The parsing logic doesn't handle IPv6 addresses.
Clean it all up.

Rather than do the sorting at runtime, run the tables through `sort`.
This lets us constify them and speed up runtime slightly.

Mark all the read-only strings in this file as const.

The vast majority of these aren't used outside of this file, so mark
them all static accordingly.

Some of the globs might expand into files that start with a dash, so
pass -- everywhere to keep problems from showing up.  Some call sites
don't actually need this, but better to be consistent.

There's no need to cast the char* to a struct in6_addr*, so delete
that logic.

Switch the hardcoded 80 limit to the INET6_ADDRSTRLEN constant.

Make sure the buffer we pass into inet_ntop is always NUL terminated.

This is only used in this file, so localize it.

This might end up violating alignment requirements, so memcpy the
variable through a short variable instead.  For most systems, this
will optimize into the same code anyways, and for the rest, we need
to do it this way to avoid unaligned accesses crashing.

URL: https://bugs.gentoo.org/558436

This avoids casting from a char* pointer to a struct in_addr* pointer
which have different alignment requirements, and moves away from the
deprecated inet_ntoa function.

URL: https://bugs.gentoo.org/558436

The former is the standard name now while the latter is the old one.

The code assumes that sizeof(sin_addr.s_addr) == sizeof(long) == 4 which
fails badly on 64bit systems -- we end up reading 4 extra bytes into the
storage.  Instead, load things indirectly via uint32_t variables since
these are IPv4 addresses.

Use inet_ntop everywhere so that we only have one code path between IPv4
and IPv6.  This also fixes some alignment warnings (due to gethostname
returning char* pointers which we then cast up to in_addr structs).

URL: https://bugs.gentoo.org/558436

Most callers never modify this structure, so constify it everywhere.

Most callers never modify this structure, so constify it everywhere.

These strings are static data set in sub-modules and never modified.

This string is never modified, so constify it.

These are only used internally to initialize themselves, so mark them
static.

These functions are almost entirely the same, so re-use the existing
function rather than duplicate the body.

Wrong conditional includes intended for support of libc5 and glibc
2.0 prevented compilation under systems with alternative libcs,
such as musl. For simplicity, remove these includes necessary for
libc5 and glibc 2.0.

Currently uses sysconf(_SC_TC_CLK) to be more portable.

Make sure we use 64-bit filesystem functions everywhere.  This applies not
only to being able to read large files (which generally doesn't apply to
us), but also being able to simply stat them (as they might be using large
inodes).

No L2CAP or RFCOMM stats doesn't imply no support for Bluetooth; merely a
protocol missing.

An address type field was added, messing up our l2cap status parsing.

When an interface has transferred exbibytes
(> 0.8 EiB, i.e. > 819 PiB) of traffic,
the short display is rounded incorrectly.

For example:
bytes 2154408931384050514 (275.0 PiB)
while correct is (1913.4 PiB)

This happens because we times the rx/tx bytes values by 10,
then calculate the short version from that result:

lib/interface.c:ife_print_long()

tx = ptr->stats.tx_bytes;
short_tx = tx * 10;
if (tx > 1125899906842624ull) {
  short_tx /= 1125899906842624ull;
  Text = "PiB";
}

But multiplying anything more than 819 PiB by 10 overflows a ull
which is a uint64_t (max value of 9223372036854775807).

We'll never get accuracy over 8192 PiB (2^64) when using ull,
but we can at least correctly handle values between 819 - 8192 PiB.

The reason is that debugfs is accessible only by root user:
_PATH_SYS_BLUETOOTH_L2CAP  /sys/kernel/debug/bluetooth/l2cap
_PATH_SYS_BLUETOOTH_RFCOMM /sys/kernel/debug/bluetooth/rfcom

URL: https://www.kernel.org/doc/Documentation/filesystems/debugfs.txt
URL: https://bugzilla.redhat.com/show_bug.cgi?id=1162284

This reverts commit 343192d1.

This fix from RedHat was actually a fix for one of their custom patches.
Applying it to mainline breaks interface stats.

When using a bucket of protocols (like -A inet), do not warn/abort when
some protocols are not supported.

URL: https://bugzilla.redhat.com/1063906
URL: https://bugzilla.redhat.com/1063913

For virtual interfaces created using the ifcfg-ethN:X scripts the
ifconfig and netstat -i report statistics of the last real adapter
listed in /proc/dev/net.

URL: https://bugzilla.redhat.com/143981

The display of "netstat -o" (on|off|keepalive|unkn-X) is not accurate.
I think that "unkn-4" should be "probe0" that is working "probe0 timer
(= ICSK_TIME_PROBE0 status = TCP Window Size is Zero)" in kernel.

URL: https://bugzilla.redhat.com/466845

A bunch of these funcs are only used by interface.c, so drop them from
interface.h and mark them static.  Also mark a bunch of buffers as const
when they aren't written to.