[PATCH RFC net-next v2 1/3] vsock/test: Introduce vsock_bind_try() helper

[Michal Luczaj]

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 <sgarz...@redhat.com>
Signed-off-by: Michal Luczaj <m...@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