Create a socket and bind() it. If binding failed, gracefully return an
error code while preserving `errno`.

Base vsock_bind() on top of it.

Suggested-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Michal Luczaj <mhal@rbox.co>
---
 tools/testing/vsock/util.c | 24 +++++++++++++++++++++---
 tools/testing/vsock/util.h |  1 +
 2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/tools/testing/vsock/util.c b/tools/testing/vsock/util.c
index 0c7e9cbcbc85cde9c8764fc3bb623cde2f6c77a6..b7b3fb2221c1682ecde58cf12e2f0b0ded1cff39 100644
--- a/tools/testing/vsock/util.c
+++ b/tools/testing/vsock/util.c
@@ -121,15 +121,17 @@ bool vsock_wait_sent(int fd)
 	return !ret;
 }
 
-/* Create socket <type>, bind to <cid, port> and return the file descriptor. */
-int vsock_bind(unsigned int cid, unsigned int port, int type)
+/* Create socket <type>, bind to <cid, port>.
+ * Return the file descriptor, or -1 on error.
+ */
+int vsock_bind_try(unsigned int cid, unsigned int port, int type)
 {
 	struct sockaddr_vm sa = {
 		.svm_family = AF_VSOCK,
 		.svm_cid = cid,
 		.svm_port = port,
 	};
-	int fd;
+	int fd, saved_errno;
 
 	fd = socket(AF_VSOCK, type, 0);
 	if (fd < 0) {
@@ -138,6 +140,22 @@ int vsock_bind(unsigned int cid, unsigned int port, int type)
 	}
 
 	if (bind(fd, (struct sockaddr *)&sa, sizeof(sa))) {
+		saved_errno = errno;
+		close(fd);
+		errno = saved_errno;
+		fd = -1;
+	}
+
+	return fd;
+}
+
+/* Create socket <type>, bind to <cid, port> and return the file descriptor. */
+int vsock_bind(unsigned int cid, unsigned int port, int type)
+{
+	int fd;
+
+	fd = vsock_bind_try(cid, port, type);
+	if (fd < 0) {
 		perror("bind");
 		exit(EXIT_FAILURE);
 	}
diff --git a/tools/testing/vsock/util.h b/tools/testing/vsock/util.h
index 5e2db67072d5053804a9bb93934b625ea78bcd7a..0afe7cbae12e5194172c639ccfbeb8b81f7c25ac 100644
--- a/tools/testing/vsock/util.h
+++ b/tools/testing/vsock/util.h
@@ -44,6 +44,7 @@ int vsock_connect(unsigned int cid, unsigned int port, int type);
 int vsock_accept(unsigned int cid, unsigned int port,
 		 struct sockaddr_vm *clientaddrp, int type);
 int vsock_stream_connect(unsigned int cid, unsigned int port);
+int vsock_bind_try(unsigned int cid, unsigned int port, int type);
 int vsock_bind(unsigned int cid, unsigned int port, int type);
 int vsock_bind_connect(unsigned int cid, unsigned int port,
 		       unsigned int bind_port, int type);

-- 
2.49.0

On Wed, Jun 11, 2025 at 09:56:50PM +0200, Michal Luczaj wrote:
>Create a socket and bind() it. If binding failed, gracefully return an
>error code while preserving `errno`.
>
>Base vsock_bind() on top of it.
>
>Suggested-by: Stefano Garzarella <sgarzare@redhat.com>
>Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
>Signed-off-by: Michal Luczaj <mhal@rbox.co>
>---
> tools/testing/vsock/util.c | 24 +++++++++++++++++++++---
> tools/testing/vsock/util.h |  1 +
> 2 files changed, 22 insertions(+), 3 deletions(-)
>
>diff --git a/tools/testing/vsock/util.c b/tools/testing/vsock/util.c
>index 0c7e9cbcbc85cde9c8764fc3bb623cde2f6c77a6..b7b3fb2221c1682ecde58cf12e2f0b0ded1cff39 100644
>--- a/tools/testing/vsock/util.c
>+++ b/tools/testing/vsock/util.c
>@@ -121,15 +121,17 @@ bool vsock_wait_sent(int fd)
> 	return !ret;
> }
>
>-/* Create socket <type>, bind to <cid, port> and return the file descriptor. */
>-int vsock_bind(unsigned int cid, unsigned int port, int type)
>+/* Create socket <type>, bind to <cid, port>.
>+ * Return the file descriptor, or -1 on error.
>+ */
>+int vsock_bind_try(unsigned int cid, unsigned int port, int type)
> {
> 	struct sockaddr_vm sa = {
> 		.svm_family = AF_VSOCK,
> 		.svm_cid = cid,
> 		.svm_port = port,
> 	};
>-	int fd;
>+	int fd, saved_errno;
>
> 	fd = socket(AF_VSOCK, type, 0);
> 	if (fd < 0) {
>@@ -138,6 +140,22 @@ int vsock_bind(unsigned int cid, unsigned int port, int type)
> 	}
>
> 	if (bind(fd, (struct sockaddr *)&sa, sizeof(sa))) {
>+		saved_errno = errno;
>+		close(fd);
>+		errno = saved_errno;
>+		fd = -1;
>+	}
>+
>+	return fd;
>+}
>+
>+/* Create socket <type>, bind to <cid, port> and return the file descriptor. */
>+int vsock_bind(unsigned int cid, unsigned int port, int type)
>+{
>+	int fd;
>+
>+	fd = vsock_bind_try(cid, port, type);
>+	if (fd < 0) {
> 		perror("bind");
> 		exit(EXIT_FAILURE);
> 	}
>diff --git a/tools/testing/vsock/util.h b/tools/testing/vsock/util.h
>index 5e2db67072d5053804a9bb93934b625ea78bcd7a..0afe7cbae12e5194172c639ccfbeb8b81f7c25ac 100644
>--- a/tools/testing/vsock/util.h
>+++ b/tools/testing/vsock/util.h
>@@ -44,6 +44,7 @@ int vsock_connect(unsigned int cid, unsigned int port, int type);
> int vsock_accept(unsigned int cid, unsigned int port,
> 		 struct sockaddr_vm *clientaddrp, int type);
> int vsock_stream_connect(unsigned int cid, unsigned int port);
>+int vsock_bind_try(unsigned int cid, unsigned int port, int type);
> int vsock_bind(unsigned int cid, unsigned int port, int type);
> int vsock_bind_connect(unsigned int cid, unsigned int port,
> 		       unsigned int bind_port, int type);
>
>-- 
>2.49.0
>

Reviewed-by: Luigi Leonardi <leonardi@redhat.com>