netdev - Re: [PATCH net 1/3] sctp: use the same clock as if sock source timestamps were on

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Date:	Fri, 4 Dec 2015 15:31:05 -0500
From:	Vlad Yasevich <vyasevich@...il.com>
To:	Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
	netdev@...r.kernel.org
Cc:	Neil Horman <nhorman@...driver.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	syzkaller <syzkaller@...glegroups.com>,
	linux-sctp@...r.kernel.org, Kostya Serebryany <kcc@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	Maciej Żenczykowski <maze@...gle.com>,
	Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH net 1/3] sctp: use the same clock as if sock source
 timestamps were on

On 12/04/2015 12:14 PM, Marcelo Ricardo Leitner wrote:
> SCTP echoes a cookie o INIT ACK chunks that contains a timestamp, for
> detecting stale cookies. This cookie is echoed back to the server by the
> client and then that timestamp is checked.
> 
> Thing is, if the listening socket is using packet timestamping, the
> cookie is encoded with ktime_get() value and checked against
> ktime_get_real(), as done by __net_timestamp().
> 
> The fix is to sctp also use ktime_get_real(), so we can compare bananas
> with bananas later no matter if packet timestamping was enabled or not.
> 
> Fixes: 52db882f3fc2 ("net: sctp: migrate cookie life from timeval to ktime")
> Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>

Acked-by: Vlad Yasevich <vyasevich@...il.com>

-vlad

> ---
>  net/sctp/sm_make_chunk.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
> index 763e06a55155b2a9e0a9d918ecc1fe2dd6d9e0c0..5d6a03fad3789a12290f5f14c5a7efa69c98f41a 100644
> --- a/net/sctp/sm_make_chunk.c
> +++ b/net/sctp/sm_make_chunk.c
> @@ -1652,7 +1652,7 @@ static sctp_cookie_param_t *sctp_pack_cookie(const struct sctp_endpoint *ep,
>  
>  	/* Set an expiration time for the cookie.  */
>  	cookie->c.expiration = ktime_add(asoc->cookie_life,
> -					 ktime_get());
> +					 ktime_get_real());
>  
>  	/* Copy the peer's init packet.  */
>  	memcpy(&cookie->c.peer_init[0], init_chunk->chunk_hdr,
> @@ -1780,7 +1780,7 @@ no_hmac:
>  	if (sock_flag(ep->base.sk, SOCK_TIMESTAMP))
>  		kt = skb_get_ktime(skb);
>  	else
> -		kt = ktime_get();
> +		kt = ktime_get_real();
>  
>  	if (!asoc && ktime_before(bear_cookie->expiration, kt)) {
>  		/*
> 

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