Re: [PATCH bpf-next 2/7] bpf: add bpf_skc_to_mptcp_sock_proto

Mat Martineau
2022-04-25T18:35:45Z

On Mon, 25 Apr 2022, Daniel Borkmann wrote:

> On 4/21/22 12:24 AM, Mat Martineau wrote:
> [...]
>> static const struct bpf_func_proto *
>> bpf_sk_base_func_proto(enum bpf_func_id func_id);
>> @@ -11279,6 +11280,19 @@ const struct bpf_func_proto
>> bpf_skc_to_unix_sock_proto = {
>> .ret_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_UNIX],
>> };
>> +BPF_CALL_1(bpf_skc_to_mptcp_sock, struct sock *, sk)
>> +{
>> + return (unsigned long)bpf_mptcp_sock_from_subflow(sk);
>> +}
>> +
>> +static const struct bpf_func_proto bpf_skc_to_mptcp_sock_proto = {
>> + .func = bpf_skc_to_mptcp_sock,
>> + .gpl_only = false,
>> + .ret_type = RET_PTR_TO_BTF_ID_OR_NULL,
>> + .arg1_type = ARG_PTR_TO_SOCK_COMMON,
>> + .ret_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_MPTCP],
>> +};
>
> BPF CI
> (https://github.com/kernel-patches/bpf/runs/6136052684?check_suite_focus=true)
> fails with:
>
> #7 base:FAIL
> libbpf: prog '_sockops': BPF program load failed: Invalid argument
> libbpf: prog '_sockops': -- BEGIN PROG LOAD LOG --
> 0: R1=ctx(off=0,imm=0) R10=fp0
> ; int op = (int)ctx->op;
> 0: (61) r2 = *(u32 *)(r1 +0) ; R1=ctx(off=0,imm=0)
> R2_w=scalar(umax=4294967295,var_off=(0x0; 0xffffffff))
> ; if (op != BPF_SOCK_OPS_TCP_CONNECT_CB)
> 1: (56) if w2 != 0x3 goto pc+50 ; R2_w=3
> ; sk = ctx->sk;
> 2: (79) r6 = *(u64 *)(r1 +184) ; R1=ctx(off=0,imm=0)
> R6_w=sock_or_null(id=1,off=0,imm=0)
> ; if (!sk)
> 3: (15) if r6 == 0x0 goto pc+48 ; R6_w=sock(off=0,imm=0)
> ; tcp_sk = bpf_tcp_sock(sk);
> 4: (bf) r1 = r6 ; R1_w=sock(off=0,imm=0)
> R6_w=sock(off=0,imm=0)
> 5: (85) call bpf_tcp_sock#96 ;
> R0_w=tcp_sock_or_null(id=2,off=0,imm=0)
> 6: (bf) r7 = r0 ;
> R0=tcp_sock_or_null(id=2,off=0,imm=0) R7=tcp_sock_or_null(id=2,off=0,imm=0)
> ; if (!tcp_sk)
> 7: (15) if r7 == 0x0 goto pc+44 ; R7=tcp_sock(off=0,imm=0)
> ; if (!tcp_sk->is_mptcp) {
> 8: (61) r1 = *(u32 *)(r7 +112) ;
> R1_w=scalar(umax=4294967295,var_off=(0x0; 0xffffffff))
> R7=tcp_sock(off=0,imm=0)
> ; if (!tcp_sk->is_mptcp) {
> 9: (56) if w1 != 0x0 goto pc+14 24: R0=tcp_sock(off=0,imm=0)
> R1_w=scalar(umax=4294967295,var_off=(0x0; 0xffffffff)) R6=sock(off=0,imm=0)
> R7=tcp_sock(off=0,imm=0) R10=fp0
> ; msk = bpf_skc_to_mptcp_sock(sk);
> 24: (bf) r1 = r6 ; R1_w=sock(off=0,imm=0)
> R6=sock(off=0,imm=0)
> 25: (85) call bpf_skc_to_mptcp_sock#194
> invalid return type 8 of func bpf_skc_to_mptcp_sock#194
> processed 34 insns (limit 1000000) max_states_per_insn 0 total_states 3
> peak_states 3 mark_read 1
> -- END PROG LOAD LOG --
> libbpf: failed to load program '_sockops'
> libbpf: failed to load object './mptcp_sock.o'
> run_test:FAIL:165
> test_base:FAIL:227
> (network_helpers.c:88: errno: Protocol not supported) Failed to create
> server socket
> test_base:FAIL:241
> RTNETLINK answers: No such file or directory
> Error talking to the kernel
> [...]
>
> Looking at bpf_skc_to_tcp6_sock(), do we similarly need a BTF_TYPE_EMIT()
> here?
>

Geliang, in addition to the BTF_TYPE_EMIT() can you also take a look at
the places in kernel/trace/bpf_trace.c and kernel/bpf/verifier.c where
bpf_skc_to_tcp6_sock and bpf_skc_to_tcp6_sock_proto are referenced?

--
Mat Martineau
Intel