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

From: Jakub Kicinski <[email-masked]>
Date: Tue, 17 Feb 2026 14:08:31 -0800

On Tue, 17 Feb 2026 10:08:29 -0800 Martin KaFai Lau wrote:
> > The reason for the CI test failure.  
> 
> Make sense, but the early point stays the same: the user-provided skb 
> can have unexpected data. Either an skb->protocol is not handled here, 
> or the earlier dst lookup has an error. I don't know what the current 
> active users left in lwt are. Unless there is an issue with missing 
> skb_dst() in other mainstream program types (e.g., tc), I would prefer 
> to add a check in bpf_lwt_push_ip_encap() instead of complicating 
> bpf_prog_test_run_skb() further.

Can bpf_prog_test_run_skb() simply not support LWT then?
Having fastpath checks for test harness really feels like duct tape