[Sheepdog] [PATCH] fix a bug in rx() when read() returns 0 but connection is not marked as closed.

[levin li]

On 2012年04月25日 09:05, Huxinwei wrote:
>> -----Original Message-----
>> From: MORITA Kazutaka [mailto:morita.kazutaka at gmail.com]
>> Sent: Tuesday, April 24, 2012 5:21 PM
>> To: Huxinwei
>> Cc: Li Wenpeng; sheepdog at lists.wpkg.org
>> Subject: Re: [Sheepdog] [PATCH] fix a bug in rx() when read() returns 0 but
>> connection is not marked as closed.
>>
>> On Tue, Apr 24, 2012 at 5:40 PM, Huxinwei<huxinwei at huawei.com>  wrote:
>>> I proposed something similar a while ago.
>>> The connection is actually staying in CLOSE_WAIT status while this happens.
>> I'd suggest you consider something more reliable.
>>
>> Is there any case that read() returns zero but the connection is not closed?
> What if reading is interrupted by a signal ?
> Read() returns 0 while errno is EINTR then ?
Thanks for pointing it out, I learned from the manual for read(),
The manual says "zero indicates end of file",
so I thought when read() returns zero on a blocking socket
means connection closed, maybe I am wrong.

But can we just check EINTR when read() return zero instead of
calling getsockopt() ?

thanks,
levin
>> Thanks,
>>
>> Kazutaka
>>
>>> +               else if (!ret) { //FIXME: is this the best place to check?
>>> +                       int r;
>>> +                       struct tcp_info ti;
>>> +                       socklen_t l = sizeof(struct tcp_info);
>>> +                       r = getsockopt(conn->fd, SOL_TCP, TCP_INFO,
>> (void*)&ti,&l);
>>> +                       if (r<  0) panic("this is really wired");
>>> +                       if (ti.tcpi_state == TCP_CLOSE_WAIT) {
>>> +                               conn->c_rx_state = C_IO_CLOSED;
>>> +                               conn->c_tx_state = C_IO_CLOSED;
>>> +                       }
>>> +               }
>>>
>>> FYI.
>>>
>>>> -----Original Message-----
>>>> From: sheepdog-bounces at lists.wpkg.org
>>>> [mailto:sheepdog-bounces at lists.wpkg.org] On Behalf Of Li Wenpeng
>>>> Sent: Tuesday, April 24, 2012 4:00 PM
>>>> To: sheepdog at lists.wpkg.org
>>>> Subject: [Sheepdog] [PATCH] fix a bug in rx() when read() returns 0 but
>>>> connection is not marked as closed.
>>>>
>>>> From: levin li<xingke.lwp at taobao.com>
>>>>
>>>> if read() returns 0，it means connection closed, but previous
>>>> read() may set errno to EAGAIN, in which case rx() would just
>>>> return 0 without set connection state as C_IO_CLOSED
>>>>
>>>> Signed-off-by: levin li<xingke.lwp at taobao.com>
>>>> ---
>>>>   lib/net.c |    7 ++++++-
>>>>   1 files changed, 6 insertions(+), 1 deletions(-)
>>>>
>>>> diff --git a/lib/net.c b/lib/net.c
>>>> index 260ae38..8ac7c9e 100644
>>>> --- a/lib/net.c
>>>> +++ b/lib/net.c
>>>> @@ -70,7 +70,12 @@ int rx(struct connection *conn, enum conn_state
>>>> next_state)
>>>>        int ret;
>>>>
>>>>        ret = read(conn->fd, conn->rx_buf, conn->rx_length);
>>>> -     if (!ret || ret<  0) {
>>>> +     if (!ret) {
>>>> +             conn->c_rx_state = C_IO_CLOSED;
>>>> +             return 0;
>>>> +     }
>>>> +
>>>> +     if (ret<  0) {
>>>>                if (errno != EAGAIN)
>>>>                        conn->c_rx_state = C_IO_CLOSED;
>>>>                return 0;
>>>> --
>>>> 1.7.1
>>>>
>>>> --
>>>> sheepdog mailing list
>>>> sheepdog at lists.wpkg.org
>>>> http://lists.wpkg.org/mailman/listinfo/sheepdog
>>> --
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