On 02/08/2019 06:56 AM, Martin Lau wrote: > On Thu, Feb 07, 2019 at 11:21:41PM +0100, Daniel Borkmann wrote: >> On 02/07/2019 08:27 AM, Martin Lau wrote: >> [...] >>> Following up the discussion in the iovisor conf call. >>> >>> One of discussion was about: >>> other than tw, can __sk_buff->sk always return a >>> fullsock (PTR_TO_SOCKET_OR_NULL). In request_sock case, >>> it is doable because it can trace back to the listener sock. >>> >>> However, that will go back to the sock_common accessing question. >>> In particular, how to access the sock_common's fields of the >>> request_sock itself? Those fields in the request_sock are different >>> from its listener sock. e.g. the skc_daddr and skc_dport. >>> >>> Also, if the sock_common fields of tw is needed, it will become weird >>> because likely a new "struct bpf_tw_sock" is needed which is OK >>> but all sock_common fields need to be copied from bpf_sock >>> to bpf_tw_sock. >>> >>> I think reading a sk from a ctx should return the >>> most basic type PTR_TO_SOCK_COMMON_OR_NULL (unless the running >>> ctx can guarantee that it always has a fullsock). >>> Currently, it is __sk_buff->sk. Later, sock_ops->sk...etc. >>> One single 'struct bpf_sock' and limit fullsock field access >>> at verification time. The bpf_prog then moves down the chain >>> based on what it needs. It could be fullsock, tcp_sock...etc. >>> >>> I think that will be the most flexible way to write bpf_prog >>> while also avoid having duplicate fields in different >>> bpf struct in uapi. >> >> Ok, thanks for following up and sorry for late reply, lets go with >> sock_common then. What's the plan to moving forward with accessing >> full sk in case of req sk? Separate helper or backed into the newly >> added bpf_sk_fullsock() one? Presumably latter? > I will add sk_to_full_sk() to bpf_sk_fullsock() and bpf_tcp_sock().
Ok, sounds good, thanks!
