Does CFHostGetAddressing() support ipv6 DNS entrie

问题:

I am trying to use CFHostGetAddressing to do a simple DNS lookup. However, I notice that it returns an array of sockaddr structs, which I guess means it can only do IPV4.

Is there a way to support DNS entries with IPV6 addresses in iOS? Perhaps a similar API that returns an array of sockaddr_storage structs?

回答1:

The CFHostGetAddressing() documentation might be misleading, because struct sockaddr is a structure that covers all the common elements of the various socket addresses (IPv4, IPv6, ...). It is usually only used to pass a generic pointer to the socket functions.

Actually CFHostGetAddressing() works well with IPv6. It returns an array of CFData elements where each element contains a struct sockaddr_in or a struct sockaddr_in6.

Using the code from your previous question as a starting point, the following should work:

let hostRef = CFHostCreateWithName(kCFAllocatorDefault, "localhost").takeRetainedValue()
var resolved = CFHostStartInfoResolution(hostRef, CFHostInfoType.Addresses, nil)
let addresses = CFHostGetAddressing(hostRef, &resolved).takeRetainedValue() as NSArray

for addr in addresses as [NSData] {
    var sockaddr = UnsafePointer<sockaddr_storage>.alloc(1)
    addr.getBytes(sockaddr, length: sizeof(sockaddr_storage))
    // ...
    sockaddr.destroy()
}