feat(tcp): Add 'bindtodevice' option (#408)

src/options.c

@@ -54,6 +54,33 @@ int opt_meth_getoption(lua_State *L, p_opt opt, p_socket ps)
     return opt->func(L, ps);
 }
 
+/*------------------------------------------------------*/
+/* binds socket to network interface */
+int opt_set_bindtodevice(lua_State *L, p_socket ps)
+{
+#ifdef __APPLE__
+    return luaL_error(L, "SO_BINDTODEVICE is not supported on this operating system");
+#else
+    const char *dev = luaL_checkstring(L, 3);
+    return opt_set(L, ps, SOL_SOCKET, SO_BINDTODEVICE, (char*)dev, strlen(dev)+1);
+#endif
+}
+
+int opt_get_bindtodevice(lua_State *L, p_socket ps)
+{
+#ifdef __APPLE__
+    return luaL_error(L, "SO_BINDTODEVICE is not supported on this operating system");
+#else
+    char dev[IFNAMSIZ];
+    int len = sizeof(dev);
+    int err = opt_get(L, ps, SOL_SOCKET, SO_BINDTODEVICE, &dev, &len);
+    if (err)
+        return err;
+    lua_pushstring(L, dev);
+    return 1;
+#endif
+}
+
 /*------------------------------------------------------*/
 /* enables reuse of local address */
 int opt_set_reuseaddr(lua_State *L, p_socket ps)

src/options.h

@@ -53,6 +53,9 @@ int opt_get_tcp_keepintvl(lua_State *L, p_socket ps);
 int opt_set_tcp_defer_accept(lua_State *L, p_socket ps);
 #endif
 
+int opt_set_bindtodevice(lua_State *L, p_socket ps);
+int opt_get_bindtodevice(lua_State *L, p_socket ps);
+
 int opt_set_keepalive(lua_State *L, p_socket ps);
 int opt_get_keepalive(lua_State *L, p_socket ps);
 

src/tcp.c

@@ -71,6 +71,7 @@ static luaL_Reg tcp_methods[] = {
 
 /* socket option handlers */
 static t_opt optget[] = {
+    {"bindtodevice", opt_get_bindtodevice},
     {"keepalive",   opt_get_keepalive},
     {"reuseaddr",   opt_get_reuseaddr},
     {"reuseport",   opt_get_reuseport},
@@ -92,6 +93,7 @@ static t_opt optget[] = {
 };
 
 static t_opt optset[] = {
+    {"bindtodevice", opt_set_bindtodevice},
     {"keepalive",   opt_set_keepalive},
     {"reuseaddr",   opt_set_reuseaddr},
     {"reuseport",   opt_set_reuseport},