Relax assertions in sockaddr_storage_to_addr to match the documentation.

Fixes nix-rust#1479

src/sys/socket/mod.rs

@@ -1748,21 +1748,21 @@ pub fn sockaddr_storage_to_addr(
     addr: &sockaddr_storage,
     len: usize) -> Result<SockAddr> {
 
-    assert!(len <= mem::size_of::<sockaddr_un>());
+    assert!(len <= mem::size_of::<sockaddr_storage>());
     if len < mem::size_of_val(&addr.ss_family) {
         return Err(Error::from(Errno::ENOTCONN));
     }
 
     match c_int::from(addr.ss_family) {
         libc::AF_INET => {
-            assert_eq!(len as usize, mem::size_of::<sockaddr_in>());
+            assert!(len as usize >= mem::size_of::<sockaddr_in>());
             let sin = unsafe {
                 *(addr as *const sockaddr_storage as *const sockaddr_in)
             };
             Ok(SockAddr::Inet(InetAddr::V4(sin)))
         }
         libc::AF_INET6 => {
-            assert_eq!(len as usize, mem::size_of::<sockaddr_in6>());
+            assert!(len as usize >= mem::size_of::<sockaddr_in6>());
             let sin6 = unsafe {
                 *(addr as *const _ as *const sockaddr_in6)
             };
@@ -1778,10 +1778,10 @@ pub fn sockaddr_storage_to_addr(
         #[cfg(any(target_os = "android", target_os = "linux"))]
         libc::AF_PACKET => {
             use libc::sockaddr_ll;
+            // Don't assert anything about the size.
             // Apparently the Linux kernel can return smaller sizes when
             // the value in the last element of sockaddr_ll (`sll_addr`) is
             // smaller than the declared size of that field
-            assert!(len as usize <= mem::size_of::<sockaddr_ll>());
             let sll = unsafe {
                 *(addr as *const _ as *const sockaddr_ll)
             };

test/sys/test_socket.rs

@@ -1,19 +1,21 @@
-use nix::sys::socket::{AddressFamily, InetAddr, UnixAddr, getsockname};
+use nix::sys::socket::{AddressFamily, InetAddr, SockAddr, UnixAddr, getsockname, sockaddr, sockaddr_in6, sockaddr_storage_to_addr};
 use std::collections::hash_map::DefaultHasher;
 use std::hash::{Hash, Hasher};
+use std::mem::{self, MaybeUninit};
 use std::net::{self, Ipv6Addr, SocketAddr, SocketAddrV6};
 use std::os::unix::io::RawFd;
 use std::path::Path;
 use std::slice;
 use std::str::FromStr;
-use libc::c_char;
+use libc::{c_char, sockaddr_storage};
 #[cfg(any(target_os = "linux", target_os= "android"))]
 use crate::*;
 
 #[test]
 pub fn test_inetv4_addr_to_sock_addr() {
     let actual: net::SocketAddr = FromStr::from_str("127.0.0.1:3000").unwrap();
     let addr = InetAddr::from_std(&actual);
+    let sockaddr = SockAddr::new_inet(addr);
 
     match addr {
         InetAddr::V4(addr) => {
@@ -31,6 +33,22 @@ pub fn test_inetv4_addr_to_sock_addr() {
 
     let inet = addr.to_std();
     assert_eq!(actual, inet);
+
+    let (storage, ffi_size) = {
+        let mut storage = MaybeUninit::<sockaddr_storage>::zeroed();
+        let storage_ptr = storage.as_mut_ptr().cast::<sockaddr>();
+        let (ffi_ptr, ffi_size) = sockaddr.as_ffi_pair();
+        assert_eq!(mem::size_of::<sockaddr>(), ffi_size as usize);
+        unsafe {
+            storage_ptr.copy_from_nonoverlapping(ffi_ptr as *const sockaddr, 1);
+            (storage.assume_init(), ffi_size)
+        }
+    };
+
+    let from_storage = sockaddr_storage_to_addr(&storage, ffi_size as usize).unwrap();
+    assert_eq!(from_storage, sockaddr);
+    let from_storage = sockaddr_storage_to_addr(&storage, mem::size_of::<sockaddr_storage>()).unwrap();
+    assert_eq!(from_storage, sockaddr);
 }
 
 #[test]
@@ -42,6 +60,7 @@ pub fn test_inetv6_addr_to_sock_addr() {
 
     let actual = SocketAddr::V6(SocketAddrV6::new(ip, port, flowinfo, scope_id));
     let addr = InetAddr::from_std(&actual);
+    let sockaddr = SockAddr::new_inet(addr);
 
     match addr {
         InetAddr::V6(addr) => {
@@ -53,6 +72,24 @@ pub fn test_inetv6_addr_to_sock_addr() {
     }
 
     assert_eq!(actual, addr.to_std());
+
+    let (storage, ffi_size) = {
+        let mut storage = MaybeUninit::<sockaddr_storage>::zeroed();
+        let storage_ptr = storage.as_mut_ptr().cast::<sockaddr_in6>();
+        let (ffi_ptr, ffi_size) = sockaddr.as_ffi_pair();
+        // XXX this does not pass.
+        // assert_eq!(mem::size_of::<sockaddr>(), ffi_size as usize);
+        assert_eq!(mem::size_of::<sockaddr_in6>(), ffi_size as usize);
+        unsafe {
+            storage_ptr.copy_from_nonoverlapping((ffi_ptr as *const sockaddr).cast::<sockaddr_in6>(), 1);
+            (storage.assume_init(), ffi_size)
+        }
+    };
+
+    let from_storage = sockaddr_storage_to_addr(&storage, ffi_size as usize).unwrap();
+    assert_eq!(from_storage, sockaddr);
+    let from_storage = sockaddr_storage_to_addr(&storage, mem::size_of::<sockaddr_storage>()).unwrap();
+    assert_eq!(from_storage, sockaddr);
 }
 
 #[test]
@@ -1169,7 +1206,6 @@ fn loopback_address(family: AddressFamily) -> Option<nix::ifaddrs::InterfaceAddr
     use std::io;
     use std::io::Write;
     use nix::ifaddrs::getifaddrs;
-    use nix::sys::socket::SockAddr;
     use nix::net::if_::*;
 
     let addrs = match getifaddrs() {