Re: [PATCH net-next v3 03/14] net-timestamp: open gate for bpf_setsockopt/_getsockopt

[Willem de Bruijn <willemdebruijn.kernel@gmail.com>]

Jason Xing wrote:
> From: Jason Xing <kernelxing@tencent.com>
> 
> For now, we support bpf_setsockopt to set or clear timestamps flags.
> 
> Users can use something like this in bpf program to turn on the feature:
> flags = SOF_TIMESTAMPING_TX_SCHED;
> bpf_setsockopt(skops, SOL_SOCKET, SO_TIMESTAMPING, &flags, sizeof(flags));
> The specific use cases can be seen in the bpf selftest in this series.
> 
> Later, I will support each flags one by one based on this.
> 
> Signed-off-by: Jason Xing <kernelxing@tencent.com>
> ---
>  include/net/sock.h              |  4 ++--
>  include/uapi/linux/net_tstamp.h |  7 +++++++
>  net/core/filter.c               |  7 +++++--
>  net/core/sock.c                 | 34 ++++++++++++++++++++++++++-------
>  net/ipv4/udp.c                  |  2 +-
>  net/mptcp/sockopt.c             |  2 +-
>  net/socket.c                    |  2 +-
>  7 files changed, 44 insertions(+), 14 deletions(-)
> 
> diff --git a/include/net/sock.h b/include/net/sock.h
> index 5384f1e49f5c..062f405c744e 100644
> --- a/include/net/sock.h
> +++ b/include/net/sock.h
> @@ -1775,7 +1775,7 @@ static inline void skb_set_owner_edemux(struct sk_buff *skb, struct sock *sk)
>  #endif
>  
>  int sk_setsockopt(struct sock *sk, int level, int optname,
> -		  sockptr_t optval, unsigned int optlen);
> +		  sockptr_t optval, unsigned int optlen, bool bpf_timetamping);

timestamping, not timetamping

More importantly, is there perhaps a cleaner way to add a BPF
setsockopt than to have to update the existing API and all its
callers?

>  int sock_setsockopt(struct socket *sock, int level, int op,
>  		    sockptr_t optval, unsigned int optlen);
>  int do_sock_setsockopt(struct socket *sock, bool compat, int level,
> @@ -1784,7 +1784,7 @@ int do_sock_getsockopt(struct socket *sock, bool compat, int level,
>  		       int optname, sockptr_t optval, sockptr_t optlen);
>  
>  int sk_getsockopt(struct sock *sk, int level, int optname,
> -		  sockptr_t optval, sockptr_t optlen);
> +		  sockptr_t optval, sockptr_t optlen, bool bpf_timetamping);
>  int sock_gettstamp(struct socket *sock, void __user *userstamp,
>  		   bool timeval, bool time32);
>  struct sk_buff *sock_alloc_send_pskb(struct sock *sk, unsigned long header_len,
> diff --git a/include/uapi/linux/net_tstamp.h b/include/uapi/linux/net_tstamp.h
> index 858339d1c1c4..0696699cf964 100644
> --- a/include/uapi/linux/net_tstamp.h
> +++ b/include/uapi/linux/net_tstamp.h
> @@ -49,6 +49,13 @@ enum {
>  					 SOF_TIMESTAMPING_TX_SCHED | \
>  					 SOF_TIMESTAMPING_TX_ACK)
>  
> +#define SOF_TIMESTAMPING_BPF_SUPPPORTED_MASK (SOF_TIMESTAMPING_SOFTWARE | \
> +					      SOF_TIMESTAMPING_TX_SCHED | \
> +					      SOF_TIMESTAMPING_TX_SOFTWARE | \
> +					      SOF_TIMESTAMPING_TX_ACK | \
> +					      SOF_TIMESTAMPING_OPT_ID | \
> +					      SOF_TIMESTAMPING_OPT_ID_TCP)
> +

We discussed the subtle distinction between OPT_ID and OPT_ID_TCP before.

Basically, OPT_ID_TCP is a fix for OPT_ID on TCP sockets, and should always be
passed. On a new API like this one, we can even require this.

Not super important, only if it does not make the code more complex.