tools: bpftool: add "prog run" subcommand to test-run programs

Add a new "bpftool prog run" subcommand to run a loaded program on input
data (and possibly with input context) passed by the user.

Print output data (and output context if relevant) into a file or into
the console. Print return value and duration for the test run into the
console.

A "repeat" argument can be passed to run the program several times in a
row.

The command does not perform any kind of verification based on program
type (Is this program type allowed to use an input context?) or on data
consistency (Can I work with empty input data?), this is left to the
kernel.

Example invocation:

    # perl -e 'print "\x0" x 14' | ./bpftool prog run \
            pinned /sys/fs/bpf/sample_ret0 \
            data_in - data_out - repeat 5
    0000000 0000 0000 0000 0000 0000 0000 0000      | ........ ......
    Return value: 0, duration (average): 260ns

When one of data_in or ctx_in is "-", bpftool reads from standard input,
in binary format. Other formats (JSON, hexdump) might be supported (via
an optional command line keyword like "data_fmt_in") in the future if
relevant, but this would require doing more parsing in bpftool.

v2:
- Fix argument names for function check_single_stdin(). (Yonghong)

Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

tools/bpf/bpftool/main.c

@@ -117,6 +117,35 @@ bool is_prefix(const char *pfx, const char *str)
 	return !memcmp(str, pfx, strlen(pfx));
 }
 
+/* Last argument MUST be NULL pointer */
+int detect_common_prefix(const char *arg, ...)
+{
+	unsigned int count = 0;
+	const char *ref;
+	char msg[256];
+	va_list ap;
+
+	snprintf(msg, sizeof(msg), "ambiguous prefix: '%s' could be '", arg);
+	va_start(ap, arg);
+	while ((ref = va_arg(ap, const char *))) {
+		if (!is_prefix(arg, ref))
+			continue;
+		count++;
+		if (count > 1)
+			strncat(msg, "' or '", sizeof(msg) - strlen(msg) - 1);
+		strncat(msg, ref, sizeof(msg) - strlen(msg) - 1);
+	}
+	va_end(ap);
+	strncat(msg, "'", sizeof(msg) - strlen(msg) - 1);
+
+	if (count >= 2) {
+		p_err(msg);
+		return -1;
+	}
+
+	return 0;
+}
+
 void fprint_hex(FILE *f, void *arg, unsigned int n, const char *sep)
 {
 	unsigned char *data = arg;