BPF Maps

BPF maps are kernel objects which store data (used by BPF programs) in the form of key-value pairs. Applications access BPF maps using file descriptors. C/R of BPF maps involves serializing their meta-data and data:

Meta-data - This includes information such as map type, key size, value size, etc. CRIU obtains this information from the proc filesystem and using the bpf system call with argument BPF_OBJ_GET_INFO_BY_FD

Data - This is the map's contents i.e. the actual key-value pairs. CRIU relies on batch operations to read (BPF_MAP_LOOKUP_BATCH) key-value pairs from maps during the checkpoint stage and to write (BPF_MAP_UPDATE_BATCH) them during the restore phase.

Support for BPF Maps

CRIU currently supports C/R of the following BPF map types:

• BPF_MAP_TYPE_HASH
• BPF_MAP_TYPE_ARRAY

To-Do

• C/R of BTF (BPF Type Format) information
• C/R of other kinds of BPF maps

External Links

• BPF Documentation
• Notes on BPF
• An eBPF Overview