Re: static variable in xdp

["Toke Høiland-Jørgensen" <toke@redhat.com>]

Benjamin Beckmeyer <beb@eks-engel.de> writes:

> Hi all,
>
> I hope you could help me with a static variable problem in xdp.
> Here is my source:
>
> static __u32 last_xid = 0;
>
> static __always_inline int profinet_process_packet(struct xdp_md *ctx, __u64 off) {
>     void *data_end = (void *)(long)ctx->data_end;
>     void *data = (void *)(long)ctx->data;
>     struct profinet_hdr *p_hdr;
>     __u16 profinet_frame_id;
> //  static __u32 last_xid;
>
>     p_hdr = data + off;
>
>     if (p_hdr + 1 > data_end)
>         return XDP_DROP;
>
>     profinet_frame_id = bpf_htons(p_hdr->frame_id);
>
>     if ((profinet_frame_id >= 0x0100 && profinet_frame_id <=0x7fff) ||
>         (profinet_frame_id == 0x0020) ||
>         (profinet_frame_id == 0xbbff) ||
>         (profinet_frame_id == 0xfefc) ||
>         (profinet_frame_id == 0xf7ff))
>             return XDP_DROP;
>
>     if (p_hdr->xid == last_xid)
>         return XDP_DROP;
>     else
>         last_xid = p_hdr->xid;
>
>     return XDP_PASS;
> }
>
> At the moment I'm using kernel version 6.0.2 and iproute2-6.0.0.
> I also tried to load the the filter with xdp_loader (xdp_tools).
>
> Output from ip:
> $ ip link set dev eth0 xdpgeneric obj xdp_prog_kern.o sec
>  eks_filter
>
> Prog section 'eks_filter' rejected: Permission denied (13)!
>  - Type:         6
>  - Instructions: 48 (0 over limit)
>  - License:      GPL
>
> Verifier analysis:
>
> Error fetching program/map!
>
> Output from xdp_loader:
> $ ./xdp_loader -deth0 -A --filename xdp_prog_kern.o --pro
> gsec eks_filter
> libbpf: failed to guess program type based on ELF section name 'eks_filter'
> libbpf: supported section(type) names are: socket kprobe/ uprobe/ 
> kretprobe/ uretprobe/ classifier action tracepoint/ tp/ raw_tracepoint/ 
> raw_tp/ tp_btf/ xdp perf_event lwt_in lwt_out lwt_xmit lwt_seg6local 
> cgroup_skb/ingress cgroup_skb/egress cgroup/skb cgroup/sock 
> cgroup/post_bind4 cgroup/post_bind6 cgroup/dev sockops sk_skb/stream_parser 
> sk_skb/stream_verdict sk_skb sk_msg lirc_mode2 flow_dissector cgroup/bind4 
> cgroup/bind6 cgroup/connect4 cgroup/connect6 cgroup/sendmsg4 
> cgroup/sendmsg6 cgroup/recvmsg4 cgroup/recvmsg6 cgroup/sysctl 
> cgroup/getsockopt cgroup/setsockopt
> Success: Loaded BPF-object(xdp_prog_kern.o) and used section(eks_filter)
>  - XDP prog attached on device:eth0(ifindex:2)
>  - Pinning maps in /sys/fs/bpf/eth0/
> libbpf: failed to pin map: Operation not permitted
> ERR: pinning maps

This does not look like the output of the xdp-loader from xdp-tools; are
you using the code from the xdp-tutorial? Try using the one from
xdp-tools instead...

Also, there's a hint here:

> libbpf: failed to guess program type based on ELF section name 'eks_filter'

You should use SEC("xdp") for XDP programs instead of custom section
names, those are deprecated...

-Toke