/net/dst.h | 14 +++++++++++++-
net/core/dst.c | 4 ++--
net/ipv4/route.c | 12 ++++++------
net/sctp/output.c | 2 +-
net/xfrm/xfrm_policy.c | 21 +++++++++++----------
5 files changed, 33 insertions(+), 20 deletions(-)
diff --git a/include/net/dst.h b/include/net/dst.h
index 5a900dd..938b525 100644
--- a/include/net/dst.h
+++ b/include/net/dst.h
@@ -42,7 +42,19 @@ struct dst_entry
struct dst_entry *child;
struct net_device *dev;
short error;
+
+ /* A non-zero value of dst->obsolete forces by-hand validation
+ * of the route entry. Positive values are set by the generic
+ * dst layer to indicate that the entry has been forcefully
+ * destroyed.
+ *
+ * Negative values are used by the implementation layer code to
+ * force invocation of the dst_ops->check() method.
+ */
short obsolete;
+#define DST_OBSOLETE_NONE 0
+#define DST_OBSOLETE_DEAD 2
+#define DST_OBSOLETE_FORCE_CHK -1
int flags;
#define DST_HOST 1
#define DST_NOXFRM 2
@@ -200,7 +212,7 @@ extern struct dst_entry *dst_destroy(struct dst_entry * dst);
static inline void dst_free(struct dst_entry * dst)
{
- if (dst->obsolete > 1)
+ if (dst->obsolete > 0)
return;
if (!atomic_read(&dst->__refcnt)) {
dst = dst_destroy(dst);
diff --git a/net/core/dst.c b/net/core/dst.c
index cb1b348..5eb9929 100644
--- a/net/core/dst.c
+++ b/net/core/dst.c
@@ -99,7 +99,7 @@ loop:
* But we do not have state "obsoleted, but
* referenced by parent", so it is right.
*/
- if (dst->obsolete > 1)
+ if (dst->obsolete > 0)
continue;
___dst_free(dst);
@@ -193,7 +193,7 @@ static void ___dst_free(struct dst_entry * dst)
if (dst->dev == NULL || !(dst->dev->flags&IFF_UP)) {
dst->input = dst->output = dst_discard;
}
- dst->obsolete = 2;
+ dst->obsolete = DST_OBSOLETE_DEAD;
}
void __dst_free(struct dst_entry * dst)
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index f16d19b..f79a9a8 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1412,7 +1412,7 @@ void ip_rt_redirect(__be32 old_gw, __be32 daddr, __be32 new_gw,
dev_hold(rt->u.dst.dev);
if (rt->idev)
in_dev_hold(rt->idev);
- rt->u.dst.obsolete = -1;
+ rt->u.dst.obsolete = DST_OBSOLETE_FORCE_CHK;
rt->u.dst.lastuse = jiffies;
rt->u.dst.path = &rt->u.dst;
rt->u.dst.neighbour = NULL;
@@ -1865,7 +1865,7 @@ static int ip_route_input_mc(struct sk_buff *skb, __be32 daddr, __be32 saddr,
goto e_nobufs;
rth->u.dst.output = ip_rt_bug;
- rth->u.dst.obsolete = -1;
+ rth->u.dst.obsolete = DST_OBSOLETE_FORCE_CHK;
atomic_set(&rth->u.dst.__refcnt, 1);
rth->u.dst.flags= DST_HOST;
@@ -2026,7 +2026,7 @@ static int __mkroute_input(struct sk_buff *skb,
rth->fl.oif = 0;
rth->rt_spec_dst= spec_dst;
- rth->u.dst.obsolete = -1;
+ rth->u.dst.obsolete = DST_OBSOLETE_FORCE_CHK;
rth->u.dst.input = ip_forward;
rth->u.dst.output = ip_output;
rth->rt_genid = rt_genid(dev_net(rth->u.dst.dev));
@@ -2191,7 +2191,7 @@ local_input:
goto e_nobufs;
rth->u.dst.output= ip_rt_bug;
- rth->u.dst.obsolete = -1;
+ rth->u.dst.obsolete = DST_OBSOLETE_FORCE_CHK;
rth->rt_genid = rt_genid(net);
atomic_set(&rth->u.dst.__refcnt, 1);
@@ -2417,7 +2417,7 @@ static int __mkroute_output(struct rtable **result,
rth->rt_spec_dst= fl->fl4_src;
rth->u.dst.output = ip_output;
- rth->u.dst.obsolete = -1;
+ rth->u.dst.obsolete = DST_OBSOLETE_FORCE_CHK;
rth->rt_genid = rt_genid(dev_net(dev_out));
RT_CACHE_STAT_INC(out_slow_tot);
@@ -2747,7 +2747,7 @@ static int ipv4_dst_blackhole(struct net *net, struct rtable **rp, struct flowi
if (rt) {
struct dst_entry *new = &rt->u.dst;
- new->obsolete = -1;
+ new->obsolete = DST_OBSOLETE_FORCE_CHK;
atomic_set(&new->__refcnt, 1);
new->__use = 1;
new->input = dst_discard;
diff --git a/net/sctp/output.c b/net/sctp/output.c
index d494100..a6fc861 100644
--- a/net/sctp/output.c
+++ b/net/sctp/output.c
@@ -375,7 +375,7 @@ int sctp_packet_transmit(struct sctp_packet *packet)
skb_set_owner_w(nskb, sk);
/* The 'obsolete' field of dst is set to 2 when a dst is freed. */
- if (!dst || (dst->obsolete > 1)) {
+ if (!dst || dst->obsolete) {
dst_release(dst);
sctp_transport_route(tp, NULL, sctp_sk(sk));
if (asoc && (asoc->param_flags & SPP_PMTUD_ENABLE)) {
diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index cb81ca3..1ae61bd 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -1421,7 +1421,7 @@ static struct dst_entry *xfrm_bundle_create(struct xfrm_policy *policy,
dst1->xfrm = xfrm[i];
xdst->genid = xfrm[i]->genid;
- dst1->obsolete = -1;
+ dst1->obsolete = DST_OBSOLETE_FORCE_CHK;
dst1->flags |= DST_HOST;
dst1->lastuse = now;
@@ -2049,12 +2049,13 @@ EXPORT_SYMBOL(__xfrm_route_forward);
static struct dst_entry *xfrm_dst_check(struct dst_entry *dst, u32 cookie)
{
/* Code (such as __xfrm4_bundle_create()) sets dst->obsolete
- * to "-1" to force all XFRM destinations to get validated by
- * dst_ops->check on every use. We do this because when a
- * normal route referenced by an XFRM dst is obsoleted we do
- * not go looking around for all parent referencing XFRM dsts
- * so that we can invalidate them. It is just too much work.
- * Instead we make the checks here on every use. For example:
+ * to DST_OBSOLETE_FORCE_CHK to force all XFRM destinations to
+ * get validated by dst_ops->check on every use. We do this
+ * because when a normal route referenced by an XFRM dst is
+ * obsoleted we do not go looking around for all parent
+ * referencing XFRM dsts so that we can invalidate them. It
+ * is just too much work. Instead we make the checks here on
+ * every use. For example:
*
* XFRM dst A --> IPv4 dst X
*
@@ -2064,9 +2065,9 @@ static struct dst_entry *xfrm_dst_check(struct dst_entry *dst, u32 cookie)
* stale_bundle() check.
*
* When a policy's bundle is pruned, we dst_free() the XFRM
- * dst which causes it's ->obsolete field to be set to a
- * positive non-zero integer. If an XFRM dst has been pruned
- * like this, we want to force a new route lookup.
+ * dst which causes it's ->obsolete field to be set to
+ * DST_OBSOLETE_DEAD. If an XFRM dst has been pruned like
+ * this, we want to force a new route lookup.
*/
if (dst->obsolete < 0 && !stale_bundle(dst))
return dst;
--
1.7.1
--
"Thought is the essence of where you are now."
--
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