Re: [PATCH v2 bpf-next 1/2] bpf/bpf_get,set_sockopt: add option to set TCP-BPF sock ops flags

[Martin KaFai Lau <martin.lau@linux.dev>]

On 8/8/24 8:05 AM, Alan Maguire wrote:
> Currently the only opportunity to set sock ops flags dictating
> which callbacks fire for a socket is from within a TCP-BPF sockops
> program.  This is problematic if the connection is already set up
> as there is no further chance to specify callbacks for that socket.
> Add TCP_BPF_SOCK_OPS_CB_FLAGS to bpf_setsockopt() and bpf_getsockopt()
> to allow users to specify callbacks later, either via an iterator
> over sockets or via a socket-specific program triggered by a
> setsockopt() on the socket.
> 
> Previous discussion on this here [1].
> 
> [1] https://lore.kernel.org/bpf/f42f157b-6e52-dd4d-3d97-9b86c84c0b00@oracle.com/
> 
> Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
> ---
>   include/uapi/linux/bpf.h       |  3 ++-
>   net/core/filter.c              | 15 +++++++++++++++
>   tools/include/uapi/linux/bpf.h |  3 ++-
>   3 files changed, 19 insertions(+), 2 deletions(-)
> 
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 35bcf52dbc65..d4d7efc34e67 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -2851,7 +2851,7 @@ union bpf_attr {
>    * 		  **TCP_SYNCNT**, **TCP_USER_TIMEOUT**, **TCP_NOTSENT_LOWAT**,
>    * 		  **TCP_NODELAY**, **TCP_MAXSEG**, **TCP_WINDOW_CLAMP**,
>    * 		  **TCP_THIN_LINEAR_TIMEOUTS**, **TCP_BPF_DELACK_MAX**,
> - * 		  **TCP_BPF_RTO_MIN**.
> + *		  **TCP_BPF_RTO_MIN**, **TCP_BPF_SOCK_OPS_CB_FLAGS**.
>    * 		* **IPPROTO_IP**, which supports *optname* **IP_TOS**.
>    * 		* **IPPROTO_IPV6**, which supports the following *optname*\ s:
>    * 		  **IPV6_TCLASS**, **IPV6_AUTOFLOWLABEL**.
> @@ -7080,6 +7080,7 @@ enum {
>   	TCP_BPF_SYN		= 1005, /* Copy the TCP header */
>   	TCP_BPF_SYN_IP		= 1006, /* Copy the IP[46] and TCP header */
>   	TCP_BPF_SYN_MAC         = 1007, /* Copy the MAC, IP[46], and TCP header */
> +	TCP_BPF_SOCK_OPS_CB_FLAGS = 1008, /* Set TCP sock ops flags */
>   };
>   
>   enum {
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 78a6f746ea0b..67114e2fb52d 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -5278,6 +5278,11 @@ static int bpf_sol_tcp_setsockopt(struct sock *sk, int optname,
>   			return -EINVAL;
>   		inet_csk(sk)->icsk_rto_min = timeout;
>   		break;
> +	case TCP_BPF_SOCK_OPS_CB_FLAGS:
> +		if (val & ~(BPF_SOCK_OPS_ALL_CB_FLAGS))
> +			return -EINVAL;
> +		tp->bpf_sock_ops_cb_flags = val;
> +		break;
>   	default:
>   		return -EINVAL;
>   	}
> @@ -5366,6 +5371,16 @@ static int sol_tcp_sockopt(struct sock *sk, int optname,
>   		if (*optlen < 1)
>   			return -EINVAL;
>   		break;
> +	case TCP_BPF_SOCK_OPS_CB_FLAGS:
> +		if (*optlen != sizeof(int))
> +			return -EINVAL;
> +		if (getopt) {
> +			struct tcp_sock *tp = tcp_sk(sk);
> +
> +			memcpy(optval, &tp->bpf_sock_ops_cb_flags, *optlen);

bpf_sock_ops_cb_flags is a u8. memcpy with "*optlen == sizeof(int)" is an issue. 
I fixed it up by assigning to a local int first. Applied. Thanks.

> +			return 0;
> +		}
> +		return bpf_sol_tcp_setsockopt(sk, optname, optval, *optlen);
>   	default:
>   		if (getopt)
>   			return -EINVAL;
> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index 35bcf52dbc65..d4d7efc34e67 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h
> @@ -2851,7 +2851,7 @@ union bpf_attr {
>    * 		  **TCP_SYNCNT**, **TCP_USER_TIMEOUT**, **TCP_NOTSENT_LOWAT**,
>    * 		  **TCP_NODELAY**, **TCP_MAXSEG**, **TCP_WINDOW_CLAMP**,
>    * 		  **TCP_THIN_LINEAR_TIMEOUTS**, **TCP_BPF_DELACK_MAX**,
> - * 		  **TCP_BPF_RTO_MIN**.
> + *		  **TCP_BPF_RTO_MIN**, **TCP_BPF_SOCK_OPS_CB_FLAGS**.
>    * 		* **IPPROTO_IP**, which supports *optname* **IP_TOS**.
>    * 		* **IPPROTO_IPV6**, which supports the following *optname*\ s:
>    * 		  **IPV6_TCLASS**, **IPV6_AUTOFLOWLABEL**.
> @@ -7080,6 +7080,7 @@ enum {
>   	TCP_BPF_SYN		= 1005, /* Copy the TCP header */
>   	TCP_BPF_SYN_IP		= 1006, /* Copy the IP[46] and TCP header */
>   	TCP_BPF_SYN_MAC         = 1007, /* Copy the MAC, IP[46], and TCP header */
> +	TCP_BPF_SOCK_OPS_CB_FLAGS = 1008, /* Set TCP sock ops flags */
>   };
>   
>   enum {