I had tested with 5.4 and 5.15 kernel-versions with this new changes and works well. I found that the helper functions were introduced in Kernel 4.7 version. So, thinking this code should work from Kernel-4.9, as mentioned in the TAP PMD link: https://doc.dpdk.org/guides/nics/tap.html.
Yes, I understand BPF program code is very sensitive and difficult to debug. However, as per testing this work well(able to load the RSS BPF instructions) on Azure/Hyper-V platforms with failsafe/tap PMD. Thanks, Madhuker. -----Original Message----- From: Stephen Hemminger <step...@networkplumber.org> Sent: 05 January 2024 23:10 To: Madhuker Mythri <madhuker.myt...@oracle.com> Cc: ferruh.yi...@amd.com; dev@dpdk.org Subject: Re: [External] : Re: [PATCH] net/tap: Modified TAP BPF program as per the new Kernel-version upgrade requirements. On Fri, 5 Jan 2024 14:44:00 +0000 Madhuker Mythri <madhuker.myt...@oracle.com> wrote: > Hi Stephen, > > The BPF helper man pages implies in that way and the SKB data pointer access > was working till 5.4 kernel also, however from Kernel-5.15 version, we do see > eBPF verifier throws error when we use SKB data pointer access. > So, I had used this helper functions and able to resolve the errors. This is > helper functions are safe to use and also protects from any non-linear skb > data buffer access also. > > So, I think using helper functions is better and safe way to access the SKB > data, instead of pointer access. > > Thanks, > Madhuker. Using the accessors may mean it won't work with older kernels, but that is not a huge concern given how fragile this code is.
