> From: Daniel Borkmann <daniel@xxxxxxxxxxxxx> > Sent: Monday, August 31, 2020 1:33 PM > To: Ramamurthy, Harshitha <harshitha.ramamurthy@xxxxxxxxx>; > bpf@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; ast@xxxxxxxxxx; > davem@xxxxxxxxxxxxx; kuba@xxxxxxxxxx > Cc: dsahern@xxxxxxxxx; Duyck, Alexander H > <alexander.h.duyck@xxxxxxxxx>; Herbert, Tom <tom.herbert@xxxxxxxxx> > Subject: Re: [PATCH bpf-next] bpf: add bpf_get_xdp_hash helper function > > On 8/31/20 9:25 PM, Harshitha Ramamurthy wrote: > > This patch adds a helper function called bpf_get_xdp_hash to calculate > > the hash for a packet at the XDP layer. In the helper function, we > > call the kernel flow dissector in non-skb mode by passing the net > > pointer to calculate the hash. > > So this commit msg says 'what' the patch does, but says nothing about 'why' > it is needed especially given there's the 1 mio insn limit in place where it > should be easy to write that up in BPF anyway. The commit msg needs to > have a clear rationale which describes the motivation behind this helper.. > why it cannot be done in BPF itself? Okay, will add a rationale in the commit message in the next version for use-case. Thanks, Harshitha > > > Changes since RFC: > > - accounted for vlans(David Ahern) > > - return the correct hash by not using skb_get_hash(David Ahern) > > - call __skb_flow_dissect in non-skb mode > >
