Re: [bpf-next PATCH v2 05/18] bpf: create tcp_bpf_ulp allowing BPF to monitor socket TX/RX data

John Fastabend
2018-03-15T22:08:51Z

On 03/15/2018 02:59 PM, Alexei Starovoitov wrote:
> On Mon, Mar 12, 2018 at 12:23:29PM -0700, John Fastabend wrote:
>>
>> +/* User return codes for SK_MSG prog type. */
>> +enum sk_msg_action {
>> + SK_MSG_DROP = 0,
>> + SK_MSG_PASS,
>> +};
>
> do we really need new enum here?

Nope and as you noticed the actual code uses the
SK_{DROP|PASS} enum. Will remove this.

> It's the same as 'enum sk_action' and SK_DROP == SK_MSG_DROP
> and there will be only drop/pass in both enums.
> Also I don't see where these two new SK_MSG_* are used...
>
>> +
>> +/* user accessible metadata for SK_MSG packet hook, new fields must
>> + * be added to the end of this structure
>> + */
>> +struct sk_msg_md {
>> + __u32 data;
>> + __u32 data_end;
>> +};
>
> I think it's time for me to ask for forgiveness :)
> I used __u32 for data and data_end only because all other fields
> in __sk_buff were __u32 at the time and I couldn't easily figure out
> how to teach verifier to recognize 8-byte rewrites.
> Unfortunately my mistake stuck and was copied over into xdp.
> Since this is new struct let's do it right and add
> 'void *data, *data_end' here,
> since bpf prog will use them as 'void *' pointers.
> There are no compat issues here, since bpf is always 64-bit.
>

aha nice catch. Yep lets use 'void*' here. I had forgot about
that discussion and copied them here as well.

>> +static int bpf_map_msg_verdict(int _rc, struct sk_msg_buff *md)
>> +{
>> + return ((_rc == SK_PASS) ?
>> + (md->map ? __SK_REDIRECT : __SK_PASS) :
>> + __SK_DROP);
>
> you're using old SK_PASS here too ;)
> that's to my point of not adding SK_MSG_PASS...
>

+1

> Overall the patch set looks absolutely great.
> Thank you for working on it.
>

I'll fixup a few of these small things now and should have
a v3 shortly.