libvirt previously only touched an interface's disable_ipv6 setting in sysfs if it needed to be set to 1, assuming that 0 is the default. Apparently that isn't always the case though (kernel 3.15.7-1 in Arch Linux reportedly defaults a new interface's disable_ipv6 setting to 1) so this patch explicitly sets it to 0 or 1 as appropriate. --- src/network/bridge_driver.c | 41 +++++++++++++++++++++-------------------- 1 file changed, 21 insertions(+), 20 deletions(-) diff --git a/src/network/bridge_driver.c b/src/network/bridge_driver.c index 6ccc6e2..965fdec 100644 --- a/src/network/bridge_driver.c +++ b/src/network/bridge_driver.c @@ -1824,33 +1824,34 @@ networkSetIPv6Sysctls(virNetworkObjPtr network) { char *field = NULL; int ret = -1; + bool enableIPv6 = !!virNetworkDefGetIpByIndex(network->def, AF_INET6, 0); - if (!virNetworkDefGetIpByIndex(network->def, AF_INET6, 0)) { - /* Only set disable_ipv6 if there are no ipv6 addresses defined for - * the network. - */ - if (virAsprintf(&field, SYSCTL_PATH "/net/ipv6/conf/%s/disable_ipv6", - network->def->bridge) < 0) - goto cleanup; + /* set disable_ipv6 if there are no ipv6 addresses defined for the + * network. But also unset it if there *are* ipv6 addresses, as we + * can't be sure of its default value. + */ + if (virAsprintf(&field, SYSCTL_PATH "/net/ipv6/conf/%s/disable_ipv6", + network->def->bridge) < 0) + goto cleanup; - if (access(field, W_OK) < 0 && errno == ENOENT) { + if (access(field, W_OK) < 0 && errno == ENOENT) { + if (!enableIPv6) VIR_DEBUG("ipv6 appears to already be disabled on %s", network->def->bridge); - ret = 0; - goto cleanup; - } + ret = 0; + goto cleanup; + } - if (virFileWriteStr(field, "1", 0) < 0) { - virReportSystemError(errno, - _("cannot write to %s to disable IPv6 on bridge %s"), - field, network->def->bridge); - goto cleanup; - } - VIR_FREE(field); + if (virFileWriteStr(field, enableIPv6 ? "0" : "1", 0) < 0) { + virReportSystemError(errno, + _("cannot write to %s to enable/disable IPv6 " + "on bridge %s"), field, network->def->bridge); + goto cleanup; } + VIR_FREE(field); - /* The rest of the ipv6 sysctl tunables should always be set, - * whether or not we're using ipv6 on this bridge. + /* The rest of the ipv6 sysctl tunables should always be set the + * same, whether or not we're using ipv6 on this bridge. */ /* Prevent guests from hijacking the host network by sending out -- 1.9.3