nix/
ifaddrs.rs

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1//! Query network interface addresses
2//!
3//! Uses the Linux and/or BSD specific function `getifaddrs` to query the list
4//! of interfaces and their associated addresses.
5
6use cfg_if::cfg_if;
7#[cfg(apple_targets)]
8use std::convert::TryFrom;
9use std::ffi;
10use std::iter::Iterator;
11use std::mem;
12use std::option::Option;
13
14use crate::net::if_::*;
15use crate::sys::socket::{SockaddrLike, SockaddrStorage};
16use crate::{Errno, Result};
17
18/// Describes a single address for an interface as returned by `getifaddrs`.
19#[derive(Clone, Debug, Eq, Hash, PartialEq)]
20pub struct InterfaceAddress {
21    /// Name of the network interface
22    pub interface_name: String,
23    /// Flags as from `SIOCGIFFLAGS` ioctl
24    pub flags: InterfaceFlags,
25    /// Network address of this interface
26    pub address: Option<SockaddrStorage>,
27    /// Netmask of this interface
28    pub netmask: Option<SockaddrStorage>,
29    /// Broadcast address of this interface, if applicable
30    pub broadcast: Option<SockaddrStorage>,
31    /// Point-to-point destination address
32    pub destination: Option<SockaddrStorage>,
33}
34
35cfg_if! {
36    if #[cfg(any(linux_android, target_os = "emscripten", target_os = "fuchsia"))] {
37        fn get_ifu_from_sockaddr(info: &libc::ifaddrs) -> *const libc::sockaddr {
38            info.ifa_ifu
39        }
40    } else {
41        fn get_ifu_from_sockaddr(info: &libc::ifaddrs) -> *const libc::sockaddr {
42            info.ifa_dstaddr
43        }
44    }
45}
46
47/// Workaround a bug in XNU where netmasks will always have the wrong size in
48/// the sa_len field due to the kernel ignoring trailing zeroes in the structure
49/// when setting the field. See https://github.com/nix-rust/nix/issues/1709#issuecomment-1199304470
50///
51/// To fix this, we stack-allocate a new sockaddr_storage, zero it out, and
52/// memcpy sa_len of the netmask to that new storage. Finally, we reset the
53/// ss_len field to sizeof(sockaddr_storage). This is supposedly valid as all
54/// members of the sockaddr_storage are "ok" with being zeroed out (there are
55/// no pointers).
56#[cfg(apple_targets)]
57unsafe fn workaround_xnu_bug(info: &libc::ifaddrs) -> Option<SockaddrStorage> {
58    let src_sock = info.ifa_netmask;
59    if src_sock.is_null() {
60        return None;
61    }
62
63    let mut dst_sock = mem::MaybeUninit::<libc::sockaddr_storage>::zeroed();
64
65    let dst_sock = unsafe {
66        // memcpy only sa_len bytes, assume the rest is zero
67        std::ptr::copy_nonoverlapping(
68            src_sock as *const u8,
69            dst_sock.as_mut_ptr().cast(),
70            (*src_sock).sa_len.into(),
71        );
72
73        // Initialize ss_len to sizeof(libc::sockaddr_storage).
74        (*dst_sock.as_mut_ptr()).ss_len =
75            u8::try_from(mem::size_of::<libc::sockaddr_storage>()).unwrap();
76        dst_sock.assume_init()
77    };
78
79    let dst_sock_ptr =
80        &dst_sock as *const libc::sockaddr_storage as *const libc::sockaddr;
81
82    unsafe { SockaddrStorage::from_raw(dst_sock_ptr, None) }
83}
84
85impl InterfaceAddress {
86    /// Create an `InterfaceAddress` from the libc struct.
87    fn from_libc_ifaddrs(info: &libc::ifaddrs) -> InterfaceAddress {
88        let ifname = unsafe { ffi::CStr::from_ptr(info.ifa_name) };
89        let address = unsafe { SockaddrStorage::from_raw(info.ifa_addr, None) };
90        #[cfg(apple_targets)]
91        let netmask = unsafe { workaround_xnu_bug(info) };
92        #[cfg(not(apple_targets))]
93        let netmask =
94            unsafe { SockaddrStorage::from_raw(info.ifa_netmask, None) };
95        let mut addr = InterfaceAddress {
96            interface_name: ifname.to_string_lossy().to_string(),
97            flags: InterfaceFlags::from_bits_truncate(
98                info.ifa_flags as IflagsType,
99            ),
100            address,
101            netmask,
102            broadcast: None,
103            destination: None,
104        };
105
106        let ifu = get_ifu_from_sockaddr(info);
107        if addr.flags.contains(InterfaceFlags::IFF_POINTOPOINT) {
108            addr.destination = unsafe { SockaddrStorage::from_raw(ifu, None) };
109        } else if addr.flags.contains(InterfaceFlags::IFF_BROADCAST) {
110            addr.broadcast = unsafe { SockaddrStorage::from_raw(ifu, None) };
111        }
112
113        addr
114    }
115}
116
117/// Holds the results of `getifaddrs`.
118///
119/// Use the function `getifaddrs` to create this Iterator. Note that the
120/// actual list of interfaces can be iterated once and will be freed as
121/// soon as the Iterator goes out of scope.
122#[derive(Debug, Eq, Hash, PartialEq)]
123pub struct InterfaceAddressIterator {
124    base: *mut libc::ifaddrs,
125    next: *mut libc::ifaddrs,
126}
127
128impl Drop for InterfaceAddressIterator {
129    fn drop(&mut self) {
130        unsafe { libc::freeifaddrs(self.base) };
131    }
132}
133
134impl Iterator for InterfaceAddressIterator {
135    type Item = InterfaceAddress;
136    fn next(&mut self) -> Option<<Self as Iterator>::Item> {
137        match unsafe { self.next.as_ref() } {
138            Some(ifaddr) => {
139                self.next = ifaddr.ifa_next;
140                Some(InterfaceAddress::from_libc_ifaddrs(ifaddr))
141            }
142            None => None,
143        }
144    }
145}
146
147/// Get interface addresses using libc's `getifaddrs`
148///
149/// Note that the underlying implementation differs between OSes. Only the
150/// most common address families are supported by the nix crate (due to
151/// lack of time and complexity of testing). The address family is encoded
152/// in the specific variant of `SockaddrStorage` returned for the fields
153/// `address`, `netmask`, `broadcast`, and `destination`. For any entry not
154/// supported, the returned list will contain a `None` entry.
155///
156/// # Example
157/// ```
158/// let addrs = nix::ifaddrs::getifaddrs().unwrap();
159/// for ifaddr in addrs {
160///   match ifaddr.address {
161///     Some(address) => {
162///       println!("interface {} address {}",
163///                ifaddr.interface_name, address);
164///     },
165///     None => {
166///       println!("interface {} with unsupported address family",
167///                ifaddr.interface_name);
168///     }
169///   }
170/// }
171/// ```
172pub fn getifaddrs() -> Result<InterfaceAddressIterator> {
173    let mut addrs = mem::MaybeUninit::<*mut libc::ifaddrs>::uninit();
174    unsafe {
175        Errno::result(libc::getifaddrs(addrs.as_mut_ptr())).map(|_| {
176            InterfaceAddressIterator {
177                base: addrs.assume_init(),
178                next: addrs.assume_init(),
179            }
180        })
181    }
182}
183
184#[cfg(test)]
185mod tests {
186    use super::*;
187
188    // Only checks if `getifaddrs` can be invoked without panicking.
189    #[test]
190    fn test_getifaddrs() {
191        let _ = getifaddrs();
192    }
193
194    // Ensures getting the netmask works, and in particular that
195    // `workaround_xnu_bug` works properly.
196    #[test]
197    fn test_getifaddrs_netmask_correct() {
198        let addrs = getifaddrs().unwrap();
199        for iface in addrs {
200            let sock = if let Some(sock) = iface.netmask {
201                sock
202            } else {
203                continue;
204            };
205            if sock.family() == Some(crate::sys::socket::AddressFamily::Inet) {
206                let _ = sock.as_sockaddr_in().unwrap();
207                return;
208            } else if sock.family()
209                == Some(crate::sys::socket::AddressFamily::Inet6)
210            {
211                let _ = sock.as_sockaddr_in6().unwrap();
212                return;
213            }
214        }
215        panic!("No address?");
216    }
217}
nix/ifaddrs.rs

nix/
ifaddrs.rs
