netdev - Re: [PATCH net v2] udp6: set dst cache for a connected sk before udp_v6_send

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Date:   Mon, 26 Mar 2018 07:48:42 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Alexey Kodanev <alexey.kodanev@...cle.com>, netdev@...r.kernel.org
Cc:     Eric Dumazet <edumazet@...gle.com>,
        Martin KaFai Lau <kafai@...com>,
        David Miller <davem@...emloft.net>
Subject: Re: [PATCH net v2] udp6: set dst cache for a connected sk before
 udp_v6_send_skb



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@...cle.com>
> ---
> 

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

Thanks Alexey.