[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.
Signed-off-by: Laine Stump <laine(a)redhat.com>
---
src/util/virnetdevbandwidth.c | 33 +++++++++++++++++++++++++++------
tests/virnetdevbandwidthtest.c | 3 +++
2 files changed, 30 insertions(+), 6 deletions(-)
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
@@ -797,12 +797,33 @@ int
virNetDevBandWidthAddTxFilterParentQdisc(const char *ifname,
bool hierarchical_class)
{
- g_autoptr(virCommand) cmd = NULL;
+ g_autoptr(virCommand) testCmd = NULL;
+ g_autofree char *testResult = NULL;
- cmd = virCommandNew(TC);
- virCommandAddArgList(cmd, "qdisc", "add", "dev",
ifname, "root",
- "handle", "1:", "htb",
"default",
- hierarchical_class ? "2" : "1", NULL);
+ /* first check it the qdisc with handle 1: was already added for
+ * this interface by someone else
+ */
+ testCmd = virCommandNew(TC);
+ virCommandAddArgList(testCmd, "qdisc", "show", "dev",
ifname,
+ "handle", "1:", NULL);
+ virCommandSetOutputBuffer(testCmd, &testResult);
- return virCommandRun(cmd, NULL);
+ if (virCommandRun(testCmd, NULL) < 0)
+ return -1;
+
+ /* 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;
}
diff --git a/tests/virnetdevbandwidthtest.c b/tests/virnetdevbandwidthtest.c
index 75f960e402..8ee57ccc24 100644
--- a/tests/virnetdevbandwidthtest.c
+++ b/tests/virnetdevbandwidthtest.c
@@ -140,6 +140,7 @@ mymain(void)
"</bandwidth>",
TC " qdisc del dev eth0 root\n"
TC " qdisc del dev eth0 ingress\n"
+ TC " qdisc show dev eth0 handle 1:\n"
TC " qdisc add dev eth0 root handle 1: htb default 1\n"
TC " class add dev eth0 parent 1: classid 1:1 htb rate 1024kbps
quantum 87\n"
TC " qdisc add dev eth0 parent 1:1 handle 2: sfq perturb 10\n"
@@ -170,6 +171,7 @@ mymain(void)
"</bandwidth>",
TC " qdisc del dev eth0 root\n"
TC " qdisc del dev eth0 ingress\n"
+ TC " qdisc show dev eth0 handle 1:\n"
TC " qdisc add dev eth0 root handle 1: htb default 1\n"
TC " class add dev eth0 parent 1: classid 1:1 htb rate 1kbps ceil
2kbps burst 4kb quantum 1\n"
TC " qdisc add dev eth0 parent 1:1 handle 2: sfq perturb 10\n"
@@ -192,6 +194,7 @@ mymain(void)
"</bandwidth>",
TC " qdisc del dev eth0 root\n"
TC " qdisc del dev eth0 ingress\n"
+ TC " qdisc show dev eth0 handle 1:\n"
TC " qdisc add dev eth0 root handle 1: htb default 1\n"
TC " class add dev eth0 parent 1: classid 1:1 htb rate
4294967295kbps quantum 366503875\n"
TC " qdisc add dev eth0 parent 1:1 handle 2: sfq perturb 10\n"
--
2.47.0