IPv6 support

[mordner]

It seems IPv6 targets are not supported.
On my machine I get AAAA records which are preferred for time.google.com.

$ cargo test
    Updating registry `https://github.com/rust-lang/crates.io-index`
 Downloading chrono v0.4.6
 Downloading num-traits v0.2.6
 Downloading num-integer v0.1.39
   Compiling num-traits v0.2.6
   Compiling num-integer v0.1.39
   Compiling cfg-if v0.1.5
   Compiling custom_derive v0.1.7
   Compiling libc v0.2.43
   Compiling byteorder v1.2.6
   Compiling conv v0.3.3
   Compiling log v0.4.5
   Compiling log v0.3.9
   Compiling time v0.1.40
   Compiling ntp v0.5.0 (file:///home/mordner/projects/ntp)
   Compiling chrono v0.4.6
    Finished dev [unoptimized + debuginfo] target(s) in 8.01s
     Running target/debug/deps/ntp-f3e12cb312a2b718

running 2 tests
test test_request_ntp_org ... ok
test test_request_google ... FAILED

failures:

---- test_request_google stdout ----
thread 'test_request_google' panicked at 'Failed to get a ntp packet from time.google.com: Os { code: 97, kind: Other, message: "Address family not supported by protocol" }', libcore/result.rs:945:5
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
stack backtrace:
   0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace
             at libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1: std::sys_common::backtrace::print
             at libstd/sys_common/backtrace.rs:71
             at libstd/sys_common/backtrace.rs:59
   2: std::panicking::default_hook::{{closure}}
             at libstd/panicking.rs:211
   3: std::panicking::default_hook
             at libstd/panicking.rs:221
   4: std::panicking::rust_panic_with_hook
             at libstd/panicking.rs:475
   5: std::panicking::continue_panic_fmt
             at libstd/panicking.rs:390
   6: rust_begin_unwind
             at libstd/panicking.rs:325
   7: core::panicking::panic_fmt
             at libcore/panicking.rs:77
   8: core::result::unwrap_failed
             at /checkout/src/libcore/macros.rs:26
   9: <core::result::Result<T, E>>::expect
             at /checkout/src/libcore/result.rs:809
  10: ntp::test_request_google
             at src/lib.rs:113
  11: ntp::__test::TESTS::{{closure}}
             at src/lib.rs:111
  12: core::ops::function::FnOnce::call_once
             at /checkout/src/libcore/ops/function.rs:223
  13: <F as alloc::boxed::FnBox<A>>::call_box
             at libtest/lib.rs:1451
             at /checkout/src/libcore/ops/function.rs:223
             at /checkout/src/liballoc/boxed.rs:642
  14: __rust_maybe_catch_panic
             at libpanic_unwind/lib.rs:105


failures:
    test_request_google

test result: FAILED. 1 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out

error: test failed, to rerun pass '--lib'

$ host time.google.com
time.google.com has address 216.239.35.8
time.google.com has IPv6 address 2001:4860:4806:8::

$ host 0.pool.ntp.org
0.pool.ntp.org has address 93.90.200.201
0.pool.ntp.org has address 193.175.73.151
0.pool.ntp.org has address 78.47.234.59
0.pool.ntp.org has address 81.7.16.52

I guess binding to an IPv4 socket has something to do with it:
https://github.com/JeffBelgum/ntp/blob/master/src/lib.rs#L85

[mitchmindtree]

Thanks for the issue @mordner!

That function is kind of just a "simple" helper API on top of the protocol implementation itself - we should probably break up the internals of it into some smaller reusable functions to make it easier to specify what socket you want to bind to, etc.