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net: bpf: handle return value of post_bind{4,6} and add selftests for it #2349

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net: bpf: handle return value of post_bind{4,6} and add selftests for it #2349

wants to merge 4 commits into from

Commits on Jan 6, 2022

  1. adding ci files

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  2. net: bpf: handle return value of BPF_CGROUP_RUN_PROG_INET{4,6}_POST_B… 

    …IND()

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:

	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.

Signed-off-by: Menglong Dong <imagedong@tencent.com>
    @menglongdong
    menglongdong authored and Nobody committed Jan 6, 2022
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  3. bpf: selftests: add bind retry for post_bind{4, 6} 

    With previous patch, kernel is able to 'put_port' after sys_bind()
fails. Add the test for that case: rebind another port after
sys_bind() fails. If the bind success, it means previous bind
operation is already undoed.

Signed-off-by: Menglong Dong <imagedong@tencent.com>
    @menglongdong
    menglongdong authored and Nobody committed Jan 6, 2022
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  4. bpf: selftests: use C99 initializers in test_sock.c 

    Use C99 initializers for the initialization of 'tests' in test_sock.c.

Signed-off-by: Menglong Dong <imagedong@tencent.com>
    @menglongdong
    menglongdong authored and Nobody committed Jan 6, 2022
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