Re: [Qemu-devel] [PATCH 3/4] net: split hostname and service by last colon

[Kevin Wolf <kwolf@redhat.com>]

Am 02.03.2012 20:54, schrieb Laine Stump:
> On 03/02/2012 05:35 AM, Kevin Wolf wrote:
>> Am 02.03.2012 10:58, schrieb Amos Kong:
>>> On 02/03/12 11:38, Amos Kong wrote:
>>>>>> --- a/net.c
>>>>>> +++ b/net.c
>>>>>> @@ -84,7 +84,7 @@ static int get_str_sep(char *buf, int buf_size,
>>>>>> const char **pp, int sep)
>>>>>>       const char *p, *p1;
>>>>>>       int len;
>>>>>>       p = *pp;
>>>>>> -    p1 = strchr(p, sep);
>>>>>> +    p1 = strrchr(p, sep);
>>>>>>       if (!p1)
>>>>>>           return -1;
>>>>>>       len = p1 - p;
>>>>> And what if the port isn't specified? I think you would erroneously
>>>>> interpret the last part of the IP address as port.
>>> Hi Kevin, port must be specified in '-incoming' parameters and migrate 
>>> monitor cmd.
>>>
>>>   qemu-kvm ... -incoming tcp:$host:$port
>>>   (qemu) migrate -d tcp:$host:$port
>>>
>>>
>>> If use boot up guest by wrong cmdline, qemu will report an error msg.
>>>
>>> # ./x86_64-softmmu/qemu-system-x86_64 --enable-kvm -boot n -incoming 
>>> tcp:2312::8272 -monitor stdio
>>> qemu-system-x86_64: qemu: getaddrinfo: Name or service not known
>>> tcp_server_start: Invalid argument
>>> Migration failed. Exit code tcp:2312::8272(-22), exiting.
>> Which is because 2312: isn't a valid IP address, right? But what if you
>> have something like 2312::1234:8272? If you misinterpret the 8272 as a
>> port number, the remaining address is still a valid IPv6 address.
> 
> This is made irrelevant by PATCH 4/4, which allows for the IP address to
> be placed inside brackets:
> 
>    [2312::8272]:port
> 
> (at least it's irrelevant if your documentation *requires* brackets for
> all numeric ipv6-address:port pairs, which is strongly recommended by
> RFC 5952). It really is impossible to disambiguate the meaning of the
> final ":nnnn" unless you require these brackets (or 1) require full
> specification of all potential colons in the IPv6 address or require
> that the port *always* be specified, neither of which seem acceptable to
> me).

Here you're actually explaining why it's not irrelevant. You don't want
to enforce port numbers, so 2312::1234:8272 must be interpreted as an
IPv6 address without a port. This code however would take 8727 as the
port and 2312::1234 as the IPv6 address, which is not what you expected
(even after brackets are allowed - they don't make a difference because
the example doesn't use brackets).

Kevin