[RFC PATCH guest-common] tunnel: treat reader_stderr as optional parameter in read_tunnel

[RFC PATCH guest-common] tunnel: treat reader_stderr as optional parameter in read_tunnel

[Daniel Kral]

The reader_stderr parameter was introduced for a specific use case for
the users of fork_ssh_tunnel(). The other callers, such as
fork_websocket_tunnel(), do not provide the parameter and the Perl
interpreter will warn about this:

    Use of uninitialized value $reader_stderr in <HANDLE> at /usr/share/perl5/PVE/Tunnel.pm line 77.
    readline() on unopened filehandle at /usr/share/perl5/PVE/Tunnel.pm line 77.

Therefore, treat reader_stderr as an optional parameter by not reading
from the handle if it is not provided.

Fixes: 8c8aa63 ("tunnel: redirect stderr to log function")
Signed-off-by: Daniel Kral <d.kral@proxmox.com>
---
 src/PVE/Tunnel.pm | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/PVE/Tunnel.pm b/src/PVE/Tunnel.pm
index 148a8e2..68547a5 100644
--- a/src/PVE/Tunnel.pm
+++ b/src/PVE/Tunnel.pm
@@ -74,8 +74,10 @@ sub read_tunnel {
     };
     my $err = $@;
 
-    while (my $line = <$reader_stderr>) { # $reader_stderr is set up as non-blocking
-        $tunnel->{log}->('warn', $line);
+    if (defined($reader_stderr)) {
+        while (my $line = <$reader_stderr>) { # $reader_stderr is set up as non-blocking
+            $tunnel->{log}->('warn', $line);
+        }
     }
 
     die "reading from tunnel failed: $err\n" if $err;
-- 
2.47.3

Re: [RFC PATCH guest-common] tunnel: treat reader_stderr as optional parameter in read_tunnel

[Stoiko Ivanov]

Thanks for the patch (and pointing me to it off-list)!

As I ran into an unrelated issue while migrating a container - and got
distracted by the spurious error-messages this patch suppresses - I went
ahead and gave it a spin - works as advertised.

Additionally looked through `git log` in guest-common - and from a quick
glance your analysis seems on spot:

Tested-by: Stoiko Ivanov <s.ivanov@proxmox.com>
Reviewed-by: Stoiko Ivanov <s.ivanov@proxmox.com>


On Tue, 30 Jun 2026 10:43:32 +0200
Daniel Kral <d.kral@proxmox.com> wrote:

> The reader_stderr parameter was introduced for a specific use case for
> the users of fork_ssh_tunnel(). The other callers, such as
> fork_websocket_tunnel(), do not provide the parameter and the Perl
> interpreter will warn about this:
> 
>     Use of uninitialized value $reader_stderr in <HANDLE> at /usr/share/perl5/PVE/Tunnel.pm line 77.
>     readline() on unopened filehandle at /usr/share/perl5/PVE/Tunnel.pm line 77.
> 
> Therefore, treat reader_stderr as an optional parameter by not reading
> from the handle if it is not provided.
> 
> Fixes: 8c8aa63 ("tunnel: redirect stderr to log function")
> Signed-off-by: Daniel Kral <d.kral@proxmox.com>
> ---
>  src/PVE/Tunnel.pm | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/src/PVE/Tunnel.pm b/src/PVE/Tunnel.pm
> index 148a8e2..68547a5 100644
> --- a/src/PVE/Tunnel.pm
> +++ b/src/PVE/Tunnel.pm
> @@ -74,8 +74,10 @@ sub read_tunnel {
>      };
>      my $err = $@;
>  
> -    while (my $line = <$reader_stderr>) { # $reader_stderr is set up as non-blocking
> -        $tunnel->{log}->('warn', $line);
> +    if (defined($reader_stderr)) {
> +        while (my $line = <$reader_stderr>) { # $reader_stderr is set up as non-blocking
> +            $tunnel->{log}->('warn', $line);
> +        }
>      }
>  
>      die "reading from tunnel failed: $err\n" if $err;