Return a bitmap of registered vsock transports. As guesstimated by grepping
/proc/kallsyms (CONFIG_KALLSYMS=y) for known symbols of type `struct
virtio_transport`.

Suggested-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Michal Luczaj <redacted>
---
tools/testing/vsock/util.c | 60 ++++++++++++++++++++++++++++++++++++++++++++++
tools/testing/vsock/util.h | 12 ++++++++++
2 files changed, 72 insertions(+)

diff --git a/tools/testing/vsock/util.c b/tools/testing/vsock/util.c
index b7b3fb2221c1682ecde58cf12e2f0b0ded1cff39..74fb52f566148b16436251216dd9d9275f0ec95b 100644
--- a/tools/testing/vsock/util.c
+++ b/tools/testing/vsock/util.c

@@ -7,6 +7,7 @@
 * Author: Stefan Hajnoczi <stefanha@redhat.com>
 */

+#include <ctype.h>

#include <errno.h>
#include <stdio.h>
#include <stdint.h>

@@ -17,6 +18,7 @@

#include <assert.h>
#include <sys/epoll.h>
#include <sys/mman.h>
+#include <linux/kernel.h>
#include <linux/sockios.h>

#include "timeout.h"

@@ -854,3 +856,61 @@ void enable_so_linger(int fd, int timeout)

		exit(EXIT_FAILURE);
	}
}
+
+static int __get_transports(void)
+{
+	/* Order must match transports defined in util.h.
+	 * man nm: "d" The symbol is in the initialized data section.
+	 */
+	const char * const syms[] = {
+		"d loopback_transport",
+		"d virtio_transport",
+		"d vhost_transport",
+		"d vmci_transport",
+		"d hvs_transport",
+	};

+	char buf[KALLSYMS_LINE_LEN];
+	int ret = 0;
+	FILE *f;
+
+	f = fopen(KALLSYMS_PATH, "r");
+	if (!f) {
+		perror("Can't open " KALLSYMS_PATH);
+		exit(EXIT_FAILURE);
+	}
+
+	while (fgets(buf, sizeof(buf), f)) {
+		char *match;
+		int i;
+
+		assert(buf[strlen(buf) - 1] == '\n');
+
+		for (i = 0; i < ARRAY_SIZE(syms); ++i) {
+			match = strstr(buf, syms[i]);
+
+			/* Match should be followed by '\t' or '\n'.
+			 * See kallsyms.c:s_show().
+			 */
+			if (match && isspace(match[strlen(syms[i])])) {
+				ret |= _BITUL(i);
+				break;
+			}
+		}
+	}
+
+	fclose(f);
+	return ret;
+}
+
+/* Return integer with TRANSPORT_* bit set for every (known) registered vsock
+ * transport.
+ */
+int get_transports(void)
+{
+	static int tr = -1;
+
+	if (tr == -1)
+		tr = __get_transports();
+
+	return tr;
+}

diff --git a/tools/testing/vsock/util.h b/tools/testing/vsock/util.h
index 0afe7cbae12e5194172c639ccfbeb8b81f7c25ac..63953e32c3e18e1aa5c2addcf6f09f433660fa84 100644
--- a/tools/testing/vsock/util.h
+++ b/tools/testing/vsock/util.h

@@ -3,8 +3,19 @@

#define UTIL_H

#include <sys/socket.h>
+#include <linux/bitops.h>
#include <linux/vm_sockets.h>

+#define KALLSYMS_PATH		"/proc/kallsyms"
+#define KALLSYMS_LINE_LEN	512

+
+/* All known transports */
+#define TRANSPORT_LOOPBACK	_BITUL(0)
+#define TRANSPORT_VIRTIO	_BITUL(1)
+#define TRANSPORT_VHOST		_BITUL(2)
+#define TRANSPORT_VMCI		_BITUL(3)
+#define TRANSPORT_HYPERV	_BITUL(4)
+
/* Tests can either run as the client or the server */
enum test_mode {
	TEST_MODE_UNSET,

@@ -82,4 +93,5 @@ void setsockopt_timeval_check(int fd, int level, int optname,

			      struct timeval val, char const *errmsg);
void enable_so_zerocopy_check(int fd);
void enable_so_linger(int fd, int timeout);
+int get_transports(void);
#endif /* UTIL_H */

-- 
2.49.0