> On Jul 26, 2016, at 11:43, J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote:
>
> On Tue, Jul 26, 2016 at 09:51:19AM -0400, Trond Myklebust wrote:
>> We're seeing traces of the following form:
>>
>> [10952.396347] svc: transport ffff88042ba4a 000 dequeued, inuse=2
>> [10952.396351] svc: tcp_accept ffff88042ba4 a000 sock ffff88042a6e4c80
>> [10952.396362] nfsd: connect from 10.2.6.1, port=187
>> [10952.396364] svc: svc_setup_socket ffff8800b99bcf00
>> [10952.396368] setting up TCP socket for reading
>> [10952.396370] svc: svc_setup_socket created ffff8803eb10a000 (inet ffff88042b75b800)
>> [10952.396373] svc: transport ffff8803eb10a000 put into queue
>> [10952.396375] svc: transport ffff88042ba4a000 put into queue
>> [10952.396377] svc: server ffff8800bb0ec000 waiting for data (to = 3600000)
>> [10952.396380] svc: transport ffff8803eb10a000 dequeued, inuse=2
>> [10952.396381] svc_recv: found XPT_CLOSE
>> [10952.396397] svc: svc_delete_xprt(ffff8803eb10a000)
>> [10952.396398] svc: svc_tcp_sock_detach(ffff8803eb10a000)
>> [10952.396399] svc: svc_sock_detach(ffff8803eb10a000)
>> [10952.396412] svc: svc_sock_free(ffff8803eb10a000)
>>
>> i.e. an immediate close of the socket after initialisation.
>
> Interesting, thanks!
>
> So the one thing I don't understand is why this is correct behavior for
> accept--I thought it wasn't supposed to return a socket until it was
> fully established.
inet_accept() appears to allow SYN_RECV:
int inet_accept(struct socket *sock, struct socket *newsock, int flags)
{
struct sock *sk1 = sock->sk;
int err = -EINVAL;
struct sock *sk2 = sk1->sk_prot->accept(sk1, flags, &err);
if (!sk2)
goto do_err;
lock_sock(sk2);
sock_rps_record_flow(sk2);
WARN_ON(!((1 << sk2->sk_state) &
(TCPF_ESTABLISHED | TCPF_SYN_RECV |
TCPF_CLOSE_WAIT | TCPF_CLOSE)));
sock_graft(sk2, newsock);
newsock->state = SS_CONNECTED;
err = 0;
release_sock(sk2);
do_err:
return err;
}
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