Re: [PATCH v5] bpf: test_run: Fix the null pointer dereference issue in bpf_lwt_xmit_push_encap

On Tue, 17 Feb 2026 15:26:33 -0800 Martin KaFai Lau wrote:

quoted

Having fastpath checks for test harness really feels like duct tape  

Adding route lookup on ip[v6]_hdr does not work well either and is a 
larger duct tape on the test_run_skb side.

Well, maybe to clarify, the responsibility of the test harness is to
generate valid inputs. Whether it's hard or not to address this issue 
in test_run_skb is a less fundamental than whether it is the correct
place to address it.

An option is to always set skb to 'some' dst (loopback or 
ipv6.fib6_null_entry) on all is_lwt cases without doing the lookup. It 
is only to get it going. It is a duct tape also imo but maybe a middle 
ground.

Sounds reasonable to me, FWIW.