arp.c: If the safe_read that fetches arp responses encounters a return of -1 with errno == EAGAIN or EWOULDBLOCK, then report the error, as it should never happen given that the function is called only once after polling for ready-reads.
arp.c: If the safe_read that fetches arp responses encounters a
return of -1 with errno == EAGAIN or EWOULDBLOCK, then report the
error, as it should never happen given that the function is called
only once after polling for ready-reads.

Further, the old code was buggy; it would subtract from the arpreply_offset
the return value of -1 in that case, which is just wrong.

niklata/ndhc