[libvirt] [PATCHv2] macvtap: log an error if on failure to connect to netlink socket

(v2 change: add log messages for 2 other previously silent error conditions in nlComm) A bug in libnl (see https://bugzilla.redhat.com/show_bug.cgi?id=677724 and https://bugzilla.redhat.com/show_bug.cgi?id=677725) makes it very easy to create a failure to connect to the netlink socket when trying to open a macvtap network device ("type='direct'" in domain interface XML). When that error occurred (during a call to libnl's nl_connect() from libvirt's nlComm(), there was no log message, leading virsh (for example) to report "unknown error". There were two other cases in nlComm where an error in a libnl function might return with failure but no error reported. In all three cases, this patch logs a message which will hopefully be more useful. Note that more detailed information about the failure might be available from libnl's nl_geterror() function, but it calls strerror(), which is not threadsafe, so we can't use it. --- src/util/macvtap.c | 13 ++++++++++--- 1 files changed, 10 insertions(+), 3 deletions(-) diff --git a/src/util/macvtap.c b/src/util/macvtap.c index a71db86..00ee4ee 100644 --- a/src/util/macvtap.c +++ b/src/util/macvtap.c @@ -123,10 +123,15 @@ int nlComm(struct nl_msg *nl_msg, struct nl_handle *nlhandle = nl_handle_alloc(); struct nlmsghdr *nlmsg = nlmsg_hdr(nl_msg); - if (!nlhandle) + if (!nlhandle) { + virReportSystemError(errno, + "%s", _("cannot allocate nlhandle for netlink")); return -1; + } if (nl_connect(nlhandle, NETLINK_ROUTE) < 0) { + virReportSystemError(errno, + "%s", _("cannot connect to netlink socket")); rc = -1; goto err_exit; } @@ -161,9 +166,11 @@ int nlComm(struct nl_msg *nl_msg, } *respbuflen = nl_recv(nlhandle, &nladdr, respbuf, NULL); - if (*respbuflen <= 0) + if (*respbuflen <= 0) { + virReportSystemError(errno, + "%s", _("nl_recv failed")); rc = -1; - + } err_exit: if (rc == -1) { VIR_FREE(*respbuf); -- 1.7.3.4