kern: wg: split address/mask construction out of wg_aip_add()

[kevans]

Summary

We'll re-use these in a future wg_aip_del() to perfectly reconstruct
what we expect to find in a_addr/a_mask.

[aly_aaronly.me]

sys/dev/wg/if_wg.c

533

This function has quite a few parameters. Why not use something like:

static int
wg_aip_addrinfo(struct wg_aip *aip, const void *addr, uint8_t cidr)
{
    switch (aip->af) {
    ...
    }
}

static int
wg_aip_add(...)
{
    ...
    ret = wg_aip_addrinfo(...);
    if (ret != 0) { ... };

    MPASS(af == AF_INET4 || af == AF_INET6);
    root = af == AF_INET ? sc->sc_aip4 : sc->sc_aip6;
    ...
}

[kevans]

sys/dev/wg/if_wg.c

533

Generally because of the next review, where we have to construct an addr/mask before we can find the existing entry.

[aly_aaronly.me]

sys/dev/wg/if_wg.c

533

I had a rough look at the next review as well, and I think it's okay to simplify this function by using an on-stack struct wg_aip aip instead of struct aip_addr a_addr, a_mask.

[kevans]

Simplify wg_aip_addrinfo() a bit more based on feedback