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Don't assume memory layout of std::net::SocketAddr (master) #122

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Nov 9, 2020
Merged

Don't assume memory layout of std::net::SocketAddr (master) #122

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4c91cf6
Don't assume memory layout of std::net::SocketAddr
faern Nov 8, 2020
86fd2dd
Add tests for SockAddr conversion
faern Nov 8, 2020
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145 changes: 119 additions & 26 deletions src/sockaddr.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,9 +3,11 @@ use std::net::{SocketAddr, SocketAddrV4, SocketAddrV6};
use std::{fmt, ptr};

use crate::sys::{
c_int, sa_family_t, sockaddr, sockaddr_in, sockaddr_in6, sockaddr_storage, socklen_t, AF_INET,
sa_family_t, sockaddr, sockaddr_in, sockaddr_in6, sockaddr_storage, socklen_t, AF_INET,
AF_INET6,
};
#[cfg(windows)]
use winapi::shared::ws2ipdef::SOCKADDR_IN6_LH_u;

/// The address of a socket.
///
Expand All @@ -24,7 +26,7 @@ impl SockAddr {
/// It is up to the user to ensure the `addr` pointer and `len` length are
/// correct.
pub unsafe fn from_raw_parts(addr: *const sockaddr, len: socklen_t) -> SockAddr {
let mut storage = MaybeUninit::<sockaddr_storage>::uninit();
let mut storage = MaybeUninit::<sockaddr_storage>::zeroed();
ptr::copy_nonoverlapping(
addr as *const _ as *const u8,
storage.as_mut_ptr() as *mut u8,
Expand All @@ -33,7 +35,7 @@ impl SockAddr {
SockAddr {
// This is safe as we written the address to `storage` above.
storage: storage.assume_init(),
len: len,
len,
}
}

Expand All @@ -55,30 +57,50 @@ impl SockAddr {
/// Returns this address as a `SocketAddr` if it is in the `AF_INET` (IP v4)
/// or `AF_INET6` (IP v6) family, otherwise returns `None`.
pub fn as_std(&self) -> Option<SocketAddr> {
self.as_inet()
.map(|a| a.into())
.or_else(|| self.as_inet6().map(|a| a.into()))
if self.storage.ss_family == AF_INET as sa_family_t {
// Safety: if the ss_family field is AF_INET then storage must be a sockaddr_in.
let addr = unsafe { &*(&self.storage as *const _ as *const sockaddr_in) };

let ip = crate::sys::from_in_addr(addr.sin_addr);
let port = u16::from_be(addr.sin_port);
Some(SocketAddr::V4(SocketAddrV4::new(ip, port)))
} else if self.storage.ss_family == AF_INET6 as sa_family_t {
// Safety: if the ss_family field is AF_INET6 then storage must be a sockaddr_in6.
let addr = unsafe { &*(&self.storage as *const _ as *const sockaddr_in6) };

let ip = crate::sys::from_in6_addr(addr.sin6_addr);
let port = u16::from_be(addr.sin6_port);
Some(SocketAddr::V6(SocketAddrV6::new(
ip,
port,
addr.sin6_flowinfo,
#[cfg(unix)]
addr.sin6_scope_id,
#[cfg(windows)]
unsafe {
*addr.u.sin6_scope_id()
},
)))
} else {
None
}
}

/// Returns this address as a `SocketAddrV4` if it is in the `AF_INET`
/// family.
pub fn as_inet(&self) -> Option<SocketAddrV4> {
if self.storage.ss_family as c_int == AF_INET {
let storage: *const sockaddr_storage = (&self.storage) as *const _;
Some(unsafe { *(storage as *const sockaddr_in as *const _) })
} else {
None
match self.as_std() {
Some(SocketAddr::V4(addr)) => Some(addr),
_ => None,
}
}

/// Returns this address as a `SocketAddrV6` if it is in the `AF_INET6`
/// family.
pub fn as_inet6(&self) -> Option<SocketAddrV6> {
if self.storage.ss_family as c_int == AF_INET6 {
let storage: *const sockaddr_storage = (&self.storage) as *const _;
Some(unsafe { *(storage as *const sockaddr_in6 as *const _) })
} else {
None
match self.as_std() {
Some(SocketAddr::V6(addr)) => Some(addr),
_ => None,
}
}
}
Expand All @@ -94,22 +116,67 @@ impl From<SocketAddr> for SockAddr {

impl From<SocketAddrV4> for SockAddr {
fn from(addr: SocketAddrV4) -> SockAddr {
unsafe {
SockAddr::from_raw_parts(
&addr as *const _ as *const _,
mem::size_of::<SocketAddrV4>() as socklen_t,
)
let sockaddr_in = sockaddr_in {
sin_family: AF_INET as sa_family_t,
sin_port: addr.port().to_be(),
sin_addr: crate::sys::to_in_addr(&addr.ip()),
sin_zero: [0; 8],
#[cfg(any(
target_os = "dragonfly",
target_os = "freebsd",
target_os = "ios",
target_os = "macos",
target_os = "netbsd",
target_os = "openbsd"
))]
sin_len: 0,
};
let mut storage = MaybeUninit::<sockaddr_storage>::zeroed();
// Safety: A `sockaddr_in` is memory compatible with a `sockaddr_storage`
unsafe { (storage.as_mut_ptr() as *mut sockaddr_in).write(sockaddr_in) };
SockAddr {
storage: unsafe { storage.assume_init() },
len: mem::size_of::<sockaddr_in>() as socklen_t,
}
}
}

impl From<SocketAddrV6> for SockAddr {
fn from(addr: SocketAddrV6) -> SockAddr {
unsafe {
SockAddr::from_raw_parts(
&addr as *const _ as *const _,
mem::size_of::<SocketAddrV6>() as socklen_t,
)
#[cfg(windows)]
let u = unsafe {
let mut u = mem::zeroed::<SOCKADDR_IN6_LH_u>();
*u.sin6_scope_id_mut() = addr.scope_id();
u
};

let sockaddr_in6 = sockaddr_in6 {
sin6_family: AF_INET6 as sa_family_t,
sin6_port: addr.port().to_be(),
sin6_addr: crate::sys::to_in6_addr(addr.ip()),
sin6_flowinfo: addr.flowinfo(),
#[cfg(unix)]
sin6_scope_id: addr.scope_id(),
#[cfg(windows)]
u,
#[cfg(any(
target_os = "dragonfly",
target_os = "freebsd",
target_os = "ios",
target_os = "macos",
target_os = "netbsd",
target_os = "openbsd"
))]
sin6_len: 0,
#[cfg(any(target_os = "solaris", target_os = "illumos"))]
__sin6_src_id: 0,
};
let mut storage = MaybeUninit::<sockaddr_storage>::zeroed();
// Safety: A `sockaddr_in6` is memory compatible with a `sockaddr_storage`
unsafe { (storage.as_mut_ptr() as *mut sockaddr_in6).write(sockaddr_in6) };
SockAddr {
storage: unsafe { storage.assume_init() },
len: mem::size_of::<sockaddr_in6>() as socklen_t,
}
}
}
Expand All @@ -134,3 +201,29 @@ impl fmt::Debug for SockAddr {
.finish()
}
}

#[cfg(test)]
mod tests {
use super::*;
use std::net::{Ipv4Addr, Ipv6Addr};

#[test]
fn conversion_v4() {
let addr = SocketAddrV4::new(Ipv4Addr::new(1, 2, 3, 4), 9876);
let sockaddr = SockAddr::from(addr);
assert_eq!(sockaddr.family(), AF_INET as sa_family_t);
assert!(sockaddr.as_inet6().is_none());
assert_eq!(sockaddr.as_inet(), Some(addr));
assert_eq!(sockaddr.as_std(), Some(SocketAddr::V4(addr)));
}

#[test]
fn conversion_v6() {
let addr = SocketAddrV6::new(Ipv6Addr::new(1, 2, 3, 4, 5, 6, 7, 8), 9876, 11, 12);
let sockaddr = SockAddr::from(addr);
assert_eq!(sockaddr.family(), AF_INET6 as sa_family_t);
assert!(sockaddr.as_inet().is_none());
assert_eq!(sockaddr.as_inet6(), Some(addr));
assert_eq!(sockaddr.as_std(), Some(SocketAddr::V6(addr)));
}
}
44 changes: 23 additions & 21 deletions src/sys/unix.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -23,7 +23,7 @@ use std::sync::atomic::{AtomicBool, Ordering};
use std::time::Duration;
use std::{cmp, fmt, io, mem};

use libc::{self, c_void, ssize_t};
use libc::{self, c_void, in6_addr, in_addr, ssize_t};

#[cfg(not(target_os = "redox"))]
use crate::RecvFlags;
Expand Down Expand Up @@ -787,13 +787,12 @@ impl Socket {
unsafe {
let imr_interface: libc::in_addr =
self.getsockopt(libc::IPPROTO_IP, libc::IP_MULTICAST_IF)?;
Ok(from_s_addr(imr_interface.s_addr))
Ok(from_in_addr(imr_interface))
}
}

pub fn set_multicast_if_v4(&self, interface: &Ipv4Addr) -> io::Result<()> {
let interface = to_s_addr(interface);
let imr_interface = libc::in_addr { s_addr: interface };
let imr_interface = to_in_addr(interface);

unsafe { self.setsockopt(libc::IPPROTO_IP, libc::IP_MULTICAST_IF, imr_interface) }
}
Expand Down Expand Up @@ -833,11 +832,9 @@ impl Socket {
}

pub fn join_multicast_v4(&self, multiaddr: &Ipv4Addr, interface: &Ipv4Addr) -> io::Result<()> {
let multiaddr = to_s_addr(multiaddr);
let interface = to_s_addr(interface);
let mreq = libc::ip_mreq {
imr_multiaddr: libc::in_addr { s_addr: multiaddr },
imr_interface: libc::in_addr { s_addr: interface },
imr_multiaddr: to_in_addr(multiaddr),
imr_interface: to_in_addr(interface),
};
unsafe { self.setsockopt(libc::IPPROTO_IP, libc::IP_ADD_MEMBERSHIP, mreq) }
}
Expand All @@ -852,11 +849,9 @@ impl Socket {
}

pub fn leave_multicast_v4(&self, multiaddr: &Ipv4Addr, interface: &Ipv4Addr) -> io::Result<()> {
let multiaddr = to_s_addr(multiaddr);
let interface = to_s_addr(interface);
let mreq = libc::ip_mreq {
imr_multiaddr: libc::in_addr { s_addr: multiaddr },
imr_interface: libc::in_addr { s_addr: interface },
imr_multiaddr: to_in_addr(multiaddr),
imr_interface: to_in_addr(interface),
};
unsafe { self.setsockopt(libc::IPPROTO_IP, libc::IP_DROP_MEMBERSHIP, mreq) }
}
Expand Down Expand Up @@ -1248,21 +1243,28 @@ fn timeval2dur(raw: libc::timeval) -> Option<Duration> {
}
}

fn to_s_addr(addr: &Ipv4Addr) -> libc::in_addr_t {
let octets = addr.octets();
u32::from_ne_bytes(octets)
pub(crate) fn to_in_addr(addr: &Ipv4Addr) -> in_addr {
// `s_addr` is stored as BE on all machines, and the array is in BE order.
// So the native endian conversion method is used so that it's never swapped.
in_addr {
s_addr: u32::from_ne_bytes(addr.octets()),
}
}

fn from_s_addr(in_addr: libc::in_addr_t) -> Ipv4Addr {
in_addr.to_be().into()
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.to_be() here was not correct really... Well it yielded the same result, but it was not optimally from an understanding point of view IMO. in_addr is stored in BE. So u32::from_be would be more correct. But both of them just swap the bytes on a LE machine and does nothing on a BE machine, so it does not matter in practice.

Anyway. My solution uses to_ne_bytes to avoid a double swap (since the From<u32> impl for Ipv4Addr swaps the bytes back again).

pub(crate) fn from_in_addr(in_addr: in_addr) -> Ipv4Addr {
Ipv4Addr::from(in_addr.s_addr.to_ne_bytes())
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@faern faern Nov 8, 2020 •
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These helper methods were really handy. Removed a lot of code from the sockaddr.rs file and got rid of a number of #[cfg(...)]s. So I made them pub(crate) so I could use them in the other module.

I also changed the abstraction one level. So instead of converting to/from the only field in the in_addr/in6_addr structs I made these helpers convert directly into that struct. This in turn helped remove some repeated code here in the two sys files as well.

}

fn to_in6_addr(addr: &Ipv6Addr) -> libc::in6_addr {
pub(crate) fn to_in6_addr(addr: &Ipv6Addr) -> libc::in6_addr {
let mut ret: libc::in6_addr = unsafe { mem::zeroed() };
ret.s6_addr = addr.octets();
return ret;
}

pub(crate) fn from_in6_addr(in6_addr: in6_addr) -> Ipv6Addr {
Ipv6Addr::from(in6_addr.s6_addr)
}

#[cfg(target_os = "android")]
fn to_ipv6mr_interface(value: u32) -> c_int {
value as c_int
Expand Down Expand Up @@ -1297,12 +1299,12 @@ fn dur2linger(dur: Option<Duration>) -> libc::linger {
#[test]
fn test_ip() {
let ip = Ipv4Addr::new(127, 0, 0, 1);
assert_eq!(ip, from_s_addr(to_s_addr(&ip)));
assert_eq!(ip, from_in_addr(to_in_addr(&ip)));

let ip = Ipv4Addr::new(127, 34, 4, 12);
let want = 127 << 0 | 34 << 8 | 4 << 16 | 12 << 24;
assert_eq!(to_s_addr(&ip), want);
assert_eq!(from_s_addr(want), ip);
assert_eq!(to_in_addr(&ip).s_addr, want);
assert_eq!(from_in_addr(in_addr { s_addr: want }), ip);
}

#[test]
Expand Down
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