[PATCH 4/5] VSOCK: add send_byte()/recv_byte() test utilities

[Stefan Hajnoczi <stefanha@redhat.com>]

Test cases will want to transfer data.  This patch adds utility
functions to do this.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 tools/testing/vsock/util.h |  2 +
 tools/testing/vsock/util.c | 99 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 101 insertions(+)

diff --git a/tools/testing/vsock/util.h b/tools/testing/vsock/util.h
index 3e6971f15caa..cf43d42591bc 100644
--- a/tools/testing/vsock/util.h
+++ b/tools/testing/vsock/util.h
@@ -35,6 +35,8 @@ unsigned int parse_cid(const char *str);
 int vsock_stream_connect(unsigned int cid, unsigned int port);
 int vsock_stream_accept(unsigned int cid, unsigned int port,
 			struct sockaddr_vm *clientaddrp);
+void send_byte(int fd, int expected_ret);
+void recv_byte(int fd, int expected_ret);
 void run_tests(const struct test_case *test_cases,
 	       const struct test_opts *opts);
 
diff --git a/tools/testing/vsock/util.c b/tools/testing/vsock/util.c
index 2be923fe9922..e28085a2a429 100644
--- a/tools/testing/vsock/util.c
+++ b/tools/testing/vsock/util.c
@@ -13,6 +13,7 @@
 
 #include <errno.h>
 #include <stdio.h>
+#include <stdint.h>
 #include <stdlib.h>
 #include <signal.h>
 #include <unistd.h>
@@ -153,6 +154,104 @@ int vsock_stream_accept(unsigned int cid, unsigned int port,
 	return client_fd;
 }
 
+/* Transmit one byte and check the return value.
+ *
+ * expected_ret:
+ *  <0 Negative errno (for testing errors)
+ *   0 End-of-file
+ *   1 Success
+ */
+void send_byte(int fd, int expected_ret)
+{
+	const uint8_t byte = 'A';
+	ssize_t nwritten;
+
+	timeout_begin(TIMEOUT);
+	do {
+		nwritten = write(fd, &byte, sizeof(byte));
+		timeout_check("write");
+	} while (nwritten < 0 && errno == EINTR);
+	timeout_end();
+
+	if (expected_ret < 0) {
+		if (nwritten != -1) {
+			fprintf(stderr, "bogus write(2) return value %zd\n",
+				nwritten);
+			exit(EXIT_FAILURE);
+		}
+		if (errno != -expected_ret) {
+			perror("write");
+			exit(EXIT_FAILURE);
+		}
+		return;
+	}
+
+	if (nwritten < 0) {
+		perror("write");
+		exit(EXIT_FAILURE);
+	}
+	if (nwritten == 0) {
+		if (expected_ret == 0)
+			return;
+
+		fprintf(stderr, "unexpected EOF while sending byte\n");
+		exit(EXIT_FAILURE);
+	}
+	if (nwritten != sizeof(byte)) {
+		fprintf(stderr, "bogus write(2) return value %zd\n", nwritten);
+		exit(EXIT_FAILURE);
+	}
+}
+
+/* Receive one byte and check the return value.
+ *
+ * expected_ret:
+ *  <0 Negative errno (for testing errors)
+ *   0 End-of-file
+ *   1 Success
+ */
+void recv_byte(int fd, int expected_ret)
+{
+	uint8_t byte;
+	ssize_t nread;
+
+	timeout_begin(TIMEOUT);
+	do {
+		nread = read(fd, &byte, sizeof(byte));
+		timeout_check("read");
+	} while (nread < 0 && errno == EINTR);
+	timeout_end();
+
+	if (expected_ret < 0) {
+		if (nread != -1) {
+			fprintf(stderr, "bogus read(2) return value %zd\n",
+				nread);
+			exit(EXIT_FAILURE);
+		}
+		if (errno != -expected_ret) {
+			perror("read");
+			exit(EXIT_FAILURE);
+		}
+		return;
+	}
+
+	if (nread < 0) {
+		perror("read");
+		exit(EXIT_FAILURE);
+	}
+	if (nread == 0) {
+		if (expected_ret == 0)
+			return;
+
+		fprintf(stderr, "unexpected EOF while receiving byte\n");
+		exit(EXIT_FAILURE);
+	}
+	if (nread != sizeof(byte)) {
+		fprintf(stderr, "bogus read(2) return value %zd\n", nread);
+		exit(EXIT_FAILURE);
+	}
+}
+
 /* Run test cases.  The program terminates if a failure occurs. */
 void run_tests(const struct test_case *test_cases,
 	       const struct test_opts *opts)
-- 
2.14.3