freebsd add basic ethernet frames support

[reference](https://github.com/freebsd/freebsd-src/blob/stable/14/sys/net/ethernet.h)

Author: devnexen

Diff for: libc-test/build.rs

@@ -2198,6 +2198,7 @@ fn test_freebsd(target: &str) {
                 "memstat.h",
                 "mqueue.h",
                 "net/bpf.h",
+                "net/ethernet.h",
                 "net/if.h",
                 "net/if_arp.h",
                 "net/if_dl.h",

Diff for: libc-test/semver/freebsd.txt

@@ -377,6 +377,17 @@ ERA_T_FMT
 EREMOTE
 ERPCMISMATCH
 ESOCKTNOSUPPORT
+ETHER_ADDR_LEN
+ETHER_CRC_LEN
+ETHER_HDR_LEN
+ETHER_IS_BROADCAST
+ETHER_IS_IPV6_MULTICAST
+ETHER_IS_MULTICAST
+ETHER_IS_ZERO
+ETHER_MIN_LEN
+ETHER_MAX_LEN
+ETHER_MAX_LEN_JUMBO
+ETHER_TYPE_LEN
 ETOOMANYREFS
 EUSERS
 EVFILT_AIO
@@ -1915,6 +1926,8 @@ endpwent
 endservent
 endutxent
 erand48
+ether_addr
+ether_header
 eui64_aton
 eui64_hostton
 eui64_ntoa

Diff for: src/unix/bsd/freebsdlike/freebsd/mod.rs

@@ -1677,6 +1677,18 @@ s_no_extra_traits! {
         pub uc_flags: c_int,
         __spare__: [c_int; 4],
     }
+
+    #[repr(packed)]
+    pub struct ether_header {
+        pub ether_dhost: [crate::u_char; ETHER_ADDR_LEN as usize],
+        pub ether_shost: [crate::u_char; ETHER_ADDR_LEN as usize],
+        pub ether_type: crate::u_short,
+    }
+
+    #[repr(packed)]
+    pub struct ether_addr {
+        pub octet: [crate::u_char; ETHER_ADDR_LEN as usize],
+    }
 }
 
 cfg_if! {
@@ -2557,6 +2569,55 @@ cfg_if! {
                     .finish()
             }
         }
+
+        // FIXME(msrv): `derive` on packed structs cannot be used below 1.67
+
+        impl PartialEq for ether_header {
+            fn eq(&self, other: &ether_header) -> bool {
+                self.ether_dhost.iter().zip(other.ether_dhost.iter()).all(|(a, b)| a == b)
+                    && self.ether_dhost.iter().zip(other.ether_shost.iter()).all(|(a, b)| a == b)
+                    && self.ether_type == other.ether_type
+            }
+        }
+
+        impl Eq for ether_header {}
+        impl fmt::Debug for ether_header {
+            fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+                f.debug_struct("ether_header")
+                    .field("ether_dhost", &{ self.ether_dhost })
+                    .field("ether_shost", &{ self.ether_shost })
+                    .field("ether_type", &{ self.ether_type })
+                    .finish()
+            }
+        }
+
+        impl hash::Hash for ether_header {
+            fn hash<H: hash::Hasher>(&self, state: &mut H) {
+                { self.ether_dhost }.hash(state);
+                { self.ether_shost }.hash(state);
+                { self.ether_type }.hash(state);
+            }
+        }
+
+        impl PartialEq for ether_addr {
+            fn eq(&self, other: &ether_addr) -> bool {
+                self.octet.iter().zip(other.octet.iter()).all(|(a, b)| a == b)
+            }
+        }
+
+        impl Eq for ether_addr {}
+        impl fmt::Debug for ether_addr {
+            fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+                f.debug_struct("ether_addr")
+                    .field("octet", &{ self.octet })
+                    .finish()
+            }
+        }
+        impl hash::Hash for ether_addr {
+            fn hash<H: hash::Hasher>(&self, state: &mut H) {
+                { self.octet }.hash(state);
+            }
+        }
     }
 }
 
@@ -4663,6 +4724,16 @@ pub const RTM_VERSION: c_int = 5;
 
 pub const RTAX_MAX: c_int = 8;
 
+// net/ethernet.h
+
+pub const ETHER_ADDR_LEN: c_int = 6;
+pub const ETHER_TYPE_LEN: c_int = 2;
+pub const ETHER_CRC_LEN: c_int = 4;
+pub const ETHER_HDR_LEN: c_int = ETHER_ADDR_LEN * 2 + ETHER_TYPE_LEN;
+pub const ETHER_MIN_LEN: c_int = 64;
+pub const ETHER_MAX_LEN: c_int = 1518;
+pub const ETHER_MAX_LEN_JUMBO: c_int = 9018;
+
 // sys/signal.h
 pub const SIGTHR: c_int = 32;
 pub const SIGLWP: c_int = SIGTHR;
@@ -4973,6 +5044,24 @@ f! {
     pub fn PROT_MAX_EXTRACT(x: c_int) -> c_int {
         (x >> 16) & (crate::PROT_READ | crate::PROT_WRITE | crate::PROT_EXEC)
     }
+
+    pub {const} fn ETHER_IS_MULTICAST(addr: *mut u_char) -> bool {
+        (*addr.add(0)) & 0x01 != 0x00
+    }
+
+    pub {const} fn ETHER_IS_IPV6_MULTICAST(addr: *mut u_char) -> bool {
+        (*addr.add(0)) == 0x33 && (*addr.add(1)) == 0x33
+    }
+
+    pub {const} fn ETHER_IS_BROADCAST(addr: *mut u_char) -> bool {
+        (*addr.add(0)) & (*addr.add(1)) & (*addr.add(2))
+            & (*addr.add(3)) & (*addr.add(4)) & (*addr.add(5)) == 0xff
+    }
+
+    pub {const} fn ETHER_IS_ZERO(addr: *mut u_char) -> bool {
+        (*addr.add(0)) | (*addr.add(1)) | (*addr.add(2))
+            | (*addr.add(3)) | (*addr.add(4)) | (*addr.add(5)) == 0x00
+    }
 }
 
 safe_f! {