From 39fd6b4bc20534fc8641abbea6e021bd2d2cda02 Mon Sep 17 00:00:00 2001
From: Christian Giese <christian@rtbrick.com>
Date: Fri, 4 Nov 2022 16:15:01 +0000
Subject: [PATCH] add config l2tp-server->lcp-padding

This config options allows to add a
fixed padding to all LCP packets send
from emulated LNS.
---
 code/bngblaster/src/bbl_config.c     |  4 ++++
 code/bngblaster/src/bbl_l2tp.c       | 15 +++++++--------
 code/bngblaster/src/bbl_l2tp.h       |  1 +
 code/bngblaster/src/bbl_protocols.c  |  5 ++++-
 code/bngblaster/src/bbl_protocols.h  |  1 +
 docsrc/sources/configuration/lns.rst |  3 +++
 6 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/code/bngblaster/src/bbl_config.c b/code/bngblaster/src/bbl_config.c
index 77e2cf45..d9fb5db9 100644
--- a/code/bngblaster/src/bbl_config.c
+++ b/code/bngblaster/src/bbl_config.c
@@ -2544,6 +2544,10 @@ json_parse_config(json_t *root)
             } else {
                 l2tp_server->hello_interval = 30;
             }
+            value = json_object_get(sub, "lcp-padding");
+            if(json_is_number(value)) {
+                l2tp_server->lcp_padding = json_number_value(value);;
+            }
         }
     } else if(json_is_object(section)) {
         fprintf(stderr, "JSON config error: List expected in L2TP server configuration but dictionary found\n");
diff --git a/code/bngblaster/src/bbl_l2tp.c b/code/bngblaster/src/bbl_l2tp.c
index 68c90bec..0f011eef 100644
--- a/code/bngblaster/src/bbl_l2tp.c
+++ b/code/bngblaster/src/bbl_l2tp.c
@@ -904,21 +904,20 @@ bbl_l2tp_data_rx(bbl_network_interface_s *interface,
     }
 
     l2tp_session->stats.data_rx++;
-    switch (l2tp->protocol) {
+    switch(l2tp->protocol) {
         case PROTOCOL_LCP:
             lcp_rx = (bbl_lcp_s*)l2tp->next;
-            if(lcp_rx->code == PPP_CODE_TERM_REQUEST) {
+            lcp_rx->padding = l2tp_session->tunnel->server->lcp_padding;
+            if(lcp_rx->code == PPP_CODE_ECHO_REQUEST) {
+                lcp_rx->code = PPP_CODE_ECHO_REPLY;
+                bbl_l2tp_send_data(l2tp_session, PROTOCOL_LCP, lcp_rx);
+            } else if(lcp_rx->code == PPP_CODE_TERM_REQUEST) {
                 l2tp_session->disconnect_code = 3;
                 l2tp_session->disconnect_protocol = 0;
                 l2tp_session->disconnect_direction = 1;
                 bbl_l2tp_send(l2tp_session->tunnel, l2tp_session, L2TP_MESSAGE_CDN);
                 bbl_l2tp_session_delete(l2tp_session);
-                return;
-            }
-            if(lcp_rx->code == PPP_CODE_ECHO_REQUEST) {
-                lcp_rx->code = PPP_CODE_ECHO_REPLY;
-                bbl_l2tp_send_data(l2tp_session, PROTOCOL_LCP, lcp_rx);
-            }
+            } 
             break;
         case PROTOCOL_PAP:
             memset(&pap_tx, 0x0, sizeof(bbl_pap_s));
diff --git a/code/bngblaster/src/bbl_l2tp.h b/code/bngblaster/src/bbl_l2tp.h
index 75565f1f..55ad9c87 100644
--- a/code/bngblaster/src/bbl_l2tp.h
+++ b/code/bngblaster/src/bbl_l2tp.h
@@ -67,6 +67,7 @@ typedef struct bbl_l2tp_server_
     uint16_t session_limit;
     uint16_t receive_window;
     uint16_t max_retry;
+    uint16_t lcp_padding;
 
     bool data_control_priority;
     bool data_length;
diff --git a/code/bngblaster/src/bbl_protocols.c b/code/bngblaster/src/bbl_protocols.c
index 5906a9ab..96d961e3 100644
--- a/code/bngblaster/src/bbl_protocols.c
+++ b/code/bngblaster/src/bbl_protocols.c
@@ -1206,7 +1206,7 @@ encode_ppp_lcp(uint8_t *buf, uint16_t *len,
             lcp_len = lcp->options_len + 4;
             *lcp_len_field = htobe16(lcp_len);
         } else {
-            /* Constuct options ... */
+            /* Options ... */
             lcp_len = 4;
             if(lcp->mru) {
                 *buf = PPP_LCP_OPTION_MRU;
@@ -1238,6 +1238,9 @@ encode_ppp_lcp(uint8_t *buf, uint16_t *len,
             *lcp_len_field = htobe16(lcp_len);
         }
     }
+    if(lcp->padding) {
+        BUMP_WRITE_BUFFER(buf, len, lcp->padding);
+    }
     return PROTOCOL_SUCCESS;
 }
 
diff --git a/code/bngblaster/src/bbl_protocols.h b/code/bngblaster/src/bbl_protocols.h
index 485bb29e..0aaff8b2 100644
--- a/code/bngblaster/src/bbl_protocols.h
+++ b/code/bngblaster/src/bbl_protocols.h
@@ -634,6 +634,7 @@ typedef struct bbl_lcp_ {
     uint16_t    vendor_value_len;
     uint8_t    *start;
     uint16_t    len;
+    uint16_t    padding;
     uint8_t    *option[PPP_MAX_OPTIONS];
     bool        unknown_options;
 } bbl_lcp_s;
diff --git a/docsrc/sources/configuration/lns.rst b/docsrc/sources/configuration/lns.rst
index 7599e6e4..cd1281f5 100644
--- a/docsrc/sources/configuration/lns.rst
+++ b/docsrc/sources/configuration/lns.rst
@@ -46,6 +46,9 @@
    * - `data-control-tos`
      - Set the L2TP tunnel TOS priority (outer IPv4 header) for all non-IP data packets (LCP, IPCP, ...)
      - 0
+   * - `lcp-padding`
+     - Add fixed padding to LCP packets send from LNS
+     - 0 
 
 The BNG Blaster supports different congestion modes for the
 reliable delivery of control messages. The ``default`` mode