From: Dominique Martinet <asmadeus@codewreck.org>
To: David Miller <davem@davemloft.net>
Cc: doronrk@fb.com, tom@quantonium.net, davejwatson@fb.com,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] kcm: remove any offset before parsing messages
Date: Tue, 18 Sep 2018 04:58:37 +0200 [thread overview]
Message-ID: <20180918025837.GA3548@nautica> (raw)
In-Reply-To: <20180917.195150.315319338322641005.davem@davemloft.net>
David Miller wrote on Mon, Sep 17, 2018:
> > No, they can see it, so it's possible to make a KCM program that works
> > right now if you are careful (I'm not sure why the offset within bpf is
> > different from the offset in the kernel though, it looks like the bpf
> > program skips the qos part of the control buffer)
>
> What helper is used in the BPF program to get this offset value?
>
> (also good info to add to the commit message)
Dave defined one himself ; for a simple protocol where the offset is in
the first four bytes of the message.
The whole bpf program could look like this:
------
struct kcm_rx_msg { int full_len; int offset; };
static inline struct kcm_rx_msg *kcm_rx_msg(struct __sk_buff *skb) {
return (struct kcm_rx_msg *)skb->cb;
}
int decode_framing(struct __sk_buff *skb) {
return load_word(skb, kcm_rx_msg(skb)->offset);
}
------
If we go towards documenting it, adding a helper would be useful yes;
buf if we pull that becomes unnecessary.
(I'll add the example program in the commit message anyway at your
suggestion)
--
Dominique Martinet
next prev parent reply other threads:[~2018-09-18 2:58 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-11 9:21 [PATCH v2] kcm: remove any offset before parsing messages Dominique Martinet
2018-09-12 5:36 ` Dominique Martinet
2018-09-18 1:45 ` David Miller
2018-09-18 1:57 ` Dominique Martinet
2018-09-18 2:40 ` David Miller
2018-09-18 2:45 ` Dominique Martinet
2018-09-18 2:51 ` David Miller
2018-09-18 2:58 ` Dominique Martinet [this message]
2018-10-31 2:56 ` Dominique Martinet
2019-02-15 1:00 ` Dominique Martinet
2019-02-15 1:20 ` Tom Herbert
2019-02-15 1:57 ` Dominique Martinet
2019-02-15 2:48 ` Tom Herbert
2019-02-15 3:31 ` Dominique Martinet
2019-02-15 4:01 ` Tom Herbert
2019-02-15 4:52 ` Dominique Martinet
2019-02-20 4:11 ` Dominique Martinet
2019-02-20 16:18 ` Tom Herbert
2019-02-21 8:22 ` Dominique Martinet
2019-02-22 19:24 ` Tom Herbert
2019-02-22 20:27 ` Dominique Martinet
2019-02-22 21:01 ` Tom Herbert
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