DevinLeamy commented on code in PR #509:
URL: https://github.com/apache/mesos/pull/509#discussion_r1520063442
##########
src/linux/ebpf.cpp:
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@@ -151,6 +163,52 @@ Try<Nothing> attach(int fd, const string& cgroup)
return Nothing();
}
+
+Try<vector<uint32_t>> attached(const string& cgroup)
+{
+ Try<int> cgroup_fd = os::open(cgroup, O_DIRECTORY | O_RDONLY | O_CLOEXEC);
+ if (cgroup_fd.isError()) {
+ return Error("Failed to open '" + cgroup + "': " + cgroup_fd.error());
+ }
+
+ // Program ids are unsigned 32-bit integers. We assume that a maximum
+ // of 32 programs are attached to a cgroup; there should only be 0 or 1 but
+ // we allow for more to be safe. We initialize our query buffer with -1 so
+ // we can distinguish between a returned program id and filler values.
+ //
+ // Example: [1, 7, 3, -1, -1, -1, ..., -1] => [1, 7, 3] are program ids.
+ const int MAX_IDS = 32;
+ vector<int32_t> buffer(MAX_IDS, -1);
+
+ bpf_attr attr;
+ memset(&attr, 0, sizeof(attr));
+ attr.query.target_fd = *cgroup_fd;
+ attr.query.attach_type = BPF_CGROUP_DEVICE;
+ attr.query.prog_cnt = MAX_IDS;
+ attr.query.prog_ids = reinterpret_cast<uint64_t>(buffer.data());
+
+ Try<int, ErrnoError> result = bpf(BPF_PROG_QUERY, &attr, sizeof(attr));
+
+ if (result.isError()) {
+ os::close(*cgroup_fd);
+ return Error(
+ "BPF syscall to find a program ids attached to '" + cgroup +
+ "' failed: " + result.error().message);
Review Comment:
Went with the second one.
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