Re: [PATCH net-next] tcp: provide SYN headers for passive connections

On Mon, 2015-05-04 at 10:41 -0400, John Heffner wrote:

Nice idea, seems handy.  But a couple (somewhat related) questions:

* Other than convenience, are there reasons not use an existing, more
general-purpose and portable mechanism like pcap?  (Permissions, I
guess?)

Very hard to synchronize when say you have 32 listeners sharing a single
port (SO_REUSEPORT), and receive one million SYN per second (when my TCP
listener scaling work is finished).

libpcap here would be a serious bottleneck, even with a clever FANIN
support on the af_packet sockets, considering use of multiqueue NIC.

* Are there conditions where, for security purposes, you don't want an
application to have access to the raw SYNs?

Not that we are aware of : We restrict the access to IP + TCP headers,
for the passive part. All information that is available there was
provided by the remote peer on a 'open way' anyway.

Thanks.