[pve-devel] [PATCH http-server 1/1] webproxy: handle unflushed write buffer

[Fabian Ebner]

Am 05.11.21 um 14:03 schrieb Fabian Grünbichler:
> for proxied requests, we usually tear down the proxy connection
> immediately when closing the source connection. this is not the correct
> course of action for bulk one-way data streams that are proxied, where
> the source connection might be closed, but the proxy connection might
> still have data in the write buffer that needs to be written out.
> 
> push_shutdown already handles this case (closing the socket/FH after it
> has been fully drained).
> 
> one example for such a proxied data stream is the 'migrate' data for a
> remote migration, which gets proxied over a websocket connection.
> terminating the proxied connection early makes the target VM crash for
> obvious reasons.
> 
> Signed-off-by: Fabian Grünbichler <f.gruenbichler at proxmox.com>
> ---
>   src/PVE/APIServer/AnyEvent.pm | 10 ++++++----
>   1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/src/PVE/APIServer/AnyEvent.pm b/src/PVE/APIServer/AnyEvent.pm
> index 86d0e2e..ecf771f 100644
> --- a/src/PVE/APIServer/AnyEvent.pm
> +++ b/src/PVE/APIServer/AnyEvent.pm
> @@ -144,7 +144,8 @@ sub client_do_disconnect {
>       };
>   
>       if (my $proxyhdl = delete $reqstate->{proxyhdl}) {
> -	&$shutdown_hdl($proxyhdl);
> +	&$shutdown_hdl($proxyhdl)
> +		if !$proxyhdl->{block_disconnect};

Style nit: fits in one line ;)

I'm not familiar with the code, so I'll just ask: can this be reached 
without going through the code below first, i.e. can it happen that 
block_disconnect is not set, but length $proxyhdl->{wbuf} > 0? Or is it 
not important in other cases (if there are any)?

>       }
>   
>       my $hdl = delete $reqstate->{hdl};
> @@ -627,9 +628,10 @@ sub websocket_proxy {
>   		    } elsif ($opcode == 8) {
>   			my $statuscode = unpack ("n", $payload);
>   			$self->dprint("websocket received close. status code: '$statuscode'");
> -			if ($reqstate->{proxyhdl}) {
> -			    $reqstate->{proxyhdl}->push_shutdown();
> -			}
> +			if (my $proxyhdl = $reqstate->{proxyhdl}) {
> +			    $proxyhdl->{block_disconnect} = 1 if length $proxyhdl->{wbuf} > 0;
> +			    $proxyhdl->push_shutdown();
> +		        }
>   			$hdl->push_shutdown();
>   		    } elsif ($opcode == 9) {
>   			# ping received, schedule pong
>