netdev - Re: [PATCH nf-next v5 0/6] Netfilter egress hook

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 30 Sep 2021 19:36:11 +0200
From:   Lukas Wunner <lukas@...ner.de>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Pablo Neira Ayuso <pablo@...filter.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        netfilter-devel@...r.kernel.org, davem@...emloft.net,
        netdev@...r.kernel.org, kadlec@...filter.org, fw@...len.de,
        ast@...nel.org, edumazet@...gle.com, tgraf@...g.ch,
        nevola@...il.com, john.fastabend@...il.com, willemb@...gle.com
Subject: Re: [PATCH nf-next v5 0/6] Netfilter egress hook

On Thu, Sep 30, 2021 at 10:19:20AM -0700, Jakub Kicinski wrote:
> On Thu, 30 Sep 2021 19:12:53 +0200 Lukas Wunner wrote:
> > On Thu, Sep 30, 2021 at 07:28:35AM -0700, Jakub Kicinski wrote:
> > > On Thu, 30 Sep 2021 11:21:42 +0200 Pablo Neira Ayuso wrote:  
> > > > this is stuffing one more bit into the skbuff  
> > > 
> > > The lifetime of this information is constrained, can't it be a percpu
> > > flag, like xmit_more?  
> > 
> > Hm, can't an skb be queued and processed later on a different cpu?
> > E.g. what about fragments?
> > 
> > That would rule out a percpu flag, leaving a flag in struct sk_buff
> > as the only option.
> 
> What queuing do you have in mind? Qdisc is after the egress hook.

Ingress queueing.  E.g. a packet may be redirected or mirrored by tc
on ingress to another interface, resulting in a recursive call to
netif_receive_skb() or dev_queue_xmit().  The packet may be bounced
around an arbitrary number of times this way.  Forwarding like that
can happen both at the tc and the netfilter "layer".

I'm concerned that a packet may be handled by different cpus along the way
and queueing might be one possibility how this could happen.

Thanks,

Lukas