ssh-generator: suppress error message for vsock EADDRNOTAVAIL

In logs in the Fedora OpenQA CI:
Nov 17 22:20:06 fedora systemd-ssh-generator[4117]: Failed to query local AF_VSOCK CID: Cannot assign requested address
Nov 17 22:20:06 fedora (generato[4088]: /usr/lib/systemd/system-generators/systemd-ssh-generator failed with exit status 1.
Nov 17 22:20:06 fedora systemd[1]: sshd-vsock.socket: Unit configuration changed while unit was running, and no socket file descriptors are open. Unit not functional until restarted.

AF_VSOCK is not configured there and systemd-ssh-generator should just exit
quietly. vsock_get_local_cid() already does some logging at debug level, so we
don't need to.

There is also a second bug, we report modifications to the unit have just
created. I think we have an issue open for this somewhere, but cannot find it.

(cherry picked from commit 8c3acba63b40cd0ebcb9863804e598744eda0b80)

src/ssh-generator/meson.build

@@ -3,15 +3,26 @@
 executables += [
         generator_template + {
                 'name' : 'systemd-ssh-generator',
-                'sources' : files('ssh-generator.c'),
+                'sources' : files(
+                        'ssh-generator.c',
+                        'ssh-util.c',
+                ),
+                'extract' : files(
+                        'ssh-util.c',
+                ),
         },
         libexec_template + {
                 'name' : 'systemd-ssh-proxy',
-                'sources' : files('ssh-proxy.c'),
+                'sources' : files(
+                        'ssh-proxy.c',
+                ),
         },
         libexec_template + {
                 'name' : 'systemd-ssh-issue',
-                'sources' : files('ssh-issue.c'),
+                'sources' : files(
+                        'ssh-issue.c',
+                ),
+                'objects' : ['systemd-ssh-generator'],
         },
 ]
 

src/ssh-generator/ssh-generator.c

@@ -17,6 +17,7 @@
 #include "socket-netlink.h"
 #include "socket-util.h"
 #include "special.h"
+#include "ssh-util.h"
 #include "string-util.h"
 #include "strv.h"
 #include "virt.h"
@@ -211,29 +212,15 @@ static int add_vsock_socket(
                 return 0;
         }
 
-        _cleanup_close_ int vsock_fd = socket(AF_VSOCK, SOCK_STREAM|SOCK_CLOEXEC, 0);
-        if (vsock_fd < 0) {
-                if (ERRNO_IS_NOT_SUPPORTED(errno)) {
-                        log_debug("Not creating AF_VSOCK ssh listener, since AF_VSOCK is not available.");
-                        return 0;
-                }
-
-                return log_error_errno(errno, "Unable to test if AF_VSOCK is available: %m");
-        }
-
-        vsock_fd = safe_close(vsock_fd);
+        r = vsock_open_or_warn(/* ret= */ NULL);
+        if (r <= 0)
+                return r;
 
         /* Determine the local CID so that we can log it to help users to connect to this VM */
         unsigned local_cid;
-        r = vsock_get_local_cid(&local_cid);
-        if (r < 0) {
-                if (ERRNO_IS_DEVICE_ABSENT(r)) {
-                        log_debug("Not creating AF_VSOCK ssh listener, since /dev/vsock is not available (even though AF_VSOCK is).");
-                        return 0;
-                }
-
-                return log_error_errno(r, "Failed to query local AF_VSOCK CID: %m");
-        }
+        r = vsock_get_local_cid_or_warn(&local_cid);
+        if (r <= 0)
+                return r;
 
         r = make_sshd_template_unit(
                         dest,

src/ssh-generator/ssh-issue.c

@@ -15,7 +15,7 @@
 #include "mkdir.h"
 #include "parse-argument.h"
 #include "pretty-print.h"
-#include "socket-util.h"
+#include "ssh-util.h"
 #include "string-util.h"
 #include "tmpfile-util.h"
 #include "virt.h"
@@ -135,33 +135,11 @@ static int acquire_cid(unsigned *ret_cid) {
                 return 0;
         }
 
-        _cleanup_close_ int vsock_fd = socket(AF_VSOCK, SOCK_STREAM|SOCK_CLOEXEC, 0);
-        if (vsock_fd < 0) {
-                if (ERRNO_IS_NOT_SUPPORTED(errno)) {
-                        log_debug("Not creating issue file, since AF_VSOCK is not available.");
-                        *ret_cid = 0;
-                        return 0;
-                }
+        r = vsock_open_or_warn(/* ret= */ NULL);
+        if (r <= 0)
+                return r;
 
-                return log_error_errno(errno, "Unable to test if AF_VSOCK is available: %m");
-        }
-
-        vsock_fd = safe_close(vsock_fd);
-
-        unsigned local_cid;
-        r = vsock_get_local_cid(&local_cid);
-        if (r < 0) {
-                if (ERRNO_IS_DEVICE_ABSENT(r)) {
-                        log_debug("Not creating issue file, since /dev/vsock is not available (even though AF_VSOCK is).");
-                        *ret_cid = 0;
-                        return 0;
-                }
-
-                return log_error_errno(r, "Failed to query local AF_VSOCK CID: %m");
-        }
-
-        *ret_cid = local_cid;
-        return 1;
+        return vsock_get_local_cid_or_warn(ret_cid);
 }
 
 static int run(int argc, char* argv[]) {

src/ssh-generator/ssh-util.c

@@ -0,0 +1,40 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <sys/socket.h>
+#include <unistd.h>
+
+#include "errno-util.h"
+#include "log.h"
+#include "socket-util.h"
+#include "ssh-util.h"
+
+int vsock_open_or_warn(int *ret) {
+        int fd = RET_NERRNO(socket(AF_VSOCK, SOCK_STREAM|SOCK_CLOEXEC, 0));
+        if (ERRNO_IS_NEG_NOT_SUPPORTED(fd))
+                log_debug_errno(fd, "AF_VSOCK is not available, ignoring: %m");
+        else if (fd < 0)
+                return log_error_errno(fd, "Unable to test if AF_VSOCK is available: %m");
+
+        if (ret)
+                *ret = fd;
+        else
+                close(fd);
+
+        return fd >= 0;
+}
+
+int vsock_get_local_cid_or_warn(unsigned *ret) {
+        int r;
+
+        r = vsock_get_local_cid(ret);
+        if (ERRNO_IS_NEG_DEVICE_ABSENT(r) || r == -EADDRNOTAVAIL) {
+                if (ERRNO_IS_NEG_DEVICE_ABSENT(r))
+                        log_debug_errno(r, "/dev/vsock is not available (even though AF_VSOCK is), ignoring: %m");
+                if (ret)
+                        *ret = 0;  /* bogus value */
+                return 0;
+        }
+        if (r < 0)
+                return log_error_errno(r, "Failed to query local AF_VSOCK CID: %m");
+        return 1;
+}

src/ssh-generator/ssh-util.h

@@ -0,0 +1,4 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+int vsock_open_or_warn(int *ret);
+int vsock_get_local_cid_or_warn(unsigned *ret);