m_bpf: add frontend support for late binding

Frontend support for kernel commit a5c90b29e5cc ("act_bpf: properly
support late binding of bpf action to a classifier").

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

diff --git a/tc/m_bpf.c b/tc/m_bpf.c
index c51f44fc6ce6e38d6b8f3961e3fbfd2b6dd97b1c..e1bb6a490c74c458d473c4d9b8a2b736c2ab03fd 100644 (file)
--- a/tc/m_bpf.c
+++ b/tc/m_bpf.c
@@ -28,7 +28,7 @@ static const enum bpf_prog_type bpf_type = BPF_PROG_TYPE_SCHED_ACT;
 
 static void explain(void)
 {
-       fprintf(stderr, "Usage: ... bpf ...\n");
+       fprintf(stderr, "Usage: ... bpf ... [ index INDEX ]\n");
        fprintf(stderr, "\n");
        fprintf(stderr, "BPF use case:\n");
        fprintf(stderr, " bytecode BPF_BYTECODE\n");
@@ -49,6 +49,9 @@ static void explain(void)
        fprintf(stderr, "\n");
        fprintf(stderr, "Where UDS_FILE points to a unix domain socket file in order\n");
        fprintf(stderr, "to hand off control of all created eBPF maps to an agent.\n");
+       fprintf(stderr, "\n");
+       fprintf(stderr, "Where optionally INDEX points to an existing action, or\n");
+       fprintf(stderr, "explicitly specifies an action index upon creation.\n");
 }
 
 static void usage(void)
@@ -64,6 +67,7 @@ static int parse_bpf(struct action_util *a, int *argc_p, char ***argv_p,
        struct rtattr *tail;
        struct tc_act_bpf parm = { 0 };
        struct sock_filter bpf_ops[BPF_MAXINSNS];
+       bool ebpf_fill = false, bpf_fill = false;
        bool ebpf = false, seen_run = false;
        const char *bpf_uds_name = NULL;
        const char *bpf_sec_name = NULL;
@@ -148,11 +152,15 @@ opt_bpf:
                                         bpf_obj, bpf_sec_name);
 
                                bpf_fd = ret;
+                               ebpf_fill = true;
                        } else {
                                bpf_len = ret;
+                               bpf_fill = true;
                        }
                } else if (matches(*argv, "help") == 0) {
                        usage();
+               } else if (matches(*argv, "index") == 0) {
+                       break;
                } else {
                        if (!seen_run)
                                goto opt_bpf;
@@ -200,21 +208,15 @@ opt_bpf:
                }
        }
 
-       if ((!bpf_len && !ebpf) || (!bpf_fd && ebpf)) {
-               fprintf(stderr, "bpf: Bytecode needs to be passed\n");
-               explain();
-               return -1;
-       }
-
        tail = NLMSG_TAIL(n);
 
        addattr_l(n, MAX_MSG, tca_id, NULL, 0);
        addattr_l(n, MAX_MSG, TCA_ACT_BPF_PARMS, &parm, sizeof(parm));
 
-       if (ebpf) {
+       if (ebpf_fill) {
                addattr32(n, MAX_MSG, TCA_ACT_BPF_FD, bpf_fd);
                addattrstrz(n, MAX_MSG, TCA_ACT_BPF_NAME, bpf_name);
-       } else {
+       } else if (bpf_fill) {
                addattr16(n, MAX_MSG, TCA_ACT_BPF_OPS_LEN, bpf_len);
                addattr_l(n, MAX_MSG, TCA_ACT_BPF_OPS, &bpf_ops,
                          bpf_len * sizeof(struct sock_filter));