In some setups the responses from the DHCP server are sent via lo, which
does not have an address of type `ARPHRD_ETHER` (the address length is
the same, though, just all zeros, by default). Note that the dhcp plugin
doesn't actually care for the MAC address or interface details, that's
only used by the farp plugin.
Fixes: 187c72d1af ("dhcp: Port the plugin to FreeBSD/macOS")
musl's headers define a lot of networking structs. For some, the
definition in the Linux UAPI headers is then suppressed by e.g.
__UAPI_DEF_ETHHDR.
Since we included musl's net/ethernet.h, which includes netinet/if_ether.h
that defines `struct ethhdr` (and the above constant), **after** we
include linux/if_ether.h, there was a compilation error because the
struct was defined multiple times.
However, simply moving that include doesn't fix the problem because for
ARP-specific structs the Linux headers don't provide __UAPI_DEF* checks.
So instead of directly including the linux/ headers, we include those
provided by the C library. For glibc these usually just include the
Linux headers, but for musl this allows them to define the struct
directly. We also need to move if.h and add packet.h, which define
other structs (or include headers that do so) that we use.
Fixes: 187c72d1af ("dhcp: Port the plugin to FreeBSD/macOS")
This also refactors the BPF handling so it can be shared between the
dhcp and farp plugins. The latter is adapted accordingly.
Closesstrongswan/strongswan#2047
Co-authored-by: Tobias Brunner <[email protected]>
Tobias Brunner