Re: [libvirt] [PATCH] 1/3 Add IPv4 and IPv6 parsing routines
On Wed, Oct 14, 2009 at 12:51:32PM +0200, Daniel Veillard wrote:
On Wed, Oct 14, 2009 at 10:49:20AM +0100, Daniel P. Berrange wrote:
> On Tue, Oct 13, 2009 at 04:12:47PM +0200, Daniel Veillard wrote:
> > * src/util/util.h src/util/util.c: two new functions virParseIPv4
> > and virParseIPv6
>
> I think this should just be a thin wrapper around getaddrinfo()
> which already knows how to parse all possible address types.
Are we allowing all possible address types in the XML ?
Well at this time we only allow IPv4 addreses in this, so we
would want to pass the AF_INET flag to restrict it. Other
areas of libvirt which could uses this code would be more
flexible. We've got an open RFE for IPv6 support
https://bugzilla.redhat.com/show_bug.cgi?id=514749
I based that parsing routing in a large part as a syntactic check
on the allowed set of addresses. For example I didn't allow
::ffff:12.34.56.78
kind of IPv6 syntax.
Why shouldn't we allow that - its valid IPv6 address syntax }
> If we avoid a custom typedef, and just use 'struct
sockaddr_storage'
> this in turn makes it easy for callers to pass the result straight
> into any socket API calls they might use. eg this could all be done
> with a couple of lines of code
>
>
> That would automatically cope with both IPv4 / 6 addresses. If
> we want to restrict it we could add a 3rd argument, 'int family'
> and use that to set hints.ai_family field - the caller would
> just pass AF_INET or AF_INET6 to specify a particular type, or
> leave it at 0 to allow any type.
Dunno, I find the getaddrinfo interface and the hints stuff
fairly incomprehensible. When I see the OpenGroup definition of
struct sockaddr_storage
struct sockaddr_storage {
sa_family_t ss_family; /* Address family. */
/*
* Following fields are implementation-defined.
*/
char _ss_pad1[_SS_PAD1SIZE];
/* 6-byte pad; this is to make implementation-defined
pad up to alignment field that follows explicit in
the data structure. */
int64_t _ss_align; /* Field to force desired structure
storage alignment. */
char _ss_pad2[_SS_PAD2SIZE];
/* 112-byte pad to achieve desired size,
_SS_MAXSIZE value minus size of ss_family
__ss_pad1, __ss_align fields is 112. */
};
NB it is not intended to use the internals of the sockaddr_storage
struct, with the exception of the ss_family field. It is provided
as a struct that is guarenteed large enough to store any type of
address. To use the data, you'd cast to the appropriate struct
based on ss_family.
eg, if ss_family == AF_INET, then you can cast to
struct sockaddr_in
which has a 'struct in_addr sin_addr' field available to get
the raw address - in this case 'in_addr' is just an int32
For AF_INET6, you would cast to sockaddr_in6, which has a
'struct in6_addr sin6_addr' which gives you easy acess to
the 16 byte array of the address.
I'm not too enthusiastic about using this for internal APIs.
And I don't see how I would check ranges for the IP addresses based
on this. Actually I don't find it helps to calculate a range,
and I prefer my good old arrays of well defined ints for that purpose.
The sockaddr_in/in6 structs both give you an array of bytes in exactly
the same manner
Daniel
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