Re: [PATCH v5 net-next 0/3] net: bpf: handle return value of post_bind{4,6} and add selftests for it

[Alexei Starovoitov]

On Thu, Jan 6, 2022 at 5:20 AM <menglong8.dong@xxxxxxxxx> wrote:
>
> From: Menglong Dong <imagedong@xxxxxxxxxxx>
>
> The return value of BPF_CGROUP_RUN_PROG_INET{4,6}_POST_BIND() in
> __inet_bind() is not handled properly. While the return value
> is non-zero, it will set inet_saddr and inet_rcv_saddr to 0 and
> exit:
> exit:
>
>         err = BPF_CGROUP_RUN_PROG_INET4_POST_BIND(sk);
>         if (err) {
>                 inet->inet_saddr = inet->inet_rcv_saddr = 0;
>                 goto out_release_sock;
>         }
>
> Let's take UDP for example and see what will happen. For UDP
> socket, it will be added to 'udp_prot.h.udp_table->hash' and
> 'udp_prot.h.udp_table->hash2' after the sk->sk_prot->get_port()
> called success. If 'inet->inet_rcv_saddr' is specified here,
> then 'sk' will be in the 'hslot2' of 'hash2' that it don't belong
> to (because inet_saddr is changed to 0), and UDP packet received
> will not be passed to this sock. If 'inet->inet_rcv_saddr' is not
> specified here, the sock will work fine, as it can receive packet
> properly, which is wired, as the 'bind()' is already failed.
>
> To undo the get_port() operation, introduce the 'put_port' field
> for 'struct proto'. For TCP proto, it is inet_put_port(); For UDP
> proto, it is udp_lib_unhash(); For icmp proto, it is
> ping_unhash().
>
> Therefore, after sys_bind() fail caused by
> BPF_CGROUP_RUN_PROG_INET4_POST_BIND(), it will be unbinded, which
> means that it can try to be binded to another port.
>
> The second patch use C99 initializers in test_sock.c
>
> The third patch is the selftests for this modification.
>
> Changes since v4:
> - use C99 initializers in test_sock.c before adding the test case

Thanks for the fix. Applied.

In the future please make sure to tag your patches with
[PATCH bpf-next]
so that BPF CI can properly test it right away.