> On Mon, Dec 20, 2021 at 07:18:42PM -0800, Yonghong Song wrote: > > > > > > On 12/20/21 12:40 PM, Tyler Wear wrote: > > > New bpf helper function BPF_FUNC_skb_change_dsfield "int > > > bpf_skb_change_dsfield(struct sk_buff *skb, u8 mask, u8 value)". > > > BPF_PROG_TYPE_CGROUP_SKB typed bpf_prog which currently can be > > > attached to the ingress and egress path. The helper is needed > > > because this type of bpf_prog cannot modify the skb directly. > > > > > > Used by a bpf_prog to specify DS field values on egress or ingress. > > > > Maybe you can expand a little bit here for your use case? > > I know DS field might help but a description of your actual use case > > will make adding this helper more compelling. > +1. More details on the use case is needed. > Also, having an individual helper for each particular header field is too specific. > > For egress, there is bpf_setsockopt() for IP_TOS and IPV6_TCLASS and it can be called in other cgroup hooks. e.g. > BPF_PROG_TYPE_SOCK_OPS during tcp ESTABLISHED event. > There is an example in tools/testing/selftests/bpf/progs/test_tcpbpf_kern.c. > Is it enough for egress? Using bpf_setsockopt() has 2 issues: 1) it changes the userspace visible state 2) won't work with udp sendmsg cmsg
