docs: networking: convert ip_dynaddr.txt to ReST

- add SPDX header;
- adjust title markup;
- mark code blocks and literals as such;
- adjust identation, whitespaces and blank lines;
- add to networking/index.rst.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/index.rst

@@ -66,6 +66,7 @@ Contents:
    hinic
    ila
    ipddp
+   ip_dynaddr
 
 .. only::  subproject and html
 

Documentation/networking/ip_dynaddr.rst

@@ -1,10 +1,15 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==================================
 IP dynamic address hack-port v0.03
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+==================================
+
 This stuff allows diald ONESHOT connections to get established by
 dynamically changing packet source address (and socket's if local procs).
 It is implemented for TCP diald-box connections(1) and IP_MASQuerading(2).
 
-If enabled[*] and forwarding interface has changed:
+If enabled\ [#]_ and forwarding interface has changed:
+
   1)  Socket (and packet) source address is rewritten ON RETRANSMISSIONS
       while in SYN_SENT state (diald-box processes).
   2)  Out-bounded MASQueraded source address changes ON OUTPUT (when
@@ -12,18 +17,24 @@ If enabled[*] and forwarding interface has changed:
       received by the tunnel.
 
 This is specially helpful for auto dialup links (diald), where the
-``actual'' outgoing address is unknown at the moment the link is
+``actual`` outgoing address is unknown at the moment the link is
 going up. So, the *same* (local AND masqueraded) connections requests that
 bring the link up will be able to get established.
 
-[*] At boot, by default no address rewriting is attempted. 
-  To enable:
+.. [#] At boot, by default no address rewriting is attempted.
+
+  To enable::
+
      # echo 1 > /proc/sys/net/ipv4/ip_dynaddr
-  To enable verbose mode:
-     # echo 2 > /proc/sys/net/ipv4/ip_dynaddr
-  To disable (default)
+
+  To enable verbose mode::
+
+    # echo 2 > /proc/sys/net/ipv4/ip_dynaddr
+
+  To disable (default)::
+
      # echo 0 > /proc/sys/net/ipv4/ip_dynaddr
 
 Enjoy!
 
--- Juanjo  <jjciarla@raiz.uncu.edu.ar>
+Juanjo  <jjciarla@raiz.uncu.edu.ar>