Re: [PATCH net v2] udp6: set dst cache for a connected sk before udp_v6_send_skb

[Eric Dumazet <eric.dumazet@gmail.com>]

On 03/26/2018 07:48 AM, Alexey Kodanev wrote:
> After commit 33c162a980fe ("ipv6: datagram: Update dst cache of a
> connected datagram sk during pmtu update"), when the error occurs on
> sending datagram in udpv6_sendmsg() due to ICMPV6_PKT_TOOBIG type,
> error handler can trigger the following path and call ip6_dst_store():
> 
>     udpv6_err()
>         ip6_sk_update_pmtu()
>             ip6_datagram_dst_update()
>                 ip6_dst_lookup_flow(), can create a RTF_CACHE clone
>                 ...
>                 ip6_dst_store()
> 
> It can happen before a connected UDP socket invokes ip6_dst_store()
> in the end of udpv6_sendmsg(), on destination release, as a result,
> the last one changes dst to the old one, preventing getting updated
> dst cache on the next udpv6_sendmsg() call.
> 
> This patch moves ip6_dst_store() in udpv6_sendmsg(), so that it is
> invoked after ip6_sk_dst_lookup_flow() and before udp_v6_send_skb().
> 
> Also, increase refcnt for dst, when passing it to ip6_dst_store()
> because after that the dst cache can be released by other calls
> to ip6_dst_store() with the same socket.
> 
> Fixes: 33c162a980fe ("ipv6: datagram: Update dst cache of a connected datagram sk during pmtu update")
> Signed-off-by: Alexey Kodanev <alexey.kodanev@oracle.com>
> ---
> 

Reviewed-by: Eric Dumazet <edumazet@google.com>

Thanks Alexey.