On 10/20/20 4:51 AM, Toke Høiland-Jørgensen wrote: > From: Toke Høiland-Jørgensen <toke@xxxxxxxxxx> > > The bpf_fib_lookup() helper performs a neighbour lookup for the destination > IP and returns BPF_FIB_LKUP_NO_NEIGH if this fails, with the expectation > that the BPF program will deal with this condition, either by passing the > packet up the stack, or by using bpf_redirect_neigh(). > > The neighbour lookup is done via a hash table (through ___neigh_lookup_noref()), > which incurs some overhead. If the caller knows this is likely to fail > anyway, it may want to skip that and go unconditionally to > bpf_redirect_neigh(). For this use case, add a flag to bpf_fib_lookup() > that will make it skip the neighbour lookup and instead always return > BPF_FIB_LKUP_RET_NO_NEIGH (but still populate the gateway and target > ifindex). > > Signed-off-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx> > --- > include/uapi/linux/bpf.h | 10 ++++++---- > net/core/filter.c | 16 ++++++++++++++-- > tools/include/uapi/linux/bpf.h | 10 ++++++---- > 3 files changed, 26 insertions(+), 10 deletions(-) Nack. Please don't. As I mentioned in my reply to Daniel, I would prefer such logic be pushed to the bpf programs. There is no reason for rare run time events to warrant a new flag and new check in the existing FIB helpers. The bpf programs can take the hit of the extra lookup.
