adding ethhdr type for linux/android for proper packet filtering.

[ref](https://docs.huihoo.com/doxygen/linux/kernel/3.7/structethhdr.html)

Author: devnexen

libc-test/build.rs

@@ -2147,6 +2147,8 @@ fn test_android(target: &str) {
         (struct_ == "sigaction" && field == "sa_sigaction") ||
         // signalfd had SIGSYS fields added in Android 4.19, but CI does not have that version yet.
         (struct_ == "signalfd_siginfo" && field == "ssi_call_addr") ||
+        // FIXME: `h_proto` is of type __be16 big endian version of __u16
+        (struct_ ==  "ethhdr" && field == "h_proto") ||
         // FIXME(android): Seems the type has been changed on NDK r26b
         (struct_ == "flock64" && (field == "l_start" || field == "l_len"))
     });

libc-test/semver/android.txt

@@ -3423,6 +3423,7 @@ epoll_create1
 epoll_ctl
 epoll_event
 epoll_wait
+ethhdr
 eventfd
 eventfd_read
 eventfd_write

libc-test/semver/linux-gnu.txt

@@ -593,6 +593,7 @@ dlvsym
 eaccess
 endutxent
 epoll_pwait2
+ethhdr
 euidaccess
 execveat
 explicit_bzero

src/unix/linux_like/android/mod.rs

@@ -47,6 +47,7 @@ pub type __u16 = c_ushort;
 pub type __s16 = c_short;
 pub type __u32 = c_uint;
 pub type __s32 = c_int;
+pub type __be16 = __u16;
 
 // linux/elf.h
 
@@ -620,6 +621,15 @@ s_no_extra_traits! {
         pub ifc_len: c_int,
         pub ifc_ifcu: __c_anonymous_ifc_ifcu,
     }
+
+    // linux/if_ether.h
+
+    #[repr(C, packed)]
+    pub struct ethhdr {
+        pub h_dest: [c_uchar; crate::ETH_ALEN as usize],
+        pub h_source: [c_uchar; crate::ETH_ALEN as usize],
+        pub h_proto: crate::__be16,
+    }
 }
 
 cfg_if! {

src/unix/linux_like/linux/gnu/mod.rs

@@ -7,6 +7,7 @@ pub type __rlimit_resource_t = c_uint;
 pub type Lmid_t = c_long;
 pub type regoff_t = c_int;
 pub type __kernel_rwf_t = c_int;
+pub type __be16 = crate::__u16;
 
 cfg_if! {
     if #[cfg(doc)] {
@@ -379,6 +380,15 @@ s_no_extra_traits! {
         __pad: [c_char; 4],
         __glibc_reserved: [c_char; 32],
     }
+
+    // linux/if_ether.h
+
+    #[repr(C, packed)]
+    pub struct ethhdr {
+        pub h_dest: [c_uchar; crate::ETH_ALEN as usize],
+        pub h_source: [c_uchar; crate::ETH_ALEN as usize],
+        pub h_proto: crate::__be16,
+    }
 }
 
 // Internal, for casts to access union fields