On Sat, Feb 23, 2019 at 05:32:14PM -0800, Eric Dumazet wrote: > > > On 02/22/2019 05:06 PM, brakmo wrote: > > From: Martin KaFai Lau <ka...@fb.com> > > > > This patch adds a new bpf helper BPF_FUNC_tcp_enter_cwr > > "int bpf_tcp_enter_cwr(struct bpf_tcp_sock *tp)". > > It is added to BPF_PROG_TYPE_CGROUP_SKB which can be attached > > to the egress path where the bpf prog is called by > > ip_finish_output() or ip6_finish_output(). The verifier > > ensures that the parameter must be a tcp_sock. > > > > This helper makes a tcp_sock enter CWR state. It can be used > > by a bpf_prog to manage egress network bandwidth limit per > > cgroupv2. A later patch will have a sample program to > > show how it can be used to limit bandwidth usage per cgroupv2. > > > > To ensure it is only called from BPF_CGROUP_INET_EGRESS, the > > attr->expected_attach_type must be specified as BPF_CGROUP_INET_EGRESS > > during load time if the prog uses this new helper. > > The newly added prog->enforce_expected_attach_type bit will also be set > > if this new helper is used. This bit is for backward compatibility reason > > because currently prog->expected_attach_type has been ignored in > > BPF_PROG_TYPE_CGROUP_SKB. During attach time, > > prog->expected_attach_type is only enforced if the > > prog->enforce_expected_attach_type bit is set. > > i.e. prog->expected_attach_type is only enforced if this new helper > > is used by the prog. > > > > BTW, it seems to me that BPF_CGROUP_INET_EGRESS can be used while the socket > lock is not held. Thanks for pointing it out.
ic. I just noticed the comments at ip6_xmit(): /* * xmit an sk_buff (used by TCP, SCTP and DCCP) * Note : socket lock is not held for SYNACK packets, but might be modified * by calls to skb_set_owner_w() and ipv6_local_error(), * which are using proper atomic operations or spinlocks. */ Is there other cases other than SYNACK? Thanks, Martin
