[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH] ssh: switch from libssh2 to libssh
From: |
Richard W.M. Jones |
Subject: |
Re: [Qemu-devel] [PATCH] ssh: switch from libssh2 to libssh |
Date: |
Thu, 20 Oct 2016 17:11:41 +0100 |
User-agent: |
Mutt/1.5.20 (2009-12-10) |
On Thu, Oct 20, 2016 at 05:44:41PM +0200, Pino Toscano wrote:
> On Thursday, 20 October 2016 16:32:50 CEST Richard W.M. Jones wrote:
> > On Thu, Oct 20, 2016 at 05:15:24PM +0200, Pino Toscano wrote:
> > > Rewrite the implementation of the ssh block driver to use libssh instead
> > > of libssh. The libssh library has various advantages over libssh:
> > > - easier API for authentication (for example for using ssh-agent)
> > > - easier API for known_hosts handling
> > > - supports newer types of keys in known_hosts
> > >
> > > Kerberos authentication can be enabled once the libssh bug for it [1] is
> > > fixed.
> > >
> > > The development version of libssh (i.e. the future 0.8.x) supports
> > > fsync, so reuse the build time check for this.
> > >
> > > [1] https://red.libssh.org/issues/242
> > >
> > > Signed-off-by: Pino Toscano <address@hidden>
> >
> >
> > When I applied this patch and compiled it with warnings enabled:
> >
> > block/ssh.c: In function ‘connect_to_ssh’:
> > block/ssh.c:643:12: warning: ‘ret’ may be used uninitialized in this
> > function [-Wmaybe-uninitialized]
> > return ret;
> > ^~~
>
> Interesting, there was no warning for me. Anyway, I think this:
>
> diff --git a/block/ssh.c b/block/ssh.c
> index 7c316db..7ff376e 100644
> --- a/block/ssh.c
> +++ b/block/ssh.c
> @@ -519,6 +519,7 @@ static int connect_to_ssh(BDRVSSHState *s, QDict *options,
> /* Create SSH session. */
> s->session = ssh_new();
> if (!s->session) {
> + ret = -EINVAL;
> goto err;
> }
>
> should fix it (added already locally).
Yes, this fixes the warning.
> > To test the patch, I used virt-builder to create a virtual machine
> > disk image on another machine (accessible over ssh). Then from my
> > laptop I ran:
> >
> > ./x86_64-softmmu/qemu-system-x86_64 -nodefconfig \
> > -M accel=kvm -cpu host -m 2048 \
> > -drive
> > file.driver=ssh,file.user=[user],file.host=[host],file.path=/var/tmp/fedora-24.img,format=raw,if=virtio
> > \
> > -serial stdio
> >
> > Unfortunately this failed with a large number of sftp errors:
> >
> > read failed: (sftp error code: 0)
> >
> > and subsequently hung. So I'm afraid I couldn't test the patch at all :-(
>
> Can you please enable the logging of the ssh driver, and libssh own
> logging too? Basically (see lines 45-46) set:
>
> #define DEBUG_SSH 1
> #define TRACE_LIBSSH 4
I'll send you the full trace privately since it's enormous.
Rich.
> > Also fsync was not supported for me, but I'm using 0.7.3 and the code
> > says I need 0.8.0.
>
> Yes, this is correct.
>
> Thanks,
> --
> Pino Toscano
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
Fedora Windows cross-compiler. Compile Windows programs, test, and
build Windows installers. Over 100 libraries supported.
http://fedoraproject.org/wiki/MinGW