Re: [PATCH 3/5] util: don't re-add the qdisc used for tx filters if it already exists

There will soon be two separate users of tc on virtual networks, and both will use the "qdisc root handle 1: htb" to add tx filters. One or the other could get the first chance to add the qdisc, and then if at a later time the other decides to use it, we need to prevent the 2nd user from attempting to re-add the qdisc (because that just generates an error). We do this by running "tc qdisc show dev $bridge handle 1:" then checking if the output of that command starts with "qdisc htb 1: root". If it does then the qdisc is already there. If not then we need to add it now.

diff --git a/src/util/virnetdevbandwidth.c b/src/util/virnetdevbandwidth.c index 09c10e9a15..ae7214a9d5 100644 --- a/src/util/virnetdevbandwidth.c +++ b/src/util/virnetdevbandwidth.c

+ + /* output will be something like: "qdisc htb 1: root refcnt ..." + * if the qdisc was already added. + */ + if (!(testResult && STRPREFIX(testResult, "qdisc htb 1: root"))) {

+ /* didn't find qdisc in output, so we need to add one */ + g_autoptr(virCommand) addCmd = virCommandNew(TC); + + virCommandAddArgList(addCmd, "qdisc", "add", "dev", ifname, "root", + "handle", "1:", "htb", "default", + hierarchical_class ? "2" : "1", NULL); + + return virCommandRun(addCmd, NULL); + } + + return 0; }