Use `struct nf_nat_range2` for kernel 4.18+

Signed-off-by: Deng Qingfang <dengqf6@mail2.sysu.edu.cn>

RFC2326 specifies the attribute client_port as the RTP/RTCP port pair on
which the client has chosen to receive media data and control info;
however some clients (mostly STBs) embed the client_port value in the
destination attribute in the form of destination=<address:port> without
specifying the client_port attribute in the SETUP message.
To support such clients check if the destination attribute contains a
port value and use it as port value for the expected RTP connection.

Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>

Fix compile issue with Werror:

nf_conntrack_rtsp.c:667:39: error: implicit declaration of function 'nf_ct_zone' [-Werror=implicit-function-declaration]
   exp_ct = nf_ct_expect_find_get(net, nf_ct_zone(ct), &t);

Fix compile warning:

nf_conntrack_rtsp.c:474:2: warning: enumeration value 'IP_CT_DIR_MAX' not handled in switch [-Wswitch]
  switch (CTINFO2DIR(ctinfo)) {
  ^~~~~~

Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>

Update source IP of the expected RTP connection according to the SOURCE
attribute value if present in the RTSP SETUP REPLY message.

Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>

Instead of passing a wildcard source to the expected RTP data connection;
use the server IP address of the RTSP SETUP packet or the RTP media source
from the SETUP URI contained in the SETUP packet.
This guarantees RTP data is only accepted from the expected source.

Signed-off-by: Alin Nastac <alin.nastac@gmail.com>
Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>

This commit moves xtables-addons from
https://github.com/openwrt/openwrt/tree/master/package/network/utils/xtables-addons
into the package feed repository to allow for dependencies on other feed
packages, such as Perl.

Signed-off-by: Philip Prindeville <philipp@redfish-solutions.com>
[fix commit message]
Signed-off-by: Jo-Philipp Wich <jo@mein.io>

Signed-off-by: Jo-Philipp Wich <jo@mein.io>