//! 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().into_owned(),

            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?");

    }

}