libxdp: Add validation for only one of fill and comp are set

Signed-off-by: Muyang Tian <[email protected]>

Author: tacslon

headers/xdp/xsk.h

@@ -259,9 +259,9 @@ struct xsk_socket_config {
  * 
  * @fill, @comp, @rx_size, @tx_size, @libxdp_flags, @xdp_flags,
  * @bind_flags
- *  If @fill and @comp are both unset, fill_save and comp_save of
- *  the umem will be assigned to them, otherwise keep what they
- *  are set in opts.
+ *  If @fill and @comp are both unset, they will be set to umem's
+ *  fill_save and comp_save respectively. Note that it is invalid
+ *  to set only one of them.
  *  If the remaining fields are unset, they will be set to 
  *  default value (see `xsk_set_xdp_socket_config()`).
  * 

lib/libxdp/xsk.c

@@ -1075,7 +1075,7 @@ struct xsk_socket *xsk_socket__create_opts(const char *ifname,
 	fill = OPTS_GET(opts, fill, NULL);
 	comp = OPTS_GET(opts, comp, NULL);
 
-	if (!umem || !(rx || tx)) {
+	if (!umem || !(rx || tx) || (fill == NULL) ^ (comp == NULL)) {
 		err = -EFAULT;
 		goto err;
 	}