netdev - Re: [PATCH net-next] udp: Add socket early demux support

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Message-ID: <CAGK4HS-bh2_hwiQAM+-4UaD8Ts5NAVEh19nBbAT8fQn1GookSw@mail.gmail.com>
Date:	Tue, 26 Jun 2012 17:06:29 -0700
From:	Vijay Subramanian <subramanian.vijay@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org, shemminger@...tta.com,
	eric.dumazet@...il.com, alexander.h.duyck@...el.com
Subject: Re: [PATCH net-next] udp: Add socket early demux support

Thanks for the reviews and feedback, Dave and Eric. They were very helpful.

On 26 June 2012 14:34, David Miller <davem@...emloft.net> wrote:
>
> You can't do this.
>
> If the UDP socket has wildcards, that means the source address of the
> route will not be validated.  This means we will start accepting
> spoofed packets.  It also means the route you are caching is going
> to be the wrong route since the keys are variable.

Thanks for this explanation.
I see why Eric wanted me to test with DNS server bound to wildcard
address. I guess the same issue exists with multicast too which I had
not even considered.

>
> You can only do an early demux where all the keys are fully specified
> and there are no wildcards.  That why for TCP we only early demux for
> established sockets.

I guess for UDP, early demux will work only if server binds to a
specific address and port instead of wildcard. But I believe
a lot of UDP servers use wildcard addresses, so use of early demux for
UDP may be limited.

Thanks,
Vijay
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