//! Query network interface addresses
//!
//! Uses the Linux and/or BSD specific function `getifaddrs` to query the list
//! of interfaces and their associated addresses.
use cfg_if::cfg_if;
#[cfg(apple_targets)]
use std::convert::TryFrom;
use std::ffi;
use std::iter::Iterator;
use std::mem;
use std::option::Option;
use crate::net::if_::*;
use crate::sys::socket::{SockaddrLike, SockaddrStorage};
use crate::{Errno, Result};
/// Describes a single address for an interface as returned by `getifaddrs`.
#[derive(Clone, Debug, Eq, Hash, PartialEq)]
pub struct InterfaceAddress {
/// Name of the network interface
pub interface_name: String,
/// Flags as from `SIOCGIFFLAGS` ioctl
pub flags: InterfaceFlags,
/// Network address of this interface
pub address: Option<SockaddrStorage>,
/// Netmask of this interface
pub netmask: Option<SockaddrStorage>,
/// Broadcast address of this interface, if applicable
pub broadcast: Option<SockaddrStorage>,
/// Point-to-point destination address
pub destination: Option<SockaddrStorage>,
}
cfg_if! {
if #[cfg(any(linux_android, target_os = "emscripten", target_os = "fuchsia"))] {
fn get_ifu_from_sockaddr(info: &libc::ifaddrs) -> *const libc::sockaddr {
info.ifa_ifu
}
} else {
fn get_ifu_from_sockaddr(info: &libc::ifaddrs) -> *const libc::sockaddr {
info.ifa_dstaddr
}
}
}
/// Workaround a bug in XNU where netmasks will always have the wrong size in
/// the sa_len field due to the kernel ignoring trailing zeroes in the structure
/// when setting the field. See
https://github.com/nix-rust/nix/issues/1709#issuecomment-1199304470
///
/// To fix this, we stack-allocate a new sockaddr_storage, zero it out, and
/// memcpy sa_len of the netmask to that new storage. Finally, we reset the
/// ss_len field to sizeof(sockaddr_storage). This is supposedly valid as all
/// members of the sockaddr_storage are "ok" with being zeroed out (there are
/// no pointers).
#[cfg(apple_targets)]
unsafe fn workaround_xnu_bug(info: &libc::ifaddrs) -> Option<SockaddrStorage> {
let src_sock = info.ifa_netmask;
if src_sock.is_null() {
return None;
}
let mut dst_sock = mem::MaybeUninit::<libc::sockaddr_storage>::zeroed();
let dst_sock = unsafe {
// memcpy only sa_len bytes, assume the rest is zero
std::ptr::copy_nonoverlapping(
src_sock as *const u8,
dst_sock.as_mut_ptr().cast(),
(*src_sock).sa_len.into(),
);
// Initialize ss_len to sizeof(libc::sockaddr_storage).
(*dst_sock.as_mut_ptr()).ss_len =
u8::try_from(mem::size_of::<libc::sockaddr_storage>()).unwrap();
dst_sock.assume_init()
};
let dst_sock_ptr =
&dst_sock as *const libc::sockaddr_storage as *const libc::sockaddr;
unsafe { SockaddrStorage::from_raw(dst_sock_ptr, None) }
}
impl InterfaceAddress {
/// Create an `InterfaceAddress` from the libc struct.
fn from_libc_ifaddrs(info: &libc::ifaddrs) -> InterfaceAddress {
let ifname = unsafe { ffi::CStr::from_ptr(info.ifa_name) };
let address = unsafe { SockaddrStorage::from_raw(info.ifa_addr, None) };
#[cfg(apple_targets)]
let netmask = unsafe { workaround_xnu_bug(info) };
#[cfg(not(apple_targets))]
let netmask =
unsafe { SockaddrStorage::from_raw(info.ifa_netmask, None) };
let mut addr = InterfaceAddress {
interface_name: ifname.to_string_lossy().to_string(),
flags: InterfaceFlags::from_bits_truncate(
info.ifa_flags as IflagsType,
),
address,
netmask,
broadcast: None,
destination: None,
};
let ifu = get_ifu_from_sockaddr(info);
if addr.flags.contains(InterfaceFlags::IFF_POINTOPOINT) {
addr.destination = unsafe { SockaddrStorage::from_raw(ifu, None) };
} else if addr.flags.contains(InterfaceFlags::IFF_BROADCAST) {
addr.broadcast = unsafe { SockaddrStorage::from_raw(ifu, None) };
}
addr
}
}
/// Holds the results of `getifaddrs`.
///
/// Use the function `getifaddrs` to create this Iterator. Note that the
/// actual list of interfaces can be iterated once and will be freed as
/// soon as the Iterator goes out of scope.
#[derive(Debug, Eq, Hash, PartialEq)]
pub struct InterfaceAddressIterator {
base: *mut libc::ifaddrs,
next: *mut libc::ifaddrs,
}
impl Drop for InterfaceAddressIterator {
fn drop(&mut self) {
unsafe { libc::freeifaddrs(self.base) };
}
}
impl Iterator for InterfaceAddressIterator {
type Item = InterfaceAddress;
fn next(&mut self) -> Option<<Self as Iterator>::Item> {
match unsafe { self.next.as_ref() } {
Some(ifaddr) => {
self.next = ifaddr.ifa_next;
Some(InterfaceAddress::from_libc_ifaddrs(ifaddr))
}
None => None,
}
}
}
/// Get interface addresses using libc's `getifaddrs`
///
/// Note that the underlying implementation differs between OSes. Only the
/// most common address families are supported by the nix crate (due to
/// lack of time and complexity of testing). The address family is encoded
/// in the specific variant of `SockaddrStorage` returned for the fields
/// `address`, `netmask`, `broadcast`, and `destination`. For any entry not
/// supported, the returned list will contain a `None` entry.
///
/// # Example
/// ```
/// let addrs = nix::ifaddrs::getifaddrs().unwrap();
/// for ifaddr in addrs {
/// match ifaddr.address {
/// Some(address) => {
/// println!("interface {} address {}",
/// ifaddr.interface_name, address);
/// },
/// None => {
/// println!("interface {} with unsupported address family",
/// ifaddr.interface_name);
/// }
/// }
/// }
/// ```
pub fn getifaddrs() -> Result<InterfaceAddressIterator> {
let mut addrs = mem::MaybeUninit::<*mut libc::ifaddrs>::uninit();
unsafe {
Errno::result(libc::getifaddrs(addrs.as_mut_ptr())).map(|_| {
InterfaceAddressIterator {
base: addrs.assume_init(),
next: addrs.assume_init(),
}
})
}
}
#[cfg(test)]
mod tests {
use super::*;
// Only checks if `getifaddrs` can be invoked without panicking.
#[test]
fn test_getifaddrs() {
let _ = getifaddrs();
}
// Ensures getting the netmask works, and in particular that
// `workaround_xnu_bug` works properly.
#[test]
fn test_getifaddrs_netmask_correct() {
let addrs = getifaddrs().unwrap();
for iface in addrs {
let sock = if let Some(sock) = iface.netmask {
sock
} else {
continue;
};
if sock.family() == Some(crate::sys::socket::AddressFamily::Inet) {
let _ = sock.as_sockaddr_in().unwrap();
return;
} else if sock.family()
== Some(crate::sys::socket::AddressFamily::Inet6)
{
let _ = sock.as_sockaddr_in6().unwrap();
return;
}
}
panic!("No address?");
}
}
