linux-kernel - Re: [NOT VERY SAFE] [TCP]: Set initial_ssthresh default to zero in Cubic and BIC.

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Date:	Mon, 15 Oct 2007 21:59:49 +0900
From:	Komuro <komurojun-mbn@...ty.com>
To:	shemminger@...ux.foundation.org
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [NOT VERY SAFE]     [TCP]: Set initial_ssthresh default to zero
 in Cubic and BIC.

Dear shemminger

>In which case it is zero because that is the default value.

The default value of snd_ssthresh is 0x7fffffff, isn't it?

[linux/net/ipv4/tcp_ipv4.c]
static int tcp_v4_init_sock(struct sock *sk)
...
        tp->snd_ssthresh = 0x7fffffff;  /* Infinity */
...

Best Regards
Komuro


> 
> Actually, tcp_sk(sk)->snd_ssthresh is not initialized,
> if initial_ssthresh is 0.
> 
> The patch should be
> 
>  static void bictcp_init(struct sock *sk)
>  {
>  	bictcp_reset(inet_csk_ca(sk));
> -	if (initial_ssthresh)
> -		tcp_sk(sk)->snd_ssthresh = initial_ssthresh;
> +
> +	tcp_sk(sk)->snd_ssthresh = initial_ssthresh;
>  }
>
-
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