Auto merge of #761 - LeoTindall:add_linux_iff_constants, r=alexcrichton

Add additional interface flags (IFF_)

Adds the three missing IFF_ constants (IFF_LOWER_UP, IFF_DORMANT, and IFF_ECHO) per nix-rust/nix#764

libc-test/build.rs

@@ -91,6 +91,9 @@ fn main() {
         cfg.header("sys/mman.h");
         cfg.header("sys/resource.h");
         cfg.header("sys/socket.h");
+        if linux && !musl {
+            cfg.header("linux/if.h");
+        }
         cfg.header("sys/time.h");
         cfg.header("sys/un.h");
         cfg.header("sys/wait.h");
@@ -663,6 +666,10 @@ fn main() {
         } else {
             cfg.header("linux/fcntl.h");
         }
+        if !musl {
+            cfg.header("net/if.h");
+            cfg.header("linux/if.h");
+        }
         cfg.header("linux/quota.h");
         cfg.skip_const(move |name| {
             match name {

src/unix/notbsd/linux/mod.rs

@@ -626,6 +626,10 @@ pub const F_TEST: ::c_int = 3;
 pub const F_TLOCK: ::c_int = 2;
 pub const F_ULOCK: ::c_int = 0;
 
+pub const IFF_LOWER_UP: ::c_int = 0x10000;
+pub const IFF_DORMANT: ::c_int = 0x20000;
+pub const IFF_ECHO: ::c_int = 0x40000;
+
 pub const ST_RDONLY: ::c_ulong = 1;
 pub const ST_NOSUID: ::c_ulong = 2;
 pub const ST_NODEV: ::c_ulong = 4;