[PATCH]:net/ipv4/route.c

[Rajasekhar Inguva]

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Hello,

The patch applies to net/ipv4/route.c , Kernel version 2.5.2

Please find a detailed description of my patch below. Firstly I would l=
ike
to apologize if my patch is

In a wrong format
Already submitted by someone and rejected by you guys.
Non-conformance to kernel coding style.

The problem:

When neighbour tables are full, an attempt is made from rt_intern_hash =
to
release a few neighbour entries that the route cache might still be
referring to. This is achieved by calling rt_garbage_collect.
rt_garbage_collect does fail sometimes to release some entries as it ch=
ecks
not only for reference counts, but also some expiry timers. This ends u=
p in
the infamous 'Neighbour table overflow' message being displayed.

The patch:

My patch solves this problem. The approach was to write a new routine
rt_delete_now, which unlike rt_garbage_collect, deletes the route cache=

entries based only on reference counts and not on expiry timers.
rt_delete_now is called from rt_intern_hash instead of rt_garbage_colle=
ct.

The reason of this approach is to act as per demand. The call to
rt_garbage_collect from rt_intern_hash is made in emergency situations
(Neighbour tables are full). At this juncture, it is better IMHO, to de=
lete
'un-referred' entries rather than finding garbage entries (un-referred =
&&
expired) and deleting them. The patch is actually a copy of
rt_garbage_collect code minus expiry time checking code.

I would be glad to receive your comments and feedback on this patch.

Regards,

Raj
(See attached file: neigh.patch)

--- /usr/src/linux/net/ipv4/route.c     Tue Jan 29 17:24:15 2002
+++ /usr/src/linux/net/patches/route.c  Tue Jan 29 17:26:22 2002
@@ -471,6 +471,37 @@
        mod_timer(&rt_flush_timer, now+delay);
        spin_unlock_bh(&rt_flush_lock);
 }
+/*
+       Called by rt_intern_hash. Deletes unused entries immediately
+       in emergency situations.
+*/
+static void rt_delete_now()
+{
+       int i;
+       struct rtable *rth, **rthp;
+
+       for(i=3Drt_hash_mask; i>=3D0; i--) {
+
+       rthp =3D &rt_hash_table[i].chain;
+       write_lock_bh(&rt_hash_table[i].lock);
+
+               while((rth=3D*rthp) !=3D NULL) {
+               if(atomic_read(&rth->u.dst.__refcnt)) {
+               rthp =3D &rth->u.rt_next;
+               continue;
+               }
+
+       *rthp =3D rth->u.rt_next;
+       rt_free(rth);
+
+       }
+
+       write_unlock_bh(&rt_hash_table[i].lock);
+
+       }
+
+}
+

 /*
    Short description of GC goals.
@@ -646,13 +677,7 @@
                           it is most likely it holds some neighbour
records.
                         */
                        if (attempts-- > 0) {
-                               int saved_elasticity =3D ip_rt_gc_elast=
icity;
-                               int saved_int =3D ip_rt_gc_min_interval=
;
-                               ip_rt_gc_elasticity     =3D 1;
-                               ip_rt_gc_min_interval   =3D 0;
-                               rt_garbage_collect();
-                               ip_rt_gc_min_interval   =3D saved_int;
-                               ip_rt_gc_elasticity     =3D saved_elast=
icity;
+                               rt_delete_now();
                                goto restart;
                        }=

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