Add struct msghdr and struct cmsghdr from lwip

src/unix/unikraft/mod.rs

@@ -461,6 +461,24 @@ s! {
         pub tm_gmtoff: ::c_long,
     }
 
+    // lwip
+    pub struct msghdr {
+        pub msg_name: *mut ::c_void,
+        pub msg_namelen: ::socklen_t,
+        pub msg_iov: *mut ::iovec,
+        pub msg_iovlen: ::c_int,
+        pub msg_control: *mut ::c_void,
+        pub msg_controllen: ::socklen_t,
+        pub msg_flags: ::c_int,
+    }
+
+    // lwip
+    pub struct cmsghdr {
+        pub cmsg_len: ::socklen_t,
+        pub cmsg_level: ::c_int,
+        pub cmsg_type: ::c_int,
+    }
+
     pub struct tms {
         pub tms_utime: ::clock_t,
         pub tms_stime: ::clock_t,