I am seeing unexpected behavior from bpf_obj_get, although this is likely due to my inexperience with BPF.
In a loader program, I create a pinned map at "sys/fs/bpf/test/xdp_stats_map". In a separate statistics program, I access the pinned map via file descriptor -- I got the file descriptor from a call to bpf_obj_get and provided the pathname above. In a polling loop, I call bpf_obj_get on the same pathname and compare this value to the original. However, instead of getting the same file descriptor, the file descriptor returned by bpf_obj_get increments by 1 each invocation (so it returns 4, 5, 6, 7, ...). I am not doing anything externally to reload the map or change the file descriptor. Why is this happening? Looking at samples/bpf/fds_example.c as example usage of bpf_obj_get, I would expect to get the same file descriptor back. Any ideas? Relevant code (filename has already been populated elsewhere): #ifndef PATH_MAX #define PATH_MAX 4096 #endif char filename[PATH_MAX]; static void stats_poll(int map_fd, __u32 map_type, int interval) { int fd; while (1) { fd = bpf_obj_get(filename); printf("filename: %s\n", filename); printf("bpf_obj_get: %d - map_fd: %d\n", fd, map_fd); sleep(interval); } } Relevant output: - BPF map (bpf_map_type:6) id:42 name:xdp_stats_map key_size:4 value_size:16 max_entries:5 filename: /sys/fs/bpf/test/xdp_stats_map bpf_obj_get: 4 - map_fd: 3 filename: /sys/fs/bpf/test/xdp_stats_map bpf_obj_get: 5 - map_fd: 3 filename: /sys/fs/bpf/test/xdp_stats_map bpf_obj_get: 6 - map_fd: 3 -=-=-=-=-=-=-=-=-=-=-=- Links: You receive all messages sent to this group. View/Reply Online (#1699): https://lists.iovisor.org/g/iovisor-dev/message/1699 Mute This Topic: https://lists.iovisor.org/mt/31870056/21656 Group Owner: iovisor-dev+ow...@lists.iovisor.org Unsubscribe: https://lists.iovisor.org/g/iovisor-dev/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-