From: Toke Høiland-Jørgensen <toke@xxxxxxxxxx> commit d1c362e1dd68a421cf9033404cf141a4ab734a5d upstream. 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 pass the packet up the stack in this case. However, with the addition of bpf_redirect_neigh() that can be used instead to perform the neighbour lookup, at the cost of a bit of duplicated work. For that we still need the target ifindex, and since bpf_fib_lookup() already has that at the time it performs the neighbour lookup, there is really no reason why it can't just return it in any case. So let's just always return the ifindex if the FIB lookup itself succeeds. Signed-off-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx> Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx> Cc: David Ahern <dsahern@xxxxxxxxx> Link: https://lore.kernel.org/bpf/20201009184234.134214-1-toke@xxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/core/filter.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/net/core/filter.c +++ b/net/core/filter.c @@ -4235,7 +4235,6 @@ static int bpf_fib_set_fwd_params(struct memcpy(params->smac, dev->dev_addr, ETH_ALEN); params->h_vlan_TCI = 0; params->h_vlan_proto = 0; - params->ifindex = dev->ifindex; return 0; } @@ -4333,6 +4332,7 @@ static int bpf_ipv4_fib_lookup(struct ne params->ipv4_dst = nh->nh_gw; params->rt_metric = res.fi->fib_priority; + params->ifindex = dev->ifindex; /* xdp and cls_bpf programs are run in RCU-bh so * rcu_read_lock_bh is not needed here @@ -4447,6 +4447,7 @@ static int bpf_ipv6_fib_lookup(struct ne dev = f6i->fib6_nh.nh_dev; params->rt_metric = f6i->fib6_metric; + params->ifindex = dev->ifindex; /* xdp and cls_bpf programs are run in RCU-bh so rcu_read_lock_bh is * not needed here. Can not use __ipv6_neigh_lookup_noref here
