[libvirt] [PATCH 05/19] vircgroup: introduce virCgroupV2DeviceDetectProg

[Pavel Hrdina]

This function will be called if libvirtd was restarted while some
domains were running.  It will try to detect existing programs attached
to the guest cgroup.

Signed-off-by: Pavel Hrdina <phrdina at redhat.com>
---
 src/util/vircgroupv2.c | 105 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 105 insertions(+)

diff --git a/src/util/vircgroupv2.c b/src/util/vircgroupv2.c
index 7a8cc040eb..86adbc4ff9 100644
--- a/src/util/vircgroupv2.c
+++ b/src/util/vircgroupv2.c
@@ -1723,6 +1723,111 @@ virCgroupV2DeviceAttachProg(virCgroupPtr group,
 }
 
 
+static int
+virCgroupV2DeviceCountMapEntries(int mapfd)
+{
+    int ret = 0;
+    int rc;
+    __u64 key = 0;
+    __u64 prevKey = 0;
+
+    while ((rc = virBPFGetNextElem(mapfd, &prevKey, &key)) == 0) {
+        ret++;
+        prevKey = key;
+    }
+
+    if (rc < 0)
+        return -1;
+
+    return ret;
+}
+
+
+# define MAX_PROG_IDS 10
+
+static int
+virCgroupV2DeviceDetectProg(virCgroupPtr group)
+{
+    int ret = -1;
+    int cgroupfd = -1;
+    unsigned int progcnt = 0;
+    unsigned int progids[MAX_PROG_IDS] = { 0 };
+    VIR_AUTOFREE(char *) path = NULL;
+
+    if (group->unified.devices.progfd > 0 && group->unified.devices.mapfd > 0)
+        return 0;
+
+    if (virCgroupV2PathOfController(group, VIR_CGROUP_CONTROLLER_DEVICES,
+                                    NULL, &path) < 0) {
+        return -1;
+    }
+
+    cgroupfd = open(path, O_RDONLY);
+    if (cgroupfd < 0) {
+        virReportSystemError(errno, _("unable to open '%s'"), path);
+        goto cleanup;
+    }
+
+    if (virBPFQueryProg(cgroupfd, MAX_PROG_IDS, BPF_CGROUP_DEVICE,
+                        &progcnt, progids) < 0) {
+        virReportSystemError(errno, "%s", _("unable to query cgroup BPF progs"));
+        goto cleanup;
+    }
+
+    if (progcnt > 0) {
+        int progfd = virBPFGetProg(progids[0]);
+        int mapfd = -1;
+        int nitems = -1;
+        struct bpf_prog_info progInfo = { 0 };
+        struct bpf_map_info mapInfo = { 0 };
+        VIR_AUTOFREE(unsigned int *) mapIDs = NULL;
+
+        if (progfd < 0) {
+            virReportSystemError(errno, "%s", _("failed to get cgroup BPF prog FD"));
+            goto cleanup;
+        }
+
+        if (virBPFGetProgInfo(progfd, &progInfo, &mapIDs) < 0) {
+            virReportSystemError(errno, "%s", _("failed to get cgroup BPF prog info"));
+            goto cleanup;
+        }
+
+        if (progInfo.nr_map_ids == 0) {
+            virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                           _("no map for cgroup BPF prog"));
+            goto cleanup;
+        }
+
+        mapfd = virBPFGetMap(mapIDs[0]);
+        if (mapfd < 0) {
+            virReportSystemError(errno, "%s", _("failed to get cgroup BPF map FD"));
+            goto cleanup;
+        }
+
+        if (virBPFGetMapInfo(mapfd, &mapInfo) < 0) {
+            virReportSystemError(errno, "%s", _("failed to get cgroup BPF map info"));
+            goto cleanup;
+        }
+
+        nitems = virCgroupV2DeviceCountMapEntries(mapfd);
+        if (nitems < 0) {
+            virReportSystemError(errno, "%s", _("failed to count cgroup BPF map items"));
+            goto cleanup;
+        }
+
+        group->unified.devices.progfd = progfd;
+        group->unified.devices.mapfd = mapfd;
+        group->unified.devices.max = mapInfo.max_entries;
+        group->unified.devices.count = nitems;
+    }
+
+    ret = 0;
+ cleanup:
+    VIR_FORCE_CLOSE(cgroupfd);
+    return ret;
+}
+
+
 virCgroupBackend virCgroupV2Backend = {
     .type = VIR_CGROUP_BACKEND_TYPE_V2,
 
-- 
2.20.1