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@davemloft.net>

diff --git a/include/net/dst.h b/include/net/dst.h
index 51610468c63db1783ab2d9aa2e5b0a5caa6f3367..0df661a0c2958f9e6997437b49feb5e2e520fec2 100644 (file)
--- a/include/net/dst.h
+++ b/include/net/dst.h
@@ -65,7 +65,19 @@ struct dst_entry {
        unsigned short          pending_confirm;
 
        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
        unsigned short          header_len;     /* more space at head required */
        unsigned short          trailer_len;    /* space to reserve at tail */
 #ifdef CONFIG_IP_ROUTE_CLASSID
@@ -359,7 +371,7 @@ 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 07bacff84aa41fee22dacc7cc77ceb89375ce719..069d51d29414a3245f9b60b66c534f78ce3b1752 100644 (file)
--- a/net/core/dst.c
+++ b/net/core/dst.c
@@ -94,7 +94,7 @@ 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);
@@ -202,7 +202,7 @@ 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/decnet/dn_route.c b/net/decnet/dn_route.c
index 47de90d8fe942ad9acc4d7c6fff81a52ae8dcdd6..23cc11dd4e40078964a2e3c1e0c8e499980ffcb8 100644 (file)
--- a/net/decnet/dn_route.c
+++ b/net/decnet/dn_route.c
@@ -1176,7 +1176,7 @@ make_route:
        if (dev_out->flags & IFF_LOOPBACK)
                flags |= RTCF_LOCAL;
 
-       rt = dst_alloc(&dn_dst_ops, dev_out, 1, 0, DST_HOST);
+       rt = dst_alloc(&dn_dst_ops, dev_out, 1, DST_OBSOLETE_NONE, DST_HOST);
        if (rt == NULL)
                goto e_nobufs;
 
@@ -1444,7 +1444,7 @@ static int dn_route_input_slow(struct sk_buff *skb)
        }
 
 make_route:
-       rt = dst_alloc(&dn_dst_ops, out_dev, 0, 0, DST_HOST);
+       rt = dst_alloc(&dn_dst_ops, out_dev, 0, DST_OBSOLETE_NONE, DST_HOST);
        if (rt == NULL)
                goto e_nobufs;
 

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index d1d579638092fc6aed80ee90a00c90314cddb34c..50d2498c9284284256f3f40a88b793f77cc8757e 100644 (file)
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1221,7 +1221,7 @@ static void rt_set_nexthop(struct rtable *rt, const struct flowi4 *fl4,
 static struct rtable *rt_dst_alloc(struct net_device *dev,
                                   bool nopolicy, bool noxfrm)
 {
-       return dst_alloc(&ipv4_dst_ops, dev, 1, -1,
+       return dst_alloc(&ipv4_dst_ops, dev, 1, DST_OBSOLETE_FORCE_CHK,
                         DST_HOST | DST_NOCACHE |
                         (nopolicy ? DST_NOPOLICY : 0) |
                         (noxfrm ? DST_NOXFRM : 0));
@@ -1969,9 +1969,10 @@ static struct dst_ops ipv4_dst_blackhole_ops = {
 
 struct dst_entry *ipv4_blackhole_route(struct net *net, struct dst_entry *dst_orig)
 {
-       struct rtable *rt = dst_alloc(&ipv4_dst_blackhole_ops, NULL, 1, 0, 0);
        struct rtable *ort = (struct rtable *) dst_orig;
+       struct rtable *rt;
 
+       rt = dst_alloc(&ipv4_dst_blackhole_ops, NULL, 1, DST_OBSOLETE_NONE, 0);
        if (rt) {
                struct dst_entry *new = &rt->dst;
 

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 84f6564dd372f2f7bfb943d582cfe12d94a50b1f..cf02cb97bbdd72d6fdc84abd1e783ca414f20d2e 100644 (file)
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -281,7 +281,7 @@ static inline struct rt6_info *ip6_dst_alloc(struct net *net,
                                             struct fib6_table *table)
 {
        struct rt6_info *rt = dst_alloc(&net->ipv6.ip6_dst_ops, dev,
-                                       0, 0, flags);
+                                       0, DST_OBSOLETE_NONE, flags);
 
        if (rt) {
                struct dst_entry *dst = &rt->dst;
@@ -985,7 +985,7 @@ struct dst_entry *ip6_blackhole_route(struct net *net, struct dst_entry *dst_ori
        struct rt6_info *rt, *ort = (struct rt6_info *) dst_orig;
        struct dst_entry *new = NULL;
 
-       rt = dst_alloc(&ip6_dst_blackhole_ops, ort->dst.dev, 1, 0, 0);
+       rt = dst_alloc(&ip6_dst_blackhole_ops, ort->dst.dev, 1, DST_OBSOLETE_NONE, 0);
        if (rt) {
                new = &rt->dst;
 

diff --git a/net/sctp/transport.c b/net/sctp/transport.c
index a6b7ee9ce28a5e41fd7bd88389823e265637b16a..ec3a12b9b802e6af0333b0e6cd166182f933f450 100644 (file)
--- a/net/sctp/transport.c
+++ b/net/sctp/transport.c
@@ -216,7 +216,7 @@ void sctp_transport_set_owner(struct sctp_transport *transport,
 void sctp_transport_pmtu(struct sctp_transport *transport, struct sock *sk)
 {
        /* If we don't have a fresh route, look one up */
-       if (!transport->dst || transport->dst->obsolete > 1) {
+       if (!transport->dst || transport->dst->obsolete) {
                dst_release(transport->dst);
                transport->af_specific->get_dst(transport, &transport->saddr,
                                                &transport->fl, sk);

diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index 65bd1ca515178e76d2062075d34eaa3b45a23738..c5a5165a5927a185043bdc83e8c9c4e25f549753 100644 (file)
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -1350,7 +1350,7 @@ static inline struct xfrm_dst *xfrm_alloc_dst(struct net *net, int family)
        default:
                BUG();
        }
-       xdst = dst_alloc(dst_ops, NULL, 0, 0, 0);
+       xdst = dst_alloc(dst_ops, NULL, 0, DST_OBSOLETE_NONE, 0);
 
        if (likely(xdst)) {
                struct dst_entry *dst = &xdst->u.dst;
@@ -1477,7 +1477,7 @@ static struct dst_entry *xfrm_bundle_create(struct xfrm_policy *policy,
                dst1->xfrm = xfrm[i];
                xdst->xfrm_genid = xfrm[i]->genid;
 
-               dst1->obsolete = -1;
+               dst1->obsolete = DST_OBSOLETE_FORCE_CHK;
                dst1->flags |= DST_HOST;
                dst1->lastuse = now;
 
@@ -2219,12 +2219,13 @@ 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
         *
@@ -2234,9 +2235,9 @@ 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;