From: Florian Westphal <fw@strlen.de>
To: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>
Cc: netfilter-devel@vger.kernel.org, steffen.klassert@secunet.com,
pablo@netfilter.org
Subject: Re: [PATCH nf-next] netfilter: nf_defrag_ipv4: Add sysctl to disable per interface
Date: Tue, 7 Nov 2017 11:30:13 +0100 [thread overview]
Message-ID: <20171107103013.GA5512@breakpoint.cc> (raw)
In-Reply-To: <1509762520-17873-1-git-send-email-subashab@codeaurora.org>
Subash Abhinov Kasiviswanathan <subashab@codeaurora.org> wrote:
> Add a sysctl nf_ipv4_defrag_skip to skip defragmentation per
> interface. This is set 0 to preserve existing behavior (always
> defrag per interface).
>
> This is useful for pure ipv4 forwarding scenarios (without NAT)
> in conjunction with xfrm. It appears that network stack defrags
> the packets and then forwards them to xfrm which then encrypts
> and then later fragments them on a different boundary compared
> to the source.
This breaks connection tracking for packets coming in via such
interfaces.
Nowadays we only enable defrag in a network namespace if the ip/nftables
ruleset requires it, so this setting would be counter-productive.
> An example of this usage is for fixing wifi calling on networks
> where certain routers are configured to drop fragments explicitly.
Yay... does that happen for all frags or is this related to df bit
somehow?
next prev parent reply other threads:[~2017-11-07 10:30 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-04 2:28 [PATCH nf-next] netfilter: nf_defrag_ipv4: Add sysctl to disable per interface Subash Abhinov Kasiviswanathan
2017-11-04 9:07 ` Steffen Klassert
2017-11-07 10:30 ` Florian Westphal [this message]
2017-11-07 18:58 ` Subash Abhinov Kasiviswanathan
2017-11-08 4:34 ` Pablo Neira Ayuso
2017-11-08 20:46 ` Subash Abhinov Kasiviswanathan
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