f_bpf: allow for optional classid and add flags

When having optional classid, most minimal command can be sth
like:

  tc filter add dev foo parent X: bpf obj prog.o

Therefore, adapt the code so that a next argument will not be
enforced as the case currently.

Also, minor cleanup on the classid, where we should rather
have used addattr32(), and add flags for exec configuration,
for example (using short notation):

  tc filter add dev foo parent X: bpf da obj prog.o
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>

include/utils.h

@@ -47,6 +47,7 @@ void incomplete_command(void) __attribute__((noreturn));
 
 #define NEXT_ARG() do { argv++; if (--argc <= 0) incomplete_command(); } while(0)
 #define NEXT_ARG_OK() (argc - 1 > 0)
+#define NEXT_ARG_FWD() do { argv++; argc--; } while(0)
 #define PREV_ARG() do { argv--; argc++; } while(0)
 
 typedef struct

tc/f_bpf.c

@@ -41,7 +41,7 @@ static void explain(void)
 	fprintf(stderr, "\n");
 	fprintf(stderr, "eBPF use case:\n");
 	fprintf(stderr, " object-file FILE [ section CLS_NAME ] [ export UDS_FILE ]");
-	fprintf(stderr, " [ verbose ]\n");
+	fprintf(stderr, " [ verbose ] [ direct-action ]\n");
 	fprintf(stderr, "\n");
 	fprintf(stderr, "Common remaining options:\n");
 	fprintf(stderr, " [ action ACTION_SPEC ]\n");
@@ -69,6 +69,7 @@ static int bpf_parse_opt(struct filter_util *qu, char *handle,
 	struct tcmsg *t = NLMSG_DATA(n);
 	const char *bpf_uds_name = NULL;
 	const char *bpf_sec_name = NULL;
+	unsigned int bpf_flags = 0;
 	char *bpf_obj = NULL;
 	struct rtattr *tail;
 	bool seen_run = false;
@@ -124,25 +125,28 @@ opt_bpf:
 			if (ebpf) {
 				bpf_uds_name = getenv(BPF_ENV_UDS);
 				bpf_obj = *argv;
-				NEXT_ARG();
 
-				if (strcmp(*argv, "section") == 0 ||
-				    strcmp(*argv, "sec") == 0) {
+				NEXT_ARG_FWD();
+
+				if (argc > 0 &&
+				    (strcmp(*argv, "section") == 0 ||
+				     strcmp(*argv, "sec") == 0)) {
 					NEXT_ARG();
 					bpf_sec_name = *argv;
-					NEXT_ARG();
+					NEXT_ARG_FWD();
 				}
-				if (!bpf_uds_name &&
+				if (argc > 0 && !bpf_uds_name &&
 				    (strcmp(*argv, "export") == 0 ||
 				     strcmp(*argv, "exp") == 0)) {
 					NEXT_ARG();
 					bpf_uds_name = *argv;
-					NEXT_ARG();
+					NEXT_ARG_FWD();
 				}
-				if (strcmp(*argv, "verbose") == 0 ||
-				    strcmp(*argv, "verb") == 0) {
+				if (argc > 0 &&
+				    (strcmp(*argv, "verbose") == 0 ||
+				     strcmp(*argv, "verb") == 0)) {
 					bpf_verbose = true;
-					NEXT_ARG();
+					NEXT_ARG_FWD();
 				}
 
 				PREV_ARG();
@@ -182,7 +186,10 @@ opt_bpf:
 				fprintf(stderr, "Illegal \"classid\"\n");
 				return -1;
 			}
-			addattr_l(n, MAX_MSG, TCA_BPF_CLASSID, &handle, 4);
+			addattr32(n, MAX_MSG, TCA_BPF_CLASSID, handle);
+		} else if (matches(*argv, "direct-action") == 0 ||
+			   matches(*argv, "da") == 0) {
+			bpf_flags |= TCA_BPF_FLAG_ACT_DIRECT;
 		} else if (matches(*argv, "action") == 0) {
 			NEXT_ARG();
 			if (parse_action(&argc, &argv, TCA_BPF_ACT, n)) {
@@ -208,10 +215,13 @@ opt_bpf:
 			explain();
 			return -1;
 		}
-		argc--;
-		argv++;
+
+		NEXT_ARG_FWD();
 	}
 
+	if (bpf_obj && bpf_flags)
+		addattr32(n, MAX_MSG, TCA_BPF_FLAGS, bpf_flags);
+
 	tail->rta_len = (((void *)n) + n->nlmsg_len) - (void *)tail;
 
 	if (bpf_uds_name)
@@ -244,6 +254,13 @@ static int bpf_print_opt(struct filter_util *qu, FILE *f,
 	else if (tb[TCA_BPF_FD])
 		fprintf(f, "pfd %u ", rta_getattr_u32(tb[TCA_BPF_FD]));
 
+	if (tb[TCA_BPF_FLAGS]) {
+		unsigned int flags = rta_getattr_u32(tb[TCA_BPF_FLAGS]);
+
+		if (flags & TCA_BPF_FLAG_ACT_DIRECT)
+			fprintf(f, "direct-action ");
+	}
+
 	if (tb[TCA_BPF_OPS] && tb[TCA_BPF_OPS_LEN]) {
 		bpf_print_ops(f, tb[TCA_BPF_OPS],
 			      rta_getattr_u16(tb[TCA_BPF_OPS_LEN]));