[PATCH] net/tap: Modified TAP BPF program as per the new Kernel-version upgrade requirements.

[Stephen Hemminger]

On Thu,  4 Jan 2024 22:57:56 +0530
madhuker.mythri at oracle.com wrote:

> From: Madhuker Mythri <madhuker.mythri at oracle.com>
> 
> When multiple queues configured, internally RSS will be enabled and thus TAP BPF RSS byte-code will be loaded on to the Kernel using BPF system calls.
> 
> Here, the problem is loading the existing BPF byte-code to the Kernel-5.15 and above versions throws errors, i.e: Kernel BPF verifier not accepted this existing BPF byte-code and system calls return error code "-7" as follows:
> ------------------------
> rss_add_actions(): Failed to load BPF section l3_l4 (7): Argument list too long
> ------------------------
> 
> RCA:  These errors started coming after from the Kernel-5.15 version, in which lots of new BPF verification restrictions were added for safe execution of byte-code on to the Kernel, due to which existing BPF program verification does not pass.
> Here are the major BPF verifier restrictions observed:
> 1) Need to use new BPF maps structure.
> 2) Kernel SKB data pointer access not allowed.
> 3) Undefined loops were not allowed(which are bounded by a variable value).
> 4) unreachable instructions(like: undefined array access).
> 
> After addressing all these Kernel BPF verifier restrictions able to load the BPF byte-code onto the Kernel successfully.
> 
> Note: This new BPF changes supports from Kernel:4.10 version.
> 
> Bugzilla Id: 1329
> 
> Signed-off-by: Madhuker Mythri <madhuker.mythri at oracle.com>
> ---
>  drivers/net/tap/bpf/tap_bpf_program.c |  243 +-
>  drivers/net/tap/tap_bpf_api.c         |    4 +-
>  drivers/net/tap/tap_bpf_insns.h       | 3781 ++++++++++++++-----------
>  3 files changed, 2151 insertions(+), 1877 deletions(-)

Patch has trailing whitespace, git complains:
$ git am /tmp/bpf.mbox
Applying: net/tap: Modified TAP BPF program as per the new Kernel-version upgrade requirements.
/home/shemminger/DPDK/main/.git/worktrees/libbpf/rebase-apply/patch:98: trailing whitespace.
	// queue match 
/home/shemminger/DPDK/main/.git/worktrees/libbpf/rebase-apply/patch:243: trailing whitespace.
			/** Is IP fragmented **/ 
/home/shemminger/DPDK/main/.git/worktrees/libbpf/rebase-apply/patch:326: trailing whitespace.
/*	bpf_printk(">>>>> rss_l3_l4 hash=0x%x queue:1=%u\n", hash, queue); */ 
warning: 3 lines add whitespace errors.