From: David Miller <davem@davemloft.net>
To: eric.dumazet@gmail.com
Cc: netdev@vger.kernel.org
Subject: Re: [PATCH net-next] tcp: reduce skb overhead in selected places
Date: Wed, 25 Jan 2017 13:17:17 -0500 (EST) [thread overview]
Message-ID: <20170125.131717.489451306351372553.davem@davemloft.net> (raw)
In-Reply-To: <1485298656.16328.355.camel@edumazet-glaptop3.roam.corp.google.com>
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Tue, 24 Jan 2017 14:57:36 -0800
> From: Eric Dumazet <edumazet@google.com>
>
> tcp_add_backlog() can use skb_condense() helper to get better
> gains and less SKB_TRUESIZE() magic. This only happens when socket
> backlog has to be used.
>
> Some attacks involve specially crafted out of order tiny TCP packets,
> clogging the ofo queue of (many) sockets.
> Then later, expensive collapse happens, trying to copy all these skbs
> into single ones.
> This unfortunately does not work if each skb has no neighbor in TCP
> sequence order.
>
> By using skb_condense() if the skb could not be coalesced to a prior
> one, we defeat these kind of threats, potentially saving 4K per skb
> (or more, since this is one page fragment).
>
> A typical NAPI driver allocates gro packets with GRO_MAX_HEAD bytes
> in skb->head, meaning the copy done by skb_condense() is limited to
> about 200 bytes.
>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
Applied, thanks Eric.
next prev parent reply other threads:[~2017-01-25 18:17 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-24 22:57 [PATCH net-next] tcp: reduce skb overhead in selected places Eric Dumazet
2017-01-25 18:17 ` David Miller [this message]
2017-01-25 18:38 ` Eric Dumazet
2017-01-25 19:03 ` David Miller
2017-01-25 21:40 ` Eric Dumazet
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