On Tue, Jan 18, 2022 at 2:23 PM Tyler Wear <twear@xxxxxxxxxxx> wrote: > > > > > -----Original Message----- > > From: Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> > > Sent: Tuesday, January 18, 2022 12:38 PM > > To: Maciej Żenczykowski <maze@xxxxxxxxxx> > > Cc: Tyler Wear (QUIC) <quic_twear@xxxxxxxxxxx>; Network Development > > <netdev@xxxxxxxxxxxxxxx>; bpf <bpf@xxxxxxxxxxxxxxx>; Yonghong Song > > <yhs@xxxxxx>; Martin KaFai Lau <kafai@xxxxxx>; Toke Høiland-Jørgensen > > <toke@xxxxxxxxxx>; Daniel Borkmann <daniel@xxxxxxxxxxxxx>; Song Liu > > <song@xxxxxxxxxx> > > Subject: Re: [PATCH bpf-next v6 1/2] Add skb_store_bytes() for > > BPF_PROG_TYPE_CGROUP_SKB > > > > WARNING: This email originated from outside of Qualcomm. Please be wary > > of any links or attachments, and do not enable macros. > > > > On Fri, Jan 14, 2022 at 1:18 PM Maciej Żenczykowski <maze@xxxxxxxxxx> > > wrote: > > > > > > > > > > This is wrong. > > > > > > > CGROUP_INET_EGRESS bpf prog cannot arbitrary change packet > > data. > > > > > > I agree with this sentiment, which is why the original proposal was > > > simply to add a helper which is only capable of modifying the > > > tos/tclass/dscp field, and not any arbitrary bytes. (note: there > > > already is such a helper to set the ECN congestion notification bits, > > > so there's somewhat of a precedent) > > > > True. bpf_skb_ecn_set_ce() is available to cg_skb progs. > > An arbitrary tos rewriting helper would screw it up. > > Patch 1 was for a ds_field helper to modify the top 6 bits of TOS, not an arbitrary rewriting. > This should suffice since it doesn't interfere with CE. I still don't hear the answer why tc bpf is not sufficient.
