• Martin KaFai Lau's avatar
    bpf: Introduce bpf sk local storage · 6ac99e8f
    Martin KaFai Lau authored
    After allowing a bpf prog to
    - directly read the skb->sk ptr
    - get the fullsock bpf_sock by "bpf_sk_fullsock()"
    - get the bpf_tcp_sock by "bpf_tcp_sock()"
    - get the listener sock by "bpf_get_listener_sock()"
    - avoid duplicating the fields of "(bpf_)sock" and "(bpf_)tcp_sock"
      into different bpf running context.
    
    this patch is another effort to make bpf's network programming
    more intuitive to do (together with memory and performance benefit).
    
    When bpf prog needs to store data for a sk, the current practice is to
    define a map with the usual 4-tuples (src/dst ip/port) as the key.
    If multiple bpf progs require to store different sk data, multiple maps
    have to be defined.  Hence, wasting memory to store the duplicated
    keys (i.e. 4 tuples here) in each of the bpf map.
    [ The smallest key could be the sk pointer itself which requires
      some enhancement in the verifier and it is a separate topic. ]
    
    Also, the bpf prog needs to clean up the elem when sk is freed.
    Otherwise, the...
    6ac99e8f