On 08/03/2017 09:22 PM, Tom Herbert wrote:
> On Thu, Aug 3, 2017 at 4:37 PM, John Fastabend <john.fastab...@gmail.com>
> wrote:
>> Recently we added a new map type called dev map used to forward XDP
>> packets between ports (6093ec2dc313). This patches introduces a
>> similar notion for sockets.
>>
>> A sockmap allows users to add participating sockets to a map. When
>> sockets are added to the map enough context is stored with the
>> map entry to use the entry with a new helper
>>
>> bpf_sk_redirect_map(map, key, flags)
>>
>> This helper (analogous to bpf_redirect_map in XDP) is given the map
>> and an entry in the map. When called from a sockmap program, discussed
>> below, the skb will be sent on the socket using skb_send_sock().
>>
>> With the above we need a bpf program to call the helper from that will
>> then implement the send logic. The initial site implemented in this
>> series is the recv_sock hook. For this to work we implemented a map
>> attach command to add attributes to a map. In sockmap we add two
>> programs a parse program and a verdict program. The parse program
>> uses strparser to build messages and pass them to the verdict program.
>> The parse program usese normal strparser semantics. The verdict
>> program is of type SOCKET_FILTER.
>>
>> The verdict program returns a verdict BPF_OK, BPF_DROP, BPF_REDIRECT.
>> When BPF_REDIRECT is returned, expected when bpf program uses
>> bpf_sk_redirect_map(), the sockmap logic will consult per cpu variables
>> set by the helper routine and pull the sock entry out of the sock map.
>> This pattern follows the existing redirect logic in cls and xdp
>> programs.
>>
> Hi John,
>
> I'm a bit confused. If the verdict program bpf_mux then? I don't see
> any use of BPF_OK,DROP, or REDIRECT. I assume I'm missing something.
>
> Tom
Ah so what I coded and what I wrote don't align perfectly here. The
verdict program _is_ bpf_mux as you guessed. I should rename the code
to use bpf_verdict (or come up with a better name). Calling it bpf_mux
was a hold out from a very specific example program I wrote up.
Then BPF_OK_DROP and BPF_REDIRECT still need to be included in below.
[...]
>> +
>> +static struct smap_psock *smap_peers_get(struct smap_psock *psock,
>> + struct sk_buff *skb)
>> +{
>> + struct sock *sock;
>> + int rc;
>> +
>> + rc = smap_mux_func(psock, skb);
>> + if (unlikely(rc < 0))
>> + return NULL;
>> +
replacing the above 3 lines with the following should align the commit
message and code,
rc = smap_mux_func(psock, skb);
if (rc != BPF_REDIRECT)
return NULL;
>> + sock = do_sk_redirect_map();
>> + if (unlikely(!sock))
>> + return NULL;
>> +
>> + return smap_psock_sk(sock);
>> +}
>> +
And then in uapi/linux/bpf.h
enum {
BPF_OK_DROP,
BPF_REDIRECT,
}
Thanks,
John
