[PATCH] Free interfaces in shutdown state

[Maria Matejka]

Hello!

I tried to implement this myself several times, yet this simple approach 
doesn't work. The configuration system also creates "pending" interfaces 
if something depends on a certain interface name. This patch would 
delete these "pending" interfaces, rendering some pointers invalid.

The right way to do this is to introduce some kind of reference counting 
to interface objects, as e.g. the cached route attribute objects do. 
Something like this is probably going to land in some future version of 
BIRD 3, anyway if you decided to implement this for version 2 as well, I 
won't complain.

Thank you for your contribution!

Maria

On 7/12/22 7:54 PM, Lorenz Brun wrote:
> When interfaces are created and destroyed by automated systems,
> a potentially unbounded amount of interfaces exist.
> This results in bird consuming ever-increasing amounts of memory and
> CPU time for the list of known interfaces.
> 
> This change frees the interface after it is in shutdown state and all
> notifications for it have been processed.
> ---
>   nest/iface.c | 11 ++++++++---
>   1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/nest/iface.c b/nest/iface.c
> index 682340c5..b4c65512 100644
> --- a/nest/iface.c
> +++ b/nest/iface.c
> @@ -324,7 +324,7 @@ if_update(struct iface *new)
>   	if_copy(i, new);
>   	if (c)
>   	  if_notify_change(c, i);
> -
> +
>   	i->flags |= IF_UPDATED;
>   	return i;
>         }
> @@ -365,10 +365,10 @@ if_end_partial_update(struct iface *i)
>   void
>   if_end_update(void)
>   {
> -  struct iface *i;
> +  struct iface *i, *x;
>     struct ifa *a, *b;
>   
> -  WALK_LIST(i, iface_list)
> +  WALK_LIST_DELSAFE(i, x, iface_list)
>       {
>         if (!(i->flags & IF_UPDATED))
>   	if_change_flags(i, (i->flags & ~IF_ADMIN_UP) | IF_SHUTDOWN);
> @@ -379,6 +379,11 @@ if_end_update(void)
>   	      ifa_delete(a);
>   	  if_end_partial_update(i);
>   	}
> +    if ((i->flags & IF_SHUTDOWN)) {
> +      WALK_LIST_DELSAFE(a, b, i->addrs)
> +        ifa_delete(a);
> +      rem_node(&i->n);
> +    }
>       }
>   }
>   
> 

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