Re: [libvirt] [PATCH] util: netdevbridge: fall back to ioctl from sysfs

On Tue, Nov 20, 2018 at 11:17:07AM +0100, Christian Ehrhardt wrote: > There are certain cases e.g. containers where the sysfs path might > exists, but might fail. Unfortunately the exact restrictions are only > known to libvirt when trying to write to it so we need to try it. > > But in case it fails there is no need to fully abort, in those cases try > to fall back to the older ioctl interface which can still work. > > That makes setting up a bridge in unprivileged LXD containers work. > > Fixes: https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/1802906 > > Signed-off-by: Christian Ehrhardt <christian.ehrhardt(a)canonical.com&gt; > --- > src/util/virnetdevbridge.c | 48 +++++++++++++++++++++----------------- > 1 file changed, 26 insertions(+), 22 deletions(-) > > diff --git a/src/util/virnetdevbridge.c b/src/util/virnetdevbridge.c > index 071ebb7b35..cbba3c9652 100644 > --- a/src/util/virnetdevbridge.c > +++ b/src/util/virnetdevbridge.c > @@ -113,6 +113,8 @@ static int virNetDevBridgeCmd(const char *brname, > * or by ioctl on older kernels. Perhaps we could just use > * ioctl for every kernel, but its not clear what the long > * term lifespan of the ioctl interface is... > + * Fall back to ioctl if sysfs interface is not available or > + * failing (e.g. due to container isolation). > */ > static int virNetDevBridgeSet(const char *brname, > const char *paramname, /* sysfs param name */ > @@ -128,29 +130,31 @@ static int virNetDevBridgeSet(const char *brname, > if (virFileExists(path)) { > char valuestr[INT_BUFSIZE_BOUND(value)]; > snprintf(valuestr, sizeof(valuestr), "%lu", value); > - if (virFileWriteStr(path, valuestr, 0) < 0) { > - virReportSystemError(errno, > - _("Unable to set bridge %s %s"), brname, paramname); > - return -1; > - } > + if (virFileWriteStr(path, valuestr, 0) >= 0) > + return 0; > + virReportSystemError(errno, > + _("Unable to set bridge %s %s via sysfs"), > + brname, paramname); The virReportSystemError line should be dropped, since we're not returning an error - we're moving onto the second code path instead.

> + } > + > + unsigned long paramid; > + if (STREQ(paramname, "stp_state")) { > + paramid = BRCTL_SET_BRIDGE_STP_STATE; > + } else if (STREQ(paramname, "forward_delay")) { > + paramid = BRCTL_SET_BRIDGE_FORWARD_DELAY; > } else { > - unsigned long paramid; > - if (STREQ(paramname, "stp_state")) { > - paramid = BRCTL_SET_BRIDGE_STP_STATE; > - } else if (STREQ(paramname, "forward_delay")) { > - paramid = BRCTL_SET_BRIDGE_FORWARD_DELAY; > - } else { > - virReportSystemError(EINVAL, > - _("Unable to set bridge %s %s"), brname, paramname); > - return -1; > - } > - unsigned long args[] = { paramid, value, 0, 0 }; > - ifr->ifr_data = (char*)&args; > - if (ioctl(fd, SIOCDEVPRIVATE, ifr) < 0) { > - virReportSystemError(errno, > - _("Unable to set bridge %s %s"), brname, paramname); > - return -1; > - } > + virReportSystemError(EINVAL, > + _("Unable to set bridge %s %s via ioctl"), > + brname, paramname); > + return -1; > + } > + unsigned long args[] = { paramid, value, 0, 0 }; > + ifr->ifr_data = (char*)&args; > + if (ioctl(fd, SIOCDEVPRIVATE, ifr) < 0) { > + virReportSystemError(errno, > + _("Failed to set bridge %s %s via ioctl"), > + brname, paramname); > + return -1; > } > > return 0; Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|