Add peek APIs to std::net
Adds "peek" APIs to `std::net` sockets, including:
- `UdpSocket.peek()`
- `UdpSocket.peek_from()`
- `TcpStream.peek()`
These methods enable socket reads without side-effects. That is, repeated calls to `peek()` return identical data. This is accomplished by providing the POSIX flag `MSG_PEEK` to the underlying socket read operations.
This also moves the current implementation of `recv_from` out of the platform-independent `sys_common` and into respective `sys/windows` and `sys/unix` implementations. This allows for more platform-dependent implementations where necessary.
Fixes#38980
These methods enable socket reads without side-effects. That is,
repeated calls to peek() return identical data. This is accomplished
by providing the POSIX flag MSG_PEEK to the underlying socket read
operations.
This also moves the current implementation of recv_from out of the
platform-independent sys_common and into respective sys/windows and
sys/unix implementations. This allows for more platform-dependent
implementations.
This is done by adding a function that can return a filename
to pass to backtrace_create_state. The filename is obtained in
a safe way by first getting the filename, locking the file so it can't
be moved, and then getting the filename again and making sure it's the same.
See: https://github.com/rust-lang/rust/pull/37359#issuecomment-260123399
Issue: #33985
