Rollup merge of #145327 - joboet:net-addr-sgx-hack, r=tgross35

std: make address resolution weirdness local to SGX

Currently, the implementations of `TcpStream::connect` and its cousins take an `io::Result<&SocketAddr>` as argument, which is very weird, as most of them then `?`-try the result immediately to access the actual address. This weirdness is however necessitated by a peculiarity of the SGX networking implementation:

SGX doesn't support DNS resolution but rather accepts hostnames in the same place as socket addresses. So, to make e.g.
```rust
TcpStream::connect("example.com:80")`
```
work, the DNS lookup returns a special error (`NonIpSockAddr`) instead, which contains the hostname being looked up. When `.to_socket_addrs()` fails, the `each_addr` function used to select an address will pass the error to the inner `TcpStream::connect` implementation, which in SGX's case will inspect the error and try recover the hostname from it. If
that succeeds, it continues with the found hostname.

This is pretty obviously a terrible hack and leads to buggy code (for instance, when users use the result of `.to_socket_addrs()` in their own `ToSocketAddrs` implementation to select from a list of possible URLs, the only URL used will be that of the last item tried). Still, without changes to the SGX usercall ABI, it cannot be avoided.

Therefore, this PR aims to minimise the impact of that weirdness and remove it from all non-SGX platforms. The inner `TcpStream::connect`, et al. functions now receive the `ToSocketAddrs` type directly and call `each_addr` (which is moved to `sys::net::connection`) themselves. On SGX, the implementation uses a special `each_addr` which contains the whole pass-hostname-through-error hack.

As well as making the code cleaner, this also opens up the possibility of reusing newly created sockets even if a connection request fails – but I've left that for another PR.

CC `@raoulstrackx`

1 files changed, 0 insertions, 21 deletions

diff --git a/library/std/src/net/mod.rs b/library/std/src/net/mod.rs
index ddd3b68dd2d..40f1a93e39d 100644
--- a/library/std/src/net/mod.rs
+++ b/library/std/src/net/mod.rs
@@ -34,7 +34,6 @@ pub use self::tcp::IntoIncoming;
 pub use self::tcp::{Incoming, TcpListener, TcpStream};
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use self::udp::UdpSocket;
-use crate::io::{self, ErrorKind};
 
 mod ip_addr;
 mod socket_addr;
@@ -67,23 +66,3 @@ pub enum Shutdown {
     #[stable(feature = "rust1", since = "1.0.0")]
     Both,
 }
-
-fn each_addr<A: ToSocketAddrs, F, T>(addr: A, mut f: F) -> io::Result<T>
-where
-    F: FnMut(io::Result<&SocketAddr>) -> io::Result<T>,
-{
-    let addrs = match addr.to_socket_addrs() {
-        Ok(addrs) => addrs,
-        Err(e) => return f(Err(e)),
-    };
-    let mut last_err = None;
-    for addr in addrs {
-        match f(Ok(&addr)) {
-            Ok(l) => return Ok(l),
-            Err(e) => last_err = Some(e),
-        }
-    }
-    Err(last_err.unwrap_or_else(|| {
-        io::const_error!(ErrorKind::InvalidInput, "could not resolve to any addresses")
-    }))
-}