Re: [PATCH net-next v4 7/8] selftests: drv-net: add primary_rx_redirect support to NetDrvContEnv

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Hardcoded little-endian byte order for BPF map updates corrupts variables on big-endian architectures.
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commit 32b478cb3da65a3aa47ba2e69fc7eb3c3f2667d9
Author: Bobby Eshleman <bobbyeshleman@meta.com>

selftests: drv-net: add primary_rx_redirect support to NetDrvContEnv

This commit adds a BPF TC program to redirect non-ICMPv6 IPv6 traffic to a
physical device when sending from a namespace with a netkit leased queue. It
introduces the primary_rx_redirect parameter to NetDrvContEnv to attach
this program and update the physical ifindex via the .bss map.

> diff --git a/tools/testing/selftests/drivers/net/lib/py/env.py b/tools/testing/selftests/drivers/net/lib/py/env.py
> index 409b419222454..af8e1de8ed7b1 100644
> --- a/tools/testing/selftests/drivers/net/lib/py/env.py
> +++ b/tools/testing/selftests/drivers/net/lib/py/env.py

[ ... ]

> @@ -505,3 +529,36 @@ class NetDrvContEnv(NetDrvEpEnv):
>          value = ipv6_bytes + ifindex_bytes
>          value_hex = ' '.join(f'{b:02x}' for b in value)
>          bpftool(f"map update id {bss_map_id} key hex 00 00 00 00 value hex {value_hex}")
> +
> +    def _attach_primary_rx_redirect_bpf(self):

[ ... ]

> +        if redirect_prog_id is None:
> +            raise Exception("Failed to get primary RX redirect BPF prog ID")
> +
> +        bss_map_id = self._find_bss_map_id(redirect_prog_id)
> +        phys_ifindex_bytes = self.ifindex.to_bytes(4, byteorder='little')

Is it safe to hardcode the byte order to little-endian here?

Since BPF .bss maps are read by the BPF program using the host's native
endianness (as volatile __u32 phys_ifindex), this might result in a
swapped 32-bit integer on big-endian architectures like s390x.

For example, an ifindex of 2 could be read as 33554432, causing
bpf_redirect_neigh() to receive an invalid interface index.

Could this use sys.byteorder instead of 'little' to ensure portability?

> +        value_hex = ' '.join(f'{b:02x}' for b in phys_ifindex_bytes)
> +        bpftool(f"map update id {bss_map_id} key hex 00 00 00 00 value hex {value_hex}")

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Sashiko AI review · https://sashiko.dev/#/patchset/20260511-tcp-dm-netkit-v4-0-841b78b99d74@meta.com?part=7