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>

1 files changed, 13 insertions, 1 deletions

diff --git a/include/net/dst.h b/include/net/dst.h
index 51610468c63d..0df661a0c295 100644
--- 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);