Subject: Re: [PATCH] sctp: check dst validity after IPsec operations

From: Vlad Yasevich <[email-masked]>
Date: Thu, 06 Sep 2012 12:04:20 -0400

On 09/06/2012 01:40 PM, Nicolas Dichtel wrote:
> dst stored in struct sctp_transport needs to be recalculated when ipsec policy
> are updated. We use flow_cache_genid for that.
>
> For example, if a SCTP connection is established and then an IPsec policy is
> set, the old SCTP flow will not be updated and thus will not use the new
> IPsec policy.
>
> Signed-off-by: Nicolas Dichtel <[email-masked]>

why doesn't this need to be done for TCP?  What makes SCTP special in 
this case?

ip_queue_xmit does an __sk_dst_check() which is essentially what 
sctp_transport_dst_check() does.  That should determine if the currently 
cached route is valid or not.

Looks like sctp may need to change to using ip_route_output_ports() call
as ip_route_output_key may not do all that is necessary

-vlad

> ---
>   include/net/sctp/sctp.h    | 3 ++-
>   include/net/sctp/structs.h | 3 +++
>   net/sctp/ipv6.c            | 1 +
>   net/sctp/protocol.c        | 1 +
>   4 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/include/net/sctp/sctp.h b/include/net/sctp/sctp.h
> index 9c6414f..3267246 100644
> --- a/include/net/sctp/sctp.h
> +++ b/include/net/sctp/sctp.h
> @@ -712,7 +712,8 @@ static inline void sctp_v4_map_v6(union sctp_addr *addr)
>    */
>   static inline struct dst_entry *sctp_transport_dst_check(struct sctp_transport *t)
>   {
> -	if (t->dst && !dst_check(t->dst, 0)) {
> +	if ((t->dst && !dst_check(t->dst, 0)) ||
> +	    (t->flow_cache_genid != atomic_read(&flow_cache_genid))) {
>   		dst_release(t->dst);
>   		t->dst = NULL;
>   	}
> diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
> index 0fef00f..9dab882 100644
> --- a/include/net/sctp/structs.h
> +++ b/include/net/sctp/structs.h
> @@ -948,6 +948,9 @@ struct sctp_transport {
>
>   	/* 64-bit random number sent with heartbeat. */
>   	__u64 hb_nonce;
> +
> +	/* used to check validity of dst */
> +	__u32 flow_cache_genid;
>   };
>
>   struct sctp_transport *sctp_transport_new(struct net *, const union sctp_addr *,
> diff --git a/net/sctp/ipv6.c b/net/sctp/ipv6.c
> index ea14cb4..2ed7410 100644
> --- a/net/sctp/ipv6.c
> +++ b/net/sctp/ipv6.c
> @@ -349,6 +349,7 @@ out:
>   		struct rt6_info *rt;
>   		rt = (struct rt6_info *)dst;
>   		t->dst = dst;
> +		t->flow_cache_genid = atomic_read(&flow_cache_genid);
>   		SCTP_DEBUG_PRINTK("rt6_dst:%pI6 rt6_src:%pI6\n",
>   			&rt->rt6i_dst.addr, &fl6->saddr);
>   	} else {
> diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
> index 2d51842..4795a1a 100644
> --- a/net/sctp/protocol.c
> +++ b/net/sctp/protocol.c
> @@ -512,6 +512,7 @@ out_unlock:
>   	rcu_read_unlock();
>   out:
>   	t->dst = dst;
> +	t->flow_cache_genid = atomic_read(&flow_cache_genid);
>   	if (dst)
>   		SCTP_DEBUG_PRINTK("rt_dst:%pI4, rt_src:%pI4\n",
>   				  &fl4->daddr, &fl4->saddr);
>