On Fri, Apr 12, 2019 at 3:02 AM Alban Crequy <alban.crequy@xxxxxxxxx> wrote:
>
> From: Alban Crequy <alban@xxxxxxxxxx>
>
> sockops programs can now access the network namespace inode via
> (struct bpf_sock_ops)->netns. This can be useful to apply different
> policies on different network namespaces.
>
> In the unlikely case where network namespaces are not compiled in
> (CONFIG_NET_NS=n), the verifier will not allow access to ->netns.
>
> Signed-off-by: Alban Crequy <alban@xxxxxxxxxx>
Acked-by: Song Liu <songliubraving@xxxxxx>
> ---
> include/uapi/linux/bpf.h | 1 +
> net/core/filter.c | 40 ++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 41 insertions(+)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 31a27dd337dc..5afaab25f205 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -3069,6 +3069,7 @@ struct bpf_sock_ops {
> __u32 sk_txhash;
> __u64 bytes_received;
> __u64 bytes_acked;
> + __u64 netns;
> };
>
> /* Definitions for bpf_sock_ops_cb_flags */
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 22eb2edf5573..f5e75b6fecb2 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -6758,6 +6758,14 @@ static bool sock_ops_is_valid_access(int off, int size,
> }
> } else {
> switch (off) {
> + case offsetof(struct bpf_sock_ops, netns):
> +#ifdef CONFIG_NET_NS
> + if (size != sizeof(__u64))
> + return false;
> +#else
> + return false;
> +#endif
> + break;
> case bpf_ctx_range_till(struct bpf_sock_ops, bytes_received,
> bytes_acked):
> if (size != sizeof(__u64))
> @@ -7908,6 +7916,38 @@ static u32 sock_ops_convert_ctx_access(enum bpf_access_type type,
> SOCK_OPS_GET_OR_SET_FIELD(sk_txhash, sk_txhash,
> struct sock, type);
> break;
> +
> + case offsetof(struct bpf_sock_ops, netns):
> +#ifdef CONFIG_NET_NS
> + /* Loading: sk_ops->sk->__sk_common.skc_net.net->ns.inum
> + * Type: (struct bpf_sock_ops_kern *)
> + * ->(struct sock *)
> + * ->(struct sock_common)
> + * .possible_net_t
> + * .(struct net *)
> + * ->(struct ns_common)
> + * .(unsigned int)
> + */
> + BUILD_BUG_ON(offsetof(struct sock, __sk_common) != 0);
> + BUILD_BUG_ON(offsetof(possible_net_t, net) != 0);
> + *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(
> + possible_net_t, net),
> + si->dst_reg, si->dst_reg,
> + offsetof(struct sock_common, skc_net));
> + *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(
> + struct ns_common, inum),
> + si->dst_reg, si->dst_reg,
> + offsetof(struct net, ns) +
> + offsetof(struct ns_common, inum));
> +#else
> + *insn++ = BPF_MOV64_IMM(si->dst_reg, 0);
> +#endif
> + break;
> +
> }
> return insn - insn_buf;
> }
> --
> 2.20.1
>
