Re: [Qemu-devel] [PATCH v7 2/5] sockets: Change inet_parse() to accept address specification without port

[Kevin Wolf <kwolf@redhat.com>]

Am 18.09.2012 15:31, schrieb Paolo Bonzini:
> Il 18/09/2012 15:22, Kevin Wolf ha scritto:
>> Am 17.09.2012 17:23, schrieb Bharata B Rao:
>>> sockets: Change inet_parse() to accept address specification without port
>>>
>>> From: Bharata B Rao <bharata@linux.vnet.ibm.com>
>>>
>>> inet_parse() expects address:port. Change it to work without explicit port
>>> specification. In addition, don't depend solely on the return value of
>>
>> Things like "in addition" in a commit message are almost always a sign
>> that the patch should be split in two.
>>
>>> sscanf but also consider the value obtained for %n directive used in sscanf.
>>> This ensures that the scanning of malformed inet address isn't flagged as
>>> success.
>>
>> Can you give an example string that would be falsely accepted? To me the
>> old checks look fine (even though the new ones are a little bit easier
>> to read, so even if they don't fix anything, they might be worth doing).
> 
> "localhost" would fail to be parsed:
> 
> -        if (2 != sscanf(str,"%64[^:]:%32[^,]%n",addr,port,&pos)) {
> +        ret = sscanf(str, "%64[^:]%n:%32[^,]%n", addr, &addr_pos,
> +            port, &port_pos);
> +        if (addr_pos == -1 || ret == EOF) {
> 
> because the : in the format string would not match and sscanf would
> return 1.

Yes, that's the part with making the port optional.

Bharata also claims that "scanning of malformed inet address" could
falsely succeed before, which I can't see (but which I suspect is what
the first two hunks of the patch are meant to address).

> However, is it correct to set the port unconditionally to an empty
> string?  Your usecase makes sense, but perhaps the default port be
> passed as an extra parameter to inet_parse instead.

I thought about this, too, but didn't care enough to mention it. Now
that we're two, yes, I'd like adding a default port parameter.

Kevin