From: Pablo Neira Ayuso <pablo@netfilter.org>
To: Michael Braun <michael-dev@fami-braun.de>
Cc: netfilter-devel@vger.kernel.org
Subject: Re: [PATCH 0/3] Avoid gretap fragmentation with nftables on bridge
Date: Wed, 27 May 2020 23:39:37 +0200 [thread overview]
Message-ID: <20200527213937.GA2714@salvia> (raw)
In-Reply-To: <cover.1588758255.git.michael-dev@fami-braun.de>
On Wed, May 06, 2020 at 11:46:22AM +0200, Michael Braun wrote:
> Hi,
>
> I have a bridge with connects an gretap tunnel with some ethernet lan.
> On the gretap device I use ignore-df to avoid packets being lost without
> icmp reject to the sender of the bridged packet.
>
> Still I want to avoid packet fragmentation with the gretap packets.
> So I though about adding an nftables rule like this:
>
> nft insert rule bridge filter FORWARD \
> ip protocol tcp \
> ip length > 1400 \
> ip frag-off & 0x4000 != 0 \
> reject with icmp type frag-needed
>
> This would reject all tcp packets with ip dont-fragment bit set that are
> bigger than some threshold (here 1400 bytes). The sender would then receive
> ICMP unreachable - fragmentation needed and reduce its packet size (as
> defined with PMTU).
Patches 1 and 2 are applied, thanks.
Patch 3 has been merged upstream as a bugfix since VLAN should be
preversed in any reject case.
prev parent reply other threads:[~2020-05-27 21:39 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-06 9:46 [PATCH 0/3] Avoid gretap fragmentation with nftables on bridge Michael Braun
2020-05-06 9:46 ` [PATCH 1/3] nftables: add frag-needed (ipv4) to reject options Michael Braun
2020-05-06 9:46 ` [PATCH 2/3] nftables: enable reject with 802.1q Michael Braun
2020-05-06 9:46 ` [PATCH 3/3] netfilter: enable reject with bridge vlan Michael Braun
2020-05-25 18:40 ` Pablo Neira Ayuso
2020-05-27 21:39 ` Pablo Neira Ayuso [this message]
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