| Message ID | 20200918121046.190240-1-nicolas.rybowski@tessares.net |
|---|---|
| State | Changes Requested |
| Delegated to: | BPF Maintainers |
| Headers | show |
| Series | [bpf-next,v3,1/5] bpf: expose is_mptcp flag to bpf_tcp_sock | expand |
On Fri, Sep 18, 2020 at 5:13 AM Nicolas Rybowski <nicolas.rybowski@tessares.net> wrote: > > is_mptcp is a field from struct tcp_sock used to indicate that the > current tcp_sock is part of the MPTCP protocol. > > In this protocol, a first socket (mptcp_sock) is created with > sk_protocol set to IPPROTO_MPTCP (=262) for control purpose but it > isn't directly on the wire. This is the role of the subflow (kernel) > sockets which are classical tcp_sock with sk_protocol set to > IPPROTO_TCP. The only way to differentiate such sockets from plain TCP > sockets is the is_mptcp field from tcp_sock. > > Such an exposure in BPF is thus required to be able to differentiate > plain TCP sockets from MPTCP subflow sockets in BPF_PROG_TYPE_SOCK_OPS > programs. > > The choice has been made to silently pass the case when CONFIG_MPTCP is > unset by defaulting is_mptcp to 0 in order to make BPF independent of > the MPTCP configuration. Another solution is to make the verifier fail > in 'bpf_tcp_sock_is_valid_ctx_access' but this will add an additional > '#ifdef CONFIG_MPTCP' in the BPF code and a same injected BPF program > will not run if MPTCP is not set. > > An example use-case is provided in > https://github.com/multipath-tcp/mptcp_net-next/tree/scripts/bpf/examples > > Suggested-by: Matthieu Baerts <matthieu.baerts@tessares.net> > Acked-by: Matthieu Baerts <matthieu.baerts@tessares.net> > Acked-by: Mat Martineau <mathew.j.martineau@linux.intel.com> > Signed-off-by: Nicolas Rybowski <nicolas.rybowski@tessares.net> Acked-by: Song Liu <songliubraving@fb.com> [...]
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index a22812561064..351b3d0a6ca8 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -4067,6 +4067,7 @@ struct bpf_tcp_sock { __u32 delivered; /* Total data packets delivered incl. rexmits */ __u32 delivered_ce; /* Like the above but only ECE marked packets */ __u32 icsk_retransmits; /* Number of unrecovered [RTO] timeouts */ + __u32 is_mptcp; /* Is MPTCP subflow? */ }; struct bpf_sock_tuple { diff --git a/net/core/filter.c b/net/core/filter.c index d266c6941967..dab48528dceb 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -5837,7 +5837,7 @@ bool bpf_tcp_sock_is_valid_access(int off, int size, enum bpf_access_type type, struct bpf_insn_access_aux *info) { if (off < 0 || off >= offsetofend(struct bpf_tcp_sock, - icsk_retransmits)) + is_mptcp)) return false; if (off % size != 0) @@ -5971,6 +5971,13 @@ u32 bpf_tcp_sock_convert_ctx_access(enum bpf_access_type type, case offsetof(struct bpf_tcp_sock, icsk_retransmits): BPF_INET_SOCK_GET_COMMON(icsk_retransmits); break; + case offsetof(struct bpf_tcp_sock, is_mptcp): +#ifdef CONFIG_MPTCP + BPF_TCP_SOCK_GET_COMMON(is_mptcp); +#else + *insn++ = BPF_MOV32_IMM(si->dst_reg, 0); +#endif + break; } return insn - insn_buf; diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index a22812561064..351b3d0a6ca8 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -4067,6 +4067,7 @@ struct bpf_tcp_sock { __u32 delivered; /* Total data packets delivered incl. rexmits */ __u32 delivered_ce; /* Like the above but only ECE marked packets */ __u32 icsk_retransmits; /* Number of unrecovered [RTO] timeouts */ + __u32 is_mptcp; /* Is MPTCP subflow? */ }; struct bpf_sock_tuple {