From f511bec26c08133f72a53db4c25465ab9d4ed9b2 Mon Sep 17 00:00:00 2001
From: Sylvain Rochet <gradator@gradator.net>
Date: Wed, 18 Feb 2015 23:12:06 +0100
Subject: [PATCH] PPP, PPPoS, only check PPPoS PCB pointer if PPPoS is not the
 only enabled lower protocol

We only need to keep track of existing PPPoS interfaces if PPPoS
is not the only enabled protocol.

PPP CORE does not have callbacks pointers for all PPPoS callbacks
which should actually be required for PPPoS (VJ config, asyncmap, ...),
there is too much callbacks to create and PPPoS must be kept light,
especially for users who are only using PPPoS.

But there is a drawback, PPP CORE does not know which
lower protocols it is talking to thanks to the abstraction,
therefore if PPPoS is enabled as well as PPPoE or PPPoL2TP there
might be situation where PPP CORE calls pppos_ config functions
on interfaces which are NOT PPPoS one. This is very unlikely to
happen because protocols not supported by PPPoE or PPPoL2TP are
disabled at LCP/IPCP negotiation but we are better safe than sorry.

So we check if passed PPP pointer to PPPoS configuration functions
is a PPPoS interface by checking against a linked list of existing
PPPoS interfaces.
---
 src/include/netif/ppp/ppp_impl.h |  6 +++++
 src/netif/ppp/pppos.c            | 41 ++++++++++++++++++++++++++++----
 2 files changed, 43 insertions(+), 4 deletions(-)

diff --git a/src/include/netif/ppp/ppp_impl.h b/src/include/netif/ppp/ppp_impl.h
index 788929f4..33e2f3d3 100644
--- a/src/include/netif/ppp/ppp_impl.h
+++ b/src/include/netif/ppp/ppp_impl.h
@@ -87,6 +87,12 @@
 #define	PPP_ESCAPE	0x7d	/* Asynchronous Control Escape */
 #define	PPP_TRANS	0x20	/* Asynchronous transparency modifier */
 
+/*
+ * Number of enabled low-level protocols
+ * Useful for low-level protocols to check whether they are alone.
+ */
+#define PPP_LINK_ENABLED_NUMBER (!!PPPOS_SUPPORT+!!PPPOE_SUPPORT+!!PPPOL2TP_SUPPORT)
+
 /*
  * Low-level links commands
  */
diff --git a/src/netif/ppp/pppos.c b/src/netif/ppp/pppos.c
index 933942f1..0640679d 100644
--- a/src/netif/ppp/pppos.c
+++ b/src/netif/ppp/pppos.c
@@ -50,13 +50,43 @@
 #include "netif/ppp/magic.h"
 #include "netif/ppp/vj.h"
 
+/*
+ * Linked list of created PPPoS interfaces
+ *
+ * We only need to keep track of existing PPPoS interfaces if PPPoS
+ * is not the only enabled protocol.
+ *
+ * PPP CORE does not have callbacks pointers for all PPPoS callbacks
+ * which should actually be required for PPPoS (VJ config, asyncmap, ...),
+ * there is too much callbacks to create and PPPoS must be kept light,
+ * especially for users who are only using PPPoS.
+ *
+ * But there is a drawback, PPP CORE does not know which
+ * lower protocols it is talking to thanks to the abstraction,
+ * therefore if PPPoS is enabled as well as PPPoE or PPPoL2TP there
+ * might be situation where PPP CORE calls pppos_ config functions
+ * on interfaces which are NOT PPPoS one. This is very unlikely to
+ * happen because protocols not supported by PPPoE or PPPoL2TP are
+ * disabled at LCP/IPCP negotiation but we are better safe than sorry.
+ *
+ * So we check if passed PPP pointer to PPPoS configuration functions
+ * is a PPPoS interface by checking against a linked list of existing
+ * PPPoS interfaces.
+ */
+#define PPPOS_PCB_LIST (PPP_LINK_ENABLED_NUMBER > 1)
+#if PPPOS_PCB_LIST
+static pppos_pcb *pppos_pcb_list;
+static u8_t pppos_exist(pppos_pcb *pppos);
+#else /* PPPOS_PCB_LIST */
+#define pppos_exist(pppos)     1
+#endif /* PPPOS_PCB_LIST */
+
 /* callbacks called from PPP core */
 static int pppos_link_command_callback(void *pcb, u8_t command);
 static int pppos_link_write_callback(void *pcb, struct pbuf *p);
 static err_t pppos_link_netif_output_callback(void *pcb, struct pbuf *pb, u_short protocol);
 
 /* Prototypes for procedures local to this file. */
-static u8_t pppos_exist(pppos_pcb *pppos);
 static void pppos_connect(pppos_pcb *pppos);
 static void pppos_disconnect(pppos_pcb *pppos);
 static err_t pppos_destroy(pppos_pcb *pppos);
@@ -135,9 +165,6 @@ ppp_get_fcs(u8_t byte)
 #define PPP_INITFCS     0xffff  /* Initial FCS value */
 #define PPP_GOODFCS     0xf0b8  /* Good final FCS value */
 
-/* linked list of created PPPoS interfaces */
-static pppos_pcb *pppos_pcb_list;
-
 
 
 /*
@@ -165,9 +192,11 @@ ppp_pcb *pppos_create(struct netif *pppif, sio_fd_t fd,
     return NULL;
   }
 
+#if PPPOS_PCB_LIST
   /* put the new interface at the head of the list */
   pppos->next = pppos_pcb_list;
   pppos_pcb_list = pppos;
+#endif /* PPPOS_PCB_LIST */
 
   pppos->ppp = ppp;
   pppos->fd = fd;
@@ -384,6 +413,7 @@ pppos_link_netif_output_callback(void *pcb, struct pbuf *pb, u_short protocol)
   return ERR_OK;
 }
 
+#if PPPOS_PCB_LIST
 static u8_t
 pppos_exist(pppos_pcb *pppos)
 {
@@ -395,6 +425,7 @@ pppos_exist(pppos_pcb *pppos)
   }
   return 0;
 }
+#endif /* PPPOS_PCB_LIST */
 
 static void
 pppos_connect(pppos_pcb *pppos)
@@ -453,6 +484,7 @@ pppos_disconnect(pppos_pcb *pppos)
 static err_t
 pppos_destroy(pppos_pcb *pppos)
 {
+#if PPPOS_PCB_LIST
   pppos_pcb **copp, *freep;
 
   /* remove interface from list */
@@ -462,6 +494,7 @@ pppos_destroy(pppos_pcb *pppos)
        break;
     }
   }
+#endif /* PPPOS_PCB_LIST */
 
   /* input pbuf left ? */
   pppos_free_current_input_packet(pppos);