PPP, move protocols initialization from ppp_clear to ppp_new

What protocols init functions are meant to is to be called once to set
the default configuration before user specific configuration is set.

Until now, we reset to the default configuration just before
reconnecting, thus without allowing any time frame to let users change
it. That was fine until one user asked to be able to do that.

This change move protocols init functions calls from ppp_clear to
ppp_new, meaning user configuration is not overwritten anymore.

PPP: Use LWIP_ARRAYSIZE at appropriate places

Use LWIP_ARRAYSIZE to simplify the code.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Reviewed-by: Sylvain Rochet <gradator@gradator.net>
[Sylvain Rochet <gradator@gradator.net>: added missing casts]
Signed-off-by: Sylvain Rochet <gradator@gradator.net>

Work on task #13907 PPP cleanups: Move PPP options from opt.h to dedicated ppp_opts.h file

PPP: more const and mixed u_char/char types fixes

PPP: fix constness in PPP related files when PRINTPKT_SUPPORT is enabled

PPP, magic, using magic_random_bytes() for CHAP/MSCHAP/EAP instead of for-loop byte where possible

PPP, removed unnecessary memset()

Everything is cleared in ppp_clear(), we don't need to clear all
structures twice.

PPP, place print packet debug codenames in ROM

PPP, CHAP, reworked to pass ppp_pcb pointer to CHAP childs (MD5, MSCHAP, MSCHAPv2)

We are going to need ppp_pcb* in MSCHAP and MSCHAPv2 for MPPE for
int mppe_keys_set, u_char mppe_send_key and u_char mppe_recv_key
which are currently global variable which must be moved to ppp_pcb.

PPP, SERVER, MSCHAP: move output message from chap_server.message struct to stack

chap_server.message is only used in one function, moved to stack.

PPP, replaced drand48() with magic_pow()

PPP, SERVER: added CHAP authentication support

PPP, SERVER, CHAP: fixed wrong pointer used on chap_timeout()

PPP, CORE, Removed (*datainput) from struct protent if not used

Data input is only used by CCP and ECP, which are not supported at this time,
remove this entry from struct protent to save some flash.

PPP, CORE, Removed useless enabled_flag from struct protent

Our struct protent are const everywhere to save RAM, enable/disable
flag on a const struct is useless, saving some flash, removed.

PPP, added const modifier on auth strings

PPP, fixed some compiler warnings

Using -Wall -pedantic -Wparentheses -Wsequence-point
-Wswitch-default -Wextra -Wundef -Wshadow -Wpointer-arith
-Wbad-function-cast -Wc++-compat -Wwrite-strings -Wold-style-definition
-Wmissing-prototypes -Wredundant-decls -Wnested-externs -Wno-address

fixed bug #43235, cleared compiler warnings when using gcc with -Wextra option

PPP, added PPP_USE_PBUF_RAM compile time option

pbuf_type PPP is using for LCP, PAP, CHAP, EAP, IPCP and IP6CP packets.

Memory allocated must be single buffered for PPP to works, it requires pbuf
that are not going to be chained when allocated. This requires setting
PBUF_POOL_BUFSIZE to at least 512 bytes, which is quite huge for small systems.

Setting PPP_USE_PBUF_RAM to 1 makes PPP use memory from heap where continuous
buffers are required, allowing you to use a smaller PBUF_POOL_BUFSIZE.

PPP, switched chap_digests linked list to a const table in .rodata/flash, saving about 100 bytes in .data segment if chap(md5) and mschap is enabled

PPP, adding const pragma to struct protent, saving about 200 bytes in .data segment

PPP, changed all the code enclosed between PPP_SERVER #if macro to our PPP PCB structure, making it easier to support PPP server in the future

PPP, using PBUF_POOL instead of PBUF_RAM pbufs for PPP negociation packets

PPP stack does not handle chained pbuf, but PPP negociation packets
are at most ~40 bytes long, so we are only checking if the payload
can fit into the allocated pbuf (p->tot_len == p->len).

PPP, renamed all functions using common names in utils.c that can conflict with lwIP user code during link operation

Moved PPP headers into include/netif/ppp/, fixing bug #37040.

merged ppp_write and ppp_write_pbuf

replaced call from ppp_write to ppp_write_pbuf

removed pcb->chap_mdtype_all

don't duplicate user and password anymore, anyway, the PPP user will have them already allocated as static strings or from configuration flash/file

ppp_settings.remote_name is now a compile time option

pcb->outpacket_buf replaced by pbuf everywhere it was used

CHAP is now using pbuf instead of pcb->outpacket_buf

PPP_PCB are now allocated using memp_alloc()

LCP global variables moved to ppp_pcb as well as input/output buffers

protent prototype switched from unit to ppp_pcb

global variables removed from chap support

PAP and CHAP are now using ppp_pcb*

moved auth.c global variables to ppp_pcb

auth.c functions now use ppp_pcb* as first argument

started the unit to ppp_pcb replacement

renamed ppp_control to ppp_pcb, replaced unit number to ppp_pcb in all ppp.h declared functions

moved ppp_settings to ppp_control, improved PPP API to really allow multiple PPP sessions

moved remote_name and explicit_remote global variable to ppp_settings

PPP server support is now optional (disabled by default, not working until PPP have a "listen" support)

cleaned depreacted __P() and __V() macros, removed the legacy varargs.h header

ppp_impl.h is back!

don't build any PPP file if PPP support is disabled

removed all useless header files, merged ppp_defs.h to ppp.h

removed session.[ch] and tty.c which are Unix-centric files and disabled

clarified a bit more ppp.[ch]

demystified a bit the PPP impl, renamed output() to ppp_output() to prevent conflict

removed all system headers except the strict minimum

removed pppd.h and ppp.c, renamed pppmy.c to ppp.c and pppmy.h to ppp.h

added pppmy.h in all .c files to easily find conflicts

removed more protent fields only used by print packets functions

print packet functions are now optional

demand support is now a compile-time option

Obviously, it requires some wiring to know if there is new activity
on a not-yet established PPP interface with the default route
already set.

I don't think any lwIP user will ever need that, all should know
when to bring the link up and down.

CHAP support is now an optional compile-time feature

MSCHAP is now an optional compile-time feature

and less and less useless auth code (will this end ?)

more and more ppp options removal

disabled almost all PPP options strings and support as well as useless file-based auth code

modified auth_reset() so that we can choose which auth we want

Revert "modified auth_reset() so that we can choose which auth we want"

This reverts commit bf10a27db89eb64a50df40a173b2d012b47586e3.

Licence issue, we cannot include GPLed source code.

modified auth_reset() so that we can choose which auth we want

also fixed MS-CHAP and MS-CHAP-V2, MD4 polarssl uses bytes as input
length, not bits

CHAP auth is now working

Early development stage of an attempt to port PPPd 2.4.5 to lwIP.

PPPoE works, PPPoS code is not ported at all.

I am using the RP-PPPoE server to do my tests using the following
configuration:

$ cat /etc/ppp/pppoe-server-options
debug
login
lcp-echo-interval 10
lcp-echo-failure 10
ms-dns 192.168.4.130
ms-dns 192.168.4.231
netmask 255.255.255.0
defaultroute
noipdefault
usepeerdns

$ cat /etc/ppp/allip
192.168.4.1-200

$ pppoe-server -C isp -L 192.168.4.254 -p /etc/ppp/allip -I tap0

Plus the usual auth-lines in /etc/ppp/pap-secrets and
/etc/ppp/chap-secrets .

And the unix port minimal "echo" project slightly modified to use
the "tcpip" API, so with threads, which I am going to commit with
NO_SYS as a -Dmacro.

It still use some of the linux'ism, such as syslog() and crypt(),

I do not want to drop the syslog() supports at the moment, this is
pretty useful to debug, and we may just convert the way the syslog() is
done to provide a trace feature to our PPP users, as a compile-time
option.