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 contains both "qdisc" and " 1:
".[*] If it does then the qdisc has already been added. If not then we
need to add it now.
[*]As of this writing, the output more exactly starts with "qdisc
htb 1: root", but our comparison is made purposefully generous to
increase the chances that it will continue to work properly if tc
modifies the format of its output.
Signed-off-by: Laine Stump <laine@xxxxxxxxxx>
---
src/util/virnetdevbandwidth.c | 35 ++++++++++++++++++++++++++++------
tests/virnetdevbandwidthtest.c | 3 +++
2 files changed, 32 insertions(+), 6 deletions(-)
diff --git a/src/util/virnetdevbandwidth.c b/src/util/virnetdevbandwidth.c
index 90eebe6576..5c6a65528c 100644
--- a/src/util/virnetdevbandwidth.c
+++ b/src/util/virnetdevbandwidth.c
@@ -805,12 +805,35 @@ 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. We just search for "qdisc" and
+ * " 1: " anywhere in the output to allow for tc changing its
+ * output format.
+ */
+ if (!(testResult && strstr(testResult, "qdisc") && strstr(testResult, " 1: "))) {
+ /* 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 c34fbd5073..8d78502b0c 100644
--- a/tests/virnetdevbandwidthtest.c
+++ b/tests/virnetdevbandwidthtest.c
@@ -147,6 +147,7 @@ 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"
@@ -177,6 +178,7 @@ 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"
@@ -199,6 +201,7 @@ 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
