Use "info2" log messages to inform about packets sent or processed.
For HELLO and ZLB messages, the log level is set to "debug" as these
are transmitted quite often and don't bring much information (this same
logging policy is used for logging packets when conf_verbose is on).
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>

Log message for any packet retransmission action using log_tunnel()
and level "info2".
Remove l2tp_conn_log() since it is no longer used.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>

Add a log message (warn level) for any discarded message type.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>

Use info1 messages to log information about main session establishment
and disconnection steps. These messages are:
  * establishment requests and their origin (CLI, ICRQ or OCRQ)
  * establishment confirmation (when session is really established)
  * PPP establishment
  * disconnection requests and their reason

Other information of interest use info2. These include:
  * Peer Session ID setting
  * Session internal structure freeing
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>

Use info1 messages to log information about main tunnel establishment
and disconnection steps. These messages are:
  * establishment requests and their origin (CLI or SCCRQ)
  * establishment confirmation (when tunnel is really established)
  * disconnection requests and their reason

Other information of interest use info2. These include:
  * Peer port update
  * Peer Tunnel ID setting
  * Tunnel internal structure freeing
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>

Adapt packet logging policy to make it consistent across L2TP packet
handling functions:
  * Don't log messages if conf_verbose is off.
  * Log HELLO and ZLB messages with log_debug and use log_info2 for
    any other message type.
  * Log retransmissions with log_info2, no matter the message type.
  * Log outgoing messages right before sending them.
  * Log incoming messages right before analysing their message type.
    This unifies the way l2tp_conn_read() and l2tp_udp_read() log
    incoming messages.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>

Implement minimal WEN messages processing, so that they get properly
acknowledged.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>

Handle incomming messages differently depending on their Message Type:
  * Close tunnel only when handling tunnel establishment messages
    fails (SCCRP and SCCCN) and everytime a StopCCN is received.
  * Never close tunnel after reception of HELLO, SLI or session
    establishment messages (ICRQ and OCRQ).
  * Ignore messages with invalid first attribute type.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>

Interpret AVPs present in CDN to provide user with better diagnostic.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>

Allocate PPP channel name using the string size to be stored and check
for allocation failure. Use two snprintf() and a _malloc() instead of
asprintf() so that allocated memory will be visible by memdebug.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>

In all reception or sending functions, return 0 on success or if
incomming message has been ignored (l2tp_recv_*() only). Return -1
upon any processing error.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>

There is no need to warn about missing Challenge when handling SCCRQ
comming from a host for which a secret exists: this will be done
automatically upon SCCRP generation (by l2tp_tunnel_genchallresp()).
Using the log message from l2tp_tunnel_genchallresp() has the advantage
of working for missing Challenge AVPs in both SCCRQ and SCCRP messages.

This patch also removes a redundant log message in l2tp_session_recv()
when handling unknown message types.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>

  * Avoid retrieving tunnel and session contexts manually; use
    l2tp_{tunnel,session}_self() instead.
  * Use l2tp_session_disconnect() instead of using an
    l2tp_send_CDN(); l2tp_session_free() sequence.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>

This reverts commit df6157ae.

This reverts commit 3108115e.

If a HELLO message can't be acknowledged just log an error as tunnel
doesn't need to get closed. If too many HELLO messages aren't
acknowledged, the peer will close the tunnel itself.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>

If tunnel or session establishment timeout expires, send StopCCN or CDN
to notify peer before closing tunnel/session.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>

Always disconnect tunnel once l2tp_tunnel_disconnect() is called,
even if sending StopCCN failed.
Change the way unknown message types are handled to comply with
new l2tp_tunnel_disconnect() signature.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>

Don't terminate tunnel in case of error while handling a duplicate
message. Such errors aren't critical enough to justify termination
of a tunnel and all of its sessions.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>

When starting a tunnel created upon user request, free it in case
of error.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>

A side effect of setting peer port to zero when sending SCCRQ messages
is that the tunnel can't send any new message before receiving first
peer's answer (this doesn't apply to retransmissions as peer port is
set in the original packet). It is then impossible to send StopCCN
messages within this time frame.

This patch fixes this issue using a new tunnel flag which indicates if
tunnel's peer port has a default value or if it has been set after
reception of peer's first message.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>

Handle tunnel timeout timers in l2tp_tunnel_start() and
l2tp_tunnel_connect(). This avoids timer code duplication across
functions that are spectific to the tunnel establishment mode.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>

Start and stop session timeout timers in l2tp_tunnel_start_session()
and l2tp_session_connect(). This unifies timers management across the
four different ways of creating sessions.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>

Define l2tp_session_incall_reply() which can be used as
parameter for l2tp_tunnel_start_session(). This removes
the need for updating session's state in l2tp_send_ICRP()
and normalises the way incomming and outgoing sessions are
handled.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>

Define l2tp_session_place_call() which can start either an incomming
or outgoing session depending on the 'sess->lns_mode' flag. This
removes the need for testing session mode before calling
l2tp_tunnel_start_session().
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>

Creating new sessions always involves the same steps:
  * Create new session context
  * Call session's first function in this context
  * Start session establishment timer

This patch starts centralising the first two steps in
l2tp_tunnel_confirm_session() (renamed l2tp_tunnel_start_session()
in order to use similar ways for starting tunnels and sessions).
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>

Handling ICRQ or OCRQ requests occurs in tunnel context, but if session
creation is rejected, a CDN has to be sent. However, l2tp_send_CDN() is
supposed to be called in session context. This means that it uselessly
switches to tunnel context before sending messages and requires a
session structure to work on.

This patch creates a new function for sending CDN from tunnel context.
It gets the session and peer session IDs from its arguments and calls
l2tp_tunnel_send() directly. The l2tp_recv_ICRQ() and l2tp_recv_OCRQ()
functions are modified to take advantage of this new function and will
now send CDN even upon early message processing error.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>

Define the l2tp_{tunnel,session}_send() functions for sending
messages in tunnel or session context. Session messages have
their session ID automatically set and switch to tunnel context
for sending messages.

Though the 'debug' parameter is removed from function prototypes,
the logging mechanism is respected: HELLO and ZLB are displayed as
'debug' messages while other message types use 'info2'.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>

Print details about errors that can occur when using the
"l2tp create tunnel" command line.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>