From: Eric Dumazet <eric.dumazet@gmail.com>
To: Florian Westphal <fw@strlen.de>, netdev@vger.kernel.org
Cc: Peter Oskolkov <posk@google.com>, Eric Dumazet <edumazet@google.com>
Subject: Re: [PATCH net-next] inet: defrag: drop non-last frags smaller than min mtu
Date: Thu, 2 Aug 2018 16:54:22 -0700 [thread overview]
Message-ID: <4b249fb2-d826-dbea-cd97-55cb336e230f@gmail.com> (raw)
In-Reply-To: <20180802234348.16559-1-fw@strlen.de>
On 08/02/2018 04:43 PM, Florian Westphal wrote:
> don't bother with pathological cases, they only waste cycles.
> IPv6 requires a minimum MTU of 1280 so we should never see fragments
> smaller than this (except last frag).
>
> For IPv4, in practice, we could probably also adopt a higher limit,
> but for now use ipv4 min mtu (68).
...
> + if (-skb_network_offset(skb) + skb->len < IPV4_MIN_MTU &&
> + ip_hdr(skb)->frag_off & htons(IP_MF))
> + goto drop;
> +
>
I am not totally sure this is legit for IPv4.
Some intermediate nodes can try to be smart and could decide to further split fragments.
I am pretty sure I have seen this behavior on some radio environments :/
Eventually we could add a sysctl to allow an admin to set the threshold ?
prev parent reply other threads:[~2018-08-03 1:47 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-02 23:43 [PATCH net-next] inet: defrag: drop non-last frags smaller than min mtu Florian Westphal
2018-08-02 23:54 ` Eric Dumazet [this message]
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