Subject: Re: [PATCH 1/2] dst: take into account policy update on check()

From: Vlad Yasevich <[email-masked]>
Date: Fri, 07 Sep 2012 10:20:51 -0400

On 09/07/2012 11:57 AM, Nicolas Dichtel wrote:
> When a xfrm policy is inserted or deleted, we must invalidate
> all dst and recalculate the route.
>

One suggestion may be to add an inline to get flow_cache_genid and then 
you can get rid of #ifdefs in the code

Otherwise, this extends what IPv6 is doing to all protocols.  Seem like 
the right thing to do, but I'll let DaveM and others make the final 
determination.

-vlad

> Signed-off-by: Nicolas Dichtel <[email-masked]>
> ---
>   include/net/dst.h     | 7 +++++++
>   net/core/dst.c        | 1 +
>   net/core/sock.c       | 4 ++--
>   net/ipv6/ip6_tunnel.c | 3 +--
>   4 files changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/include/net/dst.h b/include/net/dst.h
> index 9a78810..478e55a 100644
> --- a/include/net/dst.h
> +++ b/include/net/dst.h
> @@ -101,6 +101,9 @@ struct dst_entry {
>   	atomic_t		__refcnt;	/* client references	*/
>   	int			__use;
>   	unsigned long		lastuse;
> +#ifdef CONFIG_XFRM
> +	u32			flow_cache_genid;
> +#endif
>   	union {
>   		struct dst_entry	*next;
>   		struct rtable __rcu	*rt_next;
> @@ -457,6 +460,10 @@ static inline int dst_input(struct sk_buff *skb)
>
>   static inline struct dst_entry *dst_check(struct dst_entry *dst, u32 cookie)
>   {
> +#ifdef CONFIG_XFRM
> +	if (dst->flow_cache_genid != atomic_read(&flow_cache_genid))
> +		return NULL;
> +#endif
>   	if (dst->obsolete)
>   		dst = dst->ops->check(dst, cookie);
>   	return dst;
> diff --git a/net/core/dst.c b/net/core/dst.c
> index f6593d2..19899d3 100644
> --- a/net/core/dst.c
> +++ b/net/core/dst.c
> @@ -181,6 +181,7 @@ void *dst_alloc(struct dst_ops *ops, struct net_device *dev,
>   	dst->path = dst;
>   #ifdef CONFIG_XFRM
>   	dst->xfrm = NULL;
> +	dst->flow_cache_genid = atomic_read(&flow_cache_genid);
>   #endif
>   	dst->input = dst_discard;
>   	dst->output = dst_discard;
> diff --git a/net/core/sock.c b/net/core/sock.c
> index d765156..1d06d4e 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -491,7 +491,7 @@ struct dst_entry *__sk_dst_check(struct sock *sk, u32 cookie)
>   {
>   	struct dst_entry *dst = __sk_dst_get(sk);
>
> -	if (dst && dst->obsolete && dst->ops->check(dst, cookie) == NULL) {
> +	if (dst && dst_check(dst, cookie) == NULL) {
>   		sk_tx_queue_clear(sk);
>   		RCU_INIT_POINTER(sk->sk_dst_cache, NULL);
>   		dst_release(dst);
> @@ -506,7 +506,7 @@ struct dst_entry *sk_dst_check(struct sock *sk, u32 cookie)
>   {
>   	struct dst_entry *dst = sk_dst_get(sk);
>
> -	if (dst && dst->obsolete && dst->ops->check(dst, cookie) == NULL) {
> +	if (dst && dst_check(dst, cookie) == NULL) {
>   		sk_dst_reset(sk);
>   		dst_release(dst);
>   		return NULL;
> diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
> index cb7e2de..e96431a 100644
> --- a/net/ipv6/ip6_tunnel.c
> +++ b/net/ipv6/ip6_tunnel.c
> @@ -130,8 +130,7 @@ struct dst_entry *ip6_tnl_dst_check(struct ip6_tnl *t)
>   {
>   	struct dst_entry *dst = t->dst_cache;
>
> -	if (dst && dst->obsolete &&
> -	    dst->ops->check(dst, t->dst_cookie) == NULL) {
> +	if (dst && dst_check(dst, t->dst_cookie) == NULL) {
>   		t->dst_cache = NULL;
>   		dst_release(dst);
>   		return NULL;
>