netdev - Re: [PATCH net 2/2] ipv4: avoid using shared IP generator for connected sockets

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Date:   Wed, 26 Jan 2022 13:36:42 -0700
From:   David Ahern <dsahern@...il.com>
To:     Eric Dumazet <eric.dumazet@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     David Ahern <dsahern@...nel.org>, netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Ray Che <xijiache@...il.com>, Willy Tarreau <w@....eu>
Subject: Re: [PATCH net 2/2] ipv4: avoid using shared IP generator for
 connected sockets

On 1/26/22 1:05 PM, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
> 
> ip_select_ident_segs() has been very conservative about using
> the connected socket private generator only for packets with IP_DF
> set, claiming it was needed for some VJ compression implementations.
> 
> As mentioned in this referenced document, this can be abused.
> (Ref: Off-Path TCP Exploits of the Mixed IPID Assignment)
> 
> Before switching to pure random IPID generation and possibly hurt
> some workloads, lets use the private inet socket generator.
> 
> Not only this will remove one vulnerability, this will also
> improve performance of TCP flows using pmtudisc==IP_PMTUDISC_DONT
> 
> Fixes: 73f156a6e8c1 ("inetpeer: get rid of ip_id_count")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: Ray Che <xijiache@...il.com>
> Cc: Willy Tarreau <w@....eu>
> ---
>  include/net/ip.h | 21 ++++++++++-----------
>  1 file changed, 10 insertions(+), 11 deletions(-)
> 

Reviewed-by: David Ahern <dsahern@...nel.org>