On 02/04/2019 06:35 PM, Alexei Starovoitov wrote:
> On Sun, Feb 03, 2019 at 04:15:07PM +0800, Yafang Shao wrote:
>> Then we can enable/disable socket debugging without modifying user code.
>> That is more convenient for debugging.
>>
>> Signed-off-by: Yafang Shao <laoar.s...@gmail.com>
>> ---
>> include/net/sock.h | 8 ++++++++
>> net/core/filter.c | 3 +++
>> net/core/sock.c | 8 --------
>> 3 files changed, 11 insertions(+), 8 deletions(-)
>>
>> diff --git a/include/net/sock.h b/include/net/sock.h
>> index 2b229f7..8decee9 100644
>> --- a/include/net/sock.h
>> +++ b/include/net/sock.h
>> @@ -1935,6 +1935,14 @@ static inline void sock_confirm_neigh(struct sk_buff
>> *skb, struct neighbour *n)
>> }
>> }
>>
>> +static inline void sock_valbool_flag(struct sock *sk, int bit, int valbool)
>> +{
>> + if (valbool)
>> + sock_set_flag(sk, bit);
>> + else
>> + sock_reset_flag(sk, bit);
>> +}
>> +
>> bool sk_mc_loop(struct sock *sk);
>>
>> static inline bool sk_can_gso(const struct sock *sk)
>> diff --git a/net/core/filter.c b/net/core/filter.c
>> index 3a49f68..ce5da57 100644
>> --- a/net/core/filter.c
>> +++ b/net/core/filter.c
>> @@ -4111,6 +4111,9 @@ static unsigned long bpf_xdp_copy(void *dst_buff,
>> const void *src_buff,
>>
>> /* Only some socketops are supported */
>> switch (optname) {
>> + case SO_DEBUG:
>> + sock_valbool_flag(sk, SOCK_DBG, val);
>> + break;
>
> I'm missing the point here.
> This flag has any effect only when SOCK_DEBUGGING is set.
> But it is off in distros.
> Since it's for custom debug kernel only why bother with
> setting the flag via bpf prog?
+1, this seems like some ancient debugging interface. Back at last netconf
there was a proposal [0] to have a tcp_stats(sk, TCP_MIB_...) API for MIBs
counter such that this can be traced via BPF on a per socket basis, for
example. Might be worthwhile to work into that direction instead and potentially
get rid of the SOCK_DEBUG() statements and convert (where appropriate) to
such an interface. Thoughts?
[0] page 14,
http://vger.kernel.org/netconf2018_files/BrendanGregg_netconf2018.pdf
