Re: Multiple connection retries to the same IP address

2016-04-18 17:56 GMT+01:00 Jan Blom <[email protected]>:
> Hello,
>
> I'm using FreeTDS 0.95 and have been puzzled why the connection timeout setting seemed not to work. Digging into the problem I notice the same target IP address always appear three times, for instance looking at the config dump from osql. I have provided the fqdn name for the host in freetds.conf.
>
> The FreeTDS implementation will loop over all IP addresses when trying to connect if there is a failure. This results in a 3x total timeout duration compared to the configuration. I cannot see a good reason for this logic, given it is the same IP address in all three attempts.
>
> The reason is that the call to getaddrinfo (in tds/config.c) doesn't send in any preference regarding address type. Therefore we get back something like this:
>
> 1.
> Family        : AF_INET
> Type          : SOCK_STREAM
> Protocol      : IPPROTO_TCP
> Socket address: ('23.235.43.223', 0)
>
> 2.
> Family        : AF_INET
> Type          : SOCK_DGRAM
> Protocol      : IPPROTO_UDP
> Socket address: ('23.235.43.223', 0)
>
> 3.
> Family        : AF_INET
> Type          : SOCK_RAW
> Protocol      : IPPROTO_IP
> Socket address: ('23.235.43.223', 0)
>
> However, later on , when we actually connect the socket we will use SOCK_STREAM only. We don't care about UDP or raw sockets.
>
> My assumption would be that the tds_lookup_host() function should set
>                 hints.ai_socktype = SOCK_STREAM;
>
> This will result in only #1 above in return.
>
> Does this make sense or am I missing something here?
>
>
> Thanks for your time and support!
> Jan Blom
>


Make sense. It's just that the change was quite recent, previously we
took into account just the first address so we didn't had this issue.
I think your suggestion should go as a patch.

Frediano