xdp prog to drop unknown ethertype 0xcafe frm Veritas Cluster that increments bond interfaces drop counter

xdpdropcafe.c

#include <linux/if_ether.h>
#include <linux/bpf.h>
#include <arpa/inet.h>

#define SEC(NAME) __attribute__((section(NAME), used))

SEC("xdpdropcafe")
int xdp_dropcafe(struct xdp_md *xdp) {
	void *data_end = (void *)(long)xdp->data_end;
	void *data = (void *)(long)xdp->data;
	struct ethhdr *eth = data;

	// Require to pass the ebpf validation tests
	if (eth + 1 > data_end)
		return XDP_DROP;

	// Just drop it
	if (eth->h_proto == htons(0xcafe))
		return XDP_DROP;

	// Let the stack process it
	return XDP_PASS;
}

char _license[] SEC("license") = "GPL";


// Compile with:
//   PROG="xdpdropcafe"
//   clang -O2 -Wall -Wno-compare-distinct-pointer-types -target bpf -c "${PROG}.c" -o "${PROG}.o"
// Load with:
//   PIN="/sys/fs/bpf/$PROG"
//   bpftool prog load "./${PROG}.o" "$PIN"
// List target ifaces:
//   typeset -a IFACES
//   for bondmaster in $(</sys/class/net/bonding_masters); do
//     IFACES+=($bondmaster)
//     for iface in /sys/class/net/$bondmaster/lower_*; do
//       slave="${iface##*lower_}"
//       IFACES+=($slave)
//     done
//   done
// Attach with:
//   for iface in "${IFACES[@]}"; do
//     bpftool net attach xdp pinned $PIN dev $iface
//   done