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

[Amos Kong]

----- Original Message -----
> 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).

In the migration context, host/port are all necessary, so it's right to parse 
"8272" to a port.
However, for IPv6 brackets must be mandatory if you require a port.


BTW, the DNS delay issue existed in the past (gethostbyname()), it should be 
fixed by another patchset.
I will post my V2 (without fix of DNS delay) later.

> 
> Kevin
>