Add options and functionality for running with other XDP programs via xdp-loader. (#86)

src/common/config.h

@@ -57,4 +57,13 @@
 
 // If enabled, uses a newer bpf_loop() function when choosing a source port for a new connection.
 // This allows for a much higher source port range. However, it requires a more recent kernel.
-#define USE_NEW_LOOP
+#define USE_NEW_LOOP
+
+// Whether to enable chaining multiple XDP programs with this tool (1 = enable. 0 = disable).
+#define XDP_MULTIPROG_ENABLED 1
+
+// The XDP program's run priority (used for running multiple XDP programs together).
+#define XDP_MULTIPROG_PRIORITY 10
+
+// The action that indicates it should go onto the next program (default XDP_PASS).
+#define XDP_MULTIPROG_ACTION XDP_PASS

src/loader/utils/xdp.c

@@ -113,6 +113,10 @@ int attach_xdp(struct xdp_program *prog, char** mode, int ifidx, int detach, int
 {
     int err;
 
+    // Before attaching, set chaining options.
+    xdp_program__set_run_prio(prog, XDP_MULTIPROG_PRIORITY);
+    xdp_program__set_chain_call_enabled(prog, XDP_MULTIPROG_ACTION, XDP_MULTIPROG_ENABLED);
+
     u32 attach_mode = XDP_MODE_NATIVE;
 
     *mode = "DRV/native";