LoadAndAssign not loading all XDP programs and program array map statically initialized not populated about ebpf

[ti-mo]

See #578.

This is a characteristic of program arrays. If all userspace references are gone (no more pins/fds), all its entries are removed. In your program, after the call to link.AttachXDP, there are no more references to objs and the runtime is free to collect it and any resources it points to, including all *Maps. *Map has a finalizer that calls Close() on itself when it's collected, causing the underlying fd to be closed, clearing the map.

Your code has two problems:

• Due to what I wrote above, omitting Close() is an error. Uncommenting defer objs.Close() will make sure there's a reference to objs until your main returns: https://github.com/vincentmli/go-xdpdns/blob/cf67ba09050a4525a89f6041850dd63bcd956cde/main.go#LL178C22-L178C22.
• jmp_rate_table and jmp_cookie_table don't have their pinning flags set, so they won't be pinned despite setting CollectionOptions.Maps.PinPath. Since your program is short-lived, this always clears the prog arrays instantly.

[vincentmli]

sorry to re-open this, I thought maybe I had the program array map defined wrong result in program array map not populated by ebpf-go library, but after I test using https://github.com/vincentmli/XDPeriments/blob/master/Cookies/xdp_dns_cookies_user.c to load same bpf object file, the program array map is populated properly, so I think this has something to do with LoadAndAssign, here is the program array map:

struct {
        __uint(type, BPF_MAP_TYPE_PROG_ARRAY);
        __uint(max_entries, 3);
        __uint(key_size, sizeof(uint32_t));
        __uint(value_size, sizeof(uint32_t));
        __array(values, int (void *));
} jmp_rate_table SEC(".maps") = {
        .values = {
                [DO_RATE_LIMIT_IPV6] = (void *)&xdp_do_rate_limit_ipv6,
                [DO_RATE_LIMIT_IPV4] = (void *)&xdp_do_rate_limit_ipv4,
        },
};