Merge sockaddr reading functionality into luomu-common

oherrala · oherrala · commit 75329f2a18f3 · 2026-03-13T11:14:49.000+02:00
We had almost same sockaddr reading code in luomu-getifaddr and
luomu-libpcap. Now both places use shared code from luomu-common. The
code is behind "libc" feature flag because it requires libc as external
dependency and we want to keep luomu-common as dependency free by
default.
diff --git a/luomu-common/Cargo.toml b/luomu-common/Cargo.toml
@@ -11,6 +11,12 @@ rust-version.workspace = true
 homepage.workspace = true
 repository.workspace = true
 
+[features]
+default = []
+
+[dependencies]
+libc = { version = "0.2", optional = true }
+
 [dev-dependencies]
 quickcheck.workspace = true
 
diff --git a/luomu-common/src/lib.rs b/luomu-common/src/lib.rs
@@ -21,6 +21,9 @@ pub use tagged_macaddr::TaggedMacAddr;
 /// forwardable
 pub mod ipaddr;
 
+#[cfg(feature = "libc")]
+pub mod sockaddr;
+
 /// Invalid address error
 #[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct InvalidAddress;
diff --git a/luomu-common/src/sockaddr.rs b/luomu-common/src/sockaddr.rs
@@ -0,0 +1,118 @@
+#![allow(unsafe_code)]
+//! Utilities to handle [libc::sockaddr] and related structs.
+
+use std::net::{Ipv4Addr, Ipv6Addr};
+
+use crate::Address;
+
+/// Length of MAC address in bytes
+const MAC_ADDR_LEN: usize = 6;
+
+/// Reads address information from given socket address pointer.
+///
+/// Address may contain IP address or Link address, the returned [Address]
+/// reflects which one was read. [None] is returned if no address was available,
+/// or it could not be read.
+// We do our best to validate that the pointer given in `ifa_addr` is valid.
+#[allow(clippy::not_unsafe_ptr_arg_deref)]
+pub fn from_sockaddr(ifa_addr: *const libc::sockaddr) -> Option<Address> {
+    if ifa_addr.is_null() {
+        return None;
+    }
+
+    let family = i32::from(unsafe { (*ifa_addr).sa_family });
+
+    #[cfg(target_os = "macos")]
+    let sa_len = usize::from(unsafe { (*ifa_addr).sa_len });
+
+    match family {
+        #[cfg(target_os = "macos")]
+        libc::AF_INET if sa_len < 16 => {
+            debug_assert!((5..=8).contains(&sa_len), "invalid sa_len {sa_len} for AF_INET");
+            // We keep ifa_addr as sockaddr, but read it like it's sockaddr_in:
+            //
+            //   pub struct sockaddr_in {
+            //       pub sin_len: u8,
+            //       pub sin_family: u8,
+            //       pub sin_port: u16,     \ These two are in sockaddr.sa_data
+            //       pub sin_addr: u32,     /
+            //       pub sin_zero: [c_char; 8],
+            //   }
+            //
+            // We want to read the partial bytes from sin_addr, the length is
+            // dictated by sa_len. sockaddr.sa_data contains first sin_port
+            // which we skip and then sin_addr.
+            let len = sa_len.saturating_sub(2); // remove length of sin_len and sin_family
+            let mut iret = [0i8; 4];
+            let sa_data: &[i8] = unsafe { std::slice::from_raw_parts((*ifa_addr).sa_data.as_ptr(), len) };
+            iret[0..len - 2].copy_from_slice(&sa_data[2..len]);
+            let uret: [u8; 4] = unsafe { std::mem::transmute(iret) };
+            Some(Address::from(Ipv4Addr::from_octets(uret)))
+        }
+
+        libc::AF_INET => {
+            #[cfg(target_os = "macos")]
+            debug_assert_eq!(sa_len, 16, "invalid sa_len {sa_len} for AF_INET");
+            let a: libc::sockaddr_in = unsafe { *(ifa_addr.cast::<libc::sockaddr_in>()) };
+            Some(Address::from(Ipv4Addr::from_bits(u32::from_be(
+                a.sin_addr.s_addr,
+            ))))
+        }
+
+        libc::AF_INET6 => {
+            #[cfg(target_os = "macos")]
+            debug_assert_eq!(sa_len, 28, "invalid sa_len {sa_len} for AF_INET6");
+            let a: libc::sockaddr_in6 = unsafe { *(ifa_addr.cast::<libc::sockaddr_in6>()) };
+            Some(Address::from(Ipv6Addr::from_octets(a.sin6_addr.s6_addr)))
+        }
+
+        #[cfg(target_os = "macos")]
+        libc::AF_LINK => {
+            debug_assert!(
+                sa_len == 20 || sa_len == 24,
+                "invalid sa_len {sa_len} for AF_LINK"
+            );
+            // MAC address for this interface
+            let a: libc::sockaddr_dl = unsafe { *(ifa_addr.cast::<libc::sockaddr_dl>()) };
+            // length of the address
+            let a_len = usize::from(a.sdl_alen);
+            // length of the name
+            let n_len = usize::from(a.sdl_nlen);
+            // If seems that name is stored to sdl_data before the mac
+            // address of the interface. However, libc::sockaddr_dl::sdl_data has been
+            // defined to contain 12 bytes. Thus, if name of the interface
+            // is longer than 6 bytes (characters), we can not read the MAC
+            // address of that interface.
+            if a_len != MAC_ADDR_LEN || n_len + a_len > a.sdl_data.len() {
+                return None;
+            }
+            // also, sdl_data has been defined as i8 for whatever reason,
+            // we need bytes for mac address, thus a bit of unsafery
+            let data = &a.sdl_data;
+            let sdl_data_as_u8: &[u8] =
+                unsafe { std::slice::from_raw_parts(data.as_ptr().cast::<u8>(), data.len()) };
+            let mut address = [0u8; MAC_ADDR_LEN];
+            // mac address stored after name
+            // You may want to look into LLADDR() macro somewhere on Mac OS headers
+            let offset = usize::from(a.sdl_nlen);
+            address[..MAC_ADDR_LEN].copy_from_slice(&sdl_data_as_u8[offset..offset + MAC_ADDR_LEN]);
+            Some(Address::from(address))
+        }
+
+        #[cfg(target_os = "linux")]
+        libc::AF_PACKET => {
+            // Mac address of the interface
+            let a: libc::sockaddr_ll = unsafe { *(ifa_addr.cast::<libc::sockaddr_ll>()) };
+            let a_len = usize::from(a.sll_halen);
+            debug_assert!(a_len == MAC_ADDR_LEN);
+            if a_len != MAC_ADDR_LEN {
+                return None;
+            }
+            let mut address = [0u8; MAC_ADDR_LEN];
+            address[..MAC_ADDR_LEN].copy_from_slice(&a.sll_addr[..MAC_ADDR_LEN]);
+            Some(Address::from(address))
+        }
+
+        _ => None,
+    }
+}
diff --git a/luomu-getifaddrs/Cargo.toml b/luomu-getifaddrs/Cargo.toml
@@ -15,7 +15,7 @@ repository.workspace = true
 bitflags.workspace = true
 cfg-if.workspace = true
 libc.workspace = true
-luomu-common.workspace = true
+luomu-common = { workspace = true, features = [ "libc" ] }
 
 [lints]
 workspace = true
diff --git a/luomu-getifaddrs/src/lib.rs b/luomu-getifaddrs/src/lib.rs
@@ -5,22 +5,17 @@
 use std::ffi::CStr;
 use std::io;
 use std::mem::MaybeUninit;
-use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};
+use std::net::IpAddr;
 
+use luomu_common::sockaddr::from_sockaddr;
 use luomu_common::{Address, MacAddr};
 
-#[cfg(target_os = "macos")]
-use std::slice;
-
 mod flags;
 pub use flags::Flags;
 
 mod stats;
 pub use stats::IfStats;
 
-/// Length of MAC address in bytes
-const MAC_ADDR_LEN: usize = 6;
-
 /// Returns a linked list describing the network interfaces of
 /// the local system.
 pub fn getifaddrs() -> io::Result<IfAddrs> {
@@ -117,27 +112,6 @@ impl Iterator for IfAddrs {
     }
 }
 
-/// Returns address family value from [libc::sockaddr]
-const fn sa_get_family(sa: *const libc::sockaddr) -> i32 {
-    unsafe { *sa }.sa_family as libc::c_int
-}
-
-/// Returns given [libc::sockaddr] pointer as a pointer to [libc::sockaddr_in]
-const fn sa_as_sockaddr_in(sa: *const libc::sockaddr) -> libc::sockaddr_in {
-    unsafe { *(sa.cast::<libc::sockaddr_in>()) }
-}
-
-/// Returns given [libc::sockaddr] pointer as a pointer to [libc::sockaddr_in6]
-const fn sa_as_sockaddr_in6(sa: *const libc::sockaddr) -> libc::sockaddr_in6 {
-    unsafe { *(sa.cast::<libc::sockaddr_in6>()) }
-}
-
-#[cfg(target_os = "macos")]
-/// Returns given [libc::sockaddr] pointer as a pointer to [libc::sockaddr_dl]
-const fn sa_as_sockaddr_dl(sa: *const libc::sockaddr) -> libc::sockaddr_dl {
-    unsafe { *(sa.cast::<libc::sockaddr_dl>()) }
-}
-
 /// This struct provides access to information about network interface.
 pub struct IfAddr {
     /// pointer for the interface data
@@ -179,21 +153,21 @@ impl IfAddr {
 
     /// Interface address
     pub fn addr(&self) -> Option<Address> {
-        IfAddr::read_addr(self.ifa().ifa_addr)
+        from_sockaddr(self.ifa().ifa_addr)
     }
 
     /// Interface netmask
     pub fn netmask(&self) -> Option<IpAddr> {
-        IfAddr::read_addr(self.ifa().ifa_netmask).and_then(|a| a.as_ip())
+        from_sockaddr(self.ifa().ifa_netmask).and_then(|a| a.as_ip())
     }
 
     /// Destination address for Point-to-Point link
     pub fn dstaddr(&self) -> Option<IpAddr> {
         cfg_if::cfg_if! {
             if #[cfg(target_os = "macos")] {
-                IfAddr::read_addr(self.ifa().ifa_dstaddr).and_then(|a| a.as_ip())
+                from_sockaddr(self.ifa().ifa_dstaddr).and_then(|a| a.as_ip())
             } else if #[cfg(target_os = "linux")] {
-                IfAddr::read_addr(self.ifa().ifa_ifu).and_then(|a| a.as_ip())
+                from_sockaddr(self.ifa().ifa_ifu).and_then(|a| a.as_ip())
             }
         }
     }
@@ -204,7 +178,7 @@ impl IfAddr {
             return None;
         }
 
-        let family = sa_get_family(self.ifa().ifa_addr);
+        let family = i32::from(unsafe { *self.ifa().ifa_addr }.sa_family);
 
         #[cfg(target_os = "linux")]
         if family != libc::AF_PACKET {
@@ -220,96 +194,6 @@ impl IfAddr {
         let link_stats = unsafe { &*(ifa_data as *const stats::LinkStats) };
         Some(*link_stats)
     }
-
-    /// Reads address information from given socket address pointer.
-    ///
-    /// Address may contain IP address or Link address, the returned
-    /// [Addr] reflects which one was read. [None] is returned if no address
-    /// was available, or it could not be read.
-    fn read_addr(ifa_addr: *const libc::sockaddr) -> Option<Address> {
-        if ifa_addr.is_null() {
-            return None;
-        }
-
-        let family = sa_get_family(ifa_addr);
-
-        match family {
-            #[cfg(target_os = "macos")]
-            libc::AF_INET if unsafe { *ifa_addr }.sa_len < 16 => {
-                let len = unsafe { *ifa_addr }.sa_len;
-                debug_assert!(len >= 5 && len <= 8, "invalid sa_len {len} for AF_INET");
-                let sa_data = unsafe { *ifa_addr }.sa_data;
-                let mut ret = 0;
-                if len >= 5 {
-                    ret += u32::from(sa_data[2] as u8) << 24;
-                }
-                if len >= 6 {
-                    ret += u32::from(sa_data[3] as u8) << 16;
-                }
-                if len >= 7 {
-                    ret += u32::from(sa_data[4] as u8) << 8;
-                }
-                if len == 8 {
-                    ret += u32::from(sa_data[5] as u8);
-                }
-                Some(Address::from(Ipv4Addr::from_bits(ret)))
-            }
-            libc::AF_INET => {
-                #[cfg(target_os = "macos")]
-                debug_assert_eq!(unsafe { *ifa_addr }.sa_len, 16, "invalid sa_len for AF_INET");
-                let a: libc::sockaddr_in = sa_as_sockaddr_in(ifa_addr);
-                Some(Address::from(Ipv4Addr::from(u32::from_be(a.sin_addr.s_addr))))
-            }
-            libc::AF_INET6 => {
-                #[cfg(target_os = "macos")]
-                debug_assert_eq!(unsafe { *ifa_addr }.sa_len, 28, "invalid sa_len for AF_INET6");
-                let a: libc::sockaddr_in6 = sa_as_sockaddr_in6(ifa_addr);
-                Some(Address::from(Ipv6Addr::from(a.sin6_addr.s6_addr)))
-            }
-            #[cfg(target_os = "macos")]
-            libc::AF_LINK => {
-                // MAC address for this interface
-                let a: libc::sockaddr_dl = sa_as_sockaddr_dl(ifa_addr);
-                // length of the address
-                let a_len = usize::from(a.sdl_alen);
-                // length of the name
-                let n_len = usize::from(a.sdl_nlen);
-                // If seems that name is stored to sdl_data before the mac
-                // address of the interface. However, libc::sockaddr_dl::sdl_data has been
-                // defined to contain 12 bytes. Thus, if name of the interface
-                // is longer than 6 bytes (characters), we can not read the MAC
-                // address of that interface.
-                if a_len != MAC_ADDR_LEN || n_len + a_len > a.sdl_data.len() {
-                    return None;
-                }
-                // also, sdl_data has been defined as i8 for whatever reason,
-                // we need bytes for mac address, thus a bit of unsafery
-                let data = &a.sdl_data;
-                let sdl_data_as_u8: &[u8] =
-                    unsafe { slice::from_raw_parts(data.as_ptr().cast::<u8>(), data.len()) };
-                let mut address = [0u8; MAC_ADDR_LEN];
-                // mac address stored after name
-                // You may want to look into LLADDR() macro somewhere on Mac OS headers
-                let offset = usize::from(a.sdl_nlen);
-                address[..MAC_ADDR_LEN].copy_from_slice(&sdl_data_as_u8[offset..offset + MAC_ADDR_LEN]);
-                Some(Address::from(address))
-            }
-            #[cfg(target_os = "linux")]
-            libc::AF_PACKET => {
-                // Mac address of the interface
-                let a: libc::sockaddr_ll = unsafe { *(ifa_addr.cast::<libc::sockaddr_ll>()) };
-                let a_len = usize::from(a.sll_halen);
-                debug_assert!(a_len == MAC_ADDR_LEN);
-                if a_len != MAC_ADDR_LEN {
-                    return None;
-                }
-                let mut address = [0u8; MAC_ADDR_LEN];
-                address[..MAC_ADDR_LEN].copy_from_slice(&a.sll_addr[..MAC_ADDR_LEN]);
-                Some(Address::from(address))
-            }
-            _ => None,
-        }
-    }
 }
 
 /// A view into interface data
diff --git a/luomu-libpcap/Cargo.toml b/luomu-libpcap/Cargo.toml
@@ -18,7 +18,7 @@ async-tokio = [ "dep:futures-core", "dep:tokio" ]
 
 [dependencies]
 libc.workspace = true
-luomu-common.workspace = true
+luomu-common = { workspace = true, features = [ "libc" ] }
 luomu-libpcap-sys.workspace = true
 tracing.workspace = true
 
diff --git a/luomu-libpcap/src/functions.rs b/luomu-libpcap/src/functions.rs
