Re: [PATCH] bpf: export the net namespace for bpf_sock_ops

[Jakub Sitnicki <jakub@cloudflare.com>]

On Fri, Jun 05, 2020 at 02:40 PM CEST, Wang Li wrote:
> Sometimes we need net namespace as part of the key for BPF_MAP_TYPE_SOCKHASH to
> distinguish the connections with same five-tuples, for example when we do the
> sock_map acceleration for the proxy that uses 127.0.0.1 to 127.0.0.1 connections
> in different containers on same node.
> And we export the netns inum instead of the real pointer of struct net to avoid
> the potential security issue.
>
> Signed-off-by: Wang Li <wangli09@kuaishou.com>
> Signed-off-by: huangxuesen <huangxuesen@kuaishou.com>
> Signed-off-by: yangxingwu <yangxingwu@kuaishou.com>
> ---
>  include/uapi/linux/bpf.h       |  2 ++
>  net/core/filter.c              | 17 +++++++++++++++++
>  tools/include/uapi/linux/bpf.h |  2 ++
>  3 files changed, 21 insertions(+)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index c65b374a5090..0fe7e459f023 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -3947,6 +3947,8 @@ struct bpf_sock_ops {
>  				 * there is a full socket. If not, the
>  				 * fields read as zero.
>  				 */
> +	__u32 netns_inum;	/* The net namespace this sock belongs to */
> +

In uapi/linux/bpf.h we have a field `netns_ino` for storing net
namespace inode number in a couple structs (bpf_prog_info,
bpf_map_info). Would be nice to keep the naming constent.

>  	__u32 snd_cwnd;
>  	__u32 srtt_us;		/* Averaged RTT << 3 in usecs */
>  	__u32 bpf_sock_ops_cb_flags; /* flags defined in uapi/linux/tcp.h */
> diff --git a/net/core/filter.c b/net/core/filter.c
> index d01a244b5087..bfe448ace25f 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -8450,6 +8450,23 @@ static u32 sock_ops_convert_ctx_access(enum bpf_access_type type,
>  					       is_fullsock));
>  		break;
>
> +	case offsetof(struct bpf_sock_ops, netns_inum):
> +#ifdef CONFIG_NET_NS
> +		*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(
> +						struct bpf_sock_ops_kern, sk),
> +				      si->dst_reg, si->src_reg,
> +				      offsetof(struct bpf_sock_ops_kern, sk));
> +		*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(
> +						struct sock_common, skc_net),
> +				      si->dst_reg, si->dst_reg,
> +				      offsetof(struct sock_common, skc_net));
> +		*insn++ = BPF_LDX_MEM(BPF_W, si->dst_reg, si->dst_reg,
> +				      offsetof(struct net, ns.inum));
> +#else
> +		*insn++ = BPF_MOV32_IMM(si->dst_reg, 0);
> +#endif
> +		break;
> +
>  	case offsetof(struct bpf_sock_ops, state):
>  		BUILD_BUG_ON(sizeof_field(struct sock_common, skc_state) != 1);
>
> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index c65b374a5090..0fe7e459f023 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h
> @@ -3947,6 +3947,8 @@ struct bpf_sock_ops {
>  				 * there is a full socket. If not, the
>  				 * fields read as zero.
>  				 */
> +	__u32 netns_inum;	/* The net namespace this sock belongs to */
> +
>  	__u32 snd_cwnd;
>  	__u32 srtt_us;		/* Averaged RTT << 3 in usecs */
>  	__u32 bpf_sock_ops_cb_flags; /* flags defined in uapi/linux/tcp.h */