netdev - Re: [Patch net-next] tcp: add a tracepoint for tcp_retransmit

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Message-ID: <87a80wd7rm.fsf@stressinduktion.org>
Date:   Thu, 12 Oct 2017 11:39:57 +0200
From:   Hannes Frederic Sowa <hannes@...essinduktion.org>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Cong Wang <xiyou.wangcong@...il.com>, netdev@...r.kernel.org,
        Eric Dumazet <edumazet@...gle.com>,
        Yuchung Cheng <ycheng@...gle.com>,
        Neal Cardwell <ncardwell@...gle.com>,
        Martin KaFai Lau <kafai@...com>,
        Brendan Gregg <brendan.d.gregg@...il.com>,
        Song Liu <songliubraving@...com>
Subject: Re: [Patch net-next] tcp: add a tracepoint for tcp_retransmit_skb()

Eric Dumazet <eric.dumazet@...il.com> writes:

[...]

> Since this sock_gen_cookie() is lock-free and IRQ ready, it should be
> not be a problem to pretend it works with a const socket.
>
> I am a bit unsure about revealing in socket cookie a precise count of
> sockets created on a netns. Some attackers might use this in a side
> channel attack.

That is true. We expose this information already via the inode number
allocator for sockets. It is a bit imprecise because of using CPU
batches.