Re: [RFC PATCH v1 2/7] char-socket: return -1 in case of disconnect during tcp_chr_write

[Anton Nefedov]

> On Thu, Apr 23, 2020 at 8:43 PM Dima Stepanov <address@hidden> wrote:
>> The problem is that vhost_user_write doesn't get an error after
>> disconnect and try to call vhost_user_read(). The tcp_chr_write()
>> routine should return -1 in case of disconnect. Indicate the EIO error
>> if this routine is called in the disconnected state.
>>
>> Signed-off-by: Dima Stepanov <address@hidden>
>> ---
>>   chardev/char-socket.c | 8 +++++---
>>   1 file changed, 5 insertions(+), 3 deletions(-)
>>
>> diff --git a/chardev/char-socket.c b/chardev/char-socket.c
>> index 185fe38..c128cca 100644
>> --- a/chardev/char-socket.c
>> +++ b/chardev/char-socket.c
>> @@ -175,14 +175,16 @@ static int tcp_chr_write(Chardev *chr, const uint8_t 
>> *buf, int len)
>>           if (ret < 0 && errno != EAGAIN) {
>>               if (tcp_chr_read_poll(chr) <= 0) {
>>                   tcp_chr_disconnect_locked(chr);
>> -                return len;
>> +                /* Return an error since we made a disconnect. */
>> +                return ret;
> 
> Looks ok, but this return was introduced in commit
> b0a335e351103bf92f3f9d0bd5759311be8156ac ("qemu-char: socket backend:
> disconnect on write error"). It doesn't say why it didn't return -1
> though. Anton, could you review? thanks
> 

hej,

I think I had no special intent but to repeat the behaviour as in the
snippet below, that is to return @len when the socket is disconnected.

Seems that tcp_chr_write() worked that way since the very beginning
(commit 0bab00f).

It looks ok to me to return an error though. If some guest device doesnt
expect that I guess it should ignore the error on its side.

>>               } /* else let the read handler finish it properly */
>>           }
>>
>>           return ret;
>>       } else {
>> -        /* XXX: indicate an error ? */
>> -        return len;
>> +        /* Indicate an error. */
>> +        errno = EIO;
>> +        return -1;
>>       }
>>   }